package stacks

import (
	"context"
	"encoding/json"
	"fmt"
	"gitea.dooplex.hu/admin/felhom-controller/internal/dockerexec"
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"gopkg.in/yaml.v3"
)

// installedRecordTimeout bounds every docker call this file makes.
//
// REUSE.md's trap table says it in terms: composeExecCustomEnv and execCommand have NO context and
// NO timeout, so a hung docker CLI blocks forever. That is tolerable for the compose `up` a customer
// is waiting on; it is NOT tolerable here, because this runs AFTER every successful start, restart,
// update and deploy purely to write a note down. A bookkeeping read must never be able to wedge a
// lifecycle action. Three short reads share this budget generously.
const installedRecordTimeout = 30 * time.Second

// execRunner is this file's process boundary — the one seam the installed-images recorder uses.
//
// It is deliberately its OWN seam rather than Manager.execFn / composeExecCustomEnv: those two are
// already load-bearing for refreshStatusLocked and for the compose lifecycle, and both lack the
// context this code needs. dir "" means "do not chdir"; env nil means inherit os.Environ().
// nil in production (defaultExecRunner); tests script argv → output and never touch docker.
type execRunner func(ctx context.Context, dir string, env []string, name string, args ...string) (string, error)

func defaultExecRunner(ctx context.Context, dir string, env []string, name string, args ...string) (string, error) {
	cmd := dockerexec.CommandContext(ctx, name, args...)
	if dir != "" {
		cmd.Dir = dir
	}
	if env != nil {
		cmd.Env = env
	}
	out, err := cmd.Output()
	if err != nil {
		stderr := ""
		if ee, ok := err.(*exec.ExitError); ok {
			stderr = truncateStr(string(ee.Stderr), 500)
		}
		return string(out), fmt.Errorf("exec %s %s: %w\nstderr: %s", name, strings.Join(args, " "), err, stderr)
	}
	return string(out), nil
}

func (m *Manager) runInstalled(ctx context.Context, dir string, env []string, name string, args ...string) (string, error) {
	if m.installedExecFn != nil {
		return m.installedExecFn(ctx, dir, env, name, args...)
	}
	return defaultExecRunner(ctx, dir, env, name, args...)
}

// composeArgv splits the configured compose command into an argv prefix, mirroring
// composeExecCustomEnv's own docker-compose-v1-vs-v2 branch. One rule, two callers.
func (m *Manager) composeArgv(args ...string) (string, []string) {
	if m.composeCmd == "docker compose" {
		return "docker", append([]string{"compose"}, args...)
	}
	return "docker-compose", args
}

// --- The template side: what the compose FILE currently pins, per service ---

// composeImagesDoc is the minimal view of a compose file needed here.
//
// A REAL YAML parse and never a line scan, for the reason dbservices.go's composeServicesDoc already
// records: immich's top-level `immich_ml_cache:` volume key has exactly the shape a naive scan
// misreads as a service. Manager.checkLocalImages IS such a line scan and is deliberately not reused
// — it also cannot say which service an image belongs to, which is the whole comparison.
type composeImagesDoc struct {
	Services map[string]struct {
		Image string `yaml:"image"`
	} `yaml:"services"`
}

// ParseComposeImages returns compose SERVICE name -> the image reference the file pins for it.
//
// Services with no `image:` (a `build:`-only service — none in the catalog today) are omitted rather
// than recorded as an empty pin, because "" would compare equal to nothing useful. An unreadable or
// unparseable file returns an error: CANNOT-TELL must never read as "no images", or an app whose
// compose file is briefly mid-write would render as up to date.
func ParseComposeImages(composePath string) (map[string]string, error) {
	data, err := os.ReadFile(composePath)
	if err != nil {
		return nil, fmt.Errorf("reading compose file: %w", err)
	}
	var doc composeImagesDoc
	if err := yaml.Unmarshal(data, &doc); err != nil {
		return nil, fmt.Errorf("parsing compose file %s: %w", composePath, err)
	}
	out := make(map[string]string, len(doc.Services))
	for svc, def := range doc.Services {
		if strings.TrimSpace(def.Image) == "" {
			continue
		}
		out[svc] = strings.TrimSpace(def.Image)
	}
	return out, nil
}

// --- The container side: what is ACTUALLY running ---

// composePSEntry is the subset of `docker compose ps --format json` this needs.
type composePSEntry struct {
	ID      string `json:"ID"`
	Name    string `json:"Name"`
	Service string `json:"Service"`
}

// parseComposePS tolerates BOTH shapes compose v2 has emitted for `ps --format json`: a single JSON
// array (compose < 2.21) and newline-delimited objects (2.21+). Neither shape is guessed at from a
// version string — the output is tried as an array first and falls back to per-line objects, so an
// upgrade of the docker CLI underneath a customer's box cannot silently stop the recording.
func parseComposePS(out string) ([]composePSEntry, error) {
	trimmed := strings.TrimSpace(out)
	if trimmed == "" {
		return nil, nil
	}
	if strings.HasPrefix(trimmed, "[") {
		var arr []composePSEntry
		if err := json.Unmarshal([]byte(trimmed), &arr); err != nil {
			return nil, fmt.Errorf("parsing compose ps JSON array: %w", err)
		}
		return arr, nil
	}
	var entries []composePSEntry
	for _, line := range strings.Split(trimmed, "\n") {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		var e composePSEntry
		if err := json.Unmarshal([]byte(line), &e); err != nil {
			return nil, fmt.Errorf("parsing compose ps JSON line: %w", err)
		}
		entries = append(entries, e)
	}
	return entries, nil
}

// containerFacts is one container's two identifiers as docker reports them.
type containerFacts struct {
	ref     string // .Config.Image — the reference the container was CREATED FROM
	imageID string // .Image — the local image id it actually resolved to
}

const inspectSep = "\x1f" // ASCII unit separator: cannot occur in an image ref or an id

// observeInstalledImages reads what every compose service of this stack is running.
//
// Three short docker reads, in order: which containers belong to which service; what reference and
// image id each container carries; and what repo digest each of those images has. Nothing is read
// from docker-compose.yml — that file is the value the syncer has already moved.
func (m *Manager) observeInstalledImages(stackDir string, env []string) (map[string]InstalledImage, error) {
	ctx, cancel := context.WithTimeout(context.Background(), installedRecordTimeout)
	defer cancel()

	bin, argv := m.composeArgv("ps", "-a", "--format", "json")
	psOut, err := m.runInstalled(ctx, stackDir, env, bin, argv...)
	if err != nil {
		return nil, fmt.Errorf("listing containers: %w", err)
	}
	entries, err := parseComposePS(psOut)
	if err != nil {
		return nil, err
	}

	// service -> container id, deterministic when a service has replicas (none in the catalog, but
	// a compose `deploy.replicas` would produce several; take the first by name so two runs agree).
	sort.Slice(entries, func(i, j int) bool { return entries[i].Name < entries[j].Name })
	svcContainer := make(map[string]string)
	var ids []string
	for _, e := range entries {
		if e.Service == "" || e.ID == "" {
			continue
		}
		if _, seen := svcContainer[e.Service]; seen {
			continue
		}
		svcContainer[e.Service] = e.ID
		ids = append(ids, e.ID)
	}
	if len(ids) == 0 {
		return map[string]InstalledImage{}, nil
	}

	facts, err := m.inspectContainers(ctx, ids)
	if err != nil {
		return nil, err
	}
	digests, err := m.inspectImageDigests(ctx, facts)
	if err != nil {
		// A missing digest is a recorded empty string, never a failed recording — see the edge-case
		// table. Log and carry on with refs only.
		m.logger.Printf("[WARN] [stacks] installed-images: reading repo digests failed, recording refs only: %v", err)
		digests = map[string]string{}
	}

	now := time.Now().UTC().Format(time.RFC3339)
	out := make(map[string]InstalledImage, len(svcContainer))
	for svc, id := range svcContainer {
		f, ok := facts[id]
		if !ok {
			continue
		}
		out[svc] = InstalledImage{
			Ref:    f.ref,
			Digest: pickDigest(f.ref, digests[f.imageID]),
			At:     now,
		}
	}
	return out, nil
}

func (m *Manager) inspectContainers(ctx context.Context, ids []string) (map[string]containerFacts, error) {
	args := append([]string{"inspect", "--type", "container",
		"--format", "{{.Id}}" + inspectSep + "{{.Config.Image}}" + inspectSep + "{{.Image}}"}, ids...)
	out, err := m.runInstalled(ctx, "", nil, "docker", args...)
	if err != nil {
		return nil, fmt.Errorf("inspecting containers: %w", err)
	}
	facts := make(map[string]containerFacts, len(ids))
	for _, line := range strings.Split(strings.TrimSpace(out), "\n") {
		parts := strings.Split(strings.TrimSpace(line), inspectSep)
		if len(parts) != 3 {
			continue
		}
		facts[parts[0]] = containerFacts{ref: parts[1], imageID: parts[2]}
		// docker accepts short ids on the way in and returns full ones on the way out; key both so
		// the caller's compose-ps id (12 hex) finds its row.
		if len(parts[0]) > 12 {
			facts[parts[0][:12]] = containerFacts{ref: parts[1], imageID: parts[2]}
		}
	}
	return facts, nil
}

// inspectImageDigests maps image id -> its RepoDigests, joined by a space. Empty when an image has
// none (built or imported locally, never pulled) — recorded as an empty digest, not as a failure.
func (m *Manager) inspectImageDigests(ctx context.Context, facts map[string]containerFacts) (map[string]string, error) {
	seen := map[string]bool{}
	var imgs []string
	for _, f := range facts {
		if f.imageID != "" && !seen[f.imageID] {
			seen[f.imageID] = true
			imgs = append(imgs, f.imageID)
		}
	}
	if len(imgs) == 0 {
		return map[string]string{}, nil
	}
	sort.Strings(imgs)
	args := append([]string{"image", "inspect",
		"--format", "{{.Id}}" + inspectSep + "{{range $i, $d := .RepoDigests}}{{if $i}} {{end}}{{$d}}{{end}}"}, imgs...)
	out, err := m.runInstalled(ctx, "", nil, "docker", args...)
	if err != nil {
		return nil, fmt.Errorf("inspecting images: %w", err)
	}
	digests := make(map[string]string, len(imgs))
	for _, line := range strings.Split(strings.TrimSpace(out), "\n") {
		parts := strings.SplitN(strings.TrimSpace(line), inspectSep, 2)
		if len(parts) != 2 {
			continue
		}
		digests[parts[0]] = strings.TrimSpace(parts[1])
	}
	return digests, nil
}

// pickDigest turns a RepoDigests list into the ONE sha256 that belongs to the ref we asked for.
//
// A local image can carry several repo digests (the same bytes tagged from two registries), and
// picking the wrong one would record a digest for a repository this app never used. Match on the
// repository part of the ref first; fall back to the single entry when there is exactly one; give up
// (empty) rather than guess between several unrelated ones.
func pickDigest(ref, repoDigests string) string {
	fields := strings.Fields(repoDigests)
	if len(fields) == 0 {
		return ""
	}
	repo := refRepository(ref)
	for _, rd := range fields {
		at := strings.LastIndex(rd, "@")
		if at < 0 {
			continue
		}
		if repo != "" && rd[:at] == repo {
			return rd[at+1:]
		}
	}
	if len(fields) == 1 {
		if at := strings.LastIndex(fields[0], "@"); at >= 0 {
			return fields[0][at+1:]
		}
	}
	return ""
}

// refRepository strips the tag and/or digest from an image reference, leaving the repository.
// Careful with a registry port ("registry:5000/app:1.2"): only a colon AFTER the last slash is a tag.
func refRepository(ref string) string {
	if at := strings.LastIndex(ref, "@"); at >= 0 {
		ref = ref[:at]
	}
	slash := strings.LastIndex(ref, "/")
	if colon := strings.LastIndex(ref, ":"); colon > slash {
		ref = ref[:colon]
	}
	return ref
}

// --- The write ---

// sameInstalled compares two records on Ref and Digest ONLY, deliberately ignoring At.
// Including At would make every restart a change, and app.yaml would be rewritten — with its
// encrypted secrets — on every lifecycle action for no new information.
func sameInstalled(a, b map[string]InstalledImage) bool {
	if len(a) != len(b) {
		return false
	}
	for k, va := range a {
		vb, ok := b[k]
		if !ok || va.Ref != vb.Ref || va.Digest != vb.Digest {
			return false
		}
	}
	return true
}

// recordInstalledImages writes what this stack is ACTUALLY running into its app.yaml.
//
// ── WHY A FAILURE HERE NEVER REFUSES THE ACTION ──────────────────────────────────────────────
//
// This is deliberately the OPPOSITE of SetDesiredState, and the difference is what the field means.
// `desired_state` is the customer's INTENT: performing an act whose intent could not be recorded
// recreates exactly the ambiguity R-166 closed, so a failed write there correctly refuses the act.
// `installed_images` is an OBSERVATION. Refusing to start a customer's app because we could not write
// down which version it is would trade a real outage for a bookkeeping gap. So: log at ERROR, loudly,
// naming the app — and return. The app stays up.
//
// Called after a SUCCESSFUL compose up from StartStack, RestartStack, UpdateStack and
// runComposeDeploy. NOT from StartStackServices: that path starts only the database service for the
// R-47 restore window, and recording a partial stack there would overwrite a complete record with an
// incomplete one.
func (m *Manager) recordInstalledImages(name, stackDir string, env []string) {
	cfg := LoadAppConfig(stackDir)
	if cfg == nil {
		// No app.yaml: an infra/protected stack, or nothing deployed here. Nothing to record on.
		if m.isDebug() {
			m.logger.Printf("[DEBUG] [stacks] installed-images %s: no app.yaml — nothing to record", name)
		}
		return
	}

	observed, err := m.observeInstalledImages(stackDir, env)
	if err != nil {
		m.logger.Printf("[ERROR] [stacks] installed-images %s: could not observe running images (the app is unaffected): %v", name, err)
		return
	}
	if len(observed) == 0 {
		m.logger.Printf("[WARN] [stacks] installed-images %s: no containers observed — nothing recorded, previous record left intact", name)
		return
	}

	// A partial read is recorded AND said out loud, never written silently: a record that quietly
	// lost a service would read as a complete answer to "what is this app running".
	if tpl, terr := ParseComposeImages(filepath.Join(stackDir, "docker-compose.yml")); terr == nil && len(tpl) > len(observed) {
		var missing []string
		for svc := range tpl {
			if _, ok := observed[svc]; !ok {
				missing = append(missing, svc)
			}
		}
		sort.Strings(missing)
		m.logger.Printf("[WARN] [stacks] installed-images %s: recorded %d of %d compose service(s) — not observed: %s",
			name, len(observed), len(tpl), strings.Join(missing, ", "))
	}

	// Carry forward the first-seen timestamp of every entry whose ref+digest is unchanged, so `at`
	// answers "running since" rather than "last looked at".
	for svc, prev := range cfg.InstalledImages {
		if cur, ok := observed[svc]; ok && cur.Ref == prev.Ref && cur.Digest == prev.Digest && prev.At != "" {
			cur.At = prev.At
			observed[svc] = cur
		}
	}

	if sameInstalled(cfg.InstalledImages, observed) {
		if m.isDebug() {
			m.logger.Printf("[DEBUG] [stacks] installed-images %s: unchanged (%d service(s)) — app.yaml not rewritten", name, len(observed))
		}
		return
	}

	cfg.InstalledImages = observed
	meta := LoadMetadata(stackDir)
	if err := SaveAppConfig(stackDir, cfg, m.encKey, SensitiveEnvVars(&meta)); err != nil {
		m.logger.Printf("[ERROR] [stacks] installed-images %s: recording failed, the app is running and unaffected: %v", name, err)
		return
	}
	m.logger.Printf("[INFO] [stacks] installed-images %s: recorded %d service(s) (%s)", name, len(observed), summariseInstalled(observed))

	// Keep the in-memory view in step so the badge does not lag a full ScanStacks behind the file.
	m.mu.Lock()
	if s, ok := m.stacks[name]; ok && s.AppConfig != nil {
		s.AppConfig.InstalledImages = observed
	}
	m.mu.Unlock()
}

// summariseInstalled renders the record for ONE log line. Image refs and digests only — this file
// never logs anything out of app.yaml's env map, which holds encrypted secrets.
func summariseInstalled(m map[string]InstalledImage) string {
	svcs := make([]string, 0, len(m))
	for svc := range m {
		svcs = append(svcs, svc)
	}
	sort.Strings(svcs)
	parts := make([]string, 0, len(svcs))
	for _, svc := range svcs {
		d := m[svc].Digest
		if len(d) > 19 {
			d = d[:19] + "…"
		}
		if d == "" {
			d = "no digest"
		}
		parts = append(parts, fmt.Sprintf("%s=%s (%s)", svc, m[svc].Ref, d))
	}
	return strings.Join(parts, ", ")
}

// BackfillInstalledImages records what every deployed app is ALREADY running, for apps that have no
// record yet. Call ONCE at startup, after ScanStacks and after the recoveries.
//
// ── WHY THIS EXISTS AT ALL ───────────────────────────────────────────────────────────────────
//
// v0.233.0 wrote the record only from the four bring-up paths, so an app nobody restarts carried no
// record — and no badge — INDEFINITELY. On a quiet box that is every app, which is the box we most
// want to be able to see. The operator found it on demo-felhom the day after the release: OpenGist,
// up 15 hours, running exactly what the catalog pins, and showing nothing at all.
//
// Reading a container is a pure OBSERVATION: it starts nothing, restarts nothing, upgrades nothing
// and writes no compose file. That is what makes a backfill safe here and is why it is the same
// shape as BackfillDesiredState — with one deliberate difference, below.
//
// ── NEVER OVERWRITES AN EXISTING RECORD ──────────────────────────────────────────────────────
//
// Apps with a record are skipped entirely. The bring-up paths own updates; this only seeds absences.
//
// ── AND IT REFUSES TO SEED A PARTIAL OBSERVATION ─────────────────────────────────────────────
//
// THE TRAP, and it is the whole reason this is not a three-line loop: web.compareInstalledToTemplate
// reads a service-count mismatch as BEHIND. A crash-looping or degraded app can have fewer live
// containers than the template has services, so seeding what we can see would render
// "Frissítés elérhető" over an app that is perfectly current — a confident WRONG answer to the
// customer, which is worse than the silence it replaces.
//
// The bring-up paths do not have this problem: they run immediately after a SUCCESSFUL `compose up
// -d`, where a missing container is real news and is already logged as a WARN. A backfill runs over
// whatever state a box happens to be in at boot, so it must be stricter. An app it cannot observe
// COMPLETELY is left with no record — unknown, which renders nothing, which is the honest answer.
func (m *Manager) BackfillInstalledImages() int {
	backfilled, skippedHaveRecord, skippedIncomplete := 0, 0, 0

	for _, s := range m.GetStacks() {
		if !s.Deployed || s.Protected || s.Deploying {
			continue
		}
		if s.AppConfig != nil && len(s.AppConfig.InstalledImages) > 0 {
			skippedHaveRecord++
			continue
		}
		stackDir := filepath.Dir(s.ComposePath)

		tpl, err := ParseComposeImages(s.ComposePath)
		if err != nil || len(tpl) == 0 {
			// Cannot tell what a complete observation would even BE. Leave it unknown.
			skippedIncomplete++
			continue
		}
		observed, err := m.observeInstalledImages(stackDir, m.stackEnv(stackDir))
		if err != nil {
			m.logger.Printf("[WARN] [stacks] installed-images backfill: %s: %v", s.Name, err)
			skippedIncomplete++
			continue
		}
		if !observationCoversTemplate(observed, tpl) {
			// Stopped, degraded, crash-looping, or mid-anything. See the comment above: a partial
			// seed would render as "behind" on an app that is current.
			skippedIncomplete++
			continue
		}

		cfg := LoadAppConfig(stackDir)
		if cfg == nil {
			skippedIncomplete++
			continue
		}
		cfg.InstalledImages = observed
		meta := LoadMetadata(stackDir)
		if err := SaveAppConfig(stackDir, cfg, m.encKey, SensitiveEnvVars(&meta)); err != nil {
			m.logger.Printf("[ERROR] [stacks] installed-images backfill: %s: %v", s.Name, err)
			continue
		}
		m.mu.Lock()
		if st, ok := m.stacks[s.Name]; ok && st.AppConfig != nil {
			st.AppConfig.InstalledImages = observed
		}
		m.mu.Unlock()
		backfilled++
		m.logger.Printf("[INFO] [stacks] installed-images backfill: %s recorded %d service(s) (%s)",
			s.Name, len(observed), summariseInstalled(observed))
	}

	// A POSITIVE OBSERVABLE EITHER WAY (standing rule 3): "0 backfilled" and "the backfill never ran"
	// must not look the same in a log.
	m.logger.Printf("[INFO] [stacks] installed-images backfill: %d app(s) recorded, %d already had a record, %d left unrecorded (could not be observed completely — unknown, which renders nothing)",
		backfilled, skippedHaveRecord, skippedIncomplete)
	return backfilled
}

// observationCoversTemplate reports whether EVERY compose service the template declares was observed.
// Extra observed services are fine (a stray container is not a missing one); a missing one is not.
func observationCoversTemplate(observed map[string]InstalledImage, tpl map[string]string) bool {
	if len(observed) == 0 {
		return false
	}
	for svc := range tpl {
		if _, ok := observed[svc]; !ok {
			return false
		}
	}
	return true
}