package stacks

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

	"gopkg.in/yaml.v3"

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

// ── Media apps on every drive (v0.313.0, R-1023; `15-media-library.md` §2, §3, §7–§10) ──────────────────────────
//
// A template marks a MEDIA app in `.felhom.yml`:
//
//	media_library:
//	  folder: torrents   # optional: only <drive>/userdata/media/<folder> (the D9 limit for a download client)
//	  read_only: true    # a player (Plex, Jellyfin, Emby)
//
// The controller then adds, per PRESENT enrolled drive, the bind `<drive>/userdata/media[/<folder>]` at the SAME path
// inside the container. The binds live in `docker-compose.override.yml` in the stack dir, which `docker compose` merges
// by itself (no `-f` anywhere in this controller). So:
//
//   - A template with the marker still runs on a controller that ignores the marker: its own one-drive
//     `${USERDATA_PATH}/media…` line is untouched, and no override file is ever written.
//   - ONLY present drives (`15` §10 guard 1): a bind to an absent path makes the app unstartable (K3-4: 500 „error
//     while creating mount source path … permission denied"). A drive is present when it is a mountpoint AND its top
//     mount is not a dead filesystem (`shutdown`, K4) — so a pulled drive is never bound, and never replaced by an
//     empty folder (§10: an empty folder can read as „all files deleted").
//   - A network share is never a media drive in this build (`Kind == "network"` is skipped).
//   - The binds are literal host paths in a file no backup, export or removal reads: in no capture set, no `.fab`
//     export, never deleted by a removal (`15` §7, §8; pinned by TestMediaLibrary_OverrideIsInNoCaptureSet and the
//     R-1027 removal test).
//
// The file is rewritten before EVERY `compose up` (composeExecCustomEnv), so any start — deploy, start, restart, the
// drive notice's restart — binds exactly the drives present at that moment. Pinned by TestMediaLibrary_*.

// MediaLibrarySpec is `.felhom.yml`'s `media_library:`.
type MediaLibrarySpec struct {
	// Folder limits the bind to `media/<Folder>` (qBittorrent: torrents, Transmission: transmission). Empty = the
	// whole `media` folder (Sonarr, Radarr, the players).
	Folder string `yaml:"folder,omitempty" json:"folder,omitempty"`
	// ReadOnly binds `:ro` (the players).
	ReadOnly bool `yaml:"read_only,omitempty" json:"read_only,omitempty"`
	// Services names the compose services that get the binds. Empty = every service that binds `${USERDATA_PATH}/media…`.
	Services []string `yaml:"services,omitempty" json:"services,omitempty"`
}

// MediaOverrideFile is the compose override the controller owns for a media app.
const MediaOverrideFile = "docker-compose.override.yml"

// mediaOverrideHeader marks the file as ours: a file without it is never touched.
const mediaOverrideHeader = "# felhom-controller media_library"

// MediaDrive is one drive the media binds are made for.
type MediaDrive struct {
	Path    string // the registered drive path (the felhom-data namespace root of that drive)
	Present bool
	Why     string // why not present ("not mounted", "dead (shutdown)") — empty when present
}

// mediaDrives lists the enrolled, non-network, not decommissioned drives, each with whether it is present now. Sorted
// by path, so two renders of the same state are byte-identical.
func (m *Manager) mediaDrives() []MediaDrive {
	if m.mediaDrivesFn != nil {
		return m.mediaDrivesFn()
	}
	if m.settings == nil {
		return nil
	}
	isMount := m.isMountPoint
	if isMount == nil {
		isMount = system.IsMountPoint
	}
	var out []MediaDrive
	seen := map[string]bool{}
	for _, sp := range m.settings.GetStoragePaths() {
		p := filepath.Clean(sp.Path)
		if sp.Kind == "network" || sp.Decommissioned || p == "" || seen[p] {
			continue
		}
		seen[p] = true
		d := MediaDrive{Path: p, Present: true}
		switch {
		case sp.Disconnected || sp.EjectedAt != "":
			d.Present, d.Why = false, "removed"
		case !isMount(p):
			d.Present, d.Why = false, "not mounted"
		case system.MountIsShutdown(p):
			d.Present, d.Why = false, "dead (shutdown)"
		}
		out = append(out, d)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Path < out[j].Path })
	return out
}

// mediaBindSource is the per-drive bind source (and target) for a spec.
func mediaBindSource(drive string, spec *MediaLibrarySpec) string {
	src := filepath.Join(appbackup.UserdataDir(drive), "media")
	if f := strings.Trim(filepath.Clean("/"+spec.Folder), "/"); f != "" && f != "." {
		src = filepath.Join(src, f)
	}
	return src
}

// composeServiceBinds reads each service's short-syntax volume entries, ${…} filled from env.
func composeServiceBinds(composePath string, env map[string]string) (map[string][]string, error) {
	data, err := os.ReadFile(composePath)
	if err != nil {
		return nil, err
	}
	var doc struct {
		Services map[string]struct {
			Volumes []interface{} `yaml:"volumes"`
		} `yaml:"services"`
	}
	if err := yaml.Unmarshal(data, &doc); err != nil {
		return nil, err
	}
	out := map[string][]string{}
	for svc, s := range doc.Services {
		for _, v := range s.Volumes {
			if str, ok := v.(string); ok {
				out[svc] = append(out[svc], str)
			}
		}
	}
	_ = env
	return out, nil
}

// bindTarget is the container side of a short-syntax bind ("src:target[:mode]"), ${…} expanded.
func bindTarget(raw string, env map[string]string) string {
	parts := strings.SplitN(expandComposeVars(raw, env), ":", 3)
	if len(parts) < 2 {
		return ""
	}
	return filepath.Clean(parts[1])
}

// renderMediaOverride writes (or removes) the stack's media override for the drives present now. Returns the new file
// content ("" = no file) and whether it changed. A template without the marker gets no file; an existing file without
// our header is never touched.
func (m *Manager) renderMediaOverride(stackDir string, env []string) (string, bool) {
	meta := LoadMetadata(stackDir)
	path := filepath.Join(stackDir, MediaOverrideFile)
	old, _ := os.ReadFile(path)
	if len(old) > 0 && !strings.HasPrefix(string(old), mediaOverrideHeader) {
		m.logger.Printf("[WARN] [stacks] media_library %s: %s exists and is not ours — left alone, no per-drive binds", filepath.Base(stackDir), MediaOverrideFile)
		return string(old), false
	}
	content := ""
	if meta.MediaLibrary != nil {
		content = m.mediaOverrideContent(stackDir, env, meta.MediaLibrary)
	}
	if content == string(old) {
		return content, false
	}
	if content == "" {
		if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
			m.logger.Printf("[WARN] [stacks] media_library %s: removing the override: %v", filepath.Base(stackDir), err)
			return string(old), false
		}
		m.logger.Printf("[INFO] [stacks] media_library %s: no per-drive bind needed — override removed", filepath.Base(stackDir))
		return "", true
	}
	tmp := path + ".tmp"
	if err := os.WriteFile(tmp, []byte(content), 0o644); err != nil {
		m.logger.Printf("[ERROR] [stacks] media_library %s: writing the override: %v", filepath.Base(stackDir), err)
		return string(old), false
	}
	if err := os.Rename(tmp, path); err != nil {
		m.logger.Printf("[ERROR] [stacks] media_library %s: writing the override: %v", filepath.Base(stackDir), err)
		return string(old), false
	}
	return content, true
}

func (m *Manager) mediaOverrideContent(stackDir string, envList []string, spec *MediaLibrarySpec) string {
	name := filepath.Base(stackDir)
	env := map[string]string{}
	for _, e := range envList {
		if k, v, ok := strings.Cut(e, "="); ok {
			env[k] = v
		}
	}
	binds, err := composeServiceBinds(filepath.Join(stackDir, "docker-compose.yml"), env)
	if err != nil {
		m.logger.Printf("[WARN] [stacks] media_library %s: reading the compose: %v — no per-drive binds", name, err)
		return ""
	}
	services := spec.Services
	if len(services) == 0 {
		for svc, vs := range binds {
			for _, v := range vs {
				if strings.HasPrefix(strings.TrimSpace(v), "${USERDATA_PATH}/media") {
					services = append(services, svc)
					break
				}
			}
		}
	}
	sort.Strings(services)
	mode := ""
	if spec.ReadOnly {
		mode = ":ro"
	}
	var b strings.Builder
	var bound, skipped []string
	for _, svc := range services {
		have := map[string]bool{}
		for _, v := range binds[svc] {
			if t := bindTarget(v, env); t != "" {
				have[t] = true
			}
		}
		var lines []string
		for _, d := range m.mediaDrives() {
			src := mediaBindSource(d.Path, spec)
			if !d.Present {
				skipped = append(skipped, fmt.Sprintf("%s (%s)", d.Path, d.Why))
				continue
			}
			if have[src] {
				continue // the template's own line already binds this drive at this path
			}
			// Only on a PRESENT drive: the folder is made with the userdata convention, so Docker never makes it.
			ensure := m.mediaEnsureDirFn
			if ensure == nil {
				ensure = appbackup.EnsureUserdataDir
			}
			if err := ensure(src); err != nil {
				m.logger.Printf("[WARN] [stacks] media_library %s: cannot make %s: %v — that drive is not bound", name, src, err)
				continue
			}
			lines = append(lines, fmt.Sprintf("      - %s:%s%s", src, src, mode))
			bound = append(bound, src)
		}
		if len(lines) == 0 {
			continue
		}
		fmt.Fprintf(&b, "  %s:\n    volumes:\n%s\n", svc, strings.Join(lines, "\n"))
	}
	m.logger.Printf("[INFO] [stacks] media_library %s: per-drive binds %d [%s]; drives not bound: [%s]",
		name, len(bound), strings.Join(bound, ", "), strings.Join(uniq(skipped), ", "))
	if b.Len() == 0 {
		return ""
	}
	return mediaOverrideHeader + " — one bind per PRESENT drive (R-1023). Rewritten before every start; do not edit.\nservices:\n" + b.String()
}

func uniq(in []string) []string {
	seen := map[string]bool{}
	var out []string
	for _, s := range in {
		if !seen[s] {
			seen[s] = true
			out = append(out, s)
		}
	}
	return out
}

// MediaApps lists the deployed stacks whose template carries `media_library:`.
func (m *Manager) MediaApps() []string {
	m.mu.RLock()
	defer m.mu.RUnlock()
	var out []string
	for name, st := range m.stacks {
		if !st.Deployed || st.ComposePath == "" {
			continue
		}
		if meta := LoadMetadata(filepath.Dir(st.ComposePath)); meta.MediaLibrary != nil {
			out = append(out, name)
		}
	}
	sort.Strings(out)
	return out
}

// MediaAppsNeedingRestart renders every media app's override for the drives present NOW and returns the apps whose
// binds changed — the apps that must restart to see a drive that was added, removed or came back (the notice of
// decision 238). It writes the files; the restart itself is the household's „restart now" (RestartStack).
func (m *Manager) MediaAppsNeedingRestart() []string {
	var out []string
	for _, name := range m.MediaApps() {
		st, ok := m.GetStack(name)
		if !ok {
			continue
		}
		dir := filepath.Dir(st.ComposePath)
		if _, changed := m.renderMediaOverride(dir, m.stackEnv(dir)); changed {
			out = append(out, name)
		}
	}
	return out
}

// defaultMediaDrive is where a media app's OWN config goes (R-1031): the household's default drive when it is present,
// else the first present drive; "" when no drive is present (the deploy then refuses on the required field).
func (m *Manager) defaultMediaDrive() string {
	def := ""
	if m.settings != nil {
		for _, sp := range m.settings.GetStoragePaths() {
			if sp.IsDefault && sp.Kind != "network" && !sp.Decommissioned {
				def = filepath.Clean(sp.Path)
			}
		}
	}
	first := ""
	for _, d := range m.mediaDrives() {
		if !d.Present {
			continue
		}
		if d.Path == def {
			return def
		}
		if first == "" {
			first = d.Path
		}
	}
	return first
}

// PresentMediaDrives is the drives the media apps bind now (present, enrolled, not network, not removed).
func (m *Manager) PresentMediaDrives() []string {
	var out []string
	for _, d := range m.mediaDrives() {
		if d.Present {
			out = append(out, d.Path)
		}
	}
	return out
}