package library

import (
	"context"
	"errors"
	"fmt"
	"path"
	"strconv"
	"strings"
	"time"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"

	"pipu/api/internal/library/meta"
)

// ErrNotFound — запись не найдена.
var ErrNotFound = errors.New("library: not found")

// SourceType — тип хранилища.
type SourceType string

// Типы хранилищ.
const (
	SourceNFS   SourceType = "nfs"
	SourceLocal SourceType = "local"
)

// Source — хранилище (library_sources).
type Source struct {
	ID             uuid.UUID
	Name           string
	Type           SourceType
	NFSServer      *string
	NFSExport      *string
	NFSOptions     string
	LocalPath      *string
	TagsFirst      bool
	ScanInterval   *time.Duration
	Status         string // pending | mounted | error | disabled
	StatusMessage  *string
	LastScanAt     *time.Time
	CreatedAt      time.Time
	AcceptsUploads bool
	WriteTemplate  *string
	ExcludedDirs   []string
}

// PatternRow — шаблон пути источника.
type PatternRow struct {
	Regex     string
	IsEnabled bool
}

// FileRow — то, что сканеру нужно знать о ранее найденном файле.
type FileRow struct {
	ID          uuid.UUID
	RelPath     string
	Size        int64
	Mtime       time.Time
	ContentHash []byte
	TrackID     *uuid.UUID
	Missing     bool
}

// FileData — результат чтения файла для записи в media_files.
type FileData struct {
	RelPath     string
	Size        int64
	Mtime       time.Time
	ContentHash []byte
	Probe       Probe
	ScanError   string
}

// Store — доступ к таблицам библиотеки и каталога.
type Store struct {
	pool *pgxpool.Pool
}

// NewStore создаёт Store.
func NewStore(pool *pgxpool.Pool) *Store { return &Store{pool: pool} }

func newID() uuid.UUID { return uuid.Must(uuid.NewV7()) }

const sourceColumns = `id, name, type, nfs_server, nfs_export, nfs_options, local_path, tag_priority = 'tags_first',
	extract(epoch from scan_interval)::bigint, status, status_message, last_scan_at, created_at, accepts_uploads,
	write_template, excluded_dirs`

func scanSource(row pgx.Row) (Source, error) {
	var (
		s        Source
		typ      string
		interval *int64
	)
	err := row.Scan(&s.ID, &s.Name, &typ, &s.NFSServer, &s.NFSExport, &s.NFSOptions, &s.LocalPath, &s.TagsFirst,
		&interval, &s.Status, &s.StatusMessage, &s.LastScanAt, &s.CreatedAt, &s.AcceptsUploads, &s.WriteTemplate, &s.ExcludedDirs)
	if errors.Is(err, pgx.ErrNoRows) {
		return Source{}, ErrNotFound
	}
	if err != nil {
		return Source{}, fmt.Errorf("library: scan source: %w", err)
	}
	s.Type = SourceType(typ)
	if interval != nil {
		d := time.Duration(*interval) * time.Second
		s.ScanInterval = &d
	}
	return s, nil
}

// ListSources — все хранилища по дате создания.
func (st *Store) ListSources(ctx context.Context) ([]Source, error) {
	rows, err := st.pool.Query(ctx, `SELECT `+sourceColumns+` FROM library_sources ORDER BY created_at`)
	if err != nil {
		return nil, fmt.Errorf("library: list sources: %w", err)
	}
	defer rows.Close()
	var out []Source
	for rows.Next() {
		s, err := scanSource(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, s)
	}
	return out, rows.Err()
}

// GetSource — хранилище по id.
func (st *Store) GetSource(ctx context.Context, id uuid.UUID) (Source, error) {
	return scanSource(st.pool.QueryRow(ctx, `SELECT `+sourceColumns+` FROM library_sources WHERE id = $1`, id))
}

func intervalSeconds(d *time.Duration) *int64 {
	if d == nil {
		return nil
	}
	sec := int64(*d / time.Second)
	return &sec
}

func tagPriority(tagsFirst bool) string {
	if tagsFirst {
		return "tags_first"
	}
	return "path_first"
}

// SaveSource создаёт или полностью обновляет хранилище (кроме статуса и времени скана).
func (st *Store) SaveSource(ctx context.Context, s Source) (Source, error) {
	if s.ExcludedDirs == nil {
		s.ExcludedDirs = []string{}
	}
	return scanSource(st.pool.QueryRow(ctx, `
		INSERT INTO library_sources (id, name, type, nfs_server, nfs_export, nfs_options, local_path, tag_priority,
			scan_interval, status, status_message, accepts_uploads, write_template, excluded_dirs, created_at)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, make_interval(secs => $9::bigint), $10, $11, $12, $13, $14, now())
		ON CONFLICT (id) DO UPDATE SET name = EXCLUDED.name, nfs_server = EXCLUDED.nfs_server,
			nfs_export = EXCLUDED.nfs_export, nfs_options = EXCLUDED.nfs_options, local_path = EXCLUDED.local_path,
			tag_priority = EXCLUDED.tag_priority, scan_interval = EXCLUDED.scan_interval,
			accepts_uploads = EXCLUDED.accepts_uploads, write_template = EXCLUDED.write_template, excluded_dirs = EXCLUDED.excluded_dirs
		RETURNING `+sourceColumns,
		s.ID, s.Name, string(s.Type), s.NFSServer, s.NFSExport, s.NFSOptions, s.LocalPath, tagPriority(s.TagsFirst),
		intervalSeconds(s.ScanInterval), s.Status, s.StatusMessage, s.AcceptsUploads, s.WriteTemplate, s.ExcludedDirs))
}

// SetSourceStatus обновляет состояние подключения.
func (st *Store) SetSourceStatus(ctx context.Context, id uuid.UUID, status string, message *string) error {
	_, err := st.pool.Exec(ctx, `UPDATE library_sources SET status = $2, status_message = $3 WHERE id = $1`,
		id, status, message)
	if err != nil {
		return fmt.Errorf("library: set source status: %w", err)
	}
	return nil
}

// SetLastScan отмечает время завершения скана.
func (st *Store) SetLastScan(ctx context.Context, id uuid.UUID, at time.Time) error {
	_, err := st.pool.Exec(ctx, `UPDATE library_sources SET last_scan_at = $2 WHERE id = $1`, id, at)
	if err != nil {
		return fmt.Errorf("library: set last scan: %w", err)
	}
	return nil
}

// DeleteSource удаляет хранилище; файлы удаляются каскадно, каталог чистится отдельно (CleanupOrphans).
func (st *Store) DeleteSource(ctx context.Context, id uuid.UUID) error {
	tag, err := st.pool.Exec(ctx, `DELETE FROM library_sources WHERE id = $1`, id)
	if err != nil {
		return fmt.Errorf("library: delete source: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// Patterns — шаблоны источника по порядку.
func (st *Store) Patterns(ctx context.Context, sourceID uuid.UUID) ([]PatternRow, error) {
	rows, err := st.pool.Query(ctx,
		`SELECT regex, is_enabled FROM path_patterns WHERE source_id = $1 ORDER BY position`, sourceID)
	if err != nil {
		return nil, fmt.Errorf("library: patterns: %w", err)
	}
	return pgx.CollectRows(rows, func(r pgx.CollectableRow) (PatternRow, error) {
		var p PatternRow
		return p, r.Scan(&p.Regex, &p.IsEnabled)
	})
}

// ReplacePatterns заменяет список шаблонов источника.
func (st *Store) ReplacePatterns(ctx context.Context, sourceID uuid.UUID, patterns []PatternRow) error {
	return pgx.BeginFunc(ctx, st.pool, func(tx pgx.Tx) error {
		if _, err := tx.Exec(ctx, `DELETE FROM path_patterns WHERE source_id = $1`, sourceID); err != nil {
			return fmt.Errorf("library: replace patterns: %w", err)
		}
		for i, p := range patterns {
			if _, err := tx.Exec(ctx, `
				INSERT INTO path_patterns (id, source_id, position, regex, is_enabled) VALUES ($1, $2, $3, $4, $5)`,
				newID(), sourceID, i, p.Regex, p.IsEnabled); err != nil {
				return fmt.Errorf("library: replace patterns: %w", err)
			}
		}
		return nil
	})
}

// Files — все известные файлы источника по относительному пути.
func (st *Store) Files(ctx context.Context, sourceID uuid.UUID) (map[string]FileRow, error) {
	rows, err := st.pool.Query(ctx, `
		SELECT id, rel_path, size_bytes, mtime, content_hash, track_id, missing_since IS NOT NULL
		FROM media_files WHERE source_id = $1`, sourceID)
	if err != nil {
		return nil, fmt.Errorf("library: files: %w", err)
	}
	defer rows.Close()
	out := map[string]FileRow{}
	for rows.Next() {
		var f FileRow
		if err := rows.Scan(&f.ID, &f.RelPath, &f.Size, &f.Mtime, &f.ContentHash, &f.TrackID, &f.Missing); err != nil {
			return nil, fmt.Errorf("library: files: %w", err)
		}
		out[f.RelPath] = f
	}
	return out, rows.Err()
}

// FileByPath — файл источника по пути (точечный скан).
func (st *Store) FileByPath(ctx context.Context, sourceID uuid.UUID, rel string) (FileRow, bool, error) {
	var f FileRow
	err := st.pool.QueryRow(ctx, `
		SELECT id, rel_path, size_bytes, mtime, content_hash, track_id, missing_since IS NOT NULL
		FROM media_files WHERE source_id = $1 AND rel_path = $2`, sourceID, rel).
		Scan(&f.ID, &f.RelPath, &f.Size, &f.Mtime, &f.ContentHash, &f.TrackID, &f.Missing)
	if errors.Is(err, pgx.ErrNoRows) {
		return FileRow{}, false, nil
	}
	if err != nil {
		return FileRow{}, false, fmt.Errorf("library: file by path: %w", err)
	}
	return f, true, nil
}

// SampleFiles — случайная выборка путей источника (для предпросмотра шаблонов).
func (st *Store) SampleFiles(ctx context.Context, sourceID uuid.UUID, n int) ([]string, error) {
	rows, err := st.pool.Query(ctx, `
		SELECT f.rel_path FROM media_files f JOIN library_sources s ON s.id = f.source_id
		WHERE f.source_id = $1 AND f.missing_since IS NULL AND NOT library_path_excluded(f.rel_path, s.excluded_dirs)
		ORDER BY random() LIMIT $2`,
		sourceID, n)
	if err != nil {
		return nil, fmt.Errorf("library: sample files: %w", err)
	}
	return pgx.CollectRows(rows, pgx.RowTo[string])
}

// SaveFile записывает файл (новый — id = uuid.Nil) и возвращает его id.
func (st *Store) SaveFile(ctx context.Context, sourceID, id uuid.UUID, d FileData, trackID *uuid.UUID) (uuid.UUID, error) {
	if id == uuid.Nil {
		id = newID()
	}
	var scanErr *string
	if d.ScanError != "" {
		scanErr = &d.ScanError
	}
	p := d.Probe
	if p.Format == "" {
		p.Format = "unknown"
	}
	_, err := st.pool.Exec(ctx, `
		INSERT INTO media_files (id, source_id, rel_path, size_bytes, mtime, content_hash, format, codec, bitrate,
			sample_rate, bit_depth, channels, duration_ms, track_id, scan_error)
		VALUES ($1, $2, $3, $4, $5, $6, $7, NULLIF($8, ''), NULLIF($9, 0), NULLIF($10, 0), NULLIF($11, 0),
			NULLIF($12, 0), $13, $14, $15)
		ON CONFLICT (id) DO UPDATE SET rel_path = EXCLUDED.rel_path, size_bytes = EXCLUDED.size_bytes,
			mtime = EXCLUDED.mtime, content_hash = EXCLUDED.content_hash, format = EXCLUDED.format,
			codec = EXCLUDED.codec, bitrate = EXCLUDED.bitrate, sample_rate = EXCLUDED.sample_rate,
			bit_depth = EXCLUDED.bit_depth, channels = EXCLUDED.channels, duration_ms = EXCLUDED.duration_ms,
			track_id = EXCLUDED.track_id, scan_error = EXCLUDED.scan_error, missing_since = NULL,
			-- Содержимое изменилось — отпечатки посчитаются заново.
			sha256 = CASE WHEN media_files.content_hash IS DISTINCT FROM EXCLUDED.content_hash
				OR media_files.size_bytes <> EXCLUDED.size_bytes THEN NULL ELSE media_files.sha256 END,
			fingerprinted_at = CASE WHEN media_files.content_hash IS DISTINCT FROM EXCLUDED.content_hash
				OR media_files.size_bytes <> EXCLUDED.size_bytes THEN NULL ELSE media_files.fingerprinted_at END`,
		id, sourceID, d.RelPath, d.Size, d.Mtime, d.ContentHash, p.Format, p.Codec, p.Bitrate, p.SampleRate,
		p.BitDepth, p.Channels, p.DurationMs, trackID, scanErr)
	if err != nil {
		return uuid.Nil, fmt.Errorf("library: save file %s: %w", d.RelPath, err)
	}
	return id, nil
}

// MoveFile — переименование / перенос: путь меняется, трек (лайки, история) сохраняется.
func (st *Store) MoveFile(ctx context.Context, id uuid.UUID, relPath string, size int64, mtime time.Time) error {
	_, err := st.pool.Exec(ctx, `
		UPDATE media_files SET rel_path = $2, size_bytes = $3, mtime = $4, missing_since = NULL WHERE id = $1`,
		id, relPath, size, mtime)
	if err != nil {
		return fmt.Errorf("library: move file: %w", err)
	}
	return nil
}

// SetPresent снимает отметку «пропал» с файла, который снова на месте.
func (st *Store) SetPresent(ctx context.Context, id uuid.UUID) error {
	_, err := st.pool.Exec(ctx, `UPDATE media_files SET missing_since = NULL WHERE id = $1`, id)
	if err != nil {
		return fmt.Errorf("library: set present: %w", err)
	}
	return nil
}

// MarkMissing отмечает пропавшие файлы (если ещё не отмечены).
func (st *Store) MarkMissing(ctx context.Context, ids []uuid.UUID, at time.Time) error {
	if len(ids) == 0 {
		return nil
	}
	_, err := st.pool.Exec(ctx, `
		UPDATE media_files SET missing_since = $2 WHERE id = ANY($1) AND missing_since IS NULL`, ids, at)
	if err != nil {
		return fmt.Errorf("library: mark missing: %w", err)
	}
	return nil
}

// PurgeMissing удаляет файлы, пропавшие раньше before.
func (st *Store) PurgeMissing(ctx context.Context, sourceID uuid.UUID, before time.Time) (int64, error) {
	tag, err := st.pool.Exec(ctx, `DELETE FROM media_files f USING library_sources s
		WHERE f.source_id = s.id AND f.source_id = $1 AND f.missing_since < $2
		AND NOT library_path_excluded(f.rel_path, s.excluded_dirs)`,
		sourceID, before)
	if err != nil {
		return 0, fmt.Errorf("library: purge missing: %w", err)
	}
	return tag.RowsAffected(), nil
}

// ArtistKeyExists — есть ли исполнитель с таким ключом (для разбора «A & B»).
func (st *Store) ArtistKeyExists(ctx context.Context, key string) bool {
	var ok bool
	_ = st.pool.QueryRow(ctx, `SELECT EXISTS (SELECT 1 FROM artists WHERE name_norm = $1)`, key).Scan(&ok)
	return ok
}

// EnsureArtist находит или создаёт исполнителя по нормализованному имени.
func (st *Store) EnsureArtist(ctx context.Context, name string) (uuid.UUID, error) {
	var id uuid.UUID
	err := st.pool.QueryRow(ctx, `
		INSERT INTO artists (id, name, sort_name, name_norm) VALUES ($1, $2, $3, $4)
		ON CONFLICT (name_norm) DO UPDATE SET name_norm = EXCLUDED.name_norm
		RETURNING id`, newID(), name, meta.SortName(name), meta.Key(name)).Scan(&id)
	if err != nil {
		return uuid.Nil, fmt.Errorf("library: ensure artist %q: %w", name, err)
	}
	return id, nil
}

// EnsureAlbum находит или создаёт альбом исполнителя; год заполняется, если был пуст.
func (st *Store) EnsureAlbum(ctx context.Context, artistID uuid.UUID, title string, year int) (uuid.UUID, error) {
	var id uuid.UUID
	err := st.pool.QueryRow(ctx, `
		INSERT INTO albums (id, title, title_norm, album_artist_id, year) VALUES ($1, $2, $3, $4, NULLIF($5, 0))
		ON CONFLICT (album_artist_id, title_norm) DO UPDATE SET year = COALESCE(albums.year, EXCLUDED.year)
		RETURNING id`, newID(), title, meta.Key(title), artistID, year).Scan(&id)
	if err != nil {
		return uuid.Nil, fmt.Errorf("library: ensure album %q: %w", title, err)
	}
	return id, nil
}

// TrackInput — данные трека из метаданных файла.
type TrackInput struct {
	AlbumID    uuid.UUID
	Title      string
	Disc       int
	Track      int
	Year       int
	DurationMs int
}

// FindTrack ищет дубль: тот же альбом и название, длительность ±2 с.
func (st *Store) FindTrack(ctx context.Context, in TrackInput) (uuid.UUID, bool, error) {
	var id uuid.UUID
	err := st.pool.QueryRow(ctx, `
		SELECT id FROM tracks WHERE album_id = $1 AND title_norm = $2 AND abs(duration_ms - $3) <= 2000
		ORDER BY abs(duration_ms - $3) LIMIT 1`, in.AlbumID, meta.Key(in.Title), in.DurationMs).Scan(&id)
	if errors.Is(err, pgx.ErrNoRows) {
		return uuid.Nil, false, nil
	}
	if err != nil {
		return uuid.Nil, false, fmt.Errorf("library: find track: %w", err)
	}
	return id, true, nil
}

// SaveTrack создаёт (id = uuid.Nil) или обновляет трек.
func (st *Store) SaveTrack(ctx context.Context, id uuid.UUID, in TrackInput) (uuid.UUID, error) {
	if id == uuid.Nil {
		id = newID()
	}
	_, err := st.pool.Exec(ctx, `
		INSERT INTO tracks (id, title, title_norm, album_id, disc_no, track_no, year, duration_ms)
		VALUES ($1, $2, $3, $4, NULLIF($5, 0), NULLIF($6, 0), NULLIF($7, 0), $8)
		ON CONFLICT (id) DO UPDATE SET title = EXCLUDED.title, title_norm = EXCLUDED.title_norm,
			album_id = EXCLUDED.album_id, disc_no = EXCLUDED.disc_no, track_no = EXCLUDED.track_no,
			year = EXCLUDED.year, duration_ms = EXCLUDED.duration_ms, updated_at = now()`,
		id, in.Title, meta.Key(in.Title), in.AlbumID, in.Disc, in.Track, in.Year, in.DurationMs)
	if err != nil {
		return uuid.Nil, fmt.Errorf("library: save track: %w", err)
	}
	return id, nil
}

// SetTrackArtists заменяет исполнителей трека.
func (st *Store) SetTrackArtists(ctx context.Context, trackID uuid.UUID, ids []uuid.UUID, roles []string) error {
	return pgx.BeginFunc(ctx, st.pool, func(tx pgx.Tx) error {
		if _, err := tx.Exec(ctx, `DELETE FROM track_artists WHERE track_id = $1`, trackID); err != nil {
			return fmt.Errorf("library: track artists: %w", err)
		}
		for i, id := range ids {
			if _, err := tx.Exec(ctx, `
				INSERT INTO track_artists (track_id, artist_id, role, position) VALUES ($1, $2, $3, $4)
				ON CONFLICT DO NOTHING`, trackID, id, roles[i], i); err != nil {
				return fmt.Errorf("library: track artists: %w", err)
			}
		}
		return nil
	})
}

// SetTrackGenres заменяет жанры трека из тегов.
func (st *Store) SetTrackGenres(ctx context.Context, trackID uuid.UUID, genres []string) error {
	return pgx.BeginFunc(ctx, st.pool, func(tx pgx.Tx) error {
		if _, err := tx.Exec(ctx, `DELETE FROM track_genres WHERE track_id = $1 AND source = 'tag'`, trackID); err != nil {
			return fmt.Errorf("library: track genres: %w", err)
		}
		for _, g := range genres {
			var gid int
			if err := tx.QueryRow(ctx, `
				INSERT INTO genres (name, name_norm) VALUES ($1, $2)
				ON CONFLICT (name_norm) DO UPDATE SET name_norm = EXCLUDED.name_norm RETURNING id`,
				g, meta.Key(g)).Scan(&gid); err != nil {
				return fmt.Errorf("library: genre %q: %w", g, err)
			}
			if _, err := tx.Exec(ctx, `
				INSERT INTO track_genres (track_id, genre_id, source) VALUES ($1, $2, 'tag') ON CONFLICT DO NOTHING`,
				trackID, gid); err != nil {
				return fmt.Errorf("library: track genres: %w", err)
			}
		}
		return nil
	})
}

// RefreshPrimaryFile выбирает лучший доступный файл трека: lossless, затем битрейт.
func (st *Store) RefreshPrimaryFile(ctx context.Context, trackID uuid.UUID) error {
	_, err := st.pool.Exec(ctx, `
		UPDATE tracks SET primary_file_id = (
			SELECT id FROM media_files
			WHERE track_id = $1 AND missing_since IS NULL AND scan_error IS NULL
			ORDER BY (codec IN ('flac', 'alac', 'wavpack', 'ape', 'tta') OR codec LIKE 'pcm_%') DESC,
				bitrate DESC NULLS LAST, size_bytes DESC
			LIMIT 1)
		WHERE id = $1`, trackID)
	if err != nil {
		return fmt.Errorf("library: refresh primary file: %w", err)
	}
	return nil
}

// CleanupOrphans удаляет треки без файлов, затем пустые альбомы и исполнителей.
func (st *Store) CleanupOrphans(ctx context.Context) error {
	for _, q := range []string{
		`DELETE FROM tracks t WHERE NOT EXISTS (SELECT 1 FROM media_files f WHERE f.track_id = t.id)`,
		`DELETE FROM albums a WHERE NOT EXISTS (SELECT 1 FROM tracks t WHERE t.album_id = a.id)`,
		`DELETE FROM artists a WHERE NOT EXISTS (SELECT 1 FROM albums al WHERE al.album_artist_id = a.id)
			AND NOT EXISTS (SELECT 1 FROM track_artists ta WHERE ta.artist_id = a.id)`,
		`DELETE FROM genres g WHERE NOT EXISTS (SELECT 1 FROM track_genres tg WHERE tg.genre_id = g.id)
			AND NOT EXISTS (SELECT 1 FROM genres c WHERE c.parent_id = g.id)`,
	} {
		if _, err := st.pool.Exec(ctx, q); err != nil {
			return fmt.Errorf("library: cleanup: %w", err)
		}
	}
	return nil
}

// Counts — счётчики для статуса библиотеки.
type Counts struct {
	Artists, Albums, Tracks, Files, Missing, Errors int64
}

// Counts считает объём библиотеки.
func (st *Store) Counts(ctx context.Context) (Counts, error) {
	var c Counts
	err := st.pool.QueryRow(ctx, `
		SELECT (SELECT count(*) FROM artists), (SELECT count(*) FROM albums), (SELECT count(*) FROM tracks),
			(SELECT count(*) FROM media_files), (SELECT count(*) FROM media_files WHERE missing_since IS NOT NULL),
			(SELECT count(*) FROM media_files f JOIN library_sources s ON s.id = f.source_id
			 WHERE f.scan_error IS NOT NULL AND f.missing_since IS NULL AND NOT library_path_excluded(f.rel_path, s.excluded_dirs))`).
		Scan(&c.Artists, &c.Albums, &c.Tracks, &c.Files, &c.Missing, &c.Errors)
	if err != nil {
		return Counts{}, fmt.Errorf("library: counts: %w", err)
	}
	return c, nil
}

// FileError — файл, который не удалось прочитать.
type FileError struct {
	ID        uuid.UUID
	SourceID  uuid.UUID
	RelPath   string
	ScanError string
}

// FileErrors — страница файлов с ошибками чтения (по пути, после after).
func (st *Store) FileErrors(ctx context.Context, after string, limit int) ([]FileError, error) {
	rows, err := st.pool.Query(ctx, `
		SELECT f.id, f.source_id, f.rel_path, f.scan_error FROM media_files f JOIN library_sources s ON s.id = f.source_id
		WHERE f.scan_error IS NOT NULL AND f.missing_since IS NULL AND NOT library_path_excluded(f.rel_path, s.excluded_dirs)
		AND f.rel_path > $1 ORDER BY f.rel_path LIMIT $2`, after, limit)
	if err != nil {
		return nil, fmt.Errorf("library: file errors: %w", err)
	}
	return pgx.CollectRows(rows, func(r pgx.CollectableRow) (FileError, error) {
		var e FileError
		return e, r.Scan(&e.ID, &e.SourceID, &e.RelPath, &e.ScanError)
	})
}

// AlbumsWithoutCover — альбомы, обложку которых ещё не искали, и доступный файл первого трека.
// Альбомы без доступных файлов пропускаются: искать не в чем.
func (st *Store) AlbumsWithoutCover(ctx context.Context, limit int, after uuid.UUID) ([]CoverCandidate, error) {
	rows, err := st.pool.Query(ctx, `
		SELECT al.id, f.source_id, f.rel_path
		FROM albums al
		CROSS JOIN LATERAL (
			SELECT mf.source_id, mf.rel_path FROM tracks t
			JOIN media_files mf ON mf.id = t.primary_file_id
			JOIN library_sources s ON s.id = mf.source_id AND s.status = 'mounted'
			WHERE t.album_id = al.id AND mf.missing_since IS NULL AND mf.scan_error IS NULL
				AND NOT library_path_excluded(mf.rel_path, s.excluded_dirs)
			ORDER BY t.disc_no NULLS FIRST, t.track_no NULLS LAST
			LIMIT 1) f
		WHERE al.cover_checked_at IS NULL AND al.id > $2
		ORDER BY al.id
		LIMIT $1`, limit, after)
	if err != nil {
		return nil, fmt.Errorf("library: albums without cover: %w", err)
	}
	return pgx.CollectRows(rows, func(r pgx.CollectableRow) (CoverCandidate, error) {
		var c CoverCandidate
		return c, r.Scan(&c.AlbumID, &c.SourceID, &c.RelPath)
	})
}

// SetAlbumCover сохраняет найденную обложку (nil — обложки нет) и отмечает альбом проверенным.
func (st *Store) SetAlbumCover(ctx context.Context, albumID uuid.UUID, coverPath *string, colors []string) error {
	_, err := st.pool.Exec(ctx, `
		UPDATE albums SET cover_path = $2, cover_colors = $3, cover_checked_at = now() WHERE id = $1`,
		albumID, coverPath, colors)
	if err != nil {
		return fmt.Errorf("library: set album cover: %w", err)
	}
	return nil
}

// ResetCoverChecks — найти недостающие обложки заново после скана источника.
func (st *Store) ResetCoverChecks(ctx context.Context, sourceID uuid.UUID) error {
	_, err := st.pool.Exec(ctx, `
		UPDATE albums al SET cover_checked_at = NULL
		WHERE al.cover_path IS NULL AND EXISTS (
			SELECT 1 FROM tracks t JOIN media_files f ON f.track_id = t.id
			WHERE t.album_id = al.id AND f.source_id = $1)`, sourceID)
	if err != nil {
		return fmt.Errorf("library: reset cover checks: %w", err)
	}
	return nil
}

// AlbumCoverPath — ключ обложки альбома (nil — обложки нет).
func (st *Store) AlbumCoverPath(ctx context.Context, albumID uuid.UUID) (*string, error) {
	var p *string
	err := st.pool.QueryRow(ctx, `SELECT cover_path FROM albums WHERE id = $1`, albumID).Scan(&p)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("library: album cover: %w", err)
	}
	return p, nil
}

// AnalysisCounts — состояние очереди аудиоанализа.
type AnalysisCounts struct {
	Queued, Running, Done, Failed int
	AnalyzerVer, TopError         *string
}

// AnalysisCounts считает задачи анализа по статусам и текущую версию анализатора.
func (st *Store) AnalysisCounts(ctx context.Context) (AnalysisCounts, error) {
	var c AnalysisCounts
	err := st.pool.QueryRow(ctx, `
		WITH jobs AS (SELECT * FROM analysis_jobs WHERE NOT library_track_scan_excluded(track_id))
		SELECT count(*) FILTER (WHERE status = 'queued'), count(*) FILTER (WHERE status = 'running'),
			count(*) FILTER (WHERE status = 'done'), count(*) FILTER (WHERE status = 'failed'),
			(SELECT analyzer_ver FROM track_features ORDER BY analyzed_at DESC LIMIT 1),
			(SELECT error FROM jobs WHERE status = 'failed' AND error IS NOT NULL
			 GROUP BY error ORDER BY count(*) DESC LIMIT 1)
		FROM jobs`).Scan(&c.Queued, &c.Running, &c.Done, &c.Failed, &c.AnalyzerVer, &c.TopError)
	if err != nil {
		return AnalysisCounts{}, fmt.Errorf("library: analysis counts: %w", err)
	}
	return c, nil
}

// AnalysisError is a failed analysis job with a known file path, when available.
type AnalysisError struct {
	TrackID    uuid.UUID
	Title      string
	SourceID   *uuid.UUID
	SourceName *string
	RelPath    *string
	Error      string
}

// AnalysisErrors includes failed jobs even when their file is no longer available.
func (st *Store) AnalysisErrors(ctx context.Context, after uuid.UUID, limit int) ([]AnalysisError, error) {
	rows, err := st.pool.Query(ctx, `
		SELECT t.id, t.title, f.source_id, s.name, f.rel_path, COALESCE(a.error, '')
		FROM analysis_jobs a JOIN tracks t ON t.id = a.track_id
		LEFT JOIN LATERAL (
			SELECT mf.source_id, mf.rel_path FROM media_files mf JOIN library_sources src ON src.id = mf.source_id
			WHERE mf.track_id = t.id AND NOT library_path_excluded(mf.rel_path, src.excluded_dirs)
			ORDER BY (mf.id = t.primary_file_id) DESC NULLS LAST, (mf.missing_since IS NULL) DESC, mf.id
			LIMIT 1
		) f ON true
		LEFT JOIN library_sources s ON s.id = f.source_id
		WHERE a.status = 'failed' AND NOT library_track_scan_excluded(t.id) AND t.id > $1 ORDER BY t.id LIMIT $2`, after, limit)
	if err != nil {
		return nil, fmt.Errorf("library: analysis errors: %w", err)
	}
	return pgx.CollectRows(rows, func(r pgx.CollectableRow) (AnalysisError, error) {
		var e AnalysisError
		return e, r.Scan(&e.TrackID, &e.Title, &e.SourceID, &e.SourceName, &e.RelPath, &e.Error)
	})
}

// RetryFailedAnalysis returns failed jobs to the queue with attempts reset.
func (st *Store) RetryFailedAnalysis(ctx context.Context) (int, error) {
	tag, err := st.pool.Exec(ctx, `
		UPDATE analysis_jobs SET status = 'queued', attempts = 0, error = NULL, updated_at = now()
		WHERE status = 'failed' AND NOT library_track_scan_excluded(track_id)`)
	if err != nil {
		return 0, fmt.Errorf("library: retry analysis: %w", err)
	}
	return int(tag.RowsAffected()), nil
}

// WaveMetrics — метрики волны за 7 дней (docs/recommendations.md#1-цели-и-как-измеряем-успех).
type WaveMetrics struct {
	Served, Sessions int
	WaveRates
	ByModel []WaveModelMetrics
}

// WaveRates — доли по показам с известным исходом (nil — исходов ещё нет).
type WaveRates struct {
	ListenThrough, EarlySkip, LikeRate *float32
}

// WaveModelMetrics — метрики показов одной версии модели.
type WaveModelMetrics struct {
	ModelVer string
	Served   int
	WaveRates
}

func rates(judged, through, early, liked int) WaveRates {
	if judged == 0 {
		return WaveRates{}
	}
	lt, es, lr := float32(through)/float32(judged), float32(early)/float32(judged), float32(liked)*100/float32(judged)
	return WaveRates{ListenThrough: &lt, EarlySkip: &es, LikeRate: &lr}
}

const waveOutcomes = `count(outcome),
			count(*) FILTER (WHERE outcome IN ('complete', 'like')),
			count(*) FILTER (WHERE outcome IN ('skip_early', 'dislike')),
			count(*) FILTER (WHERE outcome = 'like')`

// WaveMetrics считает метрики по показам с известным исходом.
func (st *Store) WaveMetrics(ctx context.Context) (WaveMetrics, error) {
	var (
		m                             WaveMetrics
		judged, through, early, liked int
	)
	err := st.pool.QueryRow(ctx, `
		SELECT count(*), count(DISTINCT wave_session_id), `+waveOutcomes+`
		FROM wave_impressions WHERE served_at > now() - interval '7 days'`).
		Scan(&m.Served, &m.Sessions, &judged, &through, &early, &liked)
	if err != nil {
		return WaveMetrics{}, fmt.Errorf("library: wave metrics: %w", err)
	}
	m.WaveRates = rates(judged, through, early, liked)

	rows, err := st.pool.Query(ctx, `
		SELECT coalesce(model_ver, ''), count(*), `+waveOutcomes+`
		FROM wave_impressions WHERE served_at > now() - interval '7 days'
		GROUP BY 1 ORDER BY 2 DESC`)
	if err != nil {
		return WaveMetrics{}, fmt.Errorf("library: wave metrics by model: %w", err)
	}
	defer rows.Close()
	m.ByModel = []WaveModelMetrics{}
	for rows.Next() {
		var mm WaveModelMetrics
		if err := rows.Scan(&mm.ModelVer, &mm.Served, &judged, &through, &early, &liked); err != nil {
			return WaveMetrics{}, fmt.Errorf("library: wave metrics by model: %w", err)
		}
		mm.WaveRates = rates(judged, through, early, liked)
		m.ByModel = append(m.ByModel, mm)
	}
	return m, rows.Err()
}

// FingerprintTodo — файл, которому нужны отпечатки.
type FingerprintTodo struct {
	ID       uuid.UUID
	SourceID uuid.UUID
	RelPath  string
	SHA256   []byte // уже посчитан — повторно не читаем
}

// FilesToFingerprint — файлы смонтированных источников без SHA-256 (и без Chromaprint, если withFP), после after.
func (st *Store) FilesToFingerprint(ctx context.Context, withFP bool, after uuid.UUID, limit int) ([]FingerprintTodo, error) {
	rows, err := st.pool.Query(ctx, `
		SELECT mf.id, mf.source_id, mf.rel_path, mf.sha256
		FROM media_files mf
		JOIN library_sources s ON s.id = mf.source_id AND s.status = 'mounted'
		WHERE mf.missing_since IS NULL AND mf.scan_error IS NULL
			AND NOT library_path_excluded(mf.rel_path, s.excluded_dirs)
			AND (mf.sha256 IS NULL OR ($1 AND mf.fingerprinted_at IS NULL)) AND mf.id > $2
		ORDER BY mf.id
		LIMIT $3`, withFP, after, limit)
	if err != nil {
		return nil, fmt.Errorf("library: files to fingerprint: %w", err)
	}
	return pgx.CollectRows(rows, func(r pgx.CollectableRow) (FingerprintTodo, error) {
		var f FingerprintTodo
		return f, r.Scan(&f.ID, &f.SourceID, &f.RelPath, &f.SHA256)
	})
}

// SaveFingerprint сохраняет SHA-256 и (если есть) отпечаток Chromaprint; chromaprintDone — fpcalc отработал
// (в том числе с ошибкой), повторять не нужно.
func (st *Store) SaveFingerprint(ctx context.Context, fileID uuid.UUID, sum []byte, fp *Fingerprint, chromaprintDone bool) error {
	tx, err := st.pool.Begin(ctx)
	if err != nil {
		return fmt.Errorf("library: save fingerprint: %w", err)
	}
	defer func() { _ = tx.Rollback(ctx) }()
	if _, err := tx.Exec(ctx, `
		UPDATE media_files SET sha256 = $2, fingerprinted_at = CASE WHEN $3 THEN now() ELSE fingerprinted_at END
		WHERE id = $1`, fileID, sum, chromaprintDone); err != nil {
		return fmt.Errorf("library: save fingerprint: %w", err)
	}
	if fp != nil {
		points := make([]int32, len(fp.Points))
		for i, p := range fp.Points {
			points[i] = int32(p)
		}
		if _, err := tx.Exec(ctx, `
			INSERT INTO track_fingerprints (file_id, duration_ms, fingerprint, fp_prefix) VALUES ($1, $2, $3, $4)
			ON CONFLICT (file_id) DO UPDATE SET duration_ms = EXCLUDED.duration_ms, fingerprint = EXCLUDED.fingerprint,
				fp_prefix = EXCLUDED.fp_prefix`, fileID, fp.DurationMs, points, fp.Prefix()); err != nil {
			return fmt.Errorf("library: save fingerprint: %w", err)
		}
	}
	return tx.Commit(ctx)
}

// TemplateSamples — случайные файлы источника с метаданными каталога (для проверки шаблона записи).
func (st *Store) TemplateSamples(ctx context.Context, sourceID uuid.UUID, n int) ([]meta.TemplateSample, error) {
	rows, err := st.pool.Query(ctx, `
		SELECT mf.rel_path, t.title, al.title, aa.name, coalesce(t.year, al.year), t.track_no, t.disc_no,
			coalesce((SELECT string_agg(a.name, '; ' ORDER BY ta.position) FROM track_artists ta
				JOIN artists a ON a.id = ta.artist_id WHERE ta.track_id = t.id AND ta.role = 'main'), aa.name),
			(SELECT max(t2.disc_no) FROM tracks t2 WHERE t2.album_id = al.id),
			(SELECT g.name FROM track_genres tg JOIN genres g ON g.id = tg.genre_id
				WHERE tg.track_id = t.id ORDER BY tg.weight DESC LIMIT 1)
		FROM media_files mf
		JOIN tracks t ON t.id = mf.track_id
		JOIN albums al ON al.id = t.album_id
		JOIN artists aa ON aa.id = al.album_artist_id
		JOIN library_sources src ON src.id = mf.source_id
		WHERE mf.source_id = $1 AND mf.missing_since IS NULL AND NOT library_path_excluded(mf.rel_path, src.excluded_dirs)
		ORDER BY random() LIMIT $2`, sourceID, n)
	if err != nil {
		return nil, fmt.Errorf("library: template samples: %w", err)
	}
	return pgx.CollectRows(rows, func(r pgx.CollectableRow) (meta.TemplateSample, error) {
		var (
			rel, title, album, albumArtist, artist string
			year, track, disc, discs               *int
			genre                                  *string
		)
		if err := r.Scan(&rel, &title, &album, &albumArtist, &year, &track, &disc, &artist, &discs, &genre); err != nil {
			return meta.TemplateSample{}, err
		}
		num := func(p *int) string {
			if p == nil || *p <= 0 {
				return ""
			}
			return strconv.Itoa(*p)
		}
		f := meta.Fields{
			Artist: artist, AlbumArtist: albumArtist, Album: album, Title: title, Year: num(year), Track: num(track),
			Disc: num(disc),
		}
		if genre != nil {
			f.Genre = *genre
		}
		count := 1
		if discs != nil {
			count = *discs
		}
		ext := strings.TrimPrefix(path.Ext(rel), ".")
		return meta.TemplateSample{RelPath: rel, Input: meta.TemplateInput{Fields: f, DiscCount: count, Ext: ext}}, nil
	})
}