// Package tracks owns the track-level admin actions exposed by the
// M7 #372 track-actions menu. Today that's RemoveTrack, which deletes
// a single track (Lidarr-managed via lidarrquarantine.DeleteViaLidarr,
// or local via os.Remove) and cascades the album-empty / artist-empty
// tidy-up so we don't leak orphan rows.
package tracks

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"os"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgtype"
	"github.com/jackc/pgx/v5/pgxpool"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarr"
)

// Public errors. Handlers map these to API codes.
var (
	ErrNotFound           = errors.New("tracks: not found")
	ErrLidarrUnreachable  = errors.New("tracks: lidarr unreachable")
	ErrLidarrUnauthorized = errors.New("tracks: lidarr unauthorized")
	ErrLidarrServerError  = errors.New("tracks: lidarr server error")
)

// LidarrDeleter is the subset of *lidarrquarantine.Service the tracks
// service needs. Defined as an interface so tests can stub without
// spinning up a real Lidarr stub.
type LidarrDeleter interface {
	DeleteViaLidarr(ctx context.Context, trackID, adminID pgtype.UUID) (dbq.LidarrQuarantineAction, int, error)
}

// Service owns RemoveTrack. lidarrDeleter may be nil — non-Lidarr-managed
// tracks (no mbid) still work fine; a Lidarr-managed track with a nil
// deleter falls back to direct os.Remove of the local file.
type Service struct {
	pool          *pgxpool.Pool
	logger        *slog.Logger
	lidarrDeleter LidarrDeleter
}

// NewService constructs a Service. logger may be nil (defaults to
// slog.Default). lidarrDeleter may be nil to disable the Lidarr-aware
// path entirely.
func NewService(pool *pgxpool.Pool, logger *slog.Logger, lidarrDeleter LidarrDeleter) *Service {
	if logger == nil {
		logger = slog.Default()
	}
	return &Service{pool: pool, logger: logger, lidarrDeleter: lidarrDeleter}
}

// RemoveTrack deletes the track, runs the album-empty / artist-empty
// cascade, and returns the IDs of any rows deleted by the cascade so
// the API caller can invalidate caches.
//
// For Lidarr-managed tracks (mbid set on the track), Lidarr is told to
// delete the file first via lidarrquarantine.DeleteViaLidarr — this
// sets the import-list-exclusion flag so the next sync doesn't re-import
// the file. For local tracks (no mbid), os.Remove handles the file.
//
// Lidarr errors propagate as typed errors and the DB is left untouched
// so the operator can retry. A missing local file is tolerated — DB
// consistency takes priority over a noisy filesystem.
func (s *Service) RemoveTrack(ctx context.Context, trackID, adminID pgtype.UUID) (deletedAlbumID, deletedArtistID *pgtype.UUID, err error) {
	q := dbq.New(s.pool)

	track, err := q.GetTrackByID(ctx, trackID)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, nil, ErrNotFound
		}
		return nil, nil, fmt.Errorf("get track: %w", err)
	}

	// Lidarr-managed → Lidarr deletes the album (and so the file) first.
	// The lidarrquarantine path also deletes the local rows for every
	// track on the album, so we pre-empt the cascade-tidy step here. If
	// the lidarr deleter is nil, fall through to the local os.Remove path.
	if track.Mbid != nil && *track.Mbid != "" && s.lidarrDeleter != nil {
		_, _, lerr := s.lidarrDeleter.DeleteViaLidarr(ctx, trackID, adminID)
		switch {
		case lerr == nil:
			// lidarrquarantine.DeleteViaLidarr already removed the tracks
			// row(s) for the album. Cascade cleanup still needs to run
			// against the album/artist IDs we captured before the call.
			return s.cascadeAfterLidarr(ctx, q, track)
		case errors.Is(lerr, lidarr.ErrUnreachable):
			return nil, nil, ErrLidarrUnreachable
		case errors.Is(lerr, lidarr.ErrAuthFailed):
			return nil, nil, ErrLidarrUnauthorized
		case errors.Is(lerr, lidarr.ErrServerError):
			return nil, nil, ErrLidarrServerError
		default:
			return nil, nil, fmt.Errorf("lidarr delete: %w", lerr)
		}
	}

	// Local path: best-effort os.Remove, then DB cleanup in a tx.
	if track.FilePath != "" {
		if rerr := os.Remove(track.FilePath); rerr != nil && !errors.Is(rerr, os.ErrNotExist) {
			s.logger.Warn("track delete: file remove failed",
				"path", track.FilePath, "track_id", trackID, "err", rerr)
			// Proceed: DB consistency is the priority.
		}
	}

	return s.deleteAndCascade(ctx, trackID)
}

// deleteAndCascade runs DeleteTrack → DeleteAlbumIfEmpty →
// DeleteArtistIfEmpty in a single transaction. Returns the cascaded
// album / artist IDs (nil pointers when the cascade didn't fire because
// other tracks/albums still reference the parent).
func (s *Service) deleteAndCascade(ctx context.Context, trackID pgtype.UUID) (deletedAlbumID, deletedArtistID *pgtype.UUID, err error) {
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return nil, nil, fmt.Errorf("begin tx: %w", err)
	}
	defer func() { _ = tx.Rollback(ctx) }()

	tq := dbq.New(tx)

	deleted, err := tq.DeleteTrack(ctx, trackID)
	if err != nil {
		return nil, nil, fmt.Errorf("delete track: %w", err)
	}

	albumRow, aerr := tq.DeleteAlbumIfEmpty(ctx, deleted.AlbumID)
	switch {
	case aerr == nil:
		albumID := albumRow.ID
		deletedAlbumID = &albumID
		artistID, arerr := tq.DeleteArtistIfEmpty(ctx, albumRow.ArtistID)
		switch {
		case arerr == nil:
			id := artistID
			deletedArtistID = &id
		case errors.Is(arerr, pgx.ErrNoRows):
			// artist still has other albums or stray tracks
		default:
			return nil, nil, fmt.Errorf("delete artist if empty: %w", arerr)
		}
	case errors.Is(aerr, pgx.ErrNoRows):
		// album still has other tracks
	default:
		return nil, nil, fmt.Errorf("delete album if empty: %w", aerr)
	}

	if err := tx.Commit(ctx); err != nil {
		return nil, nil, fmt.Errorf("commit: %w", err)
	}
	return deletedAlbumID, deletedArtistID, nil
}

// cascadeAfterLidarr runs the album-empty / artist-empty checks against
// the album/artist IDs from the track snapshot we took before delegating
// to lidarrquarantine. lidarrquarantine.DeleteViaLidarr already deleted
// the tracks row(s) for the entire album, so this is a tidy-up of the
// now-orphan album + artist parents.
func (s *Service) cascadeAfterLidarr(ctx context.Context, q *dbq.Queries, track dbq.Track) (deletedAlbumID, deletedArtistID *pgtype.UUID, err error) {
	albumRow, aerr := q.DeleteAlbumIfEmpty(ctx, track.AlbumID)
	switch {
	case aerr == nil:
		albumID := albumRow.ID
		deletedAlbumID = &albumID
		artistID, arerr := q.DeleteArtistIfEmpty(ctx, albumRow.ArtistID)
		switch {
		case arerr == nil:
			id := artistID
			deletedArtistID = &id
		case errors.Is(arerr, pgx.ErrNoRows):
			// artist still has other albums
		default:
			return nil, nil, fmt.Errorf("delete artist if empty: %w", arerr)
		}
	case errors.Is(aerr, pgx.ErrNoRows):
		// album still has other tracks (unexpected after Lidarr delete,
		// but tolerate — the operator may have re-imported between calls)
	default:
		return nil, nil, fmt.Errorf("delete album if empty: %w", aerr)
	}
	return deletedAlbumID, deletedArtistID, nil
}