package engine

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"unicode"

	"github.com/cdnutter/playlink/internal/art"
	"github.com/cdnutter/playlink/internal/fsops"
	"github.com/cdnutter/playlink/internal/store"
	"github.com/cdnutter/playlink/internal/tags"
)

// FolderCoverName is the album-folder image playlink writes (read by Plex,
// Jellyfin, Navidrome and most players).
const FolderCoverName = "cover.jpg"

var folderCoverNames = []string{"cover.jpg", "folder.jpg", "cover.png", "folder.png", "front.jpg"}

// SetArt enables album art search and preparation.
func (e *Engine) SetArt(c *art.Client, s *art.Store) { e.artClient, e.artStore = c, s }

func (e *Engine) preparedArt(token string) (string, error) {
	if e.artStore == nil {
		return "", errors.New("album art is not available")
	}
	return e.artStore.Path(token)
}

// ---- settings ----

// ArtSettings are the album art options (Settings -> Album art).
type ArtSettings struct {
	Sources   []string `json:"sources"`
	GoogleKey string   `json:"google_key"`
	GoogleCX  string   `json:"google_cx"`
	MaxSize   int      `json:"max_size"` // longest side of prepared covers; 0 keeps the original
	MinSize   int      `json:"min_size"` // smallest search result shown
}

func (e *Engine) ArtSettings(ctx context.Context) ArtSettings {
	s := ArtSettings{
		GoogleKey: e.st.Setting(ctx, "art_google_key", ""),
		GoogleCX:  e.st.Setting(ctx, "art_google_cx", ""),
	}
	src := e.st.Setting(ctx, "art_sources", strings.Join([]string{art.ITunes, art.Deezer, art.MusicBrainz, art.DuckDuckGo, art.Google}, ","))
	for _, x := range strings.Split(src, ",") {
		if x != "" {
			s.Sources = append(s.Sources, x)
		}
	}
	s.MaxSize, _ = strconv.Atoi(e.st.Setting(ctx, "art_max_size", "1000"))
	s.MinSize, _ = strconv.Atoi(e.st.Setting(ctx, "art_min_size", "500"))
	return s
}

func (e *Engine) SetArtSettings(ctx context.Context, s ArtSettings) error {
	known := map[string]bool{}
	for _, x := range art.AllSources {
		known[x] = true
	}
	var src []string
	for _, x := range s.Sources {
		if !known[x] {
			return fmt.Errorf("unknown art source %q", x)
		}
		src = append(src, x)
	}
	if s.MaxSize != 0 && (s.MaxSize < 300 || s.MaxSize > 4000) {
		return errors.New("cover size must be 300-4000 pixels, or 0 to keep the original")
	}
	if s.MinSize < 100 || s.MinSize > 3000 {
		return errors.New("minimum search result size must be 100-3000 pixels")
	}
	for k, v := range map[string]string{"art_sources": strings.Join(src, ","), "art_google_key": strings.TrimSpace(s.GoogleKey),
		"art_google_cx": strings.TrimSpace(s.GoogleCX), "art_max_size": strconv.Itoa(s.MaxSize), "art_min_size": strconv.Itoa(s.MinSize)} {
		if err := e.st.SetSetting(ctx, k, v); err != nil {
			return err
		}
	}
	return nil
}

func (e *Engine) artConfig(ctx context.Context, sources []string) art.Config {
	s := e.ArtSettings(ctx)
	enabled := map[string]bool{}
	for _, x := range s.Sources {
		enabled[x] = true
	}
	var use []string
	for _, x := range sources {
		if enabled[x] {
			use = append(use, x)
		}
	}
	if len(sources) == 0 {
		use = s.Sources
	}
	return art.Config{Sources: use, GoogleKey: s.GoogleKey, GoogleCX: s.GoogleCX, MinSize: s.MinSize}
}

// SearchArt searches album art (square images only).
func (e *Engine) SearchArt(ctx context.Context, q art.Query, sources []string) ([]art.Result, map[string]string, error) {
	if e.artClient == nil {
		return nil, nil, errors.New("album art is not available")
	}
	res, errs := e.artClient.Search(ctx, q, e.artConfig(ctx, sources))
	if res == nil {
		res = []art.Result{}
	}
	return res, errs, nil
}

// PrepareArtURL downloads and prepares an image for applying.
func (e *Engine) PrepareArtURL(ctx context.Context, u string) (art.Prepared, error) {
	if e.artClient == nil || e.artStore == nil {
		return art.Prepared{}, errors.New("album art is not available")
	}
	b, err := e.artClient.FetchImage(ctx, u)
	if err != nil {
		return art.Prepared{}, err
	}
	return e.artStore.Prepare(ctx, b, e.ArtSettings(ctx).MaxSize)
}

// PrepareArtUpload prepares an uploaded image.
func (e *Engine) PrepareArtUpload(ctx context.Context, r io.Reader) (art.Prepared, error) {
	if e.artStore == nil {
		return art.Prepared{}, errors.New("album art is not available")
	}
	b, err := io.ReadAll(io.LimitReader(r, art.MaxImageBytes+1))
	if err != nil {
		return art.Prepared{}, err
	}
	if len(b) > art.MaxImageBytes {
		return art.Prepared{}, errors.New("the image is larger than 20 MB")
	}
	return e.artStore.Prepare(ctx, b, e.ArtSettings(ctx).MaxSize)
}

func (e *Engine) PreparedArtPath(token string) (string, error) { return e.preparedArt(token) }

// FetchArtThumb downloads a search result thumbnail for display.
func (e *Engine) FetchArtThumb(ctx context.Context, u string) ([]byte, error) {
	if e.artClient == nil {
		return nil, errors.New("album art is not available")
	}
	return e.artClient.FetchImage(ctx, u)
}

// ---- reading covers ----

// Cover returns the art for a song (embedded) or an album folder (its image
// file), as image bytes.
func (e *Engine) Cover(ctx context.Context, pairID int64, side, rel string) ([]byte, error) {
	l, err := e.loadPair(ctx, pairID)
	if err != nil {
		return nil, err
	}
	root, err := sideRoot(l, side)
	if err != nil {
		return nil, err
	}
	abs := root.Path
	if rel != "" {
		if abs, err = root.Resolve(rel); err != nil {
			return nil, err
		}
	}
	fi, err := os.Lstat(abs)
	if err != nil {
		return nil, err
	}
	if fi.IsDir() {
		for _, n := range folderCoverNames {
			p := filepath.Join(abs, n)
			if in, err := fsops.RegularFile(p); err == nil && in.Size < art.MaxImageBytes {
				return os.ReadFile(p)
			}
		}
		return nil, nil
	}
	if !fi.Mode().IsRegular() {
		return nil, fsops.ErrNotRegular
	}
	return e.tagTools.Cover(ctx, abs)
}

// AlbumSong is one song in the album editor.
type AlbumSong struct {
	TagFile
	HasCover   bool `json:"has_cover"`
	EmbedCover bool `json:"embed_cover"` // the format can hold embedded art
}

// Album is an album folder with its songs (disc folders included).
type Album struct {
	Folder      string      `json:"folder"`
	Songs       []AlbumSong `json:"songs"`
	FolderCover string      `json:"folder_cover,omitempty"` // name of the folder image, if any
}

func (e *Engine) AlbumSongs(ctx context.Context, pairID int64, side, folder string) (Album, error) {
	a := Album{Folder: folder, Songs: []AlbumSong{}}
	if !e.TagEditing() {
		return a, ErrNoTagTools
	}
	l, err := e.loadPair(ctx, pairID)
	if err != nil {
		return a, err
	}
	root, err := sideRoot(l, side)
	if err != nil {
		return a, err
	}
	dir := root.Path
	if folder != "" {
		if dir, err = root.Resolve(folder); err != nil {
			return a, err
		}
	}
	for _, n := range folderCoverNames {
		if _, err := fsops.RegularFile(filepath.Join(dir, n)); err == nil {
			a.FolderCover = n
			break
		}
	}
	var rels []string
	collect := func(d, prefix string) {
		ents, _ := os.ReadDir(d)
		for _, en := range ents {
			if en.Type().IsRegular() && l.hasExt(en.Name()) && !strings.HasPrefix(en.Name(), ".") {
				rels = append(rels, filepath.Join(prefix, en.Name()))
			}
		}
	}
	collect(dir, folder)
	ents, _ := os.ReadDir(dir)
	for _, en := range ents {
		if en.IsDir() && discFolder.MatchString(en.Name()) {
			collect(filepath.Join(dir, en.Name()), filepath.Join(folder, en.Name()))
		}
	}
	if len(rels) == 0 {
		return a, nil
	}
	if len(rels) > maxTagFiles {
		return a, fmt.Errorf("%w: the folder has more than %d songs", ErrInvalidBulk, maxTagFiles)
	}
	files, err := e.ReadTags(ctx, pairID, side, rels)
	if err != nil {
		return a, err
	}
	for _, f := range files {
		s := AlbumSong{TagFile: f}
		if fm, ok := tags.FormatOf(f.Rel); ok {
			s.EmbedCover = fm.EmbedsCover()
		}
		if f.Editable {
			if abs, err := root.Resolve(f.Rel); err == nil {
				s.HasCover = e.tagTools.HasCover(ctx, abs)
			}
		}
		a.Songs = append(a.Songs, s)
	}
	return a, nil
}

// ---- folder image ----

type coverDetail struct {
	Side    string `json:"side"`
	Existed bool   `json:"existed"`
	Size    int64  `json:"size"`
	Mtime   int64  `json:"mtime"`
}

// writeFolderCover writes cover.jpg into an album folder. An existing one is
// kept in quarantine first; the operation can be undone.
func (e *Engine) writeFolderCover(ctx context.Context, l *libs, side, folder, src string) error {
	e.mu.Lock()
	defer e.mu.Unlock()
	root, _ := sideRoot(l, side)
	rel := filepath.Join(folder, FolderCoverName)
	abs, err := root.Resolve(rel)
	if err != nil {
		return err
	}
	o := store.Operation{PairID: l.pair.ID, Action: store.ActCover, QuarantineSide: side, Trigger: "art"}
	setSidePath(&o, side, rel)
	old, oldErr := fsops.RegularFile(abs)
	d := coverDetail{Side: side, Existed: oldErr == nil}
	o.Detail, _ = json.Marshal(d)
	if err := e.begin(ctx, &o); err != nil {
		return err
	}
	if o.DryRun {
		return nil
	}
	tmp := filepath.Join(filepath.Dir(abs), fsops.TmpPrefix+"cover.jpg")
	_ = os.Remove(tmp)
	err = func() error {
		if d.Existed {
			q := quarantinePath(l, o.ID, side, rel)
			if err := fsops.MkdirAllLike(filepath.Dir(q)); err != nil {
				return err
			}
			if err := fsops.LinkNew(abs, old, q); err != nil {
				return fmt.Errorf("quarantine: %w", err)
			}
			e.setQuarantine(ctx, o.ID, q)
		}
		if err := fsops.CopyNew(src, tmp, 0o644); err != nil {
			return err
		}
		if err := os.Rename(tmp, abs); err != nil {
			_ = os.Remove(tmp)
			return err
		}
		in, _ := fsops.Lstat(abs)
		d.Size, d.Mtime = in.Size, in.MtimeNs
		det, _ := json.Marshal(d)
		_, _ = e.st.DB.ExecContext(ctx, `UPDATE operations SET detail = ? WHERE id = ?`, string(det), o.ID)
		return fsops.SyncDir(filepath.Dir(abs))
	}()
	return e.finish(ctx, &o, err)
}

// undoCover restores the previous folder image, or removes the new one.
func (e *Engine) undoCover(l *libs, o store.Operation) error {
	var d coverDetail
	if err := json.Unmarshal(o.Detail, &d); err != nil {
		return err
	}
	root, err := sideRoot(l, d.Side)
	if err != nil {
		return err
	}
	rel := o.RelSlave
	if d.Side == SideMaster {
		rel = o.RelMaster
	}
	abs, err := root.Resolve(rel)
	if err != nil {
		return err
	}
	cur, err := fsops.RegularFile(abs)
	if err != nil {
		return err
	}
	if !cur.Unchanged(d.Size, d.Mtime) {
		return fmt.Errorf("%s changed after it was written; refusing to undo", rel)
	}
	if d.Existed {
		qi, err := e.quarantined(l, o.QuarantinePath)
		if err != nil {
			return err
		}
		if err := fsops.ReplaceWithLink(o.QuarantinePath, qi, abs); err != nil {
			return err
		}
		dropQuarantine(l, o.QuarantinePath, qi)
		return nil
	}
	if err := os.Remove(abs); err != nil {
		return err
	}
	return fsops.SyncDir(filepath.Dir(abs))
}

// ---- automatic matching ----

// ArtMatch are the options of an automatic match.
type ArtMatch struct {
	Side        string `json:"side"`
	Folder      string `json:"folder"`
	OnlyMissing bool   `json:"only_missing"`
	Embed       bool   `json:"embed"`
	FolderFile  bool   `json:"folder_file"`
}

// matchKey normalizes an artist or album name for comparison: case,
// punctuation, a leading "The" and release labels such as "(Deluxe)" are
// ignored.
func matchKey(s string) string {
	s = stripRelease(s)
	s = strings.TrimPrefix(strings.ToLower(strings.TrimSpace(s)), "the ")
	var b strings.Builder
	for _, r := range accentFold.Replace(s) {
		if unicode.IsLetter(r) || unicode.IsDigit(r) {
			b.WriteRune(r)
		}
	}
	return b.String()
}

// bestArt picks a confident match: artist and album must both closely match.
func bestArt(results []art.Result, artist, album string) (art.Result, float64, bool) {
	ak, bk := matchKey(artist), matchKey(album)
	var best art.Result
	bestScore := 0.0
	for _, r := range results {
		if r.Artist == "" || r.Title == "" {
			continue
		}
		sa := levenshteinRatio(matchKey(r.Artist), ak)
		sb := levenshteinRatio(matchKey(r.Title), bk)
		if sa < 0.85 || sb < 0.85 {
			continue
		}
		score := sa*0.4 + sb*0.6 + float64(min(r.Width, 3000))/100000
		if score > bestScore {
			best, bestScore = r, score
		}
	}
	return best, bestScore, bestScore > 0
}

// StartArtAutoMatch finds and applies covers for the albums in a folder.
func (e *Engine) StartArtAutoMatch(pairID int64, m ArtMatch) (*Job, error) {
	if !e.TagEditing() {
		return nil, ErrNoTagTools
	}
	if e.artClient == nil || e.artStore == nil {
		return nil, errors.New("album art is not available")
	}
	if m.Side != SideMaster && m.Side != SideSlave {
		return nil, fmt.Errorf("%w: side must be master or slave", ErrInvalidBulk)
	}
	if !m.Embed && !m.FolderFile {
		return nil, fmt.Errorf("%w: choose where the art goes", ErrInvalidBulk)
	}
	return e.startJob(pairID, "art-auto-match", func(ctx context.Context, j *Job) error {
		l, err := e.loadPair(ctx, pairID)
		if err != nil {
			return err
		}
		root, _ := sideRoot(l, m.Side)
		start := root
		if m.Folder != "" {
			abs, err := root.Resolve(m.Folder)
			if err != nil {
				return err
			}
			if start, err = fsops.NewRoot(abs); err != nil {
				return err
			}
		}
		files := map[string]fsops.Info{}
		if _, err := walk(ctx, l, start, files); err != nil {
			return err
		}
		type album struct {
			artist, title string
			rels          []string
		}
		albums := map[string]*album{}
		var order []string
		j.phase("Reading tags", int64(len(files)))
		for _, rel := range sortedKeys(files) {
			j.tick()
			full := filepath.Join(m.Folder, rel)
			fields, err := e.tagCache.get(ctx, e.tagTools, filepath.Join(start.Path, rel), files[rel])
			if err != nil {
				continue
			}
			v := valuesOf(fields)
			if v.artist == "" || v.album == "" {
				j.skip(full + ": missing artist or album tag")
				continue
			}
			key := matchKey(v.artist) + "|" + matchKey(v.album)
			if albums[key] == nil {
				albums[key] = &album{artist: v.artist, title: v.album}
				order = append(order, key)
			}
			albums[key].rels = append(albums[key].rels, full)
		}
		j.phase("Finding covers", int64(len(order)))
		for _, key := range order {
			if ctx.Err() != nil {
				return ctx.Err()
			}
			a := albums[key]
			label := a.artist + " – " + a.title
			j.tick()
			need := a.rels
			if m.OnlyMissing {
				need = nil
				for _, rel := range a.rels {
					abs, _ := root.Resolve(rel)
					if fm, ok := tags.FormatOf(rel); ok && fm.EmbedsCover() && m.Embed && !e.tagTools.HasCover(ctx, abs) {
						need = append(need, rel)
					}
				}
				folderMissing := false
				if m.FolderFile {
					for _, f := range albumFolders(a.rels) {
						if abs, err := root.Resolve(f); err == nil && !hasFolderCover(abs) {
							folderMissing = true
						}
					}
				}
				if len(need) == 0 && !folderMissing {
					j.count("already have art")
					continue
				}
			}
			res, _ := e.artClient.Search(ctx, art.Query{Artist: a.artist, Album: a.title}, e.artConfig(ctx, art.MatchSources))
			best, _, ok := bestArt(res, a.artist, a.title)
			if !ok {
				j.skip(label + ": no confident match")
				continue
			}
			b, err := e.artClient.FetchImage(ctx, best.URL)
			if err != nil {
				j.skip(label + ": download failed: " + err.Error())
				continue
			}
			p, err := e.artStore.Prepare(ctx, b, e.ArtSettings(ctx).MaxSize)
			if err != nil {
				j.skip(label + ": " + err.Error())
				continue
			}
			cover, _ := e.artStore.Path(p.Token)
			if m.Embed {
				for _, rel := range need {
					if err := e.editTagsOne(ctx, j, l, m.Side, rel, nil, cover, false); err != nil {
						j.skip(rel + ": " + err.Error())
					}
				}
			}
			if m.FolderFile {
				for _, f := range albumFolders(a.rels) {
					abs, _ := root.Resolve(f)
					if m.OnlyMissing && hasFolderCover(abs) {
						continue
					}
					if err := e.writeFolderCover(ctx, l, m.Side, f, cover); err != nil {
						j.skip(f + " cover.jpg: " + err.Error())
					}
				}
			}
			j.count("albums matched")
			j.note(fmt.Sprintf("%s: %s (%dx%d)", label, best.Source, p.Width, p.Height))
		}
		return nil
	})
}

func hasFolderCover(dir string) bool {
	for _, n := range folderCoverNames {
		if _, err := fsops.RegularFile(filepath.Join(dir, n)); err == nil {
			return true
		}
	}
	return false
}