Carry the power draw to the bar over the bus, not through a file (hq ADR 0260)

Modules talk over the bus. The power module's bundle puts each fresh reading of its own
sampler in its state draw, keyed by the machine; the bar's block shows that state, which
the bar's bundle watches under the read the mesh grants it. A new catalogue check refuses
a module naming another module's path under /run or /var/lib.

modules/i3status-rust/cmd/i3status-rust-tools/blocks_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 	"text/template"
@@ -33,7 +34,7 @@ func blockTemplate(t *testing.T) *template.Template {
 
 func render(t *testing.T, tmpl *template.Template, piece string) string {
 	t.Helper()
-	view := map[string]any{"module": "power"}
+	view := map[string]any{"module": "power", "machine": "laptop"}
 	if err := json.Unmarshal([]byte(piece), &view); err != nil {
 		t.Fatal(err)
 	}
@@ -96,3 +97,24 @@ func TestTheMemoryIsWhatProgramsHoldNotTheCache(t *testing.T) {
 		t.Fatal("the memory block counts the cache as used")
 	}
 }
+
+func TestAContributedStateIsACustomBlockReadingThisMachinesValue(t *testing.T) {
+	tmpl := blockTemplate(t)
+	got := render(t, tmpl, `{"bar":"bottom","place":"status","shows":"state","options":{"state":"power.draw"}}`)
+	want := "[[block]]\nblock = \"custom\"\ncommand = \"~/.local/bin/i3status-value power.draw laptop\"\ninterval = 5\nhide_when_empty = true\n\n"
+	if got != want {
+		t.Fatalf("%q, want %q", got, want)
+	}
+	got = render(t, tmpl, `{"bar":"bottom","place":"status","shows":"state","options":{"state":"power.draw","key":"desk"}}`)
+	if !strings.Contains(got, "i3status-value power.draw desk") {
+		t.Fatalf("%q", got)
+	}
+	// And the bundle finds what it rendered.
+	f := filepath.Join(t.TempDir(), "bottom-bar.toml")
+	if err := os.WriteFile(f, []byte(got), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if w := wantedIn([]string{f}); len(w) != 1 || w[0] != (Wanted{"power.draw", "desk"}) {
+		t.Fatalf("%v", w)
+	}
+}

modules/i3status-rust/cmd/i3status-rust-tools/main.go

@@ -11,6 +11,8 @@ import (
 )
 
 func main() {
+	// The values other modules keep on the bus for their blocks (novox/hq ADR 0260).
+	go FollowValues()
 	if err := stdio.Serve("", tools()); err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)

modules/i3status-rust/cmd/i3status-rust-tools/manifest_test.go

@@ -33,6 +33,7 @@ func TestItOwnsItsFilesAsWrittenInTheModule(t *testing.T) {
 	for id, src := range map[string]string{
 		"top-bar": "files/top-bar.toml", "bottom-bar": "files/bottom-bar.toml", "icons": "files/icons/custom-icons.toml",
 		"updates": "files/bin/i3status-updates", "watchdog": "files/bin/i3bar-watchdog",
+		"value": "files/bin/i3status-value",
 	} {
 		m.sameAsSource(t, id, src)
 	}

modules/i3status-rust/cmd/i3status-rust-tools/values.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strconv"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// The values other modules keep on the bus for a block they contributed (novox/hq ADR 0260).
+//
+// A block that `shows` a state is rendered as a custom block running `i3status-value <state> <key>`.
+// i3status-rs cannot reach the bus, and this bundle can: the node's runtime launched it, and the mesh
+// granted this module a read of every state the modules on its machine offer the bar. So it watches each
+// state its bars name and leaves the value's text in this module's own directory, where the block's
+// command reads it. No file of another module is read, and nothing but the bus passes between them.
+
+// valueCall is how a bar names a value: the command the template renders.
+var valueCall = regexp.MustCompile(`i3status-value ([a-z0-9][a-z0-9-]*\.[a-z0-9][a-z0-9-]*) ([^\s"]+)`)
+
+// Wanted is one state and key a bar shows.
+type Wanted struct{ State, Key string }
+
+func (w Wanted) file() string { return w.State + "@" + w.Key }
+
+// wantedIn is every value the bars' files name, each once, in order.
+func wantedIn(files []string) []Wanted {
+	seen := map[Wanted]bool{}
+	for _, f := range files {
+		raw, err := os.ReadFile(f)
+		if err != nil {
+			continue
+		}
+		for _, m := range valueCall.FindAllStringSubmatch(string(raw), -1) {
+			seen[Wanted{State: m[1], Key: m[2]}] = true
+		}
+	}
+	out := make([]Wanted, 0, len(seen))
+	for w := range seen {
+		out = append(out, w)
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].file() < out[j].file() })
+	return out
+}
+
+// valuesDir is where the values are left: the account's runtime directory, gone at logout.
+func valuesDir() string {
+	return filepath.Join(runUserDir, strconv.Itoa(os.Getuid()), "i3status-rust", "values")
+}
+
+// keep writes one change of a value to its file: the value's `text`, or no file once it is deleted.
+func keep(dir string, w Wanted, c stdio.StateChange) error {
+	path := filepath.Join(dir, w.file())
+	if c.Op == "delete" || c.Op == "purge" {
+		if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
+			return err
+		}
+		return nil
+	}
+	var v struct {
+		Text string `json:"text"`
+	}
+	if err := json.Unmarshal(c.Value, &v); err != nil {
+		return fmt.Errorf("%s's value for %s has no text: %w", w.State, w.Key, err)
+	}
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		return err
+	}
+	tmp := path + ".new"
+	if err := os.WriteFile(tmp, []byte(v.Text+"\n"), 0o600); err != nil {
+		return err
+	}
+	return os.Rename(tmp, path)
+}
+
+// Watcher is a function that watches one key of one state; the SDK's in the bundle, a fake in a test.
+type Watcher func(state, key string, handle func(stdio.StateChange) error) error
+
+// followValues watches every value the bars name, starting the ones not yet watched each time it is
+// called; one the runtime refuses — a read not granted yet — is tried again the next time.
+func followValues(files []string, dir string, watching map[Wanted]bool, watch Watcher) []string {
+	var said []string
+	for _, w := range wantedIn(files) {
+		if watching[w] {
+			continue
+		}
+		w := w
+		err := watch(w.State, w.Key, func(c stdio.StateChange) error { return keep(dir, w, c) })
+		if err != nil {
+			said = append(said, fmt.Sprintf("cannot watch %s %s: %v", w.State, w.Key, err))
+			continue
+		}
+		watching[w] = true
+	}
+	return said
+}
+
+// FollowValues runs followValues every half minute for as long as the bundle runs, so a block a push
+// adds is followed without a restart.
+func FollowValues() {
+	watching := map[Wanted]bool{}
+	watch := func(state, key string, handle func(stdio.StateChange) error) error {
+		return stdio.State(state).Watch(key, handle)
+	}
+	for {
+		files, _ := filepath.Glob(filepath.Join(configDir(), "*.toml"))
+		for _, s := range followValues(files, valuesDir(), watching, watch) {
+			fmt.Fprintln(os.Stderr, "i3status-rust:", s)
+		}
+		time.Sleep(30 * time.Second)
+	}
+}

modules/i3status-rust/cmd/i3status-rust-tools/values_test.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"errors"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// Defends novox/hq ADR 0260: a value another module keeps reaches the bar over the bus, through this
+// module's own bundle and directory, and an old one is not shown as if it were now.
+
+func TestAValueIsKeptAsItsTextAndGoneWhenDeleted(t *testing.T) {
+	dir := t.TempDir()
+	w := Wanted{"power.draw", "laptop"}
+	if err := keep(dir, w, stdio.StateChange{Op: "put", Value: []byte(`{"text":"18.2 W machine","watts":18.2}`)}); err != nil {
+		t.Fatal(err)
+	}
+	b, err := os.ReadFile(filepath.Join(dir, "power.draw@laptop"))
+	if err != nil || string(b) != "18.2 W machine\n" {
+		t.Fatalf("%q %v", b, err)
+	}
+	if err := keep(dir, w, stdio.StateChange{Op: "delete"}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(filepath.Join(dir, "power.draw@laptop")); !os.IsNotExist(err) {
+		t.Fatal("a deleted value is still shown")
+	}
+	if err := keep(dir, w, stdio.StateChange{Op: "put", Value: []byte(`"no text"`)}); err == nil {
+		t.Fatal("a value with no text was kept")
+	}
+}
+
+func TestARefusedWatchIsTriedAgainAndAWatchedOneIsNot(t *testing.T) {
+	bar := filepath.Join(t.TempDir(), "bottom-bar.toml")
+	if err := os.WriteFile(bar, []byte(`command = "~/.local/bin/i3status-value power.draw laptop"`+"\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	watching := map[Wanted]bool{}
+	calls := 0
+	refuse := func(string, string, func(stdio.StateChange) error) error { calls++; return errors.New("not granted") }
+	if said := followValues([]string{bar}, t.TempDir(), watching, refuse); len(said) != 1 || !strings.Contains(said[0], "not granted") {
+		t.Fatalf("%v", said)
+	}
+	accept := func(state, key string, _ func(stdio.StateChange) error) error {
+		calls++
+		if state != "power.draw" || key != "laptop" {
+			t.Fatalf("watched %s %s", state, key)
+		}
+		return nil
+	}
+	followValues([]string{bar}, t.TempDir(), watching, accept)
+	followValues([]string{bar}, t.TempDir(), watching, accept)
+	if calls != 2 {
+		t.Fatalf("%d watches; once refused, once taken, then left alone", calls)
+	}
+}
+
+func TestTheBlocksCommandShowsOnlyAFreshValue(t *testing.T) {
+	runtime := t.TempDir()
+	dir := filepath.Join(runtime, "i3status-rust", "values")
+	run := func() string {
+		cmd := exec.Command("sh", "../../files/bin/i3status-value", "power.draw", "laptop")
+		cmd.Env = append(os.Environ(), "XDG_RUNTIME_DIR="+runtime)
+		out, err := cmd.Output()
+		if err != nil {
+			t.Fatal(err)
+		}
+		return strings.TrimSpace(string(out))
+	}
+	if got := run(); got != "" {
+		t.Fatalf("no value: %q", got)
+	}
+	if err := keep(dir, Wanted{"power.draw", "laptop"}, stdio.StateChange{Op: "put", Value: []byte(`{"text":"8.0 W CPU"}`)}); err != nil {
+		t.Fatal(err)
+	}
+	if got := run(); got != "8.0 W CPU" {
+		t.Fatalf("fresh: %q", got)
+	}
+	old := time.Now().Add(-31 * time.Second)
+	if err := os.Chtimes(filepath.Join(dir, "power.draw@laptop"), old, old); err != nil {
+		t.Fatal(err)
+	}
+	if got := run(); got != "" {
+		t.Fatalf("31 s old: %q", got)
+	}
+}