mesh-mail: say mail events on its own stream MAIL, granted per account by grants (hq ADR 0363)

ADR 0359 asked for a stream of its own and a bus grant from the module's
grants; ADR 0363 built both. The events leave the shared EVENTS stream, and
one family pattern per change replaces the literal per-account emits, so a
new account changes no manifest.

modules/mesh-mail/README.md

@@ -0,0 +1,58 @@
+# mesh-mail — the operator's mail accounts, watched and said on the bus
+
+One module holds the operator's mail accounts, watches them, and says each change of a message on the bus for the
+modules the operator grants it to (novox/hq ADR 0359, research 049 document 02). One instance, on the control-node.
+This is the first stage: accounts of the kind `imap`, read-only. Nothing here flags, moves, deletes, drafts or sends.
+
+## What it does
+
+- **Watches.** For each account it keeps one connection: IDLE on the inbox, ended and begun again every two minutes
+  (which proves the server still answers), and a look at every other folder every five minutes. Folders are opened
+  read-only and bodies are peeked, so watching never marks a message seen.
+- **Indexes.** One row per message and folder in its own database (`postgres-database`): metadata, flags, the text
+  for search, and the attachments' references. Each attachment is kept once, by its SHA-256, in its bucket
+  (`s3-bucket`, from `minio`).
+- **Says each change.** A message added, its flags changed, or removed is said as the event
+  `mail.<account>.message.<added|changed|removed>`: account, folder, uid, message id, date, sender, recipients,
+  subject, size, flags and attachment references; never the body, never an attachment's bytes. The events go to the
+  module's own stream `MAIL`, kept seven days, never to the shared EVENTS stream (novox/hq ADR 0363); a module hears an
+  account's part only when its `consumes` names mesh-mail and the setting `grants` names it for that account. The first look at a
+  folder indexes what is there and says nothing: the bus hears what changed since the watch began. The keeper writes
+  each event in the same step as the change it says; the bundle says it through the runtime and removes it once the
+  bus took it.
+
+## Its settings, both trusted
+
+`accounts` — per account name (a lower-case token, which names the account on the bus and its secret):
+
+```json
+{"mesh": {"kind": "imap", "address": "<the address>",
+          "incoming": {"host": "<the IMAP server>", "port": 993, "security": "tls"},
+          "outgoing": {"host": "<the SMTP server>", "port": 465, "security": "tls"},
+          "folders": ["optional: the folders watched besides the inbox; every folder when left out"]}}
+```
+
+`outgoing` is read and never used in this stage. A second `imap` account on another server is one more entry and one
+more password; no code changes. `user` signs in under another name than the address.
+
+`grants` — per account, who may read its mail: a module's name (on every machine), `<machine>.<module>`, or
+`person.<name>`. Nobody by default. It restricts the stream `MAIL` on the bus (a person's entry grants nothing there)
+and the tools `mail_search` and `mail_read`.
+
+The password of an account is the own secret `mail-credential-<account>`, given at the desk; the mesh never makes one.
+
+## Its tools
+
+| Tool | Answers |
+|---|---|
+| `mail_accounts` | each account's kind, state and why, when its server last answered, its folders; the address only to a caller granted it |
+| `mail_search` | messages of the accounts the caller is granted, by every word of a query, newest first, no body |
+| `mail_read` | one message's metadata and text, or one attachment's bytes, to a caller granted its account |
+| `mail_health` | healthy; unhealthy naming the account and why (connection down, or no answer for five minutes); waits naming `mail-credential-<account>` while its password is not given |
+
+The caller is the runtime's word, never an argument.
+
+## Its processes
+
+`prepare` brings the index's schema to this version's (numbered migrations, and `schema.sql` for a fresh database).
+`keep` watches the accounts and is judged by its unit. `watch` judges every minute and is judged by `mail_health`.

modules/mesh-mail/cmd/mesh-mail/config.go

@@ -0,0 +1,262 @@
+package main
+
+// The operator's mail accounts and who may read them (novox/hq ADR 0359 §1, §4, §5): two trusted settings, each a
+// file the mesh writes from the module's settings and changes only on the operator's approval. `accounts` says which
+// server each account is on and how to sign in (never a credential); `grants` says, per account, which callers may
+// read its mail. The password of an account is the module's own secret mail-credential-<account>, given at the desk
+// (ADR 0283 §6), at the path the secrets directory and that name make.
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
+)
+
+// The kinds of account an adapter exists for. Only `imap` is built (ADR 0359 §5); `imap-oauth` and `graph` are later
+// decisions (§7), and an account of a kind not listed here is refused by name.
+const KindIMAP = "imap"
+
+// Kinds is every kind this version has an adapter for.
+var Kinds = []string{KindIMAP}
+
+// SecretFamily is the prefix of every account's own secret: mail-credential-<account> (ADR 0283 §6).
+const SecretFamily = "mail-credential-"
+
+// accountName is what an account may be called: a member name of the secret family (ADR 0283 §6) and one token of a
+// bus subject, so never a dot, a slash or an upper-case letter.
+var accountName = regexp.MustCompile(`^[a-z0-9][a-z0-9-]{0,39}$`)
+
+// Server is where an account's mail is reached.
+type Server struct {
+	Host string `json:"host"`
+	Port int    `json:"port"`
+	// Security is tls (TLS from the first byte) or starttls (plain, then upgraded before signing in). Nothing
+	// signs in over a connection that is not encrypted.
+	Security string `json:"security"`
+}
+
+// Address is host:port.
+func (s Server) Address() string { return fmt.Sprintf("%s:%d", s.Host, s.Port) }
+
+// Account is one of the operator's mail accounts, as the setting `accounts` declares it.
+type Account struct {
+	// Name is the key the account has in the setting; set when the setting is read.
+	Name string `json:"-"`
+	Kind string `json:"kind"`
+	// Address is the account's mail address, said only to a caller granted the account.
+	Address string `json:"address"`
+	// User is the name it signs in with; the address when empty.
+	User     string  `json:"user,omitempty"`
+	Incoming Server  `json:"incoming"`
+	Outgoing *Server `json:"outgoing,omitempty"`
+	// Folders are the folders watched besides the inbox; every folder the server lists when empty.
+	Folders []string `json:"folders,omitempty"`
+}
+
+// SignInAs is the name the account signs in with.
+func (a Account) SignInAs() string {
+	if a.User != "" {
+		return a.User
+	}
+	return a.Address
+}
+
+// Secret is the name of the account's own secret.
+func (a Account) Secret() string { return SecretFamily + a.Name }
+
+// AccountsFile is the shape of the trusted setting `accounts`, as the mesh writes it.
+type AccountsFile struct {
+	Accounts map[string]Account `json:"accounts"`
+}
+
+// ReadAccounts reads the accounts setting, refusing it whole when any account in it cannot be watched: an account
+// half-understood would be watched wrongly, and the operator approved the setting as one.
+func ReadAccounts(path string) ([]Account, error) {
+	if path == "" {
+		return nil, errors.New("the module was started without its accounts setting (MESH_MAIL_ACCOUNTS)")
+	}
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("the accounts setting cannot be read: %w", err)
+	}
+	return ParseAccounts(raw)
+}
+
+// ParseAccounts reads the accounts setting's content.
+func ParseAccounts(raw []byte) ([]Account, error) {
+	var f AccountsFile
+	dec := json.NewDecoder(strings.NewReader(string(raw)))
+	dec.DisallowUnknownFields()
+	if err := dec.Decode(&f); err != nil {
+		return nil, fmt.Errorf("the accounts setting is not the module's: %v", err)
+	}
+	var out []Account
+	var problems []string
+	for name, a := range f.Accounts {
+		a.Name = name
+		if err := a.Check(); err != nil {
+			problems = append(problems, err.Error())
+			continue
+		}
+		out = append(out, a)
+	}
+	if len(problems) > 0 {
+		sort.Strings(problems)
+		return nil, errors.New("the accounts setting is refused: " + strings.Join(problems, "; "))
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
+	return out, nil
+}
+
+// Check says why an account cannot be watched, or nil.
+func (a Account) Check() error {
+	say := func(format string, args ...any) error {
+		return fmt.Errorf("the account %q: %s", a.Name, fmt.Sprintf(format, args...))
+	}
+	if !accountName.MatchString(a.Name) {
+		return say("is not an account's name: a lower-case letter or digit, then lower-case letters, digits and hyphens, at most 40")
+	}
+	known := false
+	for _, k := range Kinds {
+		known = known || a.Kind == k
+	}
+	if !known {
+		return say("is of the kind %q, and this version watches only %s", a.Kind, strings.Join(Kinds, ", "))
+	}
+	if !strings.Contains(a.Address, "@") {
+		return say("has no mail address")
+	}
+	if err := a.Incoming.check("incoming"); err != nil {
+		return say("%v", err)
+	}
+	if a.Outgoing != nil {
+		if err := a.Outgoing.check("outgoing"); err != nil {
+			return say("%v", err)
+		}
+	}
+	for _, f := range a.Folders {
+		if strings.TrimSpace(f) == "" || strings.EqualFold(f, "INBOX") {
+			return say("lists the folder %q, and the inbox is always watched", f)
+		}
+	}
+	return nil
+}
+
+func (s Server) check(which string) error {
+	switch {
+	case strings.TrimSpace(s.Host) == "" || strings.ContainsAny(s.Host, " /:"):
+		return fmt.Errorf("its %s server has no host name", which)
+	case s.Port <= 0 || s.Port > 65535:
+		return fmt.Errorf("its %s server's port %d is not a port", which, s.Port)
+	case s.Security != "tls" && s.Security != "starttls":
+		return fmt.Errorf("its %s server's security is %q, and only tls or starttls signs in", which, s.Security)
+	}
+	return nil
+}
+
+// SecretPath is where the account's own secret is placed in the secrets directory, as the manifest declares the
+// family: <dir>/mail-credential-<account>.secret.
+func SecretPath(dir string, a Account) string { return filepath.Join(dir, a.Secret()+".secret") }
+
+// ReadSecret is the account's password, or given false when nobody gave it yet: the mesh never makes a member of the
+// family, so a member not given is no file (ADR 0283 §6).
+func ReadSecret(dir string, a Account) (string, bool, error) {
+	raw, err := os.ReadFile(SecretPath(dir, a))
+	if errors.Is(err, os.ErrNotExist) {
+		return "", false, nil
+	}
+	if err != nil {
+		return "", false, err
+	}
+	pw := strings.TrimRight(string(raw), "\r\n")
+	if pw == "" {
+		return "", false, nil
+	}
+	return pw, true, nil
+}
+
+// SecretGiven says whether the account's own secret was given.
+func SecretGiven(dir string, a Account) bool {
+	_, given, err := ReadSecret(dir, a)
+	if err != nil {
+		// A file there that cannot be read was given: the keeper says what is wrong with it.
+		_, statErr := os.Stat(SecretPath(dir, a))
+		return statErr == nil
+	}
+	return given
+}
+
+// ---- grants ------------------------------------------------------------------------------------------------------
+
+// Grants is the trusted setting `grants`: per account, the callers that may read its mail (ADR 0359 §4). An entry is a
+// module's name (granted wherever it runs), a module on one machine (`<machine>.<module>`) or a person
+// (`person.<name>`), as the runtime names callers.
+type Grants map[string][]string
+
+// GrantsFile is the shape of the setting as the mesh writes it.
+type GrantsFile struct {
+	Grants Grants `json:"grants"`
+}
+
+// ReadGrants reads the grants setting. A setting that cannot be read grants nothing, and says so.
+func ReadGrants(path string) (Grants, error) {
+	if path == "" {
+		return Grants{}, errors.New("the module was started without its grants setting (MESH_MAIL_GRANTS)")
+	}
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return Grants{}, fmt.Errorf("the grants setting cannot be read: %w", err)
+	}
+	var f GrantsFile
+	dec := json.NewDecoder(strings.NewReader(string(raw)))
+	dec.DisallowUnknownFields()
+	if err := dec.Decode(&f); err != nil {
+		return Grants{}, fmt.Errorf("the grants setting is not the module's: %v", err)
+	}
+	if f.Grants == nil {
+		f.Grants = Grants{}
+	}
+	return f.Grants, nil
+}
+
+// Unproven is the caller the runtime proved nobody to be; it is granted nothing.
+const Unproven = "unproven"
+
+// Allows says whether the caller may read the account's mail. Nobody is granted an account by default, an unproven
+// caller never, and a wildcard is no entry.
+func (g Grants) Allows(caller, account string) bool {
+	if caller == "" || caller == Unproven {
+		return false
+	}
+	for _, entry := range g[account] {
+		if entry == "" || strings.ContainsAny(entry, "*>") {
+			continue
+		}
+		if entry == caller {
+			return true
+		}
+		// A module's name alone grants it on every machine: the caller is <machine>.<module>.
+		if !strings.Contains(entry, ".") {
+			if _, module, ok := strings.Cut(caller, "."); ok && module == entry && !strings.HasPrefix(caller, "person.") {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// Granted is the accounts, of those given, the caller may read.
+func (g Grants) Granted(caller string, accounts []Account) []string {
+	var out []string
+	for _, a := range accounts {
+		if g.Allows(caller, a.Name) {
+			out = append(out, a.Name)
+		}
+	}
+	return out
+}

modules/mesh-mail/cmd/mesh-mail/config_test.go

@@ -0,0 +1,108 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// The first stage's account, as the operator sets the setting `accounts` (ADR 0359 §5): its address and its server,
+// never a credential; its password is the own secret mail-credential-mesh.
+const stageOne = `{"accounts": {"mesh": {"kind": "imap", "address": "jschoubben@novox.be",
+  "incoming": {"host": "mail.novox.be", "port": 993, "security": "tls"}}}}`
+
+func TestTheFirstStagesAccountIsReadAndItsSecretNamed(t *testing.T) {
+	got, err := ParseAccounts([]byte(stageOne))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 1 || got[0].Name != "mesh" || got[0].Kind != KindIMAP || got[0].SignInAs() != "jschoubben@novox.be" ||
+		got[0].Incoming.Address() != "mail.novox.be:993" || got[0].Secret() != "mail-credential-mesh" || got[0].Outgoing != nil {
+		t.Fatalf("%+v", got)
+	}
+	if p := SecretPath("/state", got[0]); p != "/state/mail-credential-mesh.secret" {
+		t.Fatalf("the secret is placed at %s", p)
+	}
+}
+
+// A second account of the kind imap on another server — Gmail with an app password, another member of the family —
+// is configuration only: no code changes for it. Each account may also say its outgoing server, which this stage
+// reads and never uses (it sends nothing).
+func TestASecondIMAPAccountIsConfigurationOnly(t *testing.T) {
+	got, err := ParseAccounts([]byte(`{"accounts": {
+	  "mesh": {"kind": "imap", "address": "jschoubben@novox.be", "incoming": {"host": "mail.novox.be", "port": 993, "security": "tls"}},
+	  "gmail": {"kind": "imap", "address": "someone@gmail.com", "incoming": {"host": "imap.gmail.com", "port": 993, "security": "tls"},
+	    "outgoing": {"host": "smtp.gmail.com", "port": 465, "security": "tls"}, "folders": ["[Gmail]/Sent Mail"]}}}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 2 || got[0].Name != "gmail" || got[0].Secret() != "mail-credential-gmail" || got[0].Outgoing.Address() != "smtp.gmail.com:465" ||
+		!reflect.DeepEqual(got[0].Folders, []string{"[Gmail]/Sent Mail"}) {
+		t.Fatalf("%+v", got)
+	}
+}
+
+func TestAnAccountThatCannotBeWatchedRefusesTheSetting(t *testing.T) {
+	for name, raw := range map[string]string{
+		"a later kind":       `{"accounts": {"work": {"kind": "graph", "address": "a@b.c", "incoming": {"host": "h", "port": 1, "security": "tls"}}}}`,
+		"no encryption":      `{"accounts": {"x": {"kind": "imap", "address": "a@b.c", "incoming": {"host": "h", "port": 143, "security": "none"}}}}`,
+		"a name with a dot":  `{"accounts": {"my.box": {"kind": "imap", "address": "a@b.c", "incoming": {"host": "h", "port": 993, "security": "tls"}}}}`,
+		"a password in it":   `{"accounts": {"x": {"kind": "imap", "address": "a@b.c", "password": "p", "incoming": {"host": "h", "port": 993, "security": "tls"}}}}`,
+		"no address":         `{"accounts": {"x": {"kind": "imap", "incoming": {"host": "h", "port": 993, "security": "tls"}}}}`,
+		"the inbox listed":   `{"accounts": {"x": {"kind": "imap", "address": "a@b.c", "folders": ["INBOX"], "incoming": {"host": "h", "port": 993, "security": "tls"}}}}`,
+		"a bad outgoing one": `{"accounts": {"x": {"kind": "imap", "address": "a@b.c", "incoming": {"host": "h", "port": 993, "security": "tls"}, "outgoing": {"host": "", "port": 465, "security": "tls"}}}}`,
+	} {
+		if _, err := ParseAccounts([]byte(raw)); err == nil {
+			t.Errorf("%s: accepted", name)
+		}
+	}
+	if got, err := ParseAccounts([]byte(`{"accounts": {}}`)); err != nil || len(got) != 0 {
+		t.Fatalf("the manifest's default: %v %v", got, err)
+	}
+}
+
+// Grants (ADR 0359 §4): nobody by default; a module's name grants it wherever it runs; a module on one machine, or a
+// person, by its full name; never the unproven, never by a wildcard, never one account for another.
+func TestGrantsAreByAccountAndByProvenCaller(t *testing.T) {
+	g := Grants{"mesh": {"triage", "novox.desk", "person.jochen", "*"}}
+	for caller, want := range map[string]bool{
+		"novox.triage": true, "shanks.triage": true, "novox.desk": true, "g14.desk": false, "person.jochen": true,
+		"person.triage": false, "novox.other": false, Unproven: false, "": false, "novox.*": false,
+	} {
+		if got := g.Allows(caller, "mesh"); got != want {
+			t.Errorf("%s: %v", caller, got)
+		}
+	}
+	if g.Allows("novox.triage", "gmail") || (Grants{}).Allows("novox.triage", "mesh") {
+		t.Fatal("a grant reached an account it does not name")
+	}
+	dir := t.TempDir()
+	path := filepath.Join(dir, "grants.json")
+	_ = os.WriteFile(path, []byte(`{"grants": {"mesh": ["triage"]}}`), 0o600)
+	read, err := ReadGrants(path)
+	if err != nil || !read.Allows("novox.triage", "mesh") {
+		t.Fatalf("%v %v", read, err)
+	}
+	_ = os.WriteFile(path, []byte(`{"grants": {"mesh": "triage"}}`), 0o600)
+	if read, err := ReadGrants(path); err == nil || len(read) != 0 {
+		t.Fatal("a grants setting it cannot read granted something")
+	}
+}
+
+func TestASecretGivenEmptyIsNotGiven(t *testing.T) {
+	dir := t.TempDir()
+	a := testAccount()
+	if SecretGiven(dir, a) {
+		t.Fatal("given before anything was written")
+	}
+	_ = os.WriteFile(SecretPath(dir, a), []byte("\n"), 0o600)
+	if SecretGiven(dir, a) {
+		t.Fatal("an empty file is a password")
+	}
+	_ = os.WriteFile(SecretPath(dir, a), []byte("pw\n"), 0o600)
+	if pw, given, _ := ReadSecret(dir, a); !given || pw != "pw" || strings.Contains(pw, "\n") {
+		t.Fatalf("%q %v", pw, given)
+	}
+}

modules/mesh-mail/cmd/mesh-mail/health.go

@@ -0,0 +1,170 @@
+package main
+
+// How mesh-mail is (novox/hq ADR 0359 §6). Its keeper's liveness is its unit's; its watching is judged here, by the
+// watch process, once a minute, and left in a status file the bundle's tool `mail_health` reads:
+//
+//   - waits, naming the own secret mail-credential-<account>, for an account whose password nobody gave yet (ADR 0283),
+//     so the condition is needs-operator and the gate passes;
+//   - unhealthy, naming the account and why, when its connection is down or its server has not answered for
+//     SilentAfter (five minutes) — an IDLE that went silent;
+//   - healthy otherwise.
+//
+// A fault beside a wait is unhealthy and says both.
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/health"
+)
+
+// HealthTool is the module's tool the node-engine asks how it is.
+const HealthTool = "mail_health"
+
+// WatchEvery is how often the watch judges; StatusStale how old its verdict may be before the tool says it stopped.
+const (
+	WatchEvery  = time.Minute
+	StatusStale = 3 * WatchEvery
+	// SignInGrace is how long a password just given may wait for its keeper to sign in before that is a fault.
+	SignInGrace = 3 * time.Minute
+)
+
+// Judge is the module's health from what the watch reads: the accounts setting (or why it cannot be read), whether the
+// index serves, which passwords were given, and each account's state as its keeper said it.
+func Judge(accounts []Account, accountsErr, readyErr error, given func(Account) bool, states map[string]AccountState, now time.Time) health.Answer {
+	if accountsErr != nil {
+		return health.Unhealthy(accountsErr.Error())
+	}
+	var problems, fine []string
+	var waits []health.Wait
+	if readyErr != nil {
+		problems = append(problems, "the index cannot serve: "+readyErr.Error())
+	}
+	for _, a := range accounts {
+		if !given(a) {
+			waits = append(waits, health.Wait{
+				Part:   "the mail account " + a.Name,
+				Secret: a.Secret(),
+				What:   "the password of the mail account " + a.Name,
+			})
+			continue
+		}
+		if readyErr != nil {
+			continue
+		}
+		st, said := states[a.Name]
+		switch {
+		case !said:
+			problems = append(problems, fmt.Sprintf("the account %s: its keeper has said nothing of it", a.Name))
+		case st.State == AccountWaits:
+			if now.Sub(st.Said) > SignInGrace {
+				problems = append(problems, fmt.Sprintf("the account %s: its password was given, and its keeper has not signed in for %s",
+					a.Name, now.Sub(st.Said).Round(time.Second)))
+			} else {
+				fine = append(fine, a.Name+" is signing in")
+			}
+		case st.State == AccountFailing:
+			problems = append(problems, fmt.Sprintf("the account %s is not watched: %s", a.Name, st.Why))
+		case st.Heard.IsZero():
+			problems = append(problems, fmt.Sprintf("the account %s: its server has not answered since its keeper started", a.Name))
+		case now.Sub(st.Heard) > SilentAfter:
+			problems = append(problems, fmt.Sprintf("the account %s: its server has not answered for %s (its IDLE on the inbox is silent)",
+				a.Name, now.Sub(st.Heard).Round(time.Second)))
+		default:
+			fine = append(fine, fmt.Sprintf("%s is %s (%s)", a.Name, st.State, st.Why))
+		}
+	}
+	waitSaid := ""
+	if len(waits) > 0 {
+		var names []string
+		for _, w := range waits {
+			names = append(names, w.Secret)
+		}
+		waitSaid = "waits for its password: " + strings.Join(names, ", ")
+	}
+	switch {
+	case len(problems) > 0:
+		why := strings.Join(problems, "; ")
+		if waitSaid != "" {
+			why += "; and it " + waitSaid
+		}
+		return health.Unhealthy(why, waits...)
+	case len(waits) > 0:
+		why := "nothing is wrong, and it " + waitSaid
+		if len(fine) > 0 {
+			why += "; " + strings.Join(fine, "; ")
+		}
+		return health.Waiting(why, waits...)
+	case len(accounts) == 0:
+		return health.Healthy("no mail account is declared, so nothing is watched")
+	}
+	return health.Healthy(fmt.Sprintf("%d account(s) watched: %s", len(accounts), strings.Join(fine, "; ")))
+}
+
+// Status is the watch's verdict as it leaves it: the answer, and when it looked.
+type Status struct {
+	health.Answer
+	At time.Time `json:"at"`
+}
+
+func writeStatus(path string, s Status) error {
+	raw, err := json.Marshal(s)
+	if err != nil {
+		return err
+	}
+	tmp := path + ".next"
+	if err := os.WriteFile(tmp, raw, 0o600); err != nil {
+		return err
+	}
+	return os.Rename(tmp, path)
+}
+
+// ReadStatus is the watch's last verdict, as the tool answers it: unhealthy when there is none, when it cannot be read,
+// or when it is older than StatusStale.
+func ReadStatus(path string, now time.Time) health.Answer {
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return health.Unhealthy("the watch has left no verdict yet: " + err.Error())
+	}
+	var s Status
+	if err := json.Unmarshal(raw, &s); err != nil {
+		return health.Unhealthy("the watch's verdict cannot be read")
+	}
+	if age := now.Sub(s.At); age > StatusStale {
+		return health.Unhealthy(fmt.Sprintf("the watch has not looked for %s (its last verdict: %s)", age.Round(time.Second), s.Why))
+	}
+	// Read through the SDK's reader, so a wait it cannot check is never excused.
+	a, err := health.Read(mustJSON(s.Answer))
+	if err != nil {
+		return health.Unhealthy("the watch's verdict cannot be read: " + err.Error())
+	}
+	return a
+}
+
+func mustJSON(v any) []byte {
+	raw, _ := json.Marshal(v)
+	return raw
+}
+
+// watchOnce is one look: what the watch reads, judged.
+func watchOnce(ctx context.Context, env Env, open func(context.Context) (Store, func(), error), now time.Time) health.Answer {
+	accounts, accountsErr := ReadAccounts(env.Accounts)
+	var readyErr error
+	states := map[string]AccountState{}
+	st, done, err := open(ctx)
+	if err != nil {
+		readyErr = err
+	} else {
+		defer done()
+		if readyErr = st.Ready(ctx); readyErr == nil {
+			if states, err = st.States(ctx); err != nil {
+				readyErr = err
+			}
+		}
+	}
+	return Judge(accounts, accountsErr, readyErr, func(a Account) bool { return SecretGiven(env.Secrets, a) }, states, now)
+}

modules/mesh-mail/cmd/mesh-mail/health_test.go

@@ -0,0 +1,116 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/health"
+)
+
+var judgedAt = time.Date(2026, 10, 14, 18, 0, 0, 0, time.UTC)
+
+func given(names ...string) func(Account) bool {
+	return func(a Account) bool { return contains(names, a.Name) }
+}
+
+// Before the password is given, mail_health answers waits, naming the secret, which the node-engine reads as a wait
+// the controller can excuse (ADR 0283 §1, §3): the family mail-credential-* is declared issued outside the mesh.
+func TestItWaitsNamingTheSecretUntilThePasswordIsGiven(t *testing.T) {
+	a := Judge([]Account{testAccount()}, nil, nil, given(), nil, judgedAt)
+	if a.State != health.StateWaits || len(a.Waits) != 1 || a.Waits[0].Secret != "mail-credential-mesh" || a.Healthy {
+		t.Fatalf("%+v", a)
+	}
+	read, err := health.Read(mustJSON(a))
+	if err != nil || read.State != health.StateWaits {
+		t.Fatalf("the node-engine reads it as %+v (%v)", read, err)
+	}
+	if strings.Contains(a.Waits[0].What, "@") || strings.Contains(a.Why, "@") {
+		t.Fatalf("the wait says an address: %+v", a)
+	}
+}
+
+// Unhealthy, naming the account and why, when its connection is down or its server silent for five minutes.
+func TestItIsUnhealthyWhenAnAccountIsDownOrSilent(t *testing.T) {
+	acc := []Account{testAccount()}
+	down := map[string]AccountState{"mesh": {Account: "mesh", State: AccountFailing, Why: "its server mail.example cannot be reached", Said: judgedAt}}
+	if a := Judge(acc, nil, nil, given("mesh"), down, judgedAt); a.State != health.StateUnhealthy || !strings.Contains(a.Why, "the account mesh is not watched: its server") {
+		t.Fatalf("down: %+v", a)
+	}
+	silent := map[string]AccountState{"mesh": {Account: "mesh", State: AccountCurrent, Heard: judgedAt.Add(-SilentAfter - time.Second), Said: judgedAt}}
+	if a := Judge(acc, nil, nil, given("mesh"), silent, judgedAt); a.State != health.StateUnhealthy || !strings.Contains(a.Why, "IDLE on the inbox is silent") {
+		t.Fatalf("silent: %+v", a)
+	}
+	fine := map[string]AccountState{"mesh": {Account: "mesh", State: AccountCurrent, Why: "watching", Heard: judgedAt.Add(-time.Minute), Said: judgedAt}}
+	if a := Judge(acc, nil, nil, given("mesh"), fine, judgedAt); a.State != health.StateHealthy || !a.Healthy {
+		t.Fatalf("fine: %+v", a)
+	}
+	if a := Judge(acc, nil, errors.New("the schema is behind"), given("mesh"), fine, judgedAt); a.State != health.StateUnhealthy {
+		t.Fatalf("an index that cannot serve: %+v", a)
+	}
+	if a := Judge(nil, errors.New("the accounts setting is refused"), nil, given(), nil, judgedAt); a.State != health.StateUnhealthy {
+		t.Fatalf("a setting it cannot read: %+v", a)
+	}
+	// A fault beside a wait is unhealthy and says both (ADR 0283 §1).
+	two := []Account{testAccount(), {Name: "gmail", Kind: KindIMAP, Address: "x@example.com", Incoming: Server{Host: "h", Port: 993, Security: "tls"}}}
+	a := Judge(two, nil, nil, given("mesh"), down, judgedAt)
+	if a.State != health.StateUnhealthy || len(a.Waits) != 1 || a.Waits[0].Secret != "mail-credential-gmail" || !strings.Contains(a.Why, "mail-credential-gmail") {
+		t.Fatalf("both: %+v", a)
+	}
+	// A password just given is signing in for a while; not for ever.
+	signing := map[string]AccountState{"mesh": {Account: "mesh", State: AccountWaits, Said: judgedAt.Add(-time.Minute)}}
+	if a := Judge(acc, nil, nil, given("mesh"), signing, judgedAt); a.State != health.StateHealthy {
+		t.Fatalf("signing in: %+v", a)
+	}
+	signing["mesh"] = AccountState{Account: "mesh", State: AccountWaits, Said: judgedAt.Add(-SignInGrace - time.Minute)}
+	if a := Judge(acc, nil, nil, given("mesh"), signing, judgedAt); a.State != health.StateUnhealthy {
+		t.Fatalf("never signed in: %+v", a)
+	}
+	if a := Judge(nil, nil, nil, given(), nil, judgedAt); a.State != health.StateHealthy || !strings.Contains(a.Why, "nothing is watched") {
+		t.Fatalf("no account: %+v", a)
+	}
+}
+
+// The tool reads the watch's verdict, and says when the watch stopped looking.
+func TestTheHealthToolReadsTheWatchsVerdictAndSaysWhenItIsStale(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "health.json")
+	if a := ReadStatus(path, judgedAt); a.State != health.StateUnhealthy {
+		t.Fatalf("no verdict: %+v", a)
+	}
+	waits := Judge([]Account{testAccount()}, nil, nil, given(), nil, judgedAt)
+	if err := writeStatus(path, Status{Answer: waits, At: judgedAt}); err != nil {
+		t.Fatal(err)
+	}
+	if a := ReadStatus(path, judgedAt.Add(time.Minute)); a.State != health.StateWaits || a.Waits[0].Secret != "mail-credential-mesh" {
+		t.Fatalf("%+v", a)
+	}
+	if a := ReadStatus(path, judgedAt.Add(StatusStale+time.Second)); a.State != health.StateUnhealthy || !strings.Contains(a.Why, "has not looked") {
+		t.Fatalf("stale: %+v", a)
+	}
+}
+
+// One look of the watch, end to end over the files the mesh writes: the accounts setting, the secrets directory and
+// the index.
+func TestTheWatchJudgesFromTheFilesAndTheIndex(t *testing.T) {
+	dir := t.TempDir()
+	env := Env{Accounts: filepath.Join(dir, "accounts.json"), Secrets: dir}
+	writeFile(t, env.Accounts, stageOne)
+	st := newMemStore()
+	open := func(context.Context) (Store, func(), error) { return st, func() {}, nil }
+	if a := watchOnce(context.Background(), env, open, judgedAt); a.State != health.StateWaits {
+		t.Fatalf("%+v", a)
+	}
+	giveSecret(t, dir, Account{Name: "mesh"}, "pw")
+	_ = st.SetState(context.Background(), AccountState{Account: "mesh", State: AccountCurrent, Heard: judgedAt, Said: judgedAt})
+	if a := watchOnce(context.Background(), env, open, judgedAt); a.State != health.StateHealthy {
+		t.Fatalf("%+v", a)
+	}
+	raw, _ := json.Marshal(Status{Answer: health.Healthy("x"), At: judgedAt})
+	if !strings.Contains(string(raw), `"state":"healthy"`) || !strings.Contains(string(raw), `"at":`) {
+		t.Fatalf("the status file's shape: %s", raw)
+	}
+}

modules/mesh-mail/cmd/mesh-mail/imap.go

@@ -0,0 +1,520 @@
+package main
+
+// The adapter for an account of the kind `imap` (novox/hq ADR 0359 §1, §2, §5). For each account it keeps one
+// connection: IDLE on the inbox, and every PollEvery a look at every other folder. Each look compares what the server
+// holds with the index and says each difference as an event: a message added, its flags changed, or removed. The first
+// look at a folder indexes what is there without saying it — what the bus is told is what changed since the mesh
+// started watching, never the history of a mailbox.
+//
+// **It only reads.** Every folder is opened read-only (EXAMINE), and every message is fetched with BODY.PEEK, so
+// watching never marks a message seen. The client is used through reader alone, which has no command that flags,
+// moves, copies, deletes, appends or sends (§5); a test holds the code to that.
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/emersion/go-imap/v2"
+	"github.com/emersion/go-imap/v2/imapclient"
+)
+
+// How the keeper paces itself. IdleCycle is how long one IDLE lasts before it is ended and begun again, which proves
+// the server still answers; SilentAfter is how long without an answer makes the account unhealthy (§6).
+const (
+	IdleCycle   = 2 * time.Minute
+	PollEvery   = 5 * time.Minute
+	SilentAfter = 5 * time.Minute
+	RetryFirst  = 30 * time.Second
+	RetryMost   = 5 * time.Minute
+	FetchBatch  = 25
+)
+
+// reader is the part of an IMAP client the keeper uses: nothing in it changes a mailbox.
+type reader interface {
+	Login(username, password string) *imapclient.Command
+	List(ref, pattern string, options *imap.ListOptions) *imapclient.ListCommand
+	Select(mailbox string, options *imap.SelectOptions) *imapclient.SelectCommand
+	Fetch(numSet imap.NumSet, options *imap.FetchOptions) *imapclient.FetchCommand
+	Idle() (*imapclient.IdleCommand, error)
+	Caps() imap.CapSet
+	Closed() <-chan struct{}
+	Logout() *imapclient.Command
+	Close() error
+}
+
+// Dialer opens a connection to an account's server, handing what the server says unasked to the handler.
+type Dialer func(a Account, handler *imapclient.UnilateralDataHandler) (reader, error)
+
+// DialServer is the dialer for the mesh: TLS from the first byte, or STARTTLS before signing in, as the account says.
+func DialServer(a Account, handler *imapclient.UnilateralDataHandler) (reader, error) {
+	opts := &imapclient.Options{UnilateralDataHandler: handler, TLSConfig: &tls.Config{ServerName: a.Incoming.Host, MinVersion: tls.VersionTLS12}}
+	var c *imapclient.Client
+	var err error
+	switch a.Incoming.Security {
+	case "tls":
+		c, err = imapclient.DialTLS(a.Incoming.Address(), opts)
+	case "starttls":
+		c, err = imapclient.DialStartTLS(a.Incoming.Address(), opts)
+	default:
+		err = fmt.Errorf("the account %s's security %q signs in over nothing this version speaks", a.Name, a.Incoming.Security)
+	}
+	if err != nil {
+		return nil, err
+	}
+	return c, nil
+}
+
+// Keeper watches the accounts and keeps the index.
+type Keeper struct {
+	Store      Store
+	Objects    Objects
+	Dial       Dialer
+	SecretsDir string
+	Logf       func(format string, a ...any)
+	Now        func() time.Time
+
+	// Paces, for the tests; the constants above when zero.
+	IdleCycle, PollEvery, RetryFirst time.Duration
+}
+
+func (k *Keeper) now() time.Time {
+	if k.Now != nil {
+		return k.Now()
+	}
+	return time.Now()
+}
+
+func (k *Keeper) logf(format string, a ...any) {
+	if k.Logf != nil {
+		k.Logf(format, a...)
+	}
+}
+
+func orDefault(d, def time.Duration) time.Duration {
+	if d > 0 {
+		return d
+	}
+	return def
+}
+
+// Run watches every account until ctx ends.
+func (k *Keeper) Run(ctx context.Context, accounts []Account) {
+	var wg sync.WaitGroup
+	for _, a := range accounts {
+		wg.Add(1)
+		go func(a Account) {
+			defer wg.Done()
+			k.Watch(ctx, a)
+		}(a)
+	}
+	wg.Wait()
+}
+
+func (k *Keeper) say(ctx context.Context, a Account, state, why string, heard, synced time.Time) {
+	if err := k.Store.SetState(ctx, AccountState{Account: a.Name, State: state, Why: why, Heard: heard, Synced: synced, Said: k.now()}); err != nil {
+		k.logf("[mesh-mail] the account %s's state could not be kept: %v", a.Name, err)
+	}
+}
+
+// Watch keeps one account until ctx ends: waits while its secret is not given, signs in, watches, and on any fault
+// says it, waits a little longer each time, and begins again.
+func (k *Keeper) Watch(ctx context.Context, a Account) {
+	retry := orDefault(k.RetryFirst, RetryFirst)
+	var heard, synced time.Time
+	for ctx.Err() == nil {
+		pw, given, err := ReadSecret(k.SecretsDir, a)
+		switch {
+		case err != nil:
+			k.say(ctx, a, AccountFailing, "its password was given and cannot be read: "+err.Error(), heard, synced)
+		case !given:
+			k.say(ctx, a, AccountWaits, "its password ("+a.Secret()+") has not been given", heard, synced)
+		default:
+			s := &session{k: k, a: a, wake: make(chan struct{}, 1), heard: heard, synced: synced}
+			err = s.run(ctx, pw)
+			heard, synced = s.heard, s.synced
+			if ctx.Err() != nil {
+				return
+			}
+			k.say(ctx, a, AccountFailing, err.Error(), heard, synced)
+			k.logf("[mesh-mail] the account %s: %v; trying again in %s", a.Name, err, retry)
+		}
+		select {
+		case <-ctx.Done():
+			return
+		case <-time.After(retry):
+		}
+		if given && err != nil {
+			retry = min(retry*2, RetryMost)
+		} else {
+			retry = orDefault(k.RetryFirst, RetryFirst)
+		}
+	}
+}
+
+// session is one connection to one account's server.
+type session struct {
+	k      *Keeper
+	a      Account
+	c      reader
+	wake   chan struct{}
+	heard  time.Time
+	synced time.Time
+	// state and why are what the session last said of the account, and told when it said it.
+	state, why string
+	told       time.Time
+}
+
+// answered is the server having answered: kept, and told at least once a minute, so a long first look at a large
+// mailbox still shows the account alive to the health watch.
+func (s *session) answered() {
+	s.heard = s.k.now()
+	if s.state != "" && s.heard.Sub(s.told) >= time.Minute {
+		s.tell(s.state, s.why)
+	}
+}
+
+// tell says the account's state.
+func (s *session) tell(state, why string) {
+	s.state, s.why, s.told = state, why, s.k.now()
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	s.k.say(ctx, s.a, state, why, s.heard, s.synced)
+}
+
+func (s *session) poke() {
+	select {
+	case s.wake <- struct{}{}:
+	default:
+	}
+}
+
+func (s *session) run(ctx context.Context, password string) error {
+	handler := &imapclient.UnilateralDataHandler{
+		Expunge: func(uint32) { s.poke() },
+		Mailbox: func(*imapclient.UnilateralDataMailbox) { s.poke() },
+		Fetch:   func(*imapclient.FetchMessageData) { s.poke() },
+	}
+	c, err := s.k.Dial(s.a, handler)
+	if err != nil {
+		return fmt.Errorf("its server %s cannot be reached: %v", s.a.Incoming.Host, err)
+	}
+	s.c = c
+	defer c.Close()
+	if err := c.Login(s.a.SignInAs(), password).Wait(); err != nil {
+		var said *imap.Error
+		if errors.As(err, &said) {
+			return fmt.Errorf("its server refused the sign-in (%s): its password may be wrong, and is given again at the desk", strings.TrimSpace(said.Text))
+		}
+		return fmt.Errorf("signing in failed: %v", err)
+	}
+	s.answered()
+	s.tell(AccountSyncing, "signed in; looking at its folders")
+	folders, err := s.folders()
+	if err != nil {
+		return err
+	}
+	idles := c.Caps().Has(imap.CapIdle) || c.Caps().Has(imap.CapIMAP4rev2)
+	var polled time.Time
+	for ctx.Err() == nil {
+		if polled.IsZero() || s.k.now().Sub(polled) >= orDefault(s.k.PollEvery, PollEvery) {
+			for _, f := range folders {
+				if err := s.k.syncFolder(ctx, c, s.a, f, s.answered); err != nil {
+					return err
+				}
+			}
+			polled = s.k.now()
+		}
+		// The inbox last, so it is the folder selected while the session idles.
+		if err := s.k.syncFolder(ctx, c, s.a, "INBOX", s.answered); err != nil {
+			return err
+		}
+		s.synced = s.k.now()
+		s.tell(AccountCurrent, fmt.Sprintf("watching the inbox and %d other folder(s)", len(folders)))
+		if err := s.wait(ctx, idles); err != nil {
+			return err
+		}
+	}
+	_ = c.Logout().Wait()
+	return ctx.Err()
+}
+
+// wait is one IDLE on the inbox, ended by what the server says unasked, by the cycle's end or by ctx. Ending it waits
+// for the server's answer, which is what proves the connection alive.
+func (s *session) wait(ctx context.Context, idles bool) error {
+	cycle := time.NewTimer(orDefault(s.k.IdleCycle, IdleCycle))
+	defer cycle.Stop()
+	if !idles {
+		select {
+		case <-ctx.Done():
+		case <-cycle.C:
+		case <-s.c.Closed():
+			return errors.New("its server closed the connection")
+		}
+		return nil
+	}
+	idle, err := s.c.Idle()
+	if err != nil {
+		return fmt.Errorf("its server refused to IDLE on the inbox: %v", err)
+	}
+	select {
+	case <-ctx.Done():
+	case <-s.wake:
+	case <-cycle.C:
+	case <-s.c.Closed():
+	}
+	if err := idle.Close(); err != nil {
+		return fmt.Errorf("its IDLE on the inbox ended badly: %v", err)
+	}
+	if err := idle.Wait(); err != nil {
+		return fmt.Errorf("its IDLE on the inbox ended badly: %v", err)
+	}
+	s.answered()
+	return nil
+}
+
+// folders is what is watched besides the inbox: the account's list, or every folder the server can open.
+func (s *session) folders() ([]string, error) {
+	if len(s.a.Folders) > 0 {
+		return append([]string(nil), s.a.Folders...), nil
+	}
+	listed, err := s.c.List("", "*", nil).Collect()
+	if err != nil {
+		return nil, fmt.Errorf("its folders cannot be listed: %v", err)
+	}
+	s.answered()
+	var out []string
+	for _, l := range listed {
+		if strings.EqualFold(l.Mailbox, "INBOX") || hasAttr(l.Attrs, imap.MailboxAttrNoSelect) || hasAttr(l.Attrs, imap.MailboxAttrNonExistent) {
+			continue
+		}
+		out = append(out, l.Mailbox)
+	}
+	sort.Strings(out)
+	return out, nil
+}
+
+func hasAttr(attrs []imap.MailboxAttr, want imap.MailboxAttr) bool {
+	for _, a := range attrs {
+		if strings.EqualFold(string(a), string(want)) {
+			return true
+		}
+	}
+	return false
+}
+
+// syncFolder brings the index of one folder to what the server holds, and says each difference, unless this is the
+// first look at the folder.
+func (k *Keeper) syncFolder(ctx context.Context, c reader, a Account, folder string, answered func()) error {
+	sel, err := c.Select(folder, &imap.SelectOptions{ReadOnly: true}).Wait()
+	if err != nil {
+		return fmt.Errorf("the folder %s cannot be opened: %v", folder, err)
+	}
+	answered()
+	known, seen, err := k.Store.Folder(ctx, a.Name, folder)
+	if err != nil {
+		return err
+	}
+	if seen && known.UIDValidity != sel.UIDValidity {
+		k.logf("[mesh-mail] the account %s's folder %s was renumbered by its server; it is indexed afresh", a.Name, folder)
+		if err := k.Store.DropFolder(ctx, a.Name, folder); err != nil {
+			return err
+		}
+		seen = false
+	}
+	server := map[uint32][]string{}
+	if sel.NumMessages > 0 {
+		all, err := c.Fetch(imap.UIDSet{{Start: 1, Stop: 0}}, &imap.FetchOptions{UID: true, Flags: true}).Collect()
+		if err != nil {
+			return fmt.Errorf("the folder %s's messages cannot be listed: %v", folder, err)
+		}
+		answered()
+		for _, m := range all {
+			server[uint32(m.UID)] = flagStrings(m.Flags)
+		}
+	}
+	index, err := k.Store.Flags(ctx, a.Name, folder)
+	if err != nil {
+		return err
+	}
+	say := func(e *Event) *Event {
+		if seen {
+			return e
+		}
+		return nil
+	}
+	// Removed: in the index, no longer on the server.
+	for uid := range index {
+		if _, still := server[uid]; still {
+			continue
+		}
+		m, _, err := k.Store.Get(ctx, a.Name, folder, uid)
+		if err != nil {
+			return err
+		}
+		if m.UID == 0 {
+			m = Message{Account: a.Name, Folder: folder, UID: uid, UIDValidity: sel.UIDValidity}
+		}
+		if err := k.Store.Remove(ctx, a.Name, folder, uid, say(removedEvent(m))); err != nil {
+			return err
+		}
+	}
+	// Changed: on both, with other flags.
+	var added []uint32
+	for uid, flags := range server {
+		before, indexed := index[uid]
+		if !indexed {
+			added = append(added, uid)
+			continue
+		}
+		if sameStrings(before, flags) {
+			continue
+		}
+		m, _, err := k.Store.Get(ctx, a.Name, folder, uid)
+		if err != nil {
+			return err
+		}
+		m.Flags = flags
+		if err := k.Store.SetFlags(ctx, a.Name, folder, uid, flags, say(changedEvent(m, before, flags))); err != nil {
+			return err
+		}
+	}
+	// Added: on the server, not yet in the index; fetched whole, in batches, without marking them seen.
+	sort.Slice(added, func(i, j int) bool { return added[i] < added[j] })
+	for start := 0; start < len(added); start += FetchBatch {
+		batch := added[start:min(start+FetchBatch, len(added))]
+		uids := make([]imap.UID, len(batch))
+		for i, u := range batch {
+			uids[i] = imap.UID(u)
+		}
+		msgs, err := c.Fetch(imap.UIDSetNum(uids...), &imap.FetchOptions{
+			UID: true, Flags: true, Envelope: true, RFC822Size: true, InternalDate: true,
+			BodySection: []*imap.FetchItemBodySection{{Peek: true}},
+		}).Collect()
+		if err != nil {
+			return fmt.Errorf("the folder %s's new messages cannot be fetched: %v", folder, err)
+		}
+		answered()
+		for _, fm := range msgs {
+			m, err := k.index(ctx, a, folder, sel.UIDValidity, fm)
+			if err != nil {
+				return err
+			}
+			if err := k.Store.Add(ctx, m, say(addedEvent(m))); err != nil {
+				return err
+			}
+		}
+	}
+	return k.Store.SetFolder(ctx, Folder{Account: a.Name, Name: folder, UIDValidity: sel.UIDValidity, Messages: len(server), Synced: k.now()})
+}
+
+// index is a fetched message as the index keeps it: its metadata, its text, and its attachments kept in the store.
+func (k *Keeper) index(ctx context.Context, a Account, folder string, validity uint32, fm *imapclient.FetchMessageBuffer) (Message, error) {
+	m := Message{Account: a.Name, Folder: folder, UIDValidity: validity, UID: uint32(fm.UID), Size: fm.RFC822Size,
+		Flags: flagStrings(fm.Flags), Date: fm.InternalDate.UTC(), From: []Person{}, To: []Person{}, Attachments: []AttachmentRef{}}
+	if env := fm.Envelope; env != nil {
+		m.MessageID, m.Subject = env.MessageID, env.Subject
+		if len(env.InReplyTo) > 0 {
+			m.InReplyTo = env.InReplyTo[0]
+		}
+		if !env.Date.IsZero() {
+			m.Date = env.Date.UTC()
+		}
+		m.From, m.To, m.Cc = people(env.From), people(env.To), people(env.Cc)
+	}
+	var raw []byte
+	if len(fm.BodySection) > 0 {
+		raw = fm.BodySection[0].Bytes
+	}
+	parsed, err := ParseMessage(raw)
+	if err != nil {
+		k.logf("[mesh-mail] the account %s's message %d in %s is read in part: %v", a.Name, m.UID, folder, err)
+	}
+	m.Body = parsed.Text
+	for _, p := range parsed.Attachments {
+		ref, err := Keep(ctx, k.Objects, p.Data, p.Type, p.Name)
+		if err != nil {
+			return m, err
+		}
+		m.Attachments = append(m.Attachments, ref)
+	}
+	return m, nil
+}
+
+func people(as []imap.Address) []Person {
+	out := []Person{}
+	for _, a := range as {
+		if addr := a.Addr(); addr != "" {
+			out = append(out, Person{Name: a.Name, Address: addr})
+		}
+	}
+	return out
+}
+
+func flagStrings(fs []imap.Flag) []string {
+	out := make([]string, 0, len(fs))
+	for _, f := range fs {
+		if strings.EqualFold(string(f), `\Recent`) {
+			continue
+		}
+		out = append(out, string(f))
+	}
+	sort.Strings(out)
+	return out
+}
+
+func sameStrings(a, b []string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// ---- the events ---------------------------------------------------------------------------------------------------
+
+// EventKey is where an account's change is said: mail.<account>.message.<added|changed|removed> (research 049
+// document 02 §5), the account by its name in the setting, never its address.
+func EventKey(account, change string) string { return "mail." + account + ".message." + change }
+
+// Changes are the three things said of a message.
+var Changes = []string{"added", "changed", "removed"}
+
+// metadata is what an event says of a message: never its body, never an attachment's bytes (ADR 0359 §2).
+func metadata(m Message) map[string]any {
+	atts := make([]map[string]any, 0, len(m.Attachments))
+	for _, r := range m.Attachments {
+		atts = append(atts, map[string]any{"bucket": r.Bucket, "key": r.Key, "size": r.Size, "type": r.Type, "name": r.Name})
+	}
+	return map[string]any{
+		"account": m.Account, "folder": m.Folder, "uid": m.UID, "uidvalidity": m.UIDValidity,
+		"message-id": m.MessageID, "in-reply-to": m.InReplyTo, "date": m.Date.UTC().Format(time.RFC3339),
+		"from": m.From, "to": m.To, "cc": m.Cc, "subject": m.Subject, "size": m.Size, "flags": m.Flags,
+		"attachments": atts,
+	}
+}
+
+func addedEvent(m Message) *Event {
+	return &Event{Key: EventKey(m.Account, "added"), Body: metadata(m)}
+}
+
+func changedEvent(m Message, before, after []string) *Event {
+	body := metadata(m)
+	body["changes"] = map[string]any{"flags": map[string]any{"before": before, "after": after}}
+	return &Event{Key: EventKey(m.Account, "changed"), Body: body}
+}
+
+func removedEvent(m Message) *Event {
+	return &Event{Key: EventKey(m.Account, "removed"), Body: map[string]any{
+		"account": m.Account, "folder": m.Folder, "uid": m.UID, "uidvalidity": m.UIDValidity, "message-id": m.MessageID,
+	}}
+}

modules/mesh-mail/cmd/mesh-mail/imap_test.go

@@ -0,0 +1,239 @@
+package main
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/emersion/go-imap/v2"
+)
+
+// keeping starts a keeper on one account of the test server, its paces short, and stops it when the test ends.
+func keeping(t *testing.T, s *mailServer, st Store, objects Objects, secrets string) {
+	t.Helper()
+	k := &Keeper{Store: st, Objects: objects, Dial: s.dialer(), SecretsDir: secrets, Logf: t.Logf,
+		IdleCycle: 300 * time.Millisecond, PollEvery: 400 * time.Millisecond, RetryFirst: 100 * time.Millisecond}
+	ctx, cancel := context.WithCancel(context.Background())
+	done := make(chan struct{})
+	go func() { k.Watch(ctx, testAccount()); close(done) }()
+	t.Cleanup(func() { cancel(); <-done })
+}
+
+func stateOf(st Store, account string) AccountState {
+	states, _ := st.States(context.Background())
+	return states[account]
+}
+
+// float64OrUint reads a uid from an event body whether it came from memory (uint32) or from postgres (float64).
+type float64OrUint struct{ v any }
+
+func (f float64OrUint) value() uint32 {
+	switch n := f.v.(type) {
+	case uint32:
+		return n
+	case float64:
+		return uint32(n)
+	}
+	return 0
+}
+
+func uidOf(e Event) uint32 { return float64OrUint{e.Body["uid"]}.value() }
+
+func eventsNamed(st Store, key string) []Event {
+	evs, _ := st.Pending(context.Background(), 1000)
+	var out []Event
+	for _, e := range evs {
+		if e.Key == key {
+			out = append(out, e)
+		}
+	}
+	return out
+}
+
+func describe(st Store) string {
+	evs, _ := st.Pending(context.Background(), 1000)
+	var keys []string
+	for _, e := range evs {
+		keys = append(keys, e.Key)
+	}
+	s := stateOf(st, "mesh")
+	return "state " + s.State + " (" + s.Why + "); events " + strings.Join(keys, ", ")
+}
+
+// The whole watch, over a real IMAP conversation (ADR 0359 §2, §3, §5): the first look indexes what is there and says
+// nothing; then a new mail in the inbox is said within moments of its delivery, through IDLE, with its metadata and
+// its attachment by reference, never its body; its flags changed are said; its removal is said; a mail in another
+// folder is said at the next poll; and watching never marks a message seen.
+func TestTheKeeperSaysEachChangeOnTheBusAndOnlyReads(t *testing.T) {
+	eachStore(t, func(t *testing.T, st Store) {
+		s := newMailServer(t)
+		op := s.operator(t)
+		deliver(t, op, "INBOX", plainMail("before the watch", "an old letter"))
+		deliver(t, op, "Archive", plainMail("archived long ago", "an older letter"))
+		secrets := t.TempDir()
+		giveSecret(t, secrets, testAccount(), testPassword)
+		objects := newMemObjects()
+		keeping(t, s, st, objects, secrets)
+
+		eventually(t, 10*time.Second, "the first look", func() (bool, string) {
+			return stateOf(st, "mesh").State == AccountCurrent, describe(st)
+		})
+		ctx := context.Background()
+		if hits, _ := st.Search(ctx, Query{Text: "letter", Accounts: []string{"mesh"}}); len(hits) != 2 {
+			t.Fatalf("the first look indexed %d messages, not 2", len(hits))
+		}
+		if evs, _ := st.Pending(ctx, 100); len(evs) != 0 {
+			t.Fatalf("the first look said %d event(s): the history of a mailbox is not news", len(evs))
+		}
+
+		// A new mail with an attachment, delivered while the keeper idles on the inbox.
+		deliver(t, op, "INBOX", attachedMail("the invoice"))
+		var added Event
+		eventually(t, 5*time.Second, "the new mail said", func() (bool, string) {
+			evs := eventsNamed(st, "mail.mesh.message.added")
+			if len(evs) == 1 {
+				added = evs[0]
+			}
+			return len(evs) == 1, describe(st)
+		})
+		body := added.Body
+		if body["subject"] != "the invoice" || body["folder"] != "INBOX" || body["account"] != "mesh" || body["message-id"] != "att@example.org" {
+			t.Fatalf("the event says %v", body)
+		}
+		raw, _ := json.Marshal(body)
+		for _, never := range []string{"Please find", "dGhlIGludm9pY2Ug", attachmentData} {
+			if strings.Contains(string(raw), never) {
+				t.Fatalf("the event carries the body or an attachment's bytes (%q): %s", never, raw)
+			}
+		}
+		sum := sha256.Sum256([]byte(attachmentData))
+		key := hex.EncodeToString(sum[:])
+		if !strings.Contains(string(raw), `"key":"`+key+`"`) || !strings.Contains(string(raw), `"name":"invoice.pdf"`) {
+			t.Fatalf("the event does not name the attachment by its SHA-256 %s: %s", key, raw)
+		}
+		if kept, _ := objects.Get(ctx, key); string(kept) != attachmentData {
+			t.Fatalf("the attachment store keeps %q under %s", kept, key)
+		}
+		uid := uidOf(added)
+		m, ok, _ := st.Get(ctx, "mesh", "INBOX", uid)
+		if !ok || !strings.Contains(m.Body, "Please find the invoice attached.") {
+			t.Fatalf("the index keeps the text for mail_read: %+v", m)
+		}
+
+		// Flagged by the operator elsewhere: said as changed, with the flags before and after.
+		if _, err := op.Select("INBOX", nil).Wait(); err != nil {
+			t.Fatal(err)
+		}
+		if err := op.Store(imap.UIDSetNum(imap.UID(uid)), &imap.StoreFlags{Op: imap.StoreFlagsAdd, Flags: []imap.Flag{imap.FlagFlagged}, Silent: true}, nil).Close(); err != nil {
+			t.Fatal(err)
+		}
+		eventually(t, 5*time.Second, "the flag said", func() (bool, string) {
+			evs := eventsNamed(st, "mail.mesh.message.changed")
+			if len(evs) != 1 {
+				return false, describe(st)
+			}
+			raw, _ := json.Marshal(evs[0].Body["changes"])
+			return strings.Contains(string(raw), `"after":["\\Flagged"]`), string(raw)
+		})
+
+		// Never marked seen by the watching: the message is still unseen on the server.
+		fetched, err := op.Fetch(imap.UIDSetNum(imap.UID(uid)), &imap.FetchOptions{Flags: true, UID: true}).Collect()
+		if err != nil || len(fetched) != 1 {
+			t.Fatalf("%v %v", fetched, err)
+		}
+		for _, f := range fetched[0].Flags {
+			if f == imap.FlagSeen {
+				t.Fatal("watching marked the message seen")
+			}
+		}
+
+		// Deleted by the operator elsewhere: said as removed.
+		if err := op.Store(imap.UIDSetNum(imap.UID(uid)), &imap.StoreFlags{Op: imap.StoreFlagsAdd, Flags: []imap.Flag{imap.FlagDeleted}, Silent: true}, nil).Close(); err != nil {
+			t.Fatal(err)
+		}
+		if err := op.Expunge().Close(); err != nil {
+			t.Fatal(err)
+		}
+		eventually(t, 5*time.Second, "the removal said", func() (bool, string) {
+			evs := eventsNamed(st, "mail.mesh.message.removed")
+			return len(evs) == 1 && uidOf(evs[0]) == uid && evs[0].Body["message-id"] == "att@example.org", describe(st)
+		})
+		if _, ok, _ := st.Get(ctx, "mesh", "INBOX", uid); ok {
+			t.Fatal("the removed message is still indexed")
+		}
+
+		// A mail in another folder is said at the next poll.
+		deliver(t, op, "Archive", plainMail("filed away", "a letter filed"))
+		eventually(t, 5*time.Second, "the archived mail said", func() (bool, string) {
+			for _, e := range eventsNamed(st, "mail.mesh.message.added") {
+				if e.Body["folder"] == "Archive" && e.Body["subject"] == "filed away" {
+					return true, ""
+				}
+			}
+			return false, describe(st)
+		})
+		if s := stateOf(st, "mesh"); s.State != AccountCurrent || time.Since(s.Heard) > time.Minute {
+			t.Fatalf("the account is %+v", s)
+		}
+	})
+}
+
+// No password given: the account waits, and nothing is dialled. A wrong one: the account fails, saying the server
+// refused the sign-in. Given later: it is picked up without a restart.
+func TestTheKeeperWaitsForThePasswordAndSaysARefusal(t *testing.T) {
+	s := newMailServer(t)
+	st := newMemStore()
+	secrets := t.TempDir()
+	keeping(t, s, st, newMemObjects(), secrets)
+	eventually(t, 5*time.Second, "the wait", func() (bool, string) {
+		got := stateOf(st, "mesh")
+		return got.State == AccountWaits && strings.Contains(got.Why, "mail-credential-mesh"), describe(st)
+	})
+	giveSecret(t, secrets, testAccount(), "not-the-password")
+	eventually(t, 5*time.Second, "the refusal", func() (bool, string) {
+		got := stateOf(st, "mesh")
+		return got.State == AccountFailing && strings.Contains(got.Why, "refused the sign-in"), describe(st)
+	})
+	giveSecret(t, secrets, testAccount(), testPassword)
+	eventually(t, 10*time.Second, "the sign-in", func() (bool, string) {
+		return stateOf(st, "mesh").State == AccountCurrent, describe(st)
+	})
+}
+
+// It only reads (ADR 0359 §5): no code of the module, but its tests, issues a command that flags, moves, copies,
+// deletes, appends, creates, renames or sends, and every folder is opened read-only and every body peeked.
+func TestNothingButTheTestsWritesToAMailbox(t *testing.T) {
+	files, err := filepath.Glob("*.go")
+	if err != nil {
+		t.Fatal(err)
+	}
+	writes := regexp.MustCompile(`([A-Za-z_][A-Za-z0-9_]*)\.(Store|Move|Copy|Expunge|UIDExpunge|Append|Create|Delete|Rename|Subscribe|Unsubscribe|SetMetadata|SetQuota)\(`)
+	for _, f := range files {
+		if strings.HasSuffix(f, "_test.go") {
+			continue
+		}
+		raw, err := os.ReadFile(f)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, m := range writes.FindAllSubmatch(raw, -1) {
+			if string(m[1]) != "os" { // a file of the module's own, never a mailbox
+				t.Errorf("%s calls %s, which writes to a mailbox", f, m[0])
+			}
+		}
+		if strings.Contains(string(raw), "net/smtp") {
+			t.Errorf("%s speaks SMTP: this stage sends nothing", f)
+		}
+	}
+	src, _ := os.ReadFile("imap.go")
+	if !strings.Contains(string(src), "&imap.SelectOptions{ReadOnly: true}") || !strings.Contains(string(src), "{{Peek: true}}") {
+		t.Fatal("folders are not opened read-only, or bodies not peeked")
+	}
+}

modules/mesh-mail/cmd/mesh-mail/kit_test.go

@@ -0,0 +1,252 @@
+package main
+
+// What the tests stand on: an IMAP server in this process (go-imap's own in-memory server, speaking the protocol over
+// a real socket), the index in memory always and on a real postgres when one can be had (MESH_TEST_POSTGRES, or a
+// private server started here from the machine's initdb on a socket of its own, listening on no port), and the
+// attachment store in memory.
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/url"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/emersion/go-imap/v2"
+	"github.com/emersion/go-imap/v2/imapclient"
+	"github.com/emersion/go-imap/v2/imapserver"
+	"github.com/emersion/go-imap/v2/imapserver/imapmemserver"
+)
+
+func TestMain(m *testing.M) {
+	code := m.Run()
+	stopPostgres()
+	os.Exit(code)
+}
+
+// ---- the IMAP server --------------------------------------------------------------------------------------------
+
+const (
+	testUser     = "operator@example.org"
+	testPassword = "the-password"
+)
+
+type mailServer struct {
+	addr string
+	srv  *imapserver.Server
+}
+
+// newMailServer is a server holding one user with an inbox and an Archive folder.
+func newMailServer(t *testing.T) *mailServer {
+	t.Helper()
+	mem := imapmemserver.New()
+	user := imapmemserver.NewUser(testUser, testPassword)
+	for _, f := range []string{"INBOX", "Archive"} {
+		if err := user.Create(f, nil); err != nil {
+			t.Fatal(err)
+		}
+	}
+	mem.AddUser(user)
+	srv := imapserver.New(&imapserver.Options{
+		NewSession: func(*imapserver.Conn) (imapserver.Session, *imapserver.GreetingData, error) {
+			return mem.NewSession(), nil, nil
+		},
+		InsecureAuth: true,
+		Caps:         imap.CapSet{imap.CapIMAP4rev1: {}, imap.CapIMAP4rev2: {}},
+	})
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	go func() { _ = srv.Serve(ln) }()
+	t.Cleanup(func() { _ = srv.Close() })
+	return &mailServer{addr: ln.Addr().String(), srv: srv}
+}
+
+// dialer reaches the test server without TLS, which only a test does: the mesh's dialer signs in over TLS alone.
+func (s *mailServer) dialer() Dialer {
+	return func(_ Account, h *imapclient.UnilateralDataHandler) (reader, error) {
+		c, err := imapclient.DialInsecure(s.addr, &imapclient.Options{UnilateralDataHandler: h})
+		if err != nil {
+			return nil, err
+		}
+		return c, nil
+	}
+}
+
+// operator is a second client, as the operator's mail program or another sender is: it appends, flags and deletes.
+func (s *mailServer) operator(t *testing.T) *imapclient.Client {
+	t.Helper()
+	c, err := imapclient.DialInsecure(s.addr, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = c.Close() })
+	if err := c.Login(testUser, testPassword).Wait(); err != nil {
+		t.Fatal(err)
+	}
+	return c
+}
+
+func deliver(t *testing.T, c *imapclient.Client, folder, raw string) {
+	t.Helper()
+	raw = strings.ReplaceAll(raw, "\n", "\r\n")
+	cmd := c.Append(folder, int64(len(raw)), nil)
+	if _, err := cmd.Write([]byte(raw)); err != nil {
+		t.Fatal(err)
+	}
+	if err := cmd.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := cmd.Wait(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func plainMail(subject, body string) string {
+	return "From: Alice <alice@example.org>\nTo: Operator <operator@example.org>\nSubject: " + subject +
+		"\nMessage-Id: <" + strings.ReplaceAll(subject, " ", "-") + "@example.org>\nDate: Wed, 14 Oct 2026 10:00:00 +0000\n" +
+		"MIME-Version: 1.0\nContent-Type: text/plain; charset=utf-8\n\n" + body + "\n"
+}
+
+// attachmentData is an attachment's content, and attachedMail a message carrying it.
+const attachmentData = "the invoice, in full"
+
+func attachedMail(subject string) string {
+	return "From: Bob <bob@example.org>\nTo: operator@example.org\nSubject: " + subject + "\nMessage-Id: <att@example.org>\n" +
+		"Date: Wed, 14 Oct 2026 11:00:00 +0000\nMIME-Version: 1.0\nContent-Type: multipart/mixed; boundary=XYZ\n\n" +
+		"--XYZ\nContent-Type: text/plain; charset=utf-8\n\nPlease find the invoice attached.\n" +
+		"--XYZ\nContent-Type: application/pdf; name=invoice.pdf\nContent-Disposition: attachment; filename=invoice.pdf\n" +
+		"Content-Transfer-Encoding: base64\n\ndGhlIGludm9pY2UsIGluIGZ1bGw=\n--XYZ--\n"
+}
+
+// ---- the account ------------------------------------------------------------------------------------------------
+
+func testAccount() Account {
+	return Account{Name: "mesh", Kind: KindIMAP, Address: testUser, Incoming: Server{Host: "localhost", Port: 993, Security: "tls"}}
+}
+
+func giveSecret(t *testing.T, dir string, a Account, pw string) {
+	t.Helper()
+	if err := os.WriteFile(SecretPath(dir, a), []byte(pw+"\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// eventually waits for a condition, failing with what it last saw.
+func eventually(t *testing.T, within time.Duration, what string, ok func() (bool, string)) {
+	t.Helper()
+	deadline := time.Now().Add(within)
+	last := ""
+	for time.Now().Before(deadline) {
+		var done bool
+		if done, last = ok(); done {
+			return
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+	t.Fatalf("%s did not happen within %s; last seen: %s", what, within, last)
+}
+
+// ---- postgres ---------------------------------------------------------------------------------------------------
+
+var (
+	pgOnce  sync.Once
+	pgBase  string
+	pgDir   string
+	pgWhy   string
+	pgCount int
+	pgMu    sync.Mutex
+)
+
+func startPostgres() {
+	if u := os.Getenv("MESH_TEST_POSTGRES"); u != "" {
+		pgBase = u
+		return
+	}
+	initdb, err := exec.LookPath("initdb")
+	if err != nil {
+		pgWhy = "no postgres: MESH_TEST_POSTGRES is unset and the machine has no initdb"
+		return
+	}
+	pgctl := filepath.Join(filepath.Dir(initdb), "pg_ctl")
+	dir, err := os.MkdirTemp("", "mmpg")
+	if err != nil {
+		pgWhy = err.Error()
+		return
+	}
+	pgDir = dir
+	if out, err := exec.Command(initdb, "-D", dir+"/data", "-U", "postgres", "-A", "trust", "-E", "UTF8", "--no-locale").CombinedOutput(); err != nil {
+		pgWhy = fmt.Sprintf("initdb: %v: %s", err, out)
+		return
+	}
+	if out, err := exec.Command(pgctl, "-D", dir+"/data", "-l", dir+"/log", "-w", "-o",
+		"-k "+dir+" -c listen_addresses='' -F", "start").CombinedOutput(); err != nil {
+		pgWhy = fmt.Sprintf("pg_ctl start: %v: %s", err, out)
+		return
+	}
+	pgBase = "postgres://postgres@/postgres?host=" + dir
+}
+
+func stopPostgres() {
+	if pgDir == "" {
+		return
+	}
+	if initdb, err := exec.LookPath("initdb"); err == nil {
+		_ = exec.Command(filepath.Join(filepath.Dir(initdb), "pg_ctl"), "-D", pgDir+"/data", "-m", "immediate", "stop").Run()
+	}
+	_ = os.RemoveAll(pgDir)
+}
+
+// freshDatabase is a database of its own for one test, or a skip saying why there is none.
+func freshDatabase(t *testing.T) string {
+	t.Helper()
+	pgOnce.Do(startPostgres)
+	if pgBase == "" {
+		t.Skipf("NOT TESTED ON POSTGRES: %s", pgWhy)
+	}
+	pgMu.Lock()
+	pgCount++
+	name := fmt.Sprintf("mail_%d_%d", os.Getpid(), pgCount)
+	pgMu.Unlock()
+	ctx := context.Background()
+	admin, err := OpenPgStore(ctx, pgBase)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer admin.Close()
+	if _, err := admin.pool.Exec(ctx, "create database "+name); err != nil {
+		t.Fatal(err)
+	}
+	u, err := url.Parse(pgBase)
+	if err != nil {
+		t.Fatal(err)
+	}
+	u.Path = "/" + name
+	return u.String()
+}
+
+func pgStore(t *testing.T) *PgStore {
+	t.Helper()
+	s, err := OpenPgStore(context.Background(), freshDatabase(t))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(s.Close)
+	if _, err := s.Prepare(context.Background()); err != nil {
+		t.Fatal(err)
+	}
+	return s
+}
+
+// eachStore runs a test over the index in memory and on postgres.
+func eachStore(t *testing.T, run func(t *testing.T, s Store)) {
+	t.Run("memory", func(t *testing.T) { run(t, newMemStore()) })
+	t.Run("postgres", func(t *testing.T) { run(t, pgStore(t)) })
+}

modules/mesh-mail/cmd/mesh-mail/main.go

@@ -0,0 +1,250 @@
+// mesh-mail: the operator's mail accounts, watched, and each mail said on the bus (novox/hq ADR 0359). One instance,
+// on the control-node. The first stage holds the mesh's own server, read-only: no flag, move, delete, draft or send.
+//
+//	mesh-mail            the bundle the node's runtime launches: the tools mail_accounts, mail_search, mail_read and
+//	                     mail_health, and the events the keeper wrote, said on the bus as the module
+//	mesh-mail prepare    the preparation step: the index's schema brought to this version's
+//	mesh-mail keep       acts: watches every account (IDLE on the inbox, a look at the other folders every five
+//	                     minutes), keeps the index and the attachment store, and writes each change's event beside it
+//	mesh-mail watch      judges: reads every minute how each account is, and leaves its verdict for mail_health
+//
+// The two long-running processes are the act and the judge, as mesh-knowledge's are: keep is judged by its unit, watch
+// by the tool mail_health (ADR 0359 §6, ADR 0240 §3 and §7). Only the bundle reaches the bus, through the runtime that
+// launched it, so the keeper hands its events over in the index, written in the same step as the change they say,
+// and the bundle says them and removes each once the bus took it. stdout is the bundle's MCP channel; what this module
+// says, it says on stderr.
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// Module is this module's name.
+const Module = "mesh-mail"
+
+// Env is where the mesh puts what the module reads, as the manifest's environment names it.
+type Env struct {
+	Accounts string // the trusted setting accounts
+	Grants   string // the trusted setting grants
+	Secrets  string // the directory the own secrets mail-credential-<account> are placed in
+	Store    string // the attachment store's facts
+	Status   string // the watch's verdict
+}
+
+func envFromOS() Env {
+	return Env{
+		Accounts: os.Getenv("MESH_MAIL_ACCOUNTS"),
+		Grants:   os.Getenv("MESH_MAIL_GRANTS"),
+		Secrets:  os.Getenv("MESH_MAIL_SECRETS"),
+		Store:    os.Getenv("MESH_MAIL_STORE"),
+		Status:   os.Getenv("MESH_MAIL_STATUS"),
+	}
+}
+
+func logf(format string, a ...any) { fmt.Fprintf(os.Stderr, format+"\n", a...) }
+
+func main() {
+	if len(os.Args) > 1 {
+		switch os.Args[1] {
+		case "prepare":
+			os.Exit(prepare())
+		case "keep":
+			os.Exit(keep(envFromOS()))
+		case "watch":
+			os.Exit(watch(envFromOS()))
+		}
+	}
+	serve(envFromOS())
+}
+
+// ---- prepare ------------------------------------------------------------------------------------------------------
+
+func prepare() int {
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+	s, err := PgStoreFromEnv(ctx)
+	if err != nil {
+		logf("[mesh-mail] preparing the index: %v", err)
+		return 1
+	}
+	defer s.Close()
+	said, err := s.Prepare(ctx)
+	for _, line := range said {
+		logf("[mesh-mail] %s", line)
+	}
+	if err != nil {
+		logf("[mesh-mail] preparing the index failed: %v", err)
+		return 1
+	}
+	return 0
+}
+
+// ---- keep ---------------------------------------------------------------------------------------------------------
+
+// keep watches every account until it is stopped. A setting it cannot read, an index that is behind or a store it
+// cannot reach ends it with a fault, which its unit says; the mesh starts it again.
+func keep(env Env) int {
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+	accounts, err := ReadAccounts(env.Accounts)
+	if err != nil {
+		logf("[mesh-mail] %v", err)
+		return 1
+	}
+	st, err := PgStoreFromEnv(ctx)
+	if err != nil {
+		logf("[mesh-mail] the index cannot be opened: %v", err)
+		return 1
+	}
+	defer st.Close()
+	if err := st.Ready(ctx); err != nil {
+		logf("[mesh-mail] %v", err)
+		return 1
+	}
+	facts, err := ReadStoreFacts(env.Store)
+	if err != nil {
+		logf("[mesh-mail] %v", err)
+		return 1
+	}
+	k := &Keeper{Store: st, Objects: NewS3(facts), Dial: DialServer, SecretsDir: env.Secrets, Logf: logf}
+	logf("[mesh-mail] keeping %d account(s)", len(accounts))
+	k.Run(ctx, accounts)
+	return 0
+}
+
+// ---- watch --------------------------------------------------------------------------------------------------------
+
+func watch(env Env) int {
+	if env.Status == "" {
+		logf("[mesh-mail] watch was started without MESH_MAIL_STATUS")
+		return 2
+	}
+	open := func(ctx context.Context) (Store, func(), error) {
+		s, err := PgStoreFromEnv(ctx)
+		if err != nil {
+			return nil, nil, err
+		}
+		return s, s.Close, nil
+	}
+	for {
+		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+		now := time.Now().UTC()
+		answer := watchOnce(ctx, env, open, now)
+		cancel()
+		if err := writeStatus(env.Status, Status{Answer: answer, At: now}); err != nil {
+			logf("[mesh-mail] the verdict could not be written: %v", err)
+		}
+		time.Sleep(WatchEvery)
+	}
+}
+
+// ---- the bundle ---------------------------------------------------------------------------------------------------
+
+func serve(env Env) {
+	var mu sync.Mutex
+	var st *PgStore
+	b := &Bundle{
+		Env: env,
+		Index: func(ctx context.Context) (Store, error) {
+			mu.Lock()
+			defer mu.Unlock()
+			if st == nil {
+				s, err := PgStoreFromEnv(ctx)
+				if err != nil {
+					return nil, err
+				}
+				st = s
+			}
+			if err := st.Ready(ctx); err != nil {
+				return nil, err
+			}
+			return st, nil
+		},
+		Objects: func() (Objects, error) {
+			facts, err := ReadStoreFacts(env.Store)
+			if err != nil {
+				return nil, err
+			}
+			return NewS3(facts), nil
+		},
+	}
+	p := &Publisher{Index: b.Index, Emit: func(key string, body any) error { return stdio.Emit(key, body) }, Logf: logf}
+	go p.Run(context.Background())
+	if err := stdio.Serve("", b.Tools()); err != nil {
+		logf("%v", err)
+		os.Exit(1)
+	}
+}
+
+// Publisher says the events the keeper wrote, oldest first, and removes each once the bus took it. One the bus did not
+// take stays, and is said again on the next round: delivery is at least once, and a consumer reads the uid and the
+// folder to know a repeat.
+type Publisher struct {
+	Index func(ctx context.Context) (Store, error)
+	Emit  func(key string, body any) error
+	Logf  func(format string, a ...any)
+	Every time.Duration
+}
+
+// PublishBatch is how many events one round says at most.
+const PublishBatch = 100
+
+// Once says what is pending, and answers how many it said.
+func (p *Publisher) Once(ctx context.Context) (int, error) {
+	st, err := p.Index(ctx)
+	if err != nil {
+		return 0, err
+	}
+	pending, err := st.Pending(ctx, PublishBatch)
+	if err != nil {
+		return 0, err
+	}
+	var said []int64
+	var failed error
+	for _, e := range pending {
+		if err := p.Emit(e.Key, e.Body); err != nil {
+			failed = fmt.Errorf("the bus did not take %s: %v", e.Key, err)
+			break
+		}
+		said = append(said, e.ID)
+	}
+	if len(said) > 0 {
+		if err := st.Said(ctx, said); err != nil {
+			return 0, err
+		}
+	}
+	return len(said), failed
+}
+
+// Run says pending events until ctx ends: every few seconds, at once again while a round was full.
+func (p *Publisher) Run(ctx context.Context) {
+	every := p.Every
+	if every <= 0 {
+		every = 3 * time.Second
+	}
+	// The runtime takes the bundle's first calls only once Serve runs.
+	time.Sleep(every)
+	for ctx.Err() == nil {
+		c, cancel := context.WithTimeout(ctx, time.Minute)
+		n, err := p.Once(c)
+		cancel()
+		if err != nil && p.Logf != nil {
+			p.Logf("[mesh-mail] events wait to be said: %v", err)
+		}
+		if n == PublishBatch {
+			continue
+		}
+		select {
+		case <-ctx.Done():
+		case <-time.After(every):
+		}
+	}
+}

modules/mesh-mail/cmd/mesh-mail/manifest_test.go

@@ -0,0 +1,151 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// The manifest says what the code does (novox/hq ADR 0359): the database and the bucket it requires (§3), the own
+// secret family issued outside the mesh (§5, ADR 0283 §6), the two trusted settings (§4), the tools (§5), the events,
+// and its two long-running processes with their health (§6) — and it is assigned to no machine by itself.
+
+type manifest struct {
+	Module      string                       `json:"module"`
+	Slug        string                       `json:"slug"`
+	Requires    []string                     `json:"requires"`
+	Contributes map[string]map[string]any    `json:"contributes"`
+	OwnSecrets  map[string]map[string]string `json:"own-secrets"`
+	Tools       []string                     `json:"tools"`
+	Emits       []string                     `json:"emits"`
+	Streams     []struct {
+		Name       string   `json:"name"`
+		Events     []string `json:"events"`
+		MaxAgeDays int      `json:"max-age-days"`
+		Grant      struct {
+			Config string `json:"config"`
+			Events string `json:"events"`
+		} `json:"grant"`
+	} `json:"streams"`
+	Consumes  []string          `json:"consumes"`
+	Invokes   []string          `json:"invokes"`
+	Claims    []json.RawMessage `json:"claims"`
+	Resources []map[string]any  `json:"resources"`
+	Build     struct {
+		Artifacts []struct {
+			From   string            `json:"from"`
+			Binary string            `json:"binary"`
+			Loads  []string          `json:"loads"`
+			Env    map[string]string `json:"env"`
+		} `json:"artifacts"`
+	} `json:"build"`
+}
+
+func readManifest(t *testing.T) (manifest, map[string]map[string]any) {
+	t.Helper()
+	raw, err := os.ReadFile(filepath.Join("..", "..", "module.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	var m manifest
+	if err := json.Unmarshal(raw, &m); err != nil {
+		t.Fatal(err)
+	}
+	byID := map[string]map[string]any{}
+	for _, r := range m.Resources {
+		byID[r["id"].(string)] = r
+	}
+	return m, byID
+}
+
+func TestTheManifestSaysWhatTheCodeDoes(t *testing.T) {
+	m, byID := readManifest(t)
+	if m.Module != Module || !reflect.DeepEqual(m.Requires, []string{"postgres-database", "s3-bucket"}) || m.Contributes["postgres-database"]["name"] != "mail" {
+		t.Fatalf("module %s, requires %v, contributes %v", m.Module, m.Requires, m.Contributes)
+	}
+	// mesh_<node>_<slug> fits the S3 access key's 20 characters on every node.
+	if len("mesh_shanks_"+m.Slug) > 20 {
+		t.Fatalf("the slug %q overflows an S3 access key", m.Slug)
+	}
+	fam := m.OwnSecrets[SecretFamily+"*"]
+	if fam["issued-by"] != "outside" || fam["path"] != "${dir:state}/"+SecretFamily+"*.secret" || len(m.OwnSecrets) != 1 {
+		t.Fatalf("own secrets %v", m.OwnSecrets)
+	}
+	var names []string
+	for _, tool := range (&Bundle{}).Tools() {
+		names = append(names, tool.Name)
+	}
+	if !reflect.DeepEqual(m.Tools, names) || !reflect.DeepEqual(names, []string{"mail_accounts", "mail_search", "mail_read", "mail_health"}) {
+		t.Fatalf("tools %v, the code serves %v", m.Tools, names)
+	}
+	// Its events go to its own stream MAIL, kept a week, each account's part heard only by the consumers the trusted
+	// config value grants names for it (ADR 0359 §2, §4; ADR 0363): none on the shared EVENTS stream.
+	var events []string
+	for _, c := range Changes {
+		events = append(events, EventKey("*", c))
+	}
+	if len(m.Emits) != 0 || len(m.Streams) != 1 || m.Streams[0].Name != "mail" || !reflect.DeepEqual(m.Streams[0].Events, events) ||
+		m.Streams[0].MaxAgeDays != 7 || m.Streams[0].Grant.Config != "grants" || m.Streams[0].Grant.Events != "mail.{key}.**" {
+		t.Fatalf("emits %v, streams %+v; the code says %v", m.Emits, m.Streams, events)
+	}
+	// It reads its own mail and calls nothing, consumes nothing and claims no seat.
+	if len(m.Consumes)+len(m.Invokes)+len(m.Claims) != 0 {
+		t.Fatalf("consumes %v, invokes %v, claims %v", m.Consumes, m.Invokes, m.Claims)
+	}
+	// The two settings are trusted, and their defaults are an empty account list and no grant.
+	for id, want := range map[string]string{"accounts": `{"accounts":{}}`, "grants": `{"grants":{}}`} {
+		r := byID[id]
+		if r == nil || r["trusted"] != true || r["merge"] != "json" || !reflect.DeepEqual(r["takes-settings"], []any{id}) {
+			t.Fatalf("%s: %v", id, r)
+		}
+		if strings.Join(strings.Fields(r["content"].(string)), "") != want {
+			t.Fatalf("%s's default is %q", id, r["content"])
+		}
+		if _, err := ParseAccounts([]byte(byID["accounts"]["content"].(string))); err != nil {
+			t.Fatal(err)
+		}
+	}
+	a := m.Build.Artifacts
+	if len(a) != 1 || a[0].From != "cmd/mesh-mail" || a[0].Binary != Module || !reflect.DeepEqual(a[0].Loads, []string{Module}) {
+		t.Fatalf("build %+v", m.Build)
+	}
+	for k, v := range map[string]string{"MESH_MAIL_ACCOUNTS": "accounts", "MESH_MAIL_GRANTS": "grants", "MESH_MAIL_STORE": "store", "DATABASE_URL_FILE": "database-url"} {
+		if a[0].Env[k] != byID[v]["path"] {
+			t.Errorf("the bundle reads %s at %s, and the manifest writes %s at %v", k, a[0].Env[k], v, byID[v]["path"])
+		}
+	}
+	if a[0].Env["MESH_MAIL_SECRETS"] != "${dir:state}" {
+		t.Errorf("the secrets directory is %s", a[0].Env["MESH_MAIL_SECRETS"])
+	}
+}
+
+// Its processes: the preparation once, keep judged by its unit, watch by mail_health (ADR 0359 §6), the watch writing
+// the verdict the bundle's tool reads, as the account the bundle runs as.
+func TestItsProcessesAreThePreparationTheActAndTheJudge(t *testing.T) {
+	m, byID := readManifest(t)
+	prep, keep, watch := byID["prepare"], byID["keep"], byID["watch"]
+	if prep == nil || prep["run-once"] != true || prep["run"].([]any)[1] != "prepare" {
+		t.Fatalf("prepare %v", prep)
+	}
+	if keep == nil || keep["run"].([]any)[1] != "keep" || keep["health"].(map[string]any)["kind"] != "unit" {
+		t.Fatalf("keep %v", keep)
+	}
+	h, _ := watch["health"].(map[string]any)
+	if watch == nil || watch["run"].([]any)[1] != "watch" || h["kind"] != "tool" || h["tool"] != HealthTool || h["needs"] != "postgres-database" {
+		t.Fatalf("watch %v", watch)
+	}
+	if watch["user"] != "${machine:account}" || watch["env"].(map[string]any)["MESH_MAIL_STATUS"] != m.Build.Artifacts[0].Env["MESH_MAIL_STATUS"] {
+		t.Fatalf("watch writes another status than the tool reads, or as another account: %v", watch)
+	}
+	// keep runs as the machine's root, which the own secrets' files belong to; it starts again when its settings or
+	// its store change.
+	if _, as := keep["user"]; as {
+		t.Fatalf("keep runs as %v", keep["user"])
+	}
+	if !reflect.DeepEqual(keep["restart-on"], []any{"database-url", "store", "accounts"}) {
+		t.Fatalf("keep restarts on %v", keep["restart-on"])
+	}
+}

modules/mesh-mail/cmd/mesh-mail/migrations/0001-the-index-holds-messages-folders-account-states-and-events-to-say.sql

@@ -0,0 +1,46 @@
+-- mesh-mail's index (novox/hq ADR 0359 §3): one row per message and folder, what is known of each folder, each
+-- account's state as its keeper said it, and the events written with the change they say, until they are said.
+create table folder (
+    account     text        not null,
+    name        text        not null,
+    uidvalidity bigint      not null,
+    messages    integer     not null default 0,
+    synced      timestamptz not null default now(),
+    primary key (account, name));
+
+create table message (
+    account     text        not null,
+    folder      text        not null,
+    uid         bigint      not null,
+    uidvalidity bigint      not null,
+    message_id  text        not null default '',
+    in_reply_to text        not null default '',
+    date        timestamptz not null,
+    sender      jsonb       not null default '[]',
+    recipients  jsonb       not null default '[]',
+    copied      jsonb       not null default '[]',
+    people      text        not null default '',
+    subject     text        not null default '',
+    size        bigint      not null default 0,
+    flags       text[]      not null default '{}',
+    attachments jsonb       not null default '[]',
+    body        text        not null default '',
+    search      tsvector generated always as (
+        to_tsvector('simple'::regconfig, subject || ' ' || people || ' ' || body)) stored,
+    primary key (account, folder, uid));
+create index message_search on message using gin (search);
+create index message_date on message (account, date desc);
+
+create table account_state (
+    account text        primary key,
+    state   text        not null,
+    why     text        not null default '',
+    heard   timestamptz,
+    synced  timestamptz,
+    said    timestamptz not null default now());
+
+create table outbox (
+    id   bigserial   primary key,
+    key  text        not null,
+    body jsonb       not null,
+    made timestamptz not null default now());

modules/mesh-mail/cmd/mesh-mail/mime.go

@@ -0,0 +1,125 @@
+package main
+
+// A message's text and its attachments, read from its MIME source. The text is kept in the index for search and served
+// through mail_read; each attachment goes to the attachment store once, by its SHA-256 (novox/hq ADR 0359 §3).
+
+import (
+	"bytes"
+	"errors"
+	"html"
+	"io"
+	"mime"
+	"regexp"
+	"strings"
+
+	_ "github.com/emersion/go-message/charset" // the charsets mail is written in, beyond UTF-8 and ASCII
+	"github.com/emersion/go-message/mail"
+)
+
+// Part is one attachment as read from a message.
+type Part struct {
+	Name string
+	Type string
+	Data []byte
+}
+
+// MostBodyText bounds the text kept per message: a longer body is cut, and says so.
+const MostBodyText = 256 << 10
+
+// Parsed is a message's text and its attachments.
+type Parsed struct {
+	Text        string
+	Attachments []Part
+}
+
+// ParseMessage reads a message's text (its plain part; else its HTML part as text) and its attachments. A message the
+// reader cannot follow keeps what was read before the fault, and the error says what.
+func ParseMessage(raw []byte) (Parsed, error) {
+	var p Parsed
+	r, err := mail.CreateReader(bytes.NewReader(raw))
+	if r == nil {
+		return p, err
+	}
+	var plain, htmlText string
+	for {
+		part, err := r.NextPart()
+		if errors.Is(err, io.EOF) {
+			break
+		}
+		if err != nil {
+			return finish(p, plain, htmlText), err
+		}
+		switch h := part.Header.(type) {
+		case *mail.InlineHeader:
+			ct, params, _ := h.ContentType()
+			_, disp, _ := h.ContentDisposition()
+			body, readErr := io.ReadAll(io.LimitReader(part.Body, 64<<20))
+			if readErr != nil {
+				return finish(p, plain, htmlText), readErr
+			}
+			name := params["name"]
+			if name == "" {
+				name = disp["filename"]
+			}
+			switch {
+			case ct == "text/plain" && plain == "" && name == "":
+				plain = string(body)
+			case ct == "text/html" && htmlText == "" && name == "":
+				htmlText = HTMLText(string(body))
+			case !strings.HasPrefix(ct, "text/") || name != "":
+				// An inline image or a named inline file is an attachment too.
+				p.Attachments = append(p.Attachments, Part{Name: name, Type: orOctets(ct), Data: body})
+			}
+		case *mail.AttachmentHeader:
+			ct, _, _ := h.ContentType()
+			name, _ := h.Filename()
+			body, readErr := io.ReadAll(io.LimitReader(part.Body, 64<<20))
+			if readErr != nil {
+				return finish(p, plain, htmlText), readErr
+			}
+			p.Attachments = append(p.Attachments, Part{Name: name, Type: orOctets(ct), Data: body})
+		}
+	}
+	return finish(p, plain, htmlText), nil
+}
+
+func finish(p Parsed, plain, htmlText string) Parsed {
+	p.Text = plain
+	if strings.TrimSpace(p.Text) == "" {
+		p.Text = htmlText
+	}
+	p.Text = strings.ToValidUTF8(p.Text, "�")
+	if len(p.Text) > MostBodyText {
+		p.Text = strings.ToValidUTF8(p.Text[:MostBodyText], "") + "\n[the text goes on; it was cut at 256 KiB]"
+	}
+	return p
+}
+
+func orOctets(ct string) string {
+	if ct == "" {
+		return "application/octet-stream"
+	}
+	if t, _, err := mime.ParseMediaType(ct); err == nil {
+		return t
+	}
+	return ct
+}
+
+var (
+	scriptsAndStyles = regexp.MustCompile(`(?is)<(script|style|head)\b.*?</(script|style|head)>`)
+	breaks           = regexp.MustCompile(`(?i)<(br|/p|/div|/tr|/li|/h[1-6])\b[^>]*>`)
+	tags             = regexp.MustCompile(`(?s)<[^>]*>`)
+	blankLines       = regexp.MustCompile(`\n[ \t]*\n([ \t]*\n)+`)
+)
+
+// HTMLText is an HTML body as plain text: no script, style or markup, the entities read, paragraphs kept as lines.
+// Text only, so nothing of the sender's markup ever reaches whoever reads it.
+func HTMLText(s string) string {
+	s = scriptsAndStyles.ReplaceAllString(s, "")
+	s = breaks.ReplaceAllString(s, "\n")
+	s = tags.ReplaceAllString(s, "")
+	s = html.UnescapeString(s)
+	s = strings.ReplaceAll(s, "\r", "")
+	s = blankLines.ReplaceAllString(s, "\n\n")
+	return strings.TrimSpace(s)
+}

modules/mesh-mail/cmd/mesh-mail/objects.go

@@ -0,0 +1,275 @@
+package main
+
+// The attachment store (novox/hq ADR 0359 §3): each attachment kept once, by its SHA-256, in the bucket the `minio`
+// module provides this module through the `s3-bucket` provision. The mesh writes the bucket's facts and its key into
+// one file (MESH_MAIL_STORE); this speaks S3 to it with the standard library alone: a HEAD, a PUT and a GET, each
+// signed with AWS Signature Version 4, path-style, as an S3-compatible object store answers them.
+
+import (
+	"bytes"
+	"context"
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+)
+
+// Objects is the attachment store.
+type Objects interface {
+	// Bucket is the bucket's name, as an event names it.
+	Bucket() string
+	// Has says whether the key is kept.
+	Has(ctx context.Context, key string) (bool, error)
+	// Put keeps the bytes under the key.
+	Put(ctx context.Context, key, mediaType string, data []byte) error
+	// Get is the bytes kept under the key.
+	Get(ctx context.Context, key string) ([]byte, error)
+}
+
+// Keep stores an attachment once by its SHA-256 and answers its reference: the same file mailed ten times is one
+// object.
+func Keep(ctx context.Context, o Objects, data []byte, mediaType, name string) (AttachmentRef, error) {
+	sum := sha256.Sum256(data)
+	key := hex.EncodeToString(sum[:])
+	has, err := o.Has(ctx, key)
+	if err != nil {
+		return AttachmentRef{}, err
+	}
+	if !has {
+		if err := o.Put(ctx, key, mediaType, data); err != nil {
+			return AttachmentRef{}, err
+		}
+	}
+	return AttachmentRef{Bucket: o.Bucket(), Key: key, Size: int64(len(data)), Type: mediaType, Name: name}, nil
+}
+
+// StoreFacts is the file the mesh writes from the s3-bucket binding and its secret.
+type StoreFacts struct {
+	Scheme string `json:"scheme"`
+	At     string `json:"at"`
+	Port   string `json:"port"`
+	Bucket string `json:"bucket"`
+	Region string `json:"region"`
+	Key    string `json:"key"`
+	Secret string `json:"secret"`
+}
+
+// ReadStoreFacts reads the store's facts.
+func ReadStoreFacts(path string) (StoreFacts, error) {
+	var f StoreFacts
+	if path == "" {
+		return f, errors.New("the module was started without its store's facts (MESH_MAIL_STORE)")
+	}
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return f, fmt.Errorf("the store's facts cannot be read: %w", err)
+	}
+	if err := json.Unmarshal(raw, &f); err != nil {
+		return f, fmt.Errorf("the store's facts are not the module's: %v", err)
+	}
+	if f.At == "" || f.Bucket == "" || f.Key == "" || f.Secret == "" {
+		return f, errors.New("the store's facts name no address, bucket or key")
+	}
+	if f.Scheme == "" {
+		f.Scheme = "http"
+	}
+	if f.Region == "" {
+		f.Region = "us-east-1"
+	}
+	return f, nil
+}
+
+// S3 is the attachment store over S3.
+type S3 struct {
+	Endpoint string // scheme://host[:port]
+	Name     string
+	Region   string
+	Access   string
+	Secret   string
+	Client   *http.Client
+	Now      func() time.Time
+}
+
+// NewS3 is the store the facts name.
+func NewS3(f StoreFacts) *S3 {
+	host := f.At
+	if f.Port != "" {
+		host += ":" + f.Port
+	}
+	return &S3{Endpoint: f.Scheme + "://" + host, Name: f.Bucket, Region: f.Region, Access: f.Key, Secret: f.Secret,
+		Client: &http.Client{Timeout: 2 * time.Minute}, Now: time.Now}
+}
+
+func (s *S3) Bucket() string { return s.Name }
+
+func (s *S3) do(ctx context.Context, method, key, mediaType string, body []byte) (*http.Response, error) {
+	u, err := url.Parse(s.Endpoint + "/" + s.Name + "/" + key)
+	if err != nil {
+		return nil, err
+	}
+	req, err := http.NewRequestWithContext(ctx, method, u.String(), bytes.NewReader(body))
+	if err != nil {
+		return nil, err
+	}
+	if mediaType != "" {
+		req.Header.Set("Content-Type", mediaType)
+	}
+	req.ContentLength = int64(len(body))
+	Sign(req, body, s.Access, s.Secret, s.Region, s.Now().UTC())
+	return s.Client.Do(req)
+}
+
+func (s *S3) Has(ctx context.Context, key string) (bool, error) {
+	resp, err := s.do(ctx, http.MethodHead, key, "", nil)
+	if err != nil {
+		return false, fmt.Errorf("the attachment store cannot be reached: %w", err)
+	}
+	resp.Body.Close()
+	switch resp.StatusCode {
+	case http.StatusOK:
+		return true, nil
+	case http.StatusNotFound:
+		return false, nil
+	}
+	return false, fmt.Errorf("the attachment store answered %s to asking for %s", resp.Status, key)
+}
+
+func (s *S3) Put(ctx context.Context, key, mediaType string, data []byte) error {
+	resp, err := s.do(ctx, http.MethodPut, key, mediaType, data)
+	if err != nil {
+		return fmt.Errorf("the attachment store cannot be reached: %w", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode/100 != 2 {
+		said, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
+		return fmt.Errorf("the attachment store refused %s: %s %s", key, resp.Status, strings.TrimSpace(string(said)))
+	}
+	return nil
+}
+
+func (s *S3) Get(ctx context.Context, key string) ([]byte, error) {
+	resp, err := s.do(ctx, http.MethodGet, key, "", nil)
+	if err != nil {
+		return nil, fmt.Errorf("the attachment store cannot be reached: %w", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("the attachment store answered %s for %s", resp.Status, key)
+	}
+	return io.ReadAll(resp.Body)
+}
+
+// Sign signs a request with AWS Signature Version 4 for S3: every header it carries but the agent and the length is
+// signed, with the payload's hash.
+func Sign(req *http.Request, body []byte, access, secret, region string, now time.Time) {
+	payload := sha256.Sum256(body)
+	payloadHex := hex.EncodeToString(payload[:])
+	amzDate := now.Format("20060102T150405Z")
+	day := now.Format("20060102")
+	req.Header.Set("x-amz-date", amzDate)
+	req.Header.Set("x-amz-content-sha256", payloadHex)
+
+	headers := map[string]string{"host": req.URL.Host}
+	for k, v := range req.Header {
+		lk := strings.ToLower(k)
+		if lk == "user-agent" || lk == "content-length" || lk == "authorization" {
+			continue
+		}
+		headers[lk] = strings.TrimSpace(strings.Join(v, ","))
+	}
+	names := make([]string, 0, len(headers))
+	for k := range headers {
+		names = append(names, k)
+	}
+	sort.Strings(names)
+	var canonHeaders strings.Builder
+	for _, k := range names {
+		canonHeaders.WriteString(k + ":" + headers[k] + "\n")
+	}
+	signed := strings.Join(names, ";")
+	path := req.URL.EscapedPath()
+	if path == "" {
+		path = "/"
+	}
+	canonical := strings.Join([]string{req.Method, path, canonicalQuery(req.URL.Query()), canonHeaders.String(), signed, payloadHex}, "\n")
+	scope := day + "/" + region + "/s3/aws4_request"
+	sum := sha256.Sum256([]byte(canonical))
+	toSign := "AWS4-HMAC-SHA256\n" + amzDate + "\n" + scope + "\n" + hex.EncodeToString(sum[:])
+	key := hmacOf([]byte("AWS4"+secret), day)
+	key = hmacOf(key, region)
+	key = hmacOf(key, "s3")
+	key = hmacOf(key, "aws4_request")
+	sig := hex.EncodeToString(hmacOf(key, toSign))
+	req.Header.Set("Authorization", "AWS4-HMAC-SHA256 Credential="+access+"/"+scope+", SignedHeaders="+signed+", Signature="+sig)
+}
+
+func canonicalQuery(q url.Values) string {
+	keys := make([]string, 0, len(q))
+	for k := range q {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	var parts []string
+	for _, k := range keys {
+		vs := append([]string(nil), q[k]...)
+		sort.Strings(vs)
+		for _, v := range vs {
+			parts = append(parts, url.QueryEscape(k)+"="+strings.ReplaceAll(url.QueryEscape(v), "+", "%20"))
+		}
+	}
+	return strings.Join(parts, "&")
+}
+
+func hmacOf(key []byte, data string) []byte {
+	h := hmac.New(sha256.New, key)
+	h.Write([]byte(data))
+	return h.Sum(nil)
+}
+
+// ---- in memory ----------------------------------------------------------------------------------------------------
+
+type memObjects struct {
+	mu   sync.Mutex
+	name string
+	kept map[string][]byte
+	puts int
+}
+
+func newMemObjects() *memObjects { return &memObjects{name: "mail-test", kept: map[string][]byte{}} }
+
+func (m *memObjects) Bucket() string { return m.name }
+
+func (m *memObjects) Has(_ context.Context, key string) (bool, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	_, ok := m.kept[key]
+	return ok, nil
+}
+
+func (m *memObjects) Put(_ context.Context, key, _ string, data []byte) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.kept[key] = append([]byte(nil), data...)
+	m.puts++
+	return nil
+}
+
+func (m *memObjects) Get(_ context.Context, key string) ([]byte, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	b, ok := m.kept[key]
+	if !ok {
+		return nil, fmt.Errorf("%s is not kept", key)
+	}
+	return b, nil
+}

modules/mesh-mail/cmd/mesh-mail/objects_test.go

@@ -0,0 +1,104 @@
+package main
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"path/filepath"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+// The signature is AWS Signature Version 4 as S3 documents it: its own worked example, "GET Object", signs to the
+// signature AWS publishes.
+func TestTheSignatureIsTheOneS3Documents(t *testing.T) {
+	req, _ := http.NewRequest(http.MethodGet, "https://examplebucket.s3.amazonaws.com/test.txt", nil)
+	req.Header.Set("Range", "bytes=0-9")
+	Sign(req, nil, "AKIAIOSFODNN7EXAMPLE", "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY", "us-east-1", time.Date(2013, 5, 24, 0, 0, 0, 0, time.UTC))
+	want := "AWS4-HMAC-SHA256 Credential=AKIAIOSFODNN7EXAMPLE/20130524/us-east-1/s3/aws4_request, " +
+		"SignedHeaders=host;range;x-amz-content-sha256;x-amz-date, Signature=f0e8bdb87c964420e857bd35b5d6ed310bd44f0170aba48dd91039c6036bdb41"
+	if got := req.Header.Get("Authorization"); got != want {
+		t.Fatalf("signed\n%s\nnot\n%s", got, want)
+	}
+}
+
+// An attachment is kept once by its SHA-256: the same file twice is one PUT, and it reads back.
+func TestAnAttachmentIsKeptOnceByItsHash(t *testing.T) {
+	var mu sync.Mutex
+	kept := map[string][]byte{}
+	puts := 0
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !strings.HasPrefix(r.Header.Get("Authorization"), "AWS4-HMAC-SHA256 Credential=mesh_novox_mail/") {
+			w.WriteHeader(http.StatusForbidden)
+			return
+		}
+		mu.Lock()
+		defer mu.Unlock()
+		switch r.Method {
+		case http.MethodHead:
+			if _, ok := kept[r.URL.Path]; !ok {
+				w.WriteHeader(http.StatusNotFound)
+			}
+		case http.MethodPut:
+			body, _ := io.ReadAll(r.Body)
+			kept[r.URL.Path] = body
+			puts++
+		case http.MethodGet:
+			b, ok := kept[r.URL.Path]
+			if !ok {
+				w.WriteHeader(http.StatusNotFound)
+				return
+			}
+			_, _ = w.Write(b)
+		}
+	}))
+	defer srv.Close()
+	dir := t.TempDir()
+	path := filepath.Join(dir, "store.json")
+	host, port, _ := strings.Cut(strings.TrimPrefix(srv.URL, "http://"), ":")
+	writeFile(t, path, `{"scheme": "http", "at": "`+host+`", "port": "`+port+`", "bucket": "mesh-novox-mail", "region": "eu-west",
+	  "key": "mesh_novox_mail", "secret": "s3cr3t"}`)
+	facts, err := ReadStoreFacts(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	s3 := NewS3(facts)
+	ctx := context.Background()
+	a, err := Keep(ctx, s3, []byte("same file"), "text/plain", "a.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	b, err := Keep(ctx, s3, []byte("same file"), "text/plain", "b.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if a.Key != b.Key || a.Bucket != "mesh-novox-mail" || puts != 1 || len(a.Key) != 64 {
+		t.Fatalf("%+v %+v, %d put(s)", a, b, puts)
+	}
+	if _, ok := kept["/mesh-novox-mail/"+a.Key]; !ok {
+		t.Fatalf("kept %v", kept)
+	}
+	got, err := s3.Get(ctx, a.Key)
+	if err != nil || string(got) != "same file" {
+		t.Fatalf("%q %v", got, err)
+	}
+}
+
+func TestAMessagesTextAndAttachmentsAreRead(t *testing.T) {
+	p, err := ParseMessage([]byte(strings.ReplaceAll(attachedMail("x"), "\n", "\r\n")))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.TrimSpace(p.Text) != "Please find the invoice attached." || len(p.Attachments) != 1 ||
+		p.Attachments[0].Name != "invoice.pdf" || p.Attachments[0].Type != "application/pdf" || string(p.Attachments[0].Data) != attachmentData {
+		t.Fatalf("%+v", p)
+	}
+	html := "From: a@b.c\r\nSubject: s\r\nContent-Type: text/html; charset=utf-8\r\n\r\n<html><head><style>p{}</style></head><body><p>Hello &amp; welcome</p><script>alert(1)</script><p>Bye</p></body></html>"
+	p, err = ParseMessage([]byte(html))
+	if err != nil || p.Text != "Hello & welcome\nBye" {
+		t.Fatalf("%q %v", p.Text, err)
+	}
+}

modules/mesh-mail/cmd/mesh-mail/pgstore.go

@@ -0,0 +1,504 @@
+package main
+
+// The index on the mesh's postgres (novox/hq ADR 0359 §3): the database the mesh provisions for this module through
+// the postgres-database provision, its address in the file DATABASE_URL_FILE names. Its schema is numbered migrations
+// in migrations/, applied by the preparation step (`mesh-mail prepare`, ADR 0135) and recorded in the database itself;
+// a fresh database is given the consolidated schema, schema.sql, at once, with every migration recorded as applied.
+// Nothing else changes the schema: the keeper, the watch and the tools refuse a schema that is behind, and say so.
+
+import (
+	"context"
+	"crypto/sha256"
+	"embed"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+//go:embed migrations/*.sql
+var migrationFiles embed.FS
+
+//go:embed schema.sql
+var consolidated string
+
+// Migration is one numbered change of the schema.
+type Migration struct {
+	Number   int
+	Name     string
+	SQL      string
+	Checksum string
+}
+
+var migrationFile = regexp.MustCompile(`^(\d{4})-([a-z0-9-]+)\.sql$`)
+
+// Migrations are the migrations this binary carries, in order, numbered from 0001 without a gap.
+func Migrations() ([]Migration, error) {
+	entries, err := fs.ReadDir(migrationFiles, "migrations")
+	if err != nil {
+		return nil, err
+	}
+	var out []Migration
+	for _, e := range entries {
+		m := migrationFile.FindStringSubmatch(e.Name())
+		if m == nil {
+			return nil, fmt.Errorf("%s is not a migration's name (NNNN-what-it-does.sql)", e.Name())
+		}
+		n, _ := strconv.Atoi(m[1])
+		body, err := fs.ReadFile(migrationFiles, path.Join("migrations", e.Name()))
+		if err != nil {
+			return nil, err
+		}
+		if strings.TrimSpace(string(body)) == "" {
+			return nil, fmt.Errorf("%s is empty", e.Name())
+		}
+		sum := sha256.Sum256(body)
+		out = append(out, Migration{Number: n, Name: m[2], SQL: string(body), Checksum: hex.EncodeToString(sum[:])})
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Number < out[j].Number })
+	for i, m := range out {
+		if m.Number != i+1 {
+			return nil, fmt.Errorf("the migrations are not numbered 0001 on without a gap: %04d is the %d. one", m.Number, i+1)
+		}
+	}
+	return out, nil
+}
+
+const ledger = `create table if not exists migration (
+    number   integer     primary key,
+    name     text        not null,
+    checksum text        not null,
+    applied  timestamptz not null default now())`
+
+// lockKey is the advisory lock every migration run takes, so two preparations never interleave.
+const lockKey int64 = 4_250_359_001
+
+// PgStore is the Store on postgres.
+type PgStore struct{ pool *pgxpool.Pool }
+
+// PgStoreFromEnv opens the index the mesh provisioned.
+func PgStoreFromEnv(ctx context.Context) (*PgStore, error) {
+	file := os.Getenv("DATABASE_URL_FILE")
+	if file == "" {
+		return nil, errors.New("DATABASE_URL_FILE is not set: the index's database is a requirement the mesh resolves")
+	}
+	raw, err := os.ReadFile(file)
+	if err != nil {
+		return nil, fmt.Errorf("the database's address cannot be read: %w", err)
+	}
+	return OpenPgStore(ctx, strings.TrimSpace(string(raw)))
+}
+
+// OpenPgStore opens the index at an address.
+func OpenPgStore(ctx context.Context, url string) (*PgStore, error) {
+	pool, err := pgxpool.New(ctx, url)
+	if err != nil {
+		return nil, err
+	}
+	return &PgStore{pool: pool}, nil
+}
+
+// Close closes the store.
+func (s *PgStore) Close() { s.pool.Close() }
+
+// Prepare brings the schema to what this version needs, and says what it did.
+func (s *PgStore) Prepare(ctx context.Context) ([]string, error) {
+	migrations, err := Migrations()
+	if err != nil {
+		return nil, err
+	}
+	conn, err := s.pool.Acquire(ctx)
+	if err != nil {
+		return nil, err
+	}
+	defer conn.Release()
+	if _, err := conn.Exec(ctx, `select pg_advisory_lock($1)`, lockKey); err != nil {
+		return nil, fmt.Errorf("the migration lock cannot be taken: %w", err)
+	}
+	defer func() { _, _ = conn.Exec(context.WithoutCancel(ctx), `select pg_advisory_unlock($1)`, lockKey) }()
+	if _, err := conn.Exec(ctx, ledger); err != nil {
+		return nil, err
+	}
+	applied := map[int]string{}
+	rows, err := conn.Query(ctx, `select number, checksum from migration`)
+	if err != nil {
+		return nil, err
+	}
+	highest := 0
+	for rows.Next() {
+		var n int
+		var sum string
+		if err := rows.Scan(&n, &sum); err != nil {
+			rows.Close()
+			return nil, err
+		}
+		applied[n] = sum
+		highest = max(highest, n)
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	record := func(tx pgx.Tx, m Migration) error {
+		_, err := tx.Exec(ctx, `insert into migration (number, name, checksum) values ($1, $2, $3)`, m.Number, m.Name, m.Checksum)
+		return err
+	}
+	if len(applied) == 0 {
+		var exists bool
+		if err := conn.QueryRow(ctx, `select to_regclass('message') is not null`).Scan(&exists); err != nil {
+			return nil, err
+		}
+		if exists {
+			return nil, errors.New("the database holds the index's tables and no record of a migration: its contents are not known, so nothing is changed")
+		}
+		tx, err := conn.Begin(ctx)
+		if err != nil {
+			return nil, err
+		}
+		defer func() { _ = tx.Rollback(context.WithoutCancel(ctx)) }()
+		if _, err := tx.Exec(ctx, consolidated); err != nil {
+			return nil, fmt.Errorf("the consolidated schema failed, and nothing of it was kept: %w", err)
+		}
+		for _, m := range migrations {
+			if err := record(tx, m); err != nil {
+				return nil, err
+			}
+		}
+		if err := tx.Commit(ctx); err != nil {
+			return nil, err
+		}
+		return []string{fmt.Sprintf("a fresh database: the consolidated schema, through migration %04d", len(migrations))}, nil
+	}
+	var problems []string
+	var pending []Migration
+	for _, m := range migrations {
+		sum, ran := applied[m.Number]
+		switch {
+		case ran && sum != m.Checksum:
+			problems = append(problems, fmt.Sprintf("migration %04d-%s ran, and its file has changed since: write a new one", m.Number, m.Name))
+		case !ran && m.Number < highest:
+			problems = append(problems, fmt.Sprintf("migration %04d-%s never ran, and %04d did: renumber it above %04d", m.Number, m.Name, highest, highest))
+		case !ran:
+			pending = append(pending, m)
+		}
+	}
+	if len(problems) > 0 {
+		return nil, errors.New("this database and these migrations disagree: " + strings.Join(problems, "; "))
+	}
+	var said []string
+	for _, m := range pending {
+		err := func() error {
+			tx, err := conn.Begin(ctx)
+			if err != nil {
+				return err
+			}
+			defer func() { _ = tx.Rollback(context.WithoutCancel(ctx)) }()
+			if _, err := tx.Exec(ctx, m.SQL); err != nil {
+				return fmt.Errorf("migration %04d-%s failed, and nothing it did was kept: %w", m.Number, m.Name, err)
+			}
+			if err := record(tx, m); err != nil {
+				return err
+			}
+			return tx.Commit(ctx)
+		}()
+		if err != nil {
+			return said, err
+		}
+		said = append(said, fmt.Sprintf("migration %04d-%s applied", m.Number, m.Name))
+	}
+	if len(said) == 0 {
+		said = []string{fmt.Sprintf("the schema is at migration %04d, as this version needs", len(migrations))}
+	}
+	return said, nil
+}
+
+// Ready says why the index cannot serve this version, or nil.
+func (s *PgStore) Ready(ctx context.Context) error {
+	migrations, err := Migrations()
+	if err != nil {
+		return err
+	}
+	var at int
+	err = s.pool.QueryRow(ctx, `select coalesce(max(number), 0) from migration`).Scan(&at)
+	var pgErr *pgconn.PgError
+	if errors.As(err, &pgErr) && pgErr.Code == "42P01" {
+		at = 0
+	} else if err != nil {
+		return fmt.Errorf("the database cannot be reached: %w", err)
+	}
+	if at != len(migrations) {
+		return fmt.Errorf("the database's schema is at migration %04d and this version needs %04d: the preparation step "+
+			"(mesh-mail prepare) has not run", at, len(migrations))
+	}
+	return nil
+}
+
+func (s *PgStore) Folder(ctx context.Context, account, folder string) (Folder, bool, error) {
+	f := Folder{Account: account, Name: folder}
+	var validity int64
+	err := s.pool.QueryRow(ctx, `select uidvalidity, messages, synced from folder where account = $1 and name = $2`, account, folder).
+		Scan(&validity, &f.Messages, &f.Synced)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return f, false, nil
+	}
+	f.UIDValidity = uint32(validity)
+	return f, err == nil, err
+}
+
+func (s *PgStore) SetFolder(ctx context.Context, f Folder) error {
+	_, err := s.pool.Exec(ctx, `insert into folder (account, name, uidvalidity, messages, synced) values ($1, $2, $3, $4, $5)
+		on conflict (account, name) do update set uidvalidity = excluded.uidvalidity, messages = excluded.messages, synced = excluded.synced`,
+		f.Account, f.Name, int64(f.UIDValidity), f.Messages, f.Synced)
+	return err
+}
+
+func (s *PgStore) DropFolder(ctx context.Context, account, folder string) error {
+	return pgx.BeginFunc(ctx, s.pool, func(tx pgx.Tx) error {
+		if _, err := tx.Exec(ctx, `delete from message where account = $1 and folder = $2`, account, folder); err != nil {
+			return err
+		}
+		_, err := tx.Exec(ctx, `delete from folder where account = $1 and name = $2`, account, folder)
+		return err
+	})
+}
+
+func (s *PgStore) Flags(ctx context.Context, account, folder string) (map[uint32][]string, error) {
+	rows, err := s.pool.Query(ctx, `select uid, flags from message where account = $1 and folder = $2`, account, folder)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := map[uint32][]string{}
+	for rows.Next() {
+		var uid int64
+		var flags []string
+		if err := rows.Scan(&uid, &flags); err != nil {
+			return nil, err
+		}
+		out[uint32(uid)] = flags
+	}
+	return out, rows.Err()
+}
+
+func keepEvent(ctx context.Context, tx pgx.Tx, e *Event) error {
+	if e == nil {
+		return nil
+	}
+	body, err := json.Marshal(e.Body)
+	if err != nil {
+		return err
+	}
+	_, err = tx.Exec(ctx, `insert into outbox (key, body) values ($1, $2)`, e.Key, body)
+	return err
+}
+
+func (s *PgStore) Add(ctx context.Context, m Message, e *Event) error {
+	from, _ := json.Marshal(m.From)
+	to, _ := json.Marshal(m.To)
+	cc, _ := json.Marshal(orNone(m.Cc))
+	atts, _ := json.Marshal(m.Attachments)
+	flags := m.Flags
+	if flags == nil {
+		flags = []string{}
+	}
+	people := strings.Join([]string{peopleText(m.From), peopleText(m.To), peopleText(m.Cc)}, " ")
+	// An address is one word to the search, so its parts are kept beside it: "bob" finds bob@example.org.
+	people += " " + strings.NewReplacer("@", " ", ".", " ", ",", " ").Replace(people)
+	return pgx.BeginFunc(ctx, s.pool, func(tx pgx.Tx) error {
+		if _, err := tx.Exec(ctx, `insert into message (account, folder, uid, uidvalidity, message_id, in_reply_to, date, sender,
+			recipients, copied, people, subject, size, flags, attachments, body)
+			values ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16)
+			on conflict (account, folder, uid) do update set uidvalidity = excluded.uidvalidity, message_id = excluded.message_id,
+			in_reply_to = excluded.in_reply_to, date = excluded.date, sender = excluded.sender, recipients = excluded.recipients,
+			copied = excluded.copied, people = excluded.people, subject = excluded.subject, size = excluded.size,
+			flags = excluded.flags, attachments = excluded.attachments, body = excluded.body`,
+			m.Account, m.Folder, int64(m.UID), int64(m.UIDValidity), m.MessageID, m.InReplyTo, m.Date, from, to, cc, people,
+			strings.ToValidUTF8(strings.ReplaceAll(m.Subject, "\x00", ""), ""), m.Size, flags, atts,
+			strings.ReplaceAll(m.Body, "\x00", "")); err != nil {
+			return err
+		}
+		return keepEvent(ctx, tx, e)
+	})
+}
+
+func orNone(ps []Person) []Person {
+	if ps == nil {
+		return []Person{}
+	}
+	return ps
+}
+
+func (s *PgStore) SetFlags(ctx context.Context, account, folder string, uid uint32, flags []string, e *Event) error {
+	return pgx.BeginFunc(ctx, s.pool, func(tx pgx.Tx) error {
+		if _, err := tx.Exec(ctx, `update message set flags = $4 where account = $1 and folder = $2 and uid = $3`,
+			account, folder, int64(uid), flags); err != nil {
+			return err
+		}
+		return keepEvent(ctx, tx, e)
+	})
+}
+
+func (s *PgStore) Remove(ctx context.Context, account, folder string, uid uint32, e *Event) error {
+	return pgx.BeginFunc(ctx, s.pool, func(tx pgx.Tx) error {
+		if _, err := tx.Exec(ctx, `delete from message where account = $1 and folder = $2 and uid = $3`, account, folder, int64(uid)); err != nil {
+			return err
+		}
+		return keepEvent(ctx, tx, e)
+	})
+}
+
+const messageColumns = `account, folder, uid, uidvalidity, message_id, in_reply_to, date, sender, recipients, copied, subject,
+	size, flags, attachments`
+
+func scanMessage(row pgx.Row, withBody bool) (Message, error) {
+	var m Message
+	var uid, validity int64
+	var from, to, cc, atts []byte
+	dest := []any{&m.Account, &m.Folder, &uid, &validity, &m.MessageID, &m.InReplyTo, &m.Date, &from, &to, &cc, &m.Subject,
+		&m.Size, &m.Flags, &atts}
+	if withBody {
+		dest = append(dest, &m.Body)
+	}
+	if err := row.Scan(dest...); err != nil {
+		return m, err
+	}
+	m.UID, m.UIDValidity, m.Date = uint32(uid), uint32(validity), m.Date.UTC()
+	for _, f := range []struct {
+		raw  []byte
+		into any
+	}{{from, &m.From}, {to, &m.To}, {cc, &m.Cc}, {atts, &m.Attachments}} {
+		if err := json.Unmarshal(f.raw, f.into); err != nil {
+			return m, err
+		}
+	}
+	return m, nil
+}
+
+func (s *PgStore) Get(ctx context.Context, account, folder string, uid uint32) (Message, bool, error) {
+	m, err := scanMessage(s.pool.QueryRow(ctx, `select `+messageColumns+`, body from message where account = $1 and folder = $2 and uid = $3`,
+		account, folder, int64(uid)), true)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return Message{}, false, nil
+	}
+	return m, err == nil, err
+}
+
+func (s *PgStore) Search(ctx context.Context, q Query) ([]Message, error) {
+	limit := q.Limit
+	if limit <= 0 {
+		limit = 20
+	}
+	rows, err := s.pool.Query(ctx, `select `+messageColumns+` from message
+		where account = any($1) and ($2 = '' or folder = $2) and search @@ plainto_tsquery('simple'::regconfig, $3)
+		order by date desc limit $4`, q.Accounts, q.Folder, q.Text, limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Message
+	for rows.Next() {
+		m, err := scanMessage(rows, false)
+		if err != nil {
+			return nil, err
+		}
+		out = append(out, m)
+	}
+	return out, rows.Err()
+}
+
+func (s *PgStore) Folders(ctx context.Context, account string) ([]Folder, error) {
+	rows, err := s.pool.Query(ctx, `select name, uidvalidity, messages, synced from folder where account = $1 order by name`, account)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Folder
+	for rows.Next() {
+		f := Folder{Account: account}
+		var validity int64
+		if err := rows.Scan(&f.Name, &validity, &f.Messages, &f.Synced); err != nil {
+			return nil, err
+		}
+		f.UIDValidity, f.Synced = uint32(validity), f.Synced.UTC()
+		out = append(out, f)
+	}
+	return out, rows.Err()
+}
+
+func (s *PgStore) Pending(ctx context.Context, limit int) ([]Event, error) {
+	rows, err := s.pool.Query(ctx, `select id, key, body from outbox order by id limit $1`, limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Event
+	for rows.Next() {
+		var e Event
+		var body []byte
+		if err := rows.Scan(&e.ID, &e.Key, &body); err != nil {
+			return nil, err
+		}
+		if err := json.Unmarshal(body, &e.Body); err != nil {
+			return nil, err
+		}
+		out = append(out, e)
+	}
+	return out, rows.Err()
+}
+
+func (s *PgStore) Said(ctx context.Context, ids []int64) error {
+	_, err := s.pool.Exec(ctx, `delete from outbox where id = any($1)`, ids)
+	return err
+}
+
+func (s *PgStore) SetState(ctx context.Context, st AccountState) error {
+	_, err := s.pool.Exec(ctx, `insert into account_state (account, state, why, heard, synced, said) values ($1, $2, $3, $4, $5, $6)
+		on conflict (account) do update set state = excluded.state, why = excluded.why, heard = excluded.heard,
+		synced = excluded.synced, said = excluded.said`,
+		st.Account, st.State, st.Why, nullTime(st.Heard), nullTime(st.Synced), st.Said)
+	return err
+}
+
+func nullTime(t time.Time) *time.Time {
+	if t.IsZero() {
+		return nil
+	}
+	return &t
+}
+
+func (s *PgStore) States(ctx context.Context) (map[string]AccountState, error) {
+	rows, err := s.pool.Query(ctx, `select account, state, why, heard, synced, said from account_state`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := map[string]AccountState{}
+	for rows.Next() {
+		var st AccountState
+		var heard, synced *time.Time
+		if err := rows.Scan(&st.Account, &st.State, &st.Why, &heard, &synced, &st.Said); err != nil {
+			return nil, err
+		}
+		if heard != nil {
+			st.Heard = heard.UTC()
+		}
+		if synced != nil {
+			st.Synced = synced.UTC()
+		}
+		st.Said = st.Said.UTC()
+		out[st.Account] = st
+	}
+	return out, rows.Err()
+}

modules/mesh-mail/cmd/mesh-mail/pgstore_test.go

@@ -0,0 +1,99 @@
+package main
+
+import (
+	"context"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// The schema is numbered migrations and a consolidated schema for a fresh database (the mesh's rule: both). A
+// database given the consolidated schema and one given every migration in order hold the same tables and columns.
+func TestTheConsolidatedSchemaIsTheMigrationsApplied(t *testing.T) {
+	ctx := context.Background()
+	fresh := pgStore(t)
+	stepped, err := OpenPgStore(ctx, freshDatabase(t))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer stepped.Close()
+	migrations, err := Migrations()
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, m := range migrations {
+		if _, err := stepped.pool.Exec(ctx, m.SQL); err != nil {
+			t.Fatalf("migration %04d: %v", m.Number, err)
+		}
+	}
+	a, b := shape(t, fresh), shape(t, stepped)
+	if !reflect.DeepEqual(a, b) || len(a) < 25 {
+		t.Fatalf("the consolidated schema and the migrations differ:\nconsolidated %v\nmigrations   %v", a, b)
+	}
+	if !strings.Contains(consolidated, "through migration 0001") || len(migrations) != 1 {
+		t.Fatal("the consolidated schema does not say how far it is consolidated")
+	}
+	// Prepared twice, it changes nothing; and it is ready.
+	if said, err := fresh.Prepare(ctx); err != nil || !strings.Contains(said[0], "as this version needs") {
+		t.Fatalf("%v %v", said, err)
+	}
+	if err := fresh.Ready(ctx); err != nil {
+		t.Fatal(err)
+	}
+	if err := stepped.Ready(ctx); err == nil {
+		t.Fatal("a database whose migrations are not recorded is ready")
+	}
+}
+
+func shape(t *testing.T, s *PgStore) []string {
+	t.Helper()
+	rows, err := s.pool.Query(context.Background(), `select table_name || '.' || column_name || ' ' || data_type
+		from information_schema.columns where table_schema = 'public' and table_name <> 'migration' order by 1`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer rows.Close()
+	var out []string
+	for rows.Next() {
+		var c string
+		_ = rows.Scan(&c)
+		out = append(out, c)
+	}
+	return out
+}
+
+// The search finds by every word, across the accounts asked only, newest first, and answers no body.
+func TestTheIndexSearchesByWordAndAccount(t *testing.T) {
+	eachStore(t, func(t *testing.T, st Store) {
+		ctx := context.Background()
+		for i, subj := range []string{"the invoice of october", "lunch", "another invoice"} {
+			m := Message{Account: "mesh", Folder: "INBOX", UID: uint32(i + 1), Subject: subj, Date: judgedAt.AddDate(0, 0, i),
+				From: []Person{{Address: "bob@example.org"}}, To: []Person{}, Flags: []string{}, Attachments: []AttachmentRef{}, Body: "text " + subj}
+			if err := st.Add(ctx, m, nil); err != nil {
+				t.Fatal(err)
+			}
+		}
+		other := Message{Account: "gmail", Folder: "INBOX", UID: 1, Subject: "invoice elsewhere", Date: judgedAt, From: []Person{}, To: []Person{},
+			Flags: []string{}, Attachments: []AttachmentRef{}}
+		if err := st.Add(ctx, other, nil); err != nil {
+			t.Fatal(err)
+		}
+		hits, err := st.Search(ctx, Query{Text: "invoice", Accounts: []string{"mesh"}, Limit: 10})
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(hits) != 2 || hits[0].Subject != "another invoice" || hits[0].Body != "" {
+			t.Fatalf("%+v", hits)
+		}
+		if hits, _ := st.Search(ctx, Query{Text: "invoice october", Accounts: []string{"mesh"}}); len(hits) != 1 {
+			t.Fatalf("%+v", hits)
+		}
+		if hits, _ := st.Search(ctx, Query{Text: "bob", Accounts: []string{"mesh"}}); len(hits) != 3 {
+			t.Fatalf("by sender: %+v", hits)
+		}
+		got, ok, err := st.Get(ctx, "mesh", "INBOX", 2)
+		if err != nil || !ok || got.Body != "text lunch" {
+			t.Fatalf("%+v %v %v", got, ok, err)
+		}
+	})
+}

modules/mesh-mail/cmd/mesh-mail/schema.sql

@@ -0,0 +1,46 @@
+-- The consolidated schema, through migration 0001: what a fresh database is given at once (the mesh's rule: a
+-- numbered migration for the running store, and this for a fresh install).
+create table folder (
+    account     text        not null,
+    name        text        not null,
+    uidvalidity bigint      not null,
+    messages    integer     not null default 0,
+    synced      timestamptz not null default now(),
+    primary key (account, name));
+
+create table message (
+    account     text        not null,
+    folder      text        not null,
+    uid         bigint      not null,
+    uidvalidity bigint      not null,
+    message_id  text        not null default '',
+    in_reply_to text        not null default '',
+    date        timestamptz not null,
+    sender      jsonb       not null default '[]',
+    recipients  jsonb       not null default '[]',
+    copied      jsonb       not null default '[]',
+    people      text        not null default '',
+    subject     text        not null default '',
+    size        bigint      not null default 0,
+    flags       text[]      not null default '{}',
+    attachments jsonb       not null default '[]',
+    body        text        not null default '',
+    search      tsvector generated always as (
+        to_tsvector('simple'::regconfig, subject || ' ' || people || ' ' || body)) stored,
+    primary key (account, folder, uid));
+create index message_search on message using gin (search);
+create index message_date on message (account, date desc);
+
+create table account_state (
+    account text        primary key,
+    state   text        not null,
+    why     text        not null default '',
+    heard   timestamptz,
+    synced  timestamptz,
+    said    timestamptz not null default now());
+
+create table outbox (
+    id   bigserial   primary key,
+    key  text        not null,
+    body jsonb       not null,
+    made timestamptz not null default now());

modules/mesh-mail/cmd/mesh-mail/store.go

@@ -0,0 +1,332 @@
+package main
+
+// The index (novox/hq ADR 0359 §3): one row per message and folder, in the module's own database; the events still to
+// be said on the bus, written in the same step as the change they say; and each account's state as its keeper last
+// saw it, which the health watch reads. The Store is that, over postgres (pgstore.go) or in memory for the tests.
+
+import (
+	"context"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+// Person is a sender or a recipient.
+type Person struct {
+	Name    string `json:"name,omitempty"`
+	Address string `json:"address"`
+}
+
+// AttachmentRef names an attachment by its content (§3): the bucket and key it is kept under, the key being its
+// SHA-256 in hex, with its size, media type and file name.
+type AttachmentRef struct {
+	Bucket string `json:"bucket"`
+	Key    string `json:"key"`
+	Size   int64  `json:"size"`
+	Type   string `json:"type"`
+	Name   string `json:"name,omitempty"`
+}
+
+// Message is one message in one folder of one account, as indexed.
+type Message struct {
+	Account     string          `json:"account"`
+	Folder      string          `json:"folder"`
+	UIDValidity uint32          `json:"uidvalidity"`
+	UID         uint32          `json:"uid"`
+	MessageID   string          `json:"message-id,omitempty"`
+	InReplyTo   string          `json:"in-reply-to,omitempty"`
+	Date        time.Time       `json:"date"`
+	From        []Person        `json:"from"`
+	To          []Person        `json:"to"`
+	Cc          []Person        `json:"cc,omitempty"`
+	Subject     string          `json:"subject"`
+	Size        int64           `json:"size"`
+	Flags       []string        `json:"flags"`
+	Attachments []AttachmentRef `json:"attachments"`
+	// Body is the message's text, kept for search and served only through mail_read; never on the bus.
+	Body string `json:"-"`
+}
+
+// Event is one change said on the bus: its key (`mail.<account>.message.<added|changed|removed>`) and its body,
+// metadata only.
+type Event struct {
+	ID   int64
+	Key  string
+	Body map[string]any
+}
+
+// Folder is what the index knows of one folder.
+type Folder struct {
+	Account     string    `json:"-"`
+	Name        string    `json:"name"`
+	UIDValidity uint32    `json:"-"`
+	Messages    int       `json:"messages"`
+	Synced      time.Time `json:"synced"`
+}
+
+// The states an account's keeper says it is in.
+const (
+	AccountSyncing = "syncing"
+	AccountCurrent = "current"
+	AccountWaits   = "waits-for-sign-in"
+	AccountFailing = "failing"
+)
+
+// AccountState is an account as its keeper last said it: its state, why, and when the server last answered.
+type AccountState struct {
+	Account string    `json:"account"`
+	State   string    `json:"state"`
+	Why     string    `json:"why"`
+	Heard   time.Time `json:"heard,omitempty"`
+	Synced  time.Time `json:"synced,omitempty"`
+	Said    time.Time `json:"said"`
+}
+
+// Query is a search of the index.
+type Query struct {
+	Text     string
+	Accounts []string
+	Folder   string
+	Limit    int
+}
+
+// Store is the index.
+type Store interface {
+	Ready(ctx context.Context) error
+	// Folder is what the index knows of a folder; false when it never synced it.
+	Folder(ctx context.Context, account, folder string) (Folder, bool, error)
+	// SetFolder records a folder synced.
+	SetFolder(ctx context.Context, f Folder) error
+	// DropFolder forgets a folder's rows, without an event: the server renumbered it (a new UIDVALIDITY) and the
+	// next sync indexes it afresh.
+	DropFolder(ctx context.Context, account, folder string) error
+	// Flags is every indexed message of a folder, by UID, with its flags.
+	Flags(ctx context.Context, account, folder string) (map[uint32][]string, error)
+	// Add indexes a message, and keeps the event that says it when there is one, in one step.
+	Add(ctx context.Context, m Message, e *Event) error
+	// SetFlags changes a message's flags, and keeps the event, in one step.
+	SetFlags(ctx context.Context, account, folder string, uid uint32, flags []string, e *Event) error
+	// Remove removes a message, and keeps the event, in one step.
+	Remove(ctx context.Context, account, folder string, uid uint32, e *Event) error
+	// Get is one message, with its body.
+	Get(ctx context.Context, account, folder string, uid uint32) (Message, bool, error)
+	// Search finds messages, newest first, without their bodies.
+	Search(ctx context.Context, q Query) ([]Message, error)
+	// Folders is every folder the index knows of an account.
+	Folders(ctx context.Context, account string) ([]Folder, error)
+	// Pending is the events not yet said, oldest first; Said removes those said.
+	Pending(ctx context.Context, limit int) ([]Event, error)
+	Said(ctx context.Context, ids []int64) error
+	// SetState and States are each account's state, as its keeper says it.
+	SetState(ctx context.Context, s AccountState) error
+	States(ctx context.Context) (map[string]AccountState, error)
+}
+
+// ---- in memory ----------------------------------------------------------------------------------------------------
+
+type memStore struct {
+	mu       sync.Mutex
+	messages map[string]Message
+	folders  map[string]Folder
+	events   []Event
+	next     int64
+	states   map[string]AccountState
+}
+
+func newMemStore() *memStore {
+	return &memStore{messages: map[string]Message{}, folders: map[string]Folder{}, states: map[string]AccountState{}}
+}
+
+func msgKey(account, folder string, uid uint32) string {
+	return account + "\x00" + folder + "\x00" + itoa(int64(uid))
+}
+
+func folderKey(account, folder string) string { return account + "\x00" + folder }
+
+func (s *memStore) Ready(context.Context) error { return nil }
+
+func (s *memStore) Folder(_ context.Context, account, folder string) (Folder, bool, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	f, ok := s.folders[folderKey(account, folder)]
+	return f, ok, nil
+}
+
+func (s *memStore) SetFolder(_ context.Context, f Folder) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.folders[folderKey(f.Account, f.Name)] = f
+	return nil
+}
+
+func (s *memStore) DropFolder(_ context.Context, account, folder string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	for k, m := range s.messages {
+		if m.Account == account && m.Folder == folder {
+			delete(s.messages, k)
+		}
+	}
+	delete(s.folders, folderKey(account, folder))
+	return nil
+}
+
+func (s *memStore) Flags(_ context.Context, account, folder string) (map[uint32][]string, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	out := map[uint32][]string{}
+	for _, m := range s.messages {
+		if m.Account == account && m.Folder == folder {
+			out[m.UID] = append([]string(nil), m.Flags...)
+		}
+	}
+	return out, nil
+}
+
+func (s *memStore) keep(e *Event) {
+	if e == nil {
+		return
+	}
+	s.next++
+	ev := *e
+	ev.ID = s.next
+	s.events = append(s.events, ev)
+}
+
+func (s *memStore) Add(_ context.Context, m Message, e *Event) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.messages[msgKey(m.Account, m.Folder, m.UID)] = m
+	s.keep(e)
+	return nil
+}
+
+func (s *memStore) SetFlags(_ context.Context, account, folder string, uid uint32, flags []string, e *Event) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	k := msgKey(account, folder, uid)
+	if m, ok := s.messages[k]; ok {
+		m.Flags = flags
+		s.messages[k] = m
+	}
+	s.keep(e)
+	return nil
+}
+
+func (s *memStore) Remove(_ context.Context, account, folder string, uid uint32, e *Event) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	delete(s.messages, msgKey(account, folder, uid))
+	s.keep(e)
+	return nil
+}
+
+func (s *memStore) Get(_ context.Context, account, folder string, uid uint32) (Message, bool, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	m, ok := s.messages[msgKey(account, folder, uid)]
+	return m, ok, nil
+}
+
+func (s *memStore) Search(_ context.Context, q Query) ([]Message, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	words := strings.Fields(strings.ToLower(q.Text))
+	var out []Message
+	for _, m := range s.messages {
+		if !contains(q.Accounts, m.Account) || (q.Folder != "" && q.Folder != m.Folder) {
+			continue
+		}
+		hay := strings.ToLower(m.Subject + " " + m.Body + " " + peopleText(m.From) + " " + peopleText(m.To) + " " + peopleText(m.Cc))
+		all := true
+		for _, w := range words {
+			all = all && strings.Contains(hay, w)
+		}
+		if all {
+			m.Body = ""
+			out = append(out, m)
+		}
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Date.After(out[j].Date) })
+	if q.Limit > 0 && len(out) > q.Limit {
+		out = out[:q.Limit]
+	}
+	return out, nil
+}
+
+func (s *memStore) Folders(_ context.Context, account string) ([]Folder, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	var out []Folder
+	for _, f := range s.folders {
+		if f.Account == account {
+			out = append(out, f)
+		}
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
+	return out, nil
+}
+
+func (s *memStore) Pending(_ context.Context, limit int) ([]Event, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	n := min(limit, len(s.events))
+	return append([]Event(nil), s.events[:n]...), nil
+}
+
+func (s *memStore) Said(_ context.Context, ids []int64) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	said := map[int64]bool{}
+	for _, id := range ids {
+		said[id] = true
+	}
+	kept := s.events[:0]
+	for _, e := range s.events {
+		if !said[e.ID] {
+			kept = append(kept, e)
+		}
+	}
+	s.events = kept
+	return nil
+}
+
+func (s *memStore) SetState(_ context.Context, st AccountState) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.states[st.Account] = st
+	return nil
+}
+
+func (s *memStore) States(context.Context) (map[string]AccountState, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	out := map[string]AccountState{}
+	for k, v := range s.states {
+		out[k] = v
+	}
+	return out, nil
+}
+
+// ---- small helpers ------------------------------------------------------------------------------------------------
+
+func contains(list []string, s string) bool {
+	for _, x := range list {
+		if x == s {
+			return true
+		}
+	}
+	return false
+}
+
+func peopleText(ps []Person) string {
+	var parts []string
+	for _, p := range ps {
+		parts = append(parts, strings.TrimSpace(p.Name+" "+p.Address))
+	}
+	return strings.Join(parts, ", ")
+}
+
+func itoa(n int64) string { return strconv.FormatInt(n, 10) }

modules/mesh-mail/cmd/mesh-mail/tools.go

@@ -0,0 +1,311 @@
+package main
+
+// The module's tools (novox/hq ADR 0359 §5): mail_accounts, mail_search, mail_read and mail_health. Who calls is the
+// runtime's word (stdio.CallerOf), never an argument; a caller reads an account's mail — its search, a body, an
+// attachment — only when the trusted setting `grants` names it for that account (§4). Nothing here writes to a mailbox.
+
+import (
+	"context"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// Tool names, as the manifest declares them.
+const (
+	AccountsTool = "mail_accounts"
+	SearchTool   = "mail_search"
+	ReadTool     = "mail_read"
+)
+
+// Bounds of what a tool answers.
+const (
+	MostResults      = 50
+	MostQuery        = 200
+	MostBodyAnswered = 64 << 10
+	MostAttachment   = 8 << 20
+)
+
+// Bundle is what the tools reach: the settings, the index and the attachment store.
+type Bundle struct {
+	Env     Env
+	Index   func(ctx context.Context) (Store, error)
+	Objects func() (Objects, error)
+	Caller  func(args map[string]any) string
+	Now     func() time.Time
+}
+
+func (b *Bundle) now() time.Time {
+	if b.Now != nil {
+		return b.Now()
+	}
+	return time.Now()
+}
+
+func (b *Bundle) settings() ([]Account, Grants, error) {
+	accounts, err := ReadAccounts(b.Env.Accounts)
+	if err != nil {
+		return nil, nil, err
+	}
+	grants, err := ReadGrants(b.Env.Grants)
+	if err != nil {
+		// A grants setting that cannot be read grants nothing; the refusal says why.
+		return accounts, Grants{}, nil
+	}
+	return accounts, grants, nil
+}
+
+// Tools are the module's tools.
+func (b *Bundle) Tools() []stdio.Tool {
+	return []stdio.Tool{
+		{Name: AccountsTool,
+			Description: "The operator's mail accounts this module watches, each with its kind, its state (syncing, current, " +
+				"waits-for-sign-in or failing, and why), when its server last answered, when it was last brought up to date, and " +
+				"its folders with how many messages each holds. An account's mail address is said only to a caller granted that " +
+				"account; whether you are is said per account. Read-only.",
+			Input: schema(nil, map[string]any{}),
+			Run:   b.accountsTool},
+		{Name: SearchTool,
+			Description: "Search the mail of the accounts you are granted: every word of the query must be in the subject, the " +
+				"text, a sender or a recipient. Answers the newest first, at most 50: account, folder, uid, message id, date, " +
+				"sender, recipients, subject, size, flags and attachment references, never a body. Refused for an account you " +
+				"are not granted, and when you are granted none. Read-only.",
+			Input: schema([]string{"query"}, map[string]any{
+				"query":   text("the words to find, at most 200 characters"),
+				"account": text("one account by its name in mail_accounts; every account you are granted when left out"),
+				"folder":  text("one folder, such as INBOX; every folder when left out"),
+				"limit":   integer("how many to answer, at most 50 (20 when left out)"),
+			}),
+			Run: b.searchTool},
+		{Name: ReadTool,
+			Description: "Read one message of an account you are granted, as an event or mail_search names it (account, folder, " +
+				"uid): its metadata and its text (the plain part, or the HTML part as text, at most 64 KiB here). With " +
+				"attachment (its key, the SHA-256 the message's references name), that one attachment's bytes, base64, at most " +
+				"8 MiB. Refused for an account you are not granted. Never marks a message seen. Read-only.",
+			Input: schema([]string{"account", "folder", "uid"}, map[string]any{
+				"account":    text("the account, by its name in mail_accounts"),
+				"folder":     text("the folder, such as INBOX"),
+				"uid":        integer("the message's uid in that folder"),
+				"attachment": text("an attachment's key, the SHA-256 the message's references name, to answer its bytes"),
+			}),
+			Run: b.readTool},
+		{Name: HealthTool,
+			Description: "How mesh-mail is, as its watch last saw it: healthy when every account's server answered within five " +
+				"minutes; unhealthy, naming the account and why, when a connection is down or its IDLE on the inbox went silent; " +
+				"waits, naming the account's password, while the operator has not given it at the desk.",
+			Input: schema(nil, map[string]any{}),
+			Run:   func(map[string]any) (any, error) { return ReadStatus(b.Env.Status, b.now()), nil }},
+	}
+}
+
+func (b *Bundle) caller(args map[string]any) string {
+	if b.Caller != nil {
+		return b.Caller(args)
+	}
+	return stdio.CallerOf(args)
+}
+
+func (b *Bundle) accountsTool(args map[string]any) (any, error) {
+	if err := only(args); err != nil {
+		return nil, err
+	}
+	accounts, grants, err := b.settings()
+	if err != nil {
+		return nil, err
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
+	defer cancel()
+	st, err := b.Index(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("the index cannot be reached: %v", err)
+	}
+	states, err := st.States(ctx)
+	if err != nil {
+		return nil, err
+	}
+	caller := b.caller(args)
+	var out []map[string]any
+	for _, a := range accounts {
+		entry := map[string]any{"account": a.Name, "kind": a.Kind, "granted": grants.Allows(caller, a.Name)}
+		if s, ok := states[a.Name]; ok {
+			entry["state"], entry["why"] = s.State, s.Why
+			if !s.Heard.IsZero() {
+				entry["heard"] = s.Heard.UTC().Format(time.RFC3339)
+			}
+			if !s.Synced.IsZero() {
+				entry["synced"] = s.Synced.UTC().Format(time.RFC3339)
+			}
+		} else {
+			entry["state"], entry["why"] = "unknown", "its keeper has said nothing of it yet"
+		}
+		if grants.Allows(caller, a.Name) {
+			entry["address"] = a.Address
+		}
+		folders, err := st.Folders(ctx, a.Name)
+		if err != nil {
+			return nil, err
+		}
+		entry["folders"] = folders
+		out = append(out, entry)
+	}
+	return map[string]any{"accounts": out, "caller": caller}, nil
+}
+
+func (b *Bundle) searchTool(args map[string]any) (any, error) {
+	if err := only(args, "query", "account", "folder", "limit"); err != nil {
+		return nil, err
+	}
+	query, _ := args["query"].(string)
+	if strings.TrimSpace(query) == "" || len(query) > MostQuery {
+		return nil, fmt.Errorf("%s needs a query of 1 to %d characters", SearchTool, MostQuery)
+	}
+	account, _ := args["account"].(string)
+	folder, _ := args["folder"].(string)
+	limit, err := number(args, "limit", 20)
+	if err != nil {
+		return nil, err
+	}
+	if limit < 1 || limit > MostResults {
+		return nil, fmt.Errorf("limit is 1 to %d", MostResults)
+	}
+	accounts, grants, err := b.settings()
+	if err != nil {
+		return nil, err
+	}
+	caller := b.caller(args)
+	granted := grants.Granted(caller, accounts)
+	if account != "" {
+		if !grants.Allows(caller, account) {
+			return nil, refused(caller, account)
+		}
+		granted = []string{account}
+	}
+	if len(granted) == 0 {
+		return nil, fmt.Errorf("refused: %s is granted no mail account; the operator grants one through the setting grants", caller)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
+	defer cancel()
+	st, err := b.Index(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("the index cannot be reached: %v", err)
+	}
+	found, err := st.Search(ctx, Query{Text: query, Accounts: granted, Folder: folder, Limit: limit})
+	if err != nil {
+		return nil, err
+	}
+	out := make([]map[string]any, 0, len(found))
+	for _, m := range found {
+		out = append(out, metadata(m))
+	}
+	return map[string]any{"searched": granted, "found": out}, nil
+}
+
+func (b *Bundle) readTool(args map[string]any) (any, error) {
+	if err := only(args, "account", "folder", "uid", "attachment"); err != nil {
+		return nil, err
+	}
+	account, _ := args["account"].(string)
+	folder, _ := args["folder"].(string)
+	attachment, _ := args["attachment"].(string)
+	uid, err := number(args, "uid", 0)
+	if err != nil {
+		return nil, err
+	}
+	if account == "" || folder == "" || uid <= 0 {
+		return nil, fmt.Errorf("%s needs an account, a folder and a uid", ReadTool)
+	}
+	_, grants, err := b.settings()
+	if err != nil {
+		return nil, err
+	}
+	caller := b.caller(args)
+	if !grants.Allows(caller, account) {
+		return nil, refused(caller, account)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+	st, err := b.Index(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("the index cannot be reached: %v", err)
+	}
+	m, ok, err := st.Get(ctx, account, folder, uint32(uid))
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, fmt.Errorf("the account %s holds no message %d in %s", account, uid, folder)
+	}
+	if attachment != "" {
+		var ref *AttachmentRef
+		for i := range m.Attachments {
+			if m.Attachments[i].Key == attachment {
+				ref = &m.Attachments[i]
+			}
+		}
+		if ref == nil {
+			return nil, fmt.Errorf("the message names no attachment %s", attachment)
+		}
+		if ref.Size > MostAttachment {
+			return nil, fmt.Errorf("the attachment %s is %d bytes, more than the %d this tool answers", ref.Name, ref.Size, MostAttachment)
+		}
+		o, err := b.Objects()
+		if err != nil {
+			return nil, err
+		}
+		data, err := o.Get(ctx, ref.Key)
+		if err != nil {
+			return nil, err
+		}
+		return map[string]any{"attachment": ref, "base64": base64.StdEncoding.EncodeToString(data)}, nil
+	}
+	out := metadata(m)
+	body := m.Body
+	if len(body) > MostBodyAnswered {
+		body = strings.ToValidUTF8(body[:MostBodyAnswered], "") + "\n[cut at 64 KiB]"
+	}
+	out["text"] = body
+	return out, nil
+}
+
+func refused(caller, account string) error {
+	return fmt.Errorf("refused: %s is not granted the mail account %s; the operator grants it through the setting grants", caller, account)
+}
+
+// ---- arguments ----------------------------------------------------------------------------------------------------
+
+// only refuses an argument the tool does not take: never ignored, and none can say who calls.
+func only(args map[string]any, takes ...string) error {
+	for k := range args {
+		if !contains(takes, k) {
+			return fmt.Errorf("the argument %q is not taken", k)
+		}
+	}
+	return nil
+}
+
+func number(args map[string]any, key string, otherwise int) (int, error) {
+	v, ok := args[key]
+	if !ok || v == nil {
+		return otherwise, nil
+	}
+	f, ok := v.(float64)
+	if !ok || f != float64(int(f)) {
+		return 0, errors.New(key + " is a whole number")
+	}
+	return int(f), nil
+}
+
+func text(d string) map[string]any    { return map[string]any{"type": "string", "description": d} }
+func integer(d string) map[string]any { return map[string]any{"type": "integer", "description": d} }
+
+func schema(required []string, props map[string]any) map[string]any {
+	s := map[string]any{"type": "object", "properties": props, "additionalProperties": false}
+	if len(required) > 0 {
+		s["required"] = required
+	}
+	return s
+}

modules/mesh-mail/cmd/mesh-mail/tools_test.go

@@ -0,0 +1,247 @@
+package main
+
+import (
+	"bufio"
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+func writeFile(t *testing.T, path, content string) {
+	t.Helper()
+	if err := os.WriteFile(path, []byte(content), 0o600); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// runtime plays the node's runtime against the bundle over its MCP channel, as the bundle is launched: it calls tools
+// naming who called in `_meta`, as the runtime does from the subject a call arrived on, and takes what the bundle
+// publishes.
+type runtime struct {
+	t         *testing.T
+	in        *io.PipeWriter
+	mu        sync.Mutex
+	next      int
+	answers   map[string]chan map[string]any
+	published []map[string]any
+	refuse    bool
+}
+
+func startBundle(t *testing.T, tools []stdio.Tool) *runtime {
+	t.Helper()
+	inR, inW := io.Pipe()
+	outR, outW := io.Pipe()
+	r := &runtime{t: t, in: inW, answers: map[string]chan map[string]any{}}
+	go func() { _ = stdio.ServeOn(Module, tools, inR, outW) }()
+	go func() {
+		sc := bufio.NewScanner(outR)
+		sc.Buffer(make([]byte, 1<<20), 1<<24)
+		for sc.Scan() {
+			var m map[string]any
+			if json.Unmarshal(sc.Bytes(), &m) != nil {
+				continue
+			}
+			id, _ := json.Marshal(m["id"])
+			if m["method"] == "mesh/publish" {
+				r.mu.Lock()
+				refuse := r.refuse
+				if !refuse {
+					r.published = append(r.published, m["params"].(map[string]any))
+				}
+				r.mu.Unlock()
+				reply := map[string]any{"id": m["id"], "result": map[string]any{}}
+				if refuse {
+					reply = map[string]any{"id": m["id"], "error": map[string]any{"code": -32000, "message": "the bus is away"}}
+				}
+				r.send(reply)
+				continue
+			}
+			r.mu.Lock()
+			ch := r.answers[string(id)]
+			r.mu.Unlock()
+			if ch != nil {
+				ch <- m
+			}
+		}
+	}()
+	t.Cleanup(func() { _ = inW.Close(); _ = outW.Close() })
+	// Answered once the bundle serves: from then on, what it emits goes through this runtime and no other.
+	r.mu.Lock()
+	ready := make(chan map[string]any, 1)
+	r.answers[`"init"`] = ready
+	r.mu.Unlock()
+	r.send(map[string]any{"jsonrpc": "2.0", "id": "init", "method": "initialize", "params": map[string]any{}})
+	select {
+	case <-ready:
+	case <-time.After(10 * time.Second):
+		t.Fatal("the bundle did not start")
+	}
+	return r
+}
+
+func (r *runtime) send(m map[string]any) {
+	raw, _ := json.Marshal(m)
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	_, _ = r.in.Write(append(raw, '\n'))
+}
+
+// call calls a tool as the caller, answering its text and whether it was an error.
+func (r *runtime) call(tool, caller string, args map[string]any) (string, bool) {
+	r.mu.Lock()
+	r.next++
+	id := r.next
+	ch := make(chan map[string]any, 1)
+	r.answers[fmt.Sprint(id)] = ch
+	r.mu.Unlock()
+	r.send(map[string]any{"jsonrpc": "2.0", "id": id, "method": "tools/call",
+		"params": map[string]any{"name": tool, "arguments": args, "_meta": map[string]any{stdio.MetaCaller: caller}}})
+	select {
+	case m := <-ch:
+		res := m["result"].(map[string]any)
+		text := res["content"].([]any)[0].(map[string]any)["text"].(string)
+		isErr, _ := res["isError"].(bool)
+		return text, isErr
+	case <-time.After(10 * time.Second):
+		r.t.Fatalf("%s did not answer", tool)
+	}
+	return "", true
+}
+
+// aBundle is the bundle over an index holding one message with an attachment, granted to the module triage alone.
+func aBundle(t *testing.T) (*Bundle, *memStore, *memObjects) {
+	t.Helper()
+	dir := t.TempDir()
+	env := Env{Accounts: filepath.Join(dir, "accounts.json"), Grants: filepath.Join(dir, "grants.json"), Secrets: dir,
+		Status: filepath.Join(dir, "health.json")}
+	writeFile(t, env.Accounts, stageOne)
+	writeFile(t, env.Grants, `{"grants": {"mesh": ["triage"]}}`)
+	st, objects := newMemStore(), newMemObjects()
+	ctx := context.Background()
+	ref, err := Keep(ctx, objects, []byte(attachmentData), "application/pdf", "invoice.pdf")
+	if err != nil {
+		t.Fatal(err)
+	}
+	m := Message{Account: "mesh", Folder: "INBOX", UID: 7, UIDValidity: 1, MessageID: "att@example.org", Subject: "the invoice",
+		Date: judgedAt, From: []Person{{Name: "Bob", Address: "bob@example.org"}}, To: []Person{{Address: "jschoubben@novox.be"}},
+		Flags: []string{}, Attachments: []AttachmentRef{ref}, Body: "Please find the invoice attached."}
+	if err := st.Add(ctx, m, addedEvent(m)); err != nil {
+		t.Fatal(err)
+	}
+	_ = st.SetState(ctx, AccountState{Account: "mesh", State: AccountCurrent, Why: "watching", Heard: judgedAt, Said: judgedAt})
+	b := &Bundle{Env: env, Index: func(context.Context) (Store, error) { return st, nil },
+		Objects: func() (Objects, error) { return objects, nil }, Now: func() time.Time { return judgedAt }}
+	return b, st, objects
+}
+
+// The body tools answer a granted caller and refuse every other (ADR 0359 §4, "How it is checked"): the caller is the
+// runtime's word, never an argument.
+func TestTheBodyToolsAnswerAGrantedCallerAndRefuseAnyOther(t *testing.T) {
+	b, _, _ := aBundle(t)
+	rt := startBundle(t, b.Tools())
+	read := map[string]any{"account": "mesh", "folder": "INBOX", "uid": 7}
+
+	text, isErr := rt.call(ReadTool, "novox.triage", read)
+	if isErr || !strings.Contains(text, "Please find the invoice attached.") || !strings.Contains(text, `"subject":"the invoice"`) {
+		t.Fatalf("granted: %v %s", isErr, text)
+	}
+	for _, caller := range []string{"novox.other", "person.someone", Unproven} {
+		text, isErr := rt.call(ReadTool, caller, read)
+		if !isErr || !strings.Contains(text, "refused") || strings.Contains(text, "Please find") {
+			t.Fatalf("%s: %v %s", caller, isErr, text)
+		}
+		text, isErr = rt.call(SearchTool, caller, map[string]any{"query": "invoice"})
+		if !isErr || !strings.Contains(text, "refused") {
+			t.Fatalf("%s searched: %v %s", caller, isErr, text)
+		}
+	}
+	// An argument cannot name the caller.
+	if text, isErr := rt.call(ReadTool, "novox.other", map[string]any{"account": "mesh", "folder": "INBOX", "uid": 7, "caller": "novox.triage"}); !isErr || strings.Contains(text, "Please find") {
+		t.Fatalf("an argument named the caller: %s", text)
+	}
+
+	text, isErr = rt.call(SearchTool, "shanks.triage", map[string]any{"query": "invoice"})
+	if isErr || !strings.Contains(text, `"message-id":"att@example.org"`) || strings.Contains(text, "Please find") {
+		t.Fatalf("search: %v %s", isErr, text)
+	}
+
+	sum := ""
+	if m, _ := b.Index(context.Background()); m != nil {
+		got, _, _ := m.Get(context.Background(), "mesh", "INBOX", 7)
+		sum = got.Attachments[0].Key
+	}
+	text, isErr = rt.call(ReadTool, "novox.triage", map[string]any{"account": "mesh", "folder": "INBOX", "uid": 7, "attachment": sum})
+	var att struct {
+		Base64 string `json:"base64"`
+	}
+	if isErr || json.Unmarshal([]byte(text), &att) != nil {
+		t.Fatalf("attachment: %v %s", isErr, text)
+	}
+	if data, _ := base64.StdEncoding.DecodeString(att.Base64); string(data) != attachmentData {
+		t.Fatalf("the attachment read is %q", data)
+	}
+}
+
+// mail_accounts says each account's state to anyone, and its address only to a caller granted it.
+func TestTheAccountsToolSaysTheAddressOnlyToAGrantedCaller(t *testing.T) {
+	b, _, _ := aBundle(t)
+	rt := startBundle(t, b.Tools())
+	text, isErr := rt.call(AccountsTool, "novox.other", map[string]any{})
+	if isErr || !strings.Contains(text, `"state":"current"`) || strings.Contains(text, "jschoubben@") || !strings.Contains(text, `"granted":false`) {
+		t.Fatalf("ungranted: %s", text)
+	}
+	text, _ = rt.call(AccountsTool, "novox.triage", map[string]any{})
+	if !strings.Contains(text, `"address":"jschoubben@novox.be"`) || !strings.Contains(text, `"granted":true`) {
+		t.Fatalf("granted: %s", text)
+	}
+}
+
+// The events the keeper wrote are said on the bus as the module, through the runtime, with their metadata and never a
+// body; each is removed once the bus took it, and kept when it did not.
+func TestTheEventsAreSaidOnTheBusThroughTheRuntime(t *testing.T) {
+	b, st, _ := aBundle(t)
+	rt := startBundle(t, b.Tools())
+	p := &Publisher{Index: b.Index, Emit: func(key string, body any) error { return stdio.Emit(key, body) }, Logf: t.Logf}
+	ctx := context.Background()
+
+	rt.mu.Lock()
+	rt.refuse = true
+	rt.mu.Unlock()
+	if n, err := p.Once(ctx); n != 0 || err == nil {
+		t.Fatalf("said %d with the bus away (%v)", n, err)
+	}
+	if left, _ := st.Pending(ctx, 10); len(left) != 1 {
+		t.Fatalf("an event the bus did not take was dropped: %d left", len(left))
+	}
+
+	rt.mu.Lock()
+	rt.refuse = false
+	rt.mu.Unlock()
+	if n, err := p.Once(ctx); n != 1 || err != nil {
+		t.Fatalf("said %d (%v)", n, err)
+	}
+	if left, _ := st.Pending(ctx, 10); len(left) != 0 {
+		t.Fatalf("%d event(s) left after the bus took them", len(left))
+	}
+	rt.mu.Lock()
+	defer rt.mu.Unlock()
+	if len(rt.published) != 1 {
+		t.Fatalf("published %d", len(rt.published))
+	}
+	pub := rt.published[0]
+	raw, _ := json.Marshal(pub)
+	if pub["key"] != "mail.mesh.message.added" || !strings.Contains(string(raw), `"subject":"the invoice"`) ||
+		strings.Contains(string(raw), "Please find") || strings.Contains(string(raw), "dGhlIGludm9pY2Ug") {
+		t.Fatalf("published %s", raw)
+	}
+}

modules/mesh-mail/go.mod

@@ -0,0 +1,19 @@
+module mesh-mail
+
+go 1.25.0
+
+require (
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261013182924-5933eb757d44
+	github.com/emersion/go-imap/v2 v2.0.0-beta.8
+	github.com/emersion/go-message v0.18.2
+	github.com/jackc/pgx/v5 v5.11.0
+)
+
+require (
+	github.com/emersion/go-sasl v0.0.0-20241020182733-b788ff22d5a6 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
+	github.com/jackc/puddle/v2 v2.2.2 // indirect
+	golang.org/x/sync v0.17.0 // indirect
+	golang.org/x/text v0.29.0 // indirect
+)

modules/mesh-mail/go.sum

@@ -0,0 +1,65 @@
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261013182924-5933eb757d44 h1:r5xIo5qWOXQdCSMxvqJy8kV4U+P/QWXFK6971Ha6wU8=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261013182924-5933eb757d44/go.mod h1:GFuZUElBZ9A++mxgIKo97aXXo+kV0uJ/UkbhQPPIbrY=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/emersion/go-imap/v2 v2.0.0-beta.8 h1:5IXZK1E33DyeP526320J3RS7eFlCYGFgtbrfapqDPug=
+github.com/emersion/go-imap/v2 v2.0.0-beta.8/go.mod h1:dhoFe2Q0PwLrMD7oZw8ODuaD0vLYPe5uj2wcOMnvh48=
+github.com/emersion/go-message v0.18.2 h1:rl55SQdjd9oJcIoQNhubD2Acs1E6IzlZISRTK7x/Lpg=
+github.com/emersion/go-message v0.18.2/go.mod h1:XpJyL70LwRvq2a8rVbHXikPgKj8+aI0kGdHlg16ibYA=
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+github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
+github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
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+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

modules/mesh-mail/module.json

@@ -0,0 +1,189 @@
+{
+  "module": "mesh-mail",
+  "version": "1",
+  "slug": "mail",
+  "requires": [
+    "postgres-database",
+    "s3-bucket"
+  ],
+  "contributes": {
+    "postgres-database": {
+      "name": "mail"
+    }
+  },
+  "binds": {
+    "postgres-database": "${dir:state}/database.json",
+    "s3-bucket": "${dir:state}/store-binding.json"
+  },
+  "secrets": {
+    "postgres-database": "${dir:state}/database.secret",
+    "s3-bucket": "${dir:state}/store.secret"
+  },
+  "own-secrets": {
+    "mail-credential-*": {
+      "path": "${dir:state}/mail-credential-*.secret",
+      "issued-by": "outside"
+    }
+  },
+  "tools": [
+    "mail_accounts",
+    "mail_search",
+    "mail_read",
+    "mail_health"
+  ],
+  "streams": [
+    {
+      "name": "mail",
+      "events": [
+        "mail.*.message.added",
+        "mail.*.message.changed",
+        "mail.*.message.removed"
+      ],
+      "max-age-days": 7,
+      "grant": {
+        "config": "grants",
+        "events": "mail.{key}.**"
+      }
+    }
+  ],
+  "resources": [
+    {
+      "id": "state",
+      "type": "directory",
+      "mode": "0700",
+      "place": "."
+    },
+    {
+      "id": "database-url",
+      "type": "file",
+      "path": "${dir:state}/database.url",
+      "mode": "0600",
+      "content": "postgresql://${bound:postgres-database:as}:${secret:postgres-database}@${bound:postgres-database:at}:${bound:postgres-database:port}/${bound:postgres-database:as}\n"
+    },
+    {
+      "id": "store",
+      "type": "file",
+      "path": "${dir:state}/store.json",
+      "mode": "0600",
+      "content": "{\n  \"scheme\": \"${bound:s3-bucket:scheme}\",\n  \"at\": \"${bound:s3-bucket:at}\",\n  \"port\": \"${bound:s3-bucket:port}\",\n  \"bucket\": \"${bound:s3-bucket:bucket}\",\n  \"region\": \"${bound:s3-bucket:region}\",\n  \"key\": \"${bound:s3-bucket:as}\",\n  \"secret\": \"${secret:s3-bucket}\"\n}\n"
+    },
+    {
+      "id": "accounts",
+      "trusted": true,
+      "type": "file",
+      "path": "${dir:state}/accounts.json",
+      "mode": "0600",
+      "merge": "json",
+      "takes-settings": [
+        "accounts"
+      ],
+      "content": "{\n  \"accounts\": {}\n}\n"
+    },
+    {
+      "id": "grants",
+      "trusted": true,
+      "type": "file",
+      "path": "${dir:state}/grants.json",
+      "mode": "0600",
+      "merge": "json",
+      "takes-settings": [
+        "grants"
+      ],
+      "content": "{\n  \"grants\": {}\n}\n"
+    },
+    {
+      "id": "prepare",
+      "type": "process",
+      "name": "mesh-mail-prepare",
+      "artifact": "tools",
+      "run": [
+        "./mesh-mail",
+        "prepare"
+      ],
+      "run-once": true,
+      "env": {
+        "DATABASE_URL_FILE": "${dir:state}/database.url"
+      },
+      "restart-on": [
+        "database-url"
+      ]
+    },
+    {
+      "id": "keep",
+      "type": "process",
+      "name": "mesh-mail-keep",
+      "artifact": "tools",
+      "run": [
+        "./mesh-mail",
+        "keep"
+      ],
+      "env": {
+        "DATABASE_URL_FILE": "${dir:state}/database.url",
+        "MESH_MAIL_ACCOUNTS": "${dir:state}/accounts.json",
+        "MESH_MAIL_SECRETS": "${dir:state}",
+        "MESH_MAIL_STORE": "${dir:state}/store.json"
+      },
+      "restart-on": [
+        "database-url",
+        "store",
+        "accounts"
+      ],
+      "health": {
+        "kind": "unit"
+      }
+    },
+    {
+      "id": "watch",
+      "type": "process",
+      "name": "mesh-mail-watch",
+      "artifact": "tools",
+      "run": [
+        "./mesh-mail",
+        "watch"
+      ],
+      "user": "${machine:account}",
+      "env": {
+        "DATABASE_URL_FILE": "${dir:state}/database.url",
+        "MESH_MAIL_ACCOUNTS": "${dir:state}/accounts.json",
+        "MESH_MAIL_SECRETS": "${dir:state}",
+        "MESH_MAIL_STATUS": "${dir:state}/health.json"
+      },
+      "restart-on": [
+        "database-url",
+        "accounts"
+      ],
+      "health": {
+        "kind": "tool",
+        "tool": "mail_health",
+        "needs": "postgres-database",
+        "interval": "60s",
+        "timeout": "10s",
+        "looks": 2,
+        "grace": "180s"
+      }
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "tools",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/mesh-mail",
+        "binary": "mesh-mail",
+        "loads": [
+          "mesh-mail"
+        ],
+        "env": {
+          "DATABASE_URL_FILE": "${dir:state}/database.url",
+          "MESH_MAIL_ACCOUNTS": "${dir:state}/accounts.json",
+          "MESH_MAIL_GRANTS": "${dir:state}/grants.json",
+          "MESH_MAIL_SECRETS": "${dir:state}",
+          "MESH_MAIL_STORE": "${dir:state}/store.json",
+          "MESH_MAIL_STATUS": "${dir:state}/health.json"
+        }
+      }
+    ]
+  }
+}