package catalogue

import (
	"fmt"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
)

// Every module is given an identity of its own, and a container that declares `identity` runs as it (novox/hq ADR
// 0325 §2, §3, §11).
//
// **The manifest says how its image is told who to run as, and nothing else.** A container resource may declare
// `identity`: `{"user": "env:PUID", "group": "env:PGID"}` for an image that reads its user and group from its
// environment, or `{"user": "run"}` for the container runtime's own user option. It is the image's interface, as its
// ports are. The mesh fills it in: the controller allocates the module one user and group number, mesh-wide, once,
// from a range of its own (IdentityLow–IdentityHigh), and the node-engine makes the account `mesh-<module>` on each
// machine the module is assigned to and tells the image those numbers.
//
// **The range is 50000–59999, and a module's user and group numbers are one number.** Chosen above the numbers
// distributions give people (1000 up) and below the 60000s Debian keeps for its own daemons, and far from root's 0
// and every root group a distribution ships (0, adm's 4, wheel's 10): no number in it is 0 or a root group's, so §11
// holds by the range alone, and the store refuses a row outside it. Both numbers come from one sequence, so a
// module's uid and gid are equal; a number once given is never given again, even after the module is forgotten
// (the store keeps the row, inventory.AllocateIdentity).
//
// **What the controller sends, and only to an engine that reads it** (Rendering.KeepsFolders: its statement's
// contract is link.IdentityContract or later):
//
//   - the declaration's `identities`: [{module, name, uid, gid}] for each module of the machine that declares
//     `identity` on a container;
//   - a container's `identity` resolved: {"mode": "env", "user_env", "group_env", "uid", "gid"} or {"mode": "run",
//     "uid", "gid"};
//   - the owner of each of the module's directories a container declaring `identity` mounts: the identity's
//     uid:gid (§3). A directory only a process or the tools write keeps the owner it had: what writes it is not the
//     identity, and owning it by the identity would lock its writer out;
//   - an access's `users`: the module's identity where a container of it that declares `identity` mounts the
//     access, and the tool runner's account where the module's tools run there and the account's number is known,
//     each at the access's use — the node-engine keeps one entry per user on a folder at the widest use any access
//     to it gives (§4, §5), so the runner's entry is the widest of the modules whose tools use it; and `taken`,
//     whether the operator let the mesh keep that folder on that machine (§8).
//
// To an older engine none of it is sent, and a container's `identity` is taken out: it runs as its image says, as
// before. A module that declares no `identity` is composed exactly as before, on any engine.

// The range module identities are allocated from (novox/hq ADR 0325 §3, §11). The store holds the same bounds.
const (
	IdentityLow  = 50000
	IdentityHigh = 59999
)

// AllocatableID says whether n is a number the mesh may give a module's identity: inside the range, so never 0
// nor a root group's.
func AllocatableID(n int) bool { return n >= IdentityLow && n <= IdentityHigh }

// IdentityField is a container resource's field saying how its image is told who to run as.
const IdentityField = "identity"

// The two ways an image is told who to run as.
const (
	IdentityEnv = "env"
	IdentityRun = "run"
)

// IdentitySpec is a container's `identity` as its manifest declares it.
type IdentitySpec struct {
	// Mode is IdentityEnv or IdentityRun.
	Mode string
	// UserEnv and GroupEnv are the environment variables an env image reads, such as PUID and PGID.
	UserEnv, GroupEnv string
}

// ModuleIdentity is one module's allocated identity: its numbers, the same on every machine.
type ModuleIdentity struct {
	Module string
	UID    int
	GID    int
}

// IdentityName is the account a module's identity is on every machine it is assigned to.
func IdentityName(module string) string { return "mesh-" + module }

// Where an access's user comes from (novox/hq ADR 0325 §4, §5).
const (
	FromContainer  = "container"
	FromToolRunner = "tool-runner"
)

// AccessUser is one identity that uses a shared folder, as an access's `users` names it (mesh-host internal/declaration
// AccessUser): the account, its user number, the use, and where it runs. The node-engine refuses a user with no
// number, so the tool runner's account is named only where its number is known (Rendering.AccountUIDs).
type AccessUser struct {
	Identity string `json:"identity"`
	UID      int    `json:"uid"`
	Use      string `json:"use"`
	From     string `json:"from"`
}

var envName = regexp.MustCompile(`^[A-Z_][A-Z0-9_]*$`)

// ParseIdentity reads a container's `identity`, or refuses it in words.
func ParseIdentity(v any) (IdentitySpec, error) {
	fields, ok := v.(map[string]any)
	if !ok {
		return IdentitySpec{}, fmt.Errorf("identity is {\"user\": \"env:<NAME>\", \"group\": \"env:<NAME>\"} or " +
			"{\"user\": \"run\"}")
	}
	for k := range fields {
		if k != "user" && k != "group" {
			return IdentitySpec{}, fmt.Errorf("identity says %q, and it says only how the image is told its user "+
				"and group: \"user\" and \"group\", never an owner or a number (%s §1, §2)", k, ADR0325)
		}
	}
	user, _ := fields["user"].(string)
	group, hasGroup := fields["group"]
	switch {
	case user == IdentityRun:
		if hasGroup {
			return IdentitySpec{}, fmt.Errorf("identity {\"user\": \"run\"} takes no group: the runtime's user " +
				"option carries both numbers")
		}
		return IdentitySpec{Mode: IdentityRun}, nil
	case strings.HasPrefix(user, "env:"):
		g, _ := group.(string)
		if !strings.HasPrefix(g, "env:") {
			return IdentitySpec{}, fmt.Errorf("identity names its user as %q and its group as %v; an image told "+
				"its user by its environment is told its group the same way, \"env:<NAME>\"", user, group)
		}
		u, gr := strings.TrimPrefix(user, "env:"), strings.TrimPrefix(g, "env:")
		if !envName.MatchString(u) || !envName.MatchString(gr) || u == gr {
			return IdentitySpec{}, fmt.Errorf("identity names the variables %q and %q; each is an environment "+
				"variable's name, upper-case letters, digits and underscores, and the two differ", u, gr)
		}
		return IdentitySpec{Mode: IdentityEnv, UserEnv: u, GroupEnv: gr}, nil
	}
	return IdentitySpec{}, fmt.Errorf("identity says its user is %q; it is \"env:<NAME>\" or \"run\"", user)
}

// DeclaresIdentity says a module has a container that declares `identity`: it is given one (§3).
func DeclaresIdentity(m Manifest) bool {
	for _, r := range m.Resources {
		if fmt.Sprint(r["type"]) == "container" {
			if _, has := r[IdentityField]; has {
				return true
			}
		}
	}
	return false
}

// containerMounts is what a container of the manifest mounts, read from its volumes as written: the module's own
// directories by id, and its accesses by id — or, for a literal source, as "path:<path>".
func containerMounts(r map[string]any) (dirs, accesses []string) {
	volumes, _ := r["volumes"].([]any)
	for _, v := range volumes {
		s, _ := v.(string)
		source := volumeSource(s)
		if strings.HasPrefix(source, "/") {
			accesses = append(accesses, "path:"+filepath.Clean(source))
			continue
		}
		for _, m := range dirRef.FindAllStringSubmatch(source, -1) {
			dirs = append(dirs, m[1])
		}
		for _, m := range accessRef.FindAllStringSubmatch(source, -1) {
			accesses = append(accesses, m[1])
		}
	}
	return dirs, accesses
}

// volumeSource is a volume's source as written: up to its first colon outside a ${…} placeholder, so
// "${dir:config}:/config" is "${dir:config}".
func volumeSource(v string) string {
	depth := 0
	for i, r := range v {
		switch {
		case r == '{' && i > 0 && v[i-1] == '$':
			depth++
		case r == '}' && depth > 0:
			depth--
		case r == ':' && depth == 0:
			return v[:i]
		}
	}
	return v
}

// accessMode is the mode an access a container mounts was declared at, by id or by "path:<path>"; "" when the
// manifest declares no such access.
func accessMode(m Manifest, ref string) string {
	for _, a := range m.Accesses {
		if (a.ID != "" && a.ID == ref) || (a.Path != "" && ref == "path:"+filepath.Clean(a.Path)) {
			return a.At()
		}
	}
	return ""
}

// ADR0325 is how the module check names the decision its identity rules come from.
const ADR0325 = "novox/hq ADR 0325"

// identityProblems is what the module check refuses of a manifest's identities (novox/hq ADR 0325 §1, §2, §3):
//
//   - an `identity` on anything but a container, or one that is neither env:<NAME> for both nor run;
//   - **in a module that declares `identity` on a container** — it says it runs as its own identity, so it is held
//     to the decision whole: a directory of it naming an owner (§1, §3), and a container of it that declares none
//     and mounts one of the module's directories or a read-write access (§2).
//
// A module that declares no `identity` is warned of the last two (IdentityWarnings), never refused for them yet:
// every registered container module mounts its own directories without one, and refusing them would stop the
// catalogues composing before they can migrate. **This is the narrowest rule that breaks nothing registered**: no
// registered manifest declares `identity`, so no registered module is refused anything new.
func identityProblems(m Manifest) []string {
	var problems []string
	for _, r := range m.Resources {
		v, has := r[IdentityField]
		if !has {
			continue
		}
		if fmt.Sprint(r["type"]) != "container" {
			problems = append(problems, fmt.Sprintf("%s: %v is a %v and says identity; only a container says how its "+
				"image is told who to run as (%s §2)", m.Module, r["id"], r["type"], ADR0325))
			continue
		}
		if _, err := ParseIdentity(v); err != nil {
			problems = append(problems, fmt.Sprintf("%s: the container %v: %v (%s §2)", m.Module, r["id"], err, ADR0325))
		}
	}
	if !DeclaresIdentity(m) {
		return problems
	}
	return append(problems, identityRules(m)...)
}

// IdentityWarnings is what the module check warns of a module that declares no `identity` (novox/hq ADR 0325): each
// thing the decision refuses once the module migrates, said now so the catalogues can. Refusing comes when no
// registered module still does any of it. Empty for a module that declares `identity`: it is refused these instead.
func IdentityWarnings(m Manifest) []string {
	if DeclaresIdentity(m) {
		return nil
	}
	var out []string
	for _, p := range identityRules(m) {
		out = append(out, p+"; accepted while registered modules still do it, refused once they have moved")
	}
	return out
}

// identityRules is every place a manifest breaks what ADR 0325 §1–§3 refuse: a directory naming an owner, and a
// container declaring no identity that mounts the module's own directory or a read-write access.
func identityRules(m Manifest) []string {
	var out []string
	for _, r := range m.Resources {
		switch fmt.Sprint(r["type"]) {
		case "directory":
			if owner, said := r["owner"]; said {
				out = append(out, fmt.Sprintf("%s: the directory %v names its owner %v; a directory a module owns is "+
					"owned by the module's identity, and no manifest names an owner (%s §1, §3)", m.Module, r["id"],
					owner, ADR0325))
			}
		case "container":
			if _, has := r[IdentityField]; has {
				continue
			}
			dirs, accesses := containerMounts(r)
			seen := map[string]bool{}
			for _, d := range dirs {
				if !seen[d] {
					seen[d] = true
					out = append(out, fmt.Sprintf("%s: the container %v declares no identity and mounts the module's "+
						"own directory %s; only a container that declares identity mounts its module's directories, "+
						"so what writes them is the module's identity (%s §2)", m.Module, r["id"], d, ADR0325))
				}
			}
			for _, a := range accesses {
				if accessMode(m, a) == AccessReadWrite && !seen["access:"+a] {
					seen["access:"+a] = true
					out = append(out, fmt.Sprintf("%s: the container %v declares no identity and mounts the read-write "+
						"access %s; a container that runs as its image says is given no entry on a shared folder, so "+
						"it is refused write (%s §2)", m.Module, r["id"], strings.TrimPrefix(a, "path:"), ADR0325))
				}
			}
		}
	}
	return out
}

// PlacesOwnerProblem refuses an owner a `places` setting names for a module that declares `identity` (novox/hq ADR
// 0325 §1, §3): its directories are owned by its identity. Nil for a module that declares none, whose placed owner
// is still applied, and warned of by PlacesOwnerWarnings.
func PlacesOwnerProblem(m Manifest, layers []Layer) error {
	if !DeclaresIdentity(m) {
		return nil
	}
	if owned := placedOwners(m, layers); len(owned) > 0 {
		return fmt.Errorf("%s places %s with an owner, and declares identity: its directories are owned by its "+
			"identity, and no setting names an owner (%s §1, §3)", m.Module, strings.Join(owned, ", "), ADR0325)
	}
	return nil
}

// PlacesOwnerWarnings is a warning for each directory a `places` setting gives an owner, for a module that declares
// no `identity` (novox/hq ADR 0325 §1): accepted while registered modules still do it, refused once they have moved.
func PlacesOwnerWarnings(m Manifest, layers []Layer) []string {
	if DeclaresIdentity(m) {
		return nil
	}
	var out []string
	for _, id := range placedOwners(m, layers) {
		out = append(out, fmt.Sprintf("warning: %s's setting places.%s.owner names an owner; a directory a module owns "+
			"is owned by the module's identity, and no setting names an owner (%s §1, §3). Accepted while "+
			"registered modules still do it, refused once they have moved", m.Module, id, ADR0325))
	}
	return out
}

func placedOwners(m Manifest, layers []Layer) []string {
	placed, err := Places(m, layers)
	if err != nil {
		// empty-on-error: a placement Places refuses is refused by name where it is judged and composed; it names no owner here
		return nil
	}
	var out []string
	for id, p := range placed {
		if p.Owner != "" {
			out = append(out, id)
		}
	}
	sort.Strings(out)
	return out
}

// resolvedIdentity is a container's `identity` as the node-engine is told it: the mode, the variables an env image
// reads, and the module's numbers.
func resolvedIdentity(spec IdentitySpec, id ModuleIdentity) map[string]any {
	out := map[string]any{"mode": spec.Mode, "uid": id.UID, "gid": id.GID}
	if spec.Mode == IdentityEnv {
		out["user_env"], out["group_env"] = spec.UserEnv, spec.GroupEnv
	}
	return out
}

// identityFor is the identity module m runs as here, and whether one is composed: a module that declares `identity`,
// to an engine that keeps folders, with an allocation the composition was given. A number outside the range is
// refused (§11), never sent.
func identityFor(m Manifest, with Rendering) (ModuleIdentity, bool, error) {
	if !with.KeepsFolders || !DeclaresIdentity(m) {
		return ModuleIdentity{}, false, nil
	}
	id, allocated := with.Identities[m.Module]
	if !allocated {
		return ModuleIdentity{}, false, nil
	}
	if !AllocatableID(id.UID) || !AllocatableID(id.GID) {
		return ModuleIdentity{}, false, fmt.Errorf("%s's identity is %d:%d, outside %d–%d: no module identity is root "+
			"or a root group's, and none is sent (%s §11)", m.Module, id.UID, id.GID, IdentityLow, IdentityHigh, ADR0325)
	}
	id.Module = m.Module
	return id, true, nil
}

// identityInto composes one resource of module m for its identity: a container's `identity` resolved, or taken out
// where none is composed; and the owner of a directory one of its identity's containers mounts.
func identityInto(resource map[string]any, m Manifest, id ModuleIdentity, has bool, mountedByIdentity map[string]bool) error {
	switch fmt.Sprint(resource["type"]) {
	case "container":
		v, declared := resource[IdentityField]
		if !declared {
			return nil
		}
		if !has {
			delete(resource, IdentityField)
			return nil
		}
		spec, err := ParseIdentity(v)
		if err != nil {
			return fmt.Errorf("%s: the container %v: %w", m.Module, resource["id"], err)
		}
		resource[IdentityField] = resolvedIdentity(spec, id)
	case "directory":
		if has && mountedByIdentity[fmt.Sprint(resource["id"])] {
			resource["owner"] = fmt.Sprintf("%d:%d", id.UID, id.GID)
		}
	}
	return nil
}

// dirsMountedByIdentity is the ids of module m's directories one of its containers declaring `identity` mounts.
func dirsMountedByIdentity(m Manifest) map[string]bool {
	out := map[string]bool{}
	for _, r := range m.Resources {
		if fmt.Sprint(r["type"]) != "container" {
			continue
		}
		if _, has := r[IdentityField]; !has {
			continue
		}
		dirs, _ := containerMounts(r)
		for _, d := range dirs {
			out[d] = true
		}
	}
	return out
}

// identitiesOf is the declaration's `identities`, by module.
func identitiesOf(ids []ModuleIdentity) []map[string]any {
	sort.Slice(ids, func(i, j int) bool { return ids[i].Module < ids[j].Module })
	out := make([]map[string]any, 0, len(ids))
	for _, id := range ids {
		out = append(out, map[string]any{"module": id.Module, "name": IdentityName(id.Module), "uid": id.UID,
			"gid": id.GID})
	}
	return out
}

// toolsAccount is the account module m's tools run as on this machine, or empty where they run nowhere as one: no
// runtime here, no bundle it loads, or a module left out of an adopted machine's declaration.
func (r Resolution) toolsAccount(m Manifest, with Rendering) string {
	if !r.runtimeHere() || (with.Adopted && m.Filtering != nil) {
		return ""
	}
	loads := false
	for _, b := range m.Bundles {
		if len(b.Loads) > 0 {
			loads = true
		}
	}
	if !loads {
		return ""
	}
	if m.RunsAs != "" {
		return m.RunsAs
	}
	return r.Account
}

// usersInto writes `users` and `taken` on every access of module m among the resources composed so far: its identity
// where a container of it that declares `identity` mounts the access's path, and the tool runner's account where the
// module's tools run as it and its number is known, each at the access's use (§4: the engine keeps the widest).
func usersInto(out []map[string]any, owner map[string]string, m Manifest, id ModuleIdentity, has bool, account string,
	with Rendering) {
	var containers []map[string]any
	for _, res := range out {
		if res["type"] == "container" && owner[fmt.Sprint(res["id"])] == m.Module {
			if _, declares := res[IdentityField]; declares && has {
				containers = append(containers, res)
			}
		}
	}
	runnerUID, runnerKnown := with.AccountUIDs[account]
	for _, res := range out {
		if res["type"] != "access" || owner[fmt.Sprint(res["id"])] != m.Module {
			continue
		}
		path, _ := res["path"].(string)
		mode, _ := res["mode"].(string)
		if mode == "" {
			mode = AccessRead
		}
		users := []AccessUser{}
		for _, c := range containers {
			if mounts(c, path) {
				users = append(users, AccessUser{Identity: IdentityName(m.Module), UID: id.UID, Use: mode, From: FromContainer})
				break // one identity per module, whichever of its containers mounts it
			}
		}
		if account != "" && runnerKnown && runnerUID > 0 {
			users = append(users, AccessUser{Identity: account, UID: runnerUID, Use: mode, From: FromToolRunner})
		}
		if len(users) > 0 {
			res["users"] = users
		}
		res["taken"] = with.KeptFolders[filepath.Clean(path)]
	}
}

// mounts says whether a composed container mounts path, or something below it, from the machine. A path that merely
// begins with the same letters — /storage/media2 beside /storage/media — is another path.
func mounts(container map[string]any, path string) bool {
	volumes, _ := container["volumes"].([]any)
	path = filepath.Clean(path)
	for _, v := range volumes {
		s, ok := v.(string)
		if !ok {
			continue
		}
		source, _, _ := strings.Cut(s, ":")
		if !strings.HasPrefix(source, "/") {
			continue // a named volume: the runtime's, not the operator's path
		}
		source = filepath.Clean(source)
		if source == path || strings.HasPrefix(source, path+"/") {
			return true
		}
	}
	return false
}

// AccessPathOn is where access id of module m is on a machine with these settings: its placement, else the
// definition's default; false where neither says, or the module declares no such access.
func AccessPathOn(m Manifest, layers []Layer, id string) (string, bool) {
	_, byID, err := accessesFor(m, layers)
	if err != nil {
		return "", false
	}
	path, has := byID[id]
	if !has || path == "" {
		return "", false
	}
	return filepath.Clean(path), true
}