package stacks

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"

	"gitea.dooplex.hu/admin/felhom-controller/internal/dockerexec"
)

// ── Image retention (R-736, `09` §3 decision 53) ──────────────────────────────────────────────────────
//
// A remove ran `compose down --rmi local` (which never removes a registry-pulled image) and an update left the old
// version's image behind; nothing else deleted any. On scratch guest 9202 that filled the Docker disk until the box
// refused an install (2026-09-30: 84 images, 53 GB used by no container). The ruling: a box keeps, per app service,
// the image it runs now and the image before it (the undo's); it deletes older images of that app by itself; it
// NEVER deletes an image that any container (running or stopped) or any installed app's compose still names.
// Removing an app deletes that app's images under the same rule. Kept data (decision 40) is data, not images.
//
// THE KEEP SET is box-wide and rebuilt at every pass, at delete time: every container's image ID, every image an
// installed app's live compose names (by tag and by digest), and every installed app's installed_images and
// previous_images. A CANDIDATE is an image whose repository is one of THIS app's service repositories and whose ID
// is not kept. It is deleted by exact ID, never forced (Docker itself refuses an image a container uses) and never
// by prune; an ID that carries several repositories' tags is left alone. Every deletion is logged with its size.
// Pinned by internal/stacks/image_retention_test.go.

// imageDocker runs one docker command (a seam: tests never reach Docker).
var imageDocker = func(args ...string) (string, error) {
	out, err := dockerexec.Command("docker", args...).CombinedOutput()
	return string(out), err
}

var imageRetentionMu sync.Mutex

type localImage struct {
	ID, Repo, Tag, Digest, Size string
}

func splitRepoTag(ref string) (repo, tag, digest string) {
	if i := strings.Index(ref, "@"); i >= 0 {
		ref, digest = ref[:i], ref[i+1:]
	}
	if c := strings.LastIndex(ref, ":"); c > strings.LastIndex(ref, "/") {
		return ref[:c], ref[c+1:], digest
	}
	return ref, "latest", digest
}

// normRepo makes Docker Hub's short forms comparable: "library/postgres" and "docker.io/postgres" are "postgres".
func normRepo(r string) string {
	r = strings.TrimPrefix(r, "docker.io/")
	return strings.TrimPrefix(r, "library/")
}

func listLocalImages() ([]localImage, error) {
	out, err := imageDocker("image", "ls", "--digests", "--no-trunc", "--format", "{{.ID}}\t{{.Repository}}\t{{.Tag}}\t{{.Digest}}\t{{.Size}}")
	if err != nil {
		return nil, fmt.Errorf("docker image ls: %v: %s", err, truncateStr(out, 200))
	}
	var imgs []localImage
	for _, l := range strings.Split(strings.TrimSpace(out), "\n") {
		f := strings.Split(l, "\t")
		if len(f) < 5 || f[0] == "" {
			continue
		}
		imgs = append(imgs, localImage{ID: f[0], Repo: normRepo(f[1]), Tag: f[2], Digest: f[3], Size: f[4]})
	}
	return imgs, nil
}

func imagesUsedByContainers() (map[string]bool, error) {
	out, err := imageDocker("ps", "-a", "-q", "--no-trunc")
	if err != nil {
		return nil, fmt.Errorf("docker ps: %v", err)
	}
	ids := strings.Fields(out)
	used := map[string]bool{}
	if len(ids) == 0 {
		return used, nil
	}
	out, err = imageDocker(append([]string{"inspect", "--format", "{{.Image}}"}, ids...)...)
	if err != nil {
		// a container removed between the two calls fails the inspect: FAIL CLOSED — nothing is deleted
		return nil, fmt.Errorf("docker inspect containers: %v", err)
	}
	for _, id := range strings.Fields(out) {
		used[id] = true
	}
	return used, nil
}

// matchImages: the local image IDs a reference names — by repo+tag, or by repo+digest.
func matchImages(imgs []localImage, ref, digest string) []string {
	repo, tag, d := splitRepoTag(ref)
	repo = normRepo(repo)
	if digest == "" {
		digest = d
	}
	var ids []string
	for _, im := range imgs {
		if im.Repo != repo {
			continue
		}
		if (tag != "" && im.Tag == tag) || (digest != "" && im.Digest == digest) {
			ids = append(ids, im.ID)
		}
	}
	return ids
}

// imageKeepSet is the box-wide keep set (see the header). except = an app being removed (its records do not keep).
func (m *Manager) imageKeepSet(imgs []localImage, except string) (map[string]bool, error) {
	keep, err := imagesUsedByContainers()
	if err != nil {
		return nil, err
	}
	m.mu.RLock()
	type app struct {
		dir       string
		installed map[string]InstalledImage
		previous  map[string]InstalledImage
	}
	var apps []app
	for n, st := range m.stacks {
		if n == except || !st.Deployed {
			continue
		}
		a := app{dir: filepath.Dir(st.ComposePath)}
		if st.AppConfig != nil {
			a.installed, a.previous = st.AppConfig.InstalledImages, st.AppConfig.PreviousImages
		}
		apps = append(apps, a)
	}
	m.mu.RUnlock()
	for _, a := range apps {
		if refs, err := ParseComposeImages(ComposePathIn(a.dir)); err == nil {
			for _, ref := range refs {
				for _, id := range matchImages(imgs, ref, "") {
					keep[id] = true
				}
			}
		}
		for _, set := range []map[string]InstalledImage{a.installed, a.previous} {
			for _, ii := range set {
				for _, id := range matchImages(imgs, ii.Ref, ii.Digest) {
					keep[id] = true
				}
			}
		}
	}
	return keep, nil
}

// appImageRepos: the repositories an app's services use (its live compose, its records).
func appImageRepos(dir string, cfg *AppConfig) map[string]bool {
	repos := map[string]bool{}
	if refs, err := ParseComposeImages(ComposePathIn(dir)); err == nil {
		for _, r := range refs {
			rp, _, _ := splitRepoTag(r)
			repos[normRepo(rp)] = true
		}
	}
	if cfg != nil {
		for _, set := range []map[string]InstalledImage{cfg.InstalledImages, cfg.PreviousImages} {
			for _, ii := range set {
				rp, _, _ := splitRepoTag(ii.Ref)
				repos[normRepo(rp)] = true
			}
		}
	}
	return repos
}

// deleteUnkeptImages deletes every image of repos whose ID is not kept. Returns what it deleted.
func (m *Manager) deleteUnkeptImages(why string, repos map[string]bool, except string) ([]string, error) {
	imageRetentionMu.Lock()
	defer imageRetentionMu.Unlock()
	// An update IN FLIGHT has already replaced its containers and its compose; the image its undo needs is then named
	// by nothing the keep set reads. So no pass runs while any update runs (the next pass catches up).
	m.mu.RLock()
	busy := ""
	for n, st := range m.stacks {
		if st.Updating {
			busy = n
			break
		}
	}
	m.mu.RUnlock()
	if busy != "" {
		m.logger.Printf("[INFO] [stacks] image retention (%s): skipped — %s is updating (its undo may need an image nothing else names)", why, busy)
		return nil, nil
	}
	imgs, err := listLocalImages()
	if err != nil {
		return nil, err
	}
	keep, err := m.imageKeepSet(imgs, except)
	if err != nil {
		m.logger.Printf("[WARN] [stacks] image retention (%s): the keep set could not be read (%v) — NOTHING is deleted", why, err)
		return nil, err
	}
	byID := map[string][]localImage{}
	for _, im := range imgs {
		byID[im.ID] = append(byID[im.ID], im)
	}
	ids := make([]string, 0, len(byID))
	for id := range byID {
		ids = append(ids, id)
	}
	sort.Strings(ids)
	var deleted []string
	candidates := 0
	defer func() {
		// ONE line per pass, whatever it did (v0.284.1): an absent deletion line must never be read as "it ran and
		// found nothing" — this line is the positive observable that the pass ran (R-96 rule 3).
		m.logger.Printf("[INFO] [stacks] image retention (%s): pass over %d image(s) of %v — %d candidate(s), %d deleted, the rest kept",
			why, len(ids), sortedKeys(repos), candidates, len(deleted))
	}()
	for _, id := range ids {
		group := byID[id]
		if keep[id] {
			continue
		}
		inRepos, names := true, []string{}
		for _, im := range group {
			if !repos[im.Repo] || strings.Contains(im.Repo, "felhom-controller") {
				inRepos = false
			}
			names = append(names, im.Repo+":"+im.Tag)
		}
		if !inRepos {
			continue
		}
		candidates++
		if len(uniqueRepos(group)) > 1 {
			m.logger.Printf("[INFO] [stacks] image retention (%s): %s carries several repositories' names %v — left alone", why, shortID(id), names)
			continue
		}
		if out, err := imageDocker("rmi", id); err != nil {
			m.logger.Printf("[WARN] [stacks] image retention (%s): docker refused to delete %v (%s): %s", why, names, shortID(id), truncateStr(strings.TrimSpace(out), 160))
			continue
		}
		m.logger.Printf("[INFO] [stacks] image retention (%s): deleted %v (%s, %s) — no container, installed app or undo names it (decision 53)", why, names, shortID(id), group[0].Size)
		deleted = append(deleted, strings.Join(names, ","))
	}
	return deleted, nil
}

func uniqueRepos(g []localImage) map[string]bool {
	r := map[string]bool{}
	for _, im := range g {
		r[im.Repo] = true
	}
	return r
}

func shortID(id string) string {
	id = strings.TrimPrefix(id, "sha256:")
	if len(id) > 12 {
		return id[:12]
	}
	return id
}

// RetainImagesAfterUpdate is called when a guarded Update ends. previous = what the app ran BEFORE the update when it
// ended done (the image before the new one); when it was undone, the images of the attempt (the app runs the old
// ones again and the attempt is the most recent other image). It records previous_images, then deletes the app's
// older images.
func (m *Manager) RetainImagesAfterUpdate(name string, previous map[string]InstalledImage) {
	st, ok := m.GetStack(name)
	if !ok || !st.Deployed {
		return
	}
	dir := filepath.Dir(st.ComposePath)
	if len(previous) > 0 {
		m.mutateAppConfig(name, dir, "previous_images", func(cfg *AppConfig) bool {
			cfg.PreviousImages = previous
			return true
		})
		if err := m.ScanStacks(); err != nil {
			m.logger.Printf("[WARN] [stacks] image retention %s: rescan failed: %v", name, err)
		}
	}
	st, _ = m.GetStack(name)
	if _, err := m.deleteUnkeptImages("update of "+name, appImageRepos(dir, st.AppConfig), ""); err != nil {
		m.logger.Printf("[WARN] [stacks] image retention after the update of %s: %v", name, err)
	}
}

// retainAfterUpdateFn runs the retention after an update ends (a seam: the update tests do not exercise it).
var retainAfterUpdateFn = func(m *Manager, name string, previous map[string]InstalledImage) {
	go m.RetainImagesAfterUpdate(name, previous)
}

func (m *Manager) retainAfterUpdate(name string, previous map[string]InstalledImage) {
	retainAfterUpdateFn(m, name, previous)
}

// retainAfterRemoveFn runs the retention after a remove (a seam, so a test can see the remove path calls it).
var retainAfterRemoveFn = func(m *Manager, name string, repos map[string]bool) {
	go m.RetainImagesAfterRemove(name, repos)
}

// RetainImagesAfterRemove deletes a removed app's images (its repos, read BEFORE the remove) that nothing else keeps.
func (m *Manager) RetainImagesAfterRemove(name string, repos map[string]bool) {
	if len(repos) == 0 {
		return
	}
	if _, err := m.deleteUnkeptImages("remove of "+name, repos, name); err != nil {
		m.logger.Printf("[WARN] [stacks] image retention after the remove of %s: %v", name, err)
	}
}

// catalogImageRepos: every repository any catalog template or step names (the one-time sweep's reach: app images
// only — never the controller's, traefik's or another infrastructure image).
func (m *Manager) catalogImageRepos() map[string]bool {
	repos := map[string]bool{}
	root := filepath.Join(m.cfg.Paths.DataDir, "catalog-cache", "templates")
	_ = filepath.Walk(root, func(p string, info os.FileInfo, err error) error {
		if err != nil || info.IsDir() || !(strings.HasSuffix(p, "docker-compose.yml") || (strings.Contains(p, string(filepath.Separator)+"steps"+string(filepath.Separator)) && strings.HasSuffix(p, ".yml") && !strings.HasSuffix(p, ".felhom.yml"))) {
			return nil
		}
		if refs, err := ParseComposeImages(p); err == nil {
			for _, r := range refs {
				rp, _, _ := splitRepoTag(r)
				repos[normRepo(rp)] = true
			}
		}
		return nil
	})
	return repos
}

// imageRetentionMarker: the one-time sweep runs once per box (decision 53's clean-up for boxes older than it).
func (m *Manager) imageRetentionMarker() string {
	return filepath.Join(m.cfg.Paths.DataDir, "image-retention-v1.done")
}

// RunImageRetentionOnce is the one-time clean-up at the first start of this release: the same rule, applied to every
// app image the catalog names (so the images of apps removed before this release go too). Logged; a marker file
// keeps it to once. Returns what it deleted.
func (m *Manager) RunImageRetentionOnce() []string {
	if _, err := os.Stat(m.imageRetentionMarker()); err == nil {
		return nil
	}
	repos := m.catalogImageRepos()
	if len(repos) == 0 {
		m.logger.Printf("[WARN] [stacks] image retention (one-time): no catalog read — skipped, tried again at the next start")
		return nil
	}
	before, _ := imageDocker("system", "df", "--format", "{{.Type}} {{.Size}} {{.Reclaimable}}")
	deleted, err := m.deleteUnkeptImages("one-time clean-up", repos, "")
	if err != nil {
		m.logger.Printf("[WARN] [stacks] image retention (one-time): %v — tried again at the next start", err)
		return nil
	}
	after, _ := imageDocker("system", "df", "--format", "{{.Type}} {{.Size}} {{.Reclaimable}}")
	m.logger.Printf("[INFO] [stacks] image retention (one-time): deleted %d image(s). docker disk before: %s | after: %s",
		len(deleted), strings.Join(strings.Fields(firstLine(before)), " "), strings.Join(strings.Fields(firstLine(after)), " "))
	_ = os.MkdirAll(filepath.Dir(m.imageRetentionMarker()), 0o755)
	_ = os.WriteFile(m.imageRetentionMarker(), []byte(fmt.Sprintf("deleted %d\n%s\n", len(deleted), strings.Join(deleted, "\n"))), 0o644)
	return deleted
}

func sortedKeys(m map[string]bool) []string {
	out := make([]string, 0, len(m))
	for k := range m {
		out = append(out, k)
	}
	sort.Strings(out)
	return out
}