package lyrics

import (
	"context"
	"strings"

	. "github.com/Masterminds/squirrel"
	"github.com/navidrome/navidrome/conf"
	"github.com/navidrome/navidrome/log"
	"github.com/navidrome/navidrome/model"
	"github.com/navidrome/navidrome/persistence"
)

// maxLegacyLyricsCandidates bounds the duplicate window scanned by the legacy
// artist/title lookup, so source-priority resolution can still reach older
// matches without turning it into an unbounded table scan.
const maxLegacyLyricsCandidates = 10

// Provider fetches lyrics for a single media file. It is the contract
// implemented by individual lyrics sources, such as plugins.
type Provider interface {
	GetLyrics(ctx context.Context, mf *model.MediaFile) (model.LyricList, error)
}

// Lyrics resolves lyrics for media files, honoring the configured source
// priority.
type Lyrics interface {
	Provider
	GetLyricsByArtistTitle(ctx context.Context, artist, title string) (model.LyricList, error)
}

// PluginLoader discovers and loads lyrics provider plugins.
type PluginLoader interface {
	LoadLyricsProvider(name string) (Provider, bool)
}

type lyricsService struct {
	ds           model.DataStore
	pluginLoader PluginLoader
}

// NewLyrics creates a new lyrics service. pluginLoader may be nil if no plugin
// system is available.
func NewLyrics(ds model.DataStore, pluginLoader PluginLoader) Lyrics {
	return &lyricsService{ds: ds, pluginLoader: pluginLoader}
}

// GetLyrics returns lyrics for the given media file, trying sources in the
// order specified by conf.Server.LyricsPriority.
func (l *lyricsService) GetLyrics(ctx context.Context, mf *model.MediaFile) (model.LyricList, error) {
	return l.getLyricsForCandidates(ctx, []*model.MediaFile{mf})
}

// GetLyricsByArtistTitle resolves lyrics for the legacy artist/title lookup,
// scanning a bounded window of duplicate matches so source priority still wins
// across them.
func (l *lyricsService) GetLyricsByArtistTitle(ctx context.Context, artist, title string) (model.LyricList, error) {
	opts := songsByArtistTitleWithLyricsFirst(artist, title)
	opts.Max = maxLegacyLyricsCandidates
	mediaFiles, err := l.ds.MediaFile(ctx).GetAll(opts)
	if err != nil {
		return nil, err
	}
	if len(mediaFiles) == 0 {
		return nil, nil
	}
	candidates := make([]*model.MediaFile, 0, len(mediaFiles))
	for i := range mediaFiles {
		candidates = append(candidates, &mediaFiles[i])
	}
	return l.getLyricsForCandidates(ctx, candidates)
}

func songsByArtistTitleWithLyricsFirst(artist, title string) model.QueryOptions {
	return model.QueryOptions{
		Sort:  "lyrics, updated_at",
		Order: "desc",
		Filters: And{
			Eq{"missing": false},
			Eq{"title": title},
			Or{
				persistence.Exists("json_tree(participants, '$.albumartist')", Eq{"value": artist}),
				persistence.Exists("json_tree(participants, '$.artist')", Eq{"value": artist}),
			},
		},
	}
}

func (l *lyricsService) getLyricsForCandidates(ctx context.Context, mediaFiles []*model.MediaFile) (model.LyricList, error) {
	for pattern := range strings.SplitSeq(conf.Server.LyricsPriority, ",") {
		pattern = strings.TrimSpace(pattern)
		if pattern == "" {
			continue
		}

		for _, mf := range mediaFiles {
			if mf == nil {
				continue
			}

			lyricsList, err := l.getLyricsFromSource(ctx, mf, pattern)
			if err != nil {
				log.Error(ctx, "error getting lyrics", "source", pattern, err)
				continue
			}

			if len(lyricsList) > 0 {
				return lyricsList, nil
			}
		}
	}

	return nil, nil
}

func (l *lyricsService) getLyricsFromSource(ctx context.Context, mf *model.MediaFile, pattern string) (model.LyricList, error) {
	switch {
	case strings.EqualFold(pattern, "embedded"):
		return fromEmbedded(ctx, mf)
	case strings.HasPrefix(pattern, "."):
		return fromExternalFile(ctx, mf, pattern)
	default:
		return l.fromPlugin(ctx, mf, pattern)
	}
}