// Package tracks owns the track-level admin actions behind DELETE
// /api/admin/tracks/{id} and the duplicate merge. RemoveTrack's destructive
// part goes through library.DeleteTrackFile — the one path that deletes a
// track file.
//
// The web track-kebab entry that called this was removed in f7278f24; the
// endpoint was kept deliberately for a safer admin surface to rebind.
package tracks

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

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

	"git.fabledsword.com/bvandeusen/minstrel/internal/apierror"
	"git.fabledsword.com/bvandeusen/minstrel/internal/audit"
	"git.fabledsword.com/bvandeusen/minstrel/internal/library"
	syncpkg "git.fabledsword.com/bvandeusen/minstrel/internal/sync"
)

// ErrNotFound is returned when the track id doesn't resolve. Aliased
// to apierror.ErrNotFound so handlers can errors.Is against the shared
// sentinel; existing tracks.ErrNotFound callsites still resolve to the
// same pointer.
var ErrNotFound = apierror.ErrNotFound

// Service owns RemoveTrack and MergeDuplicates.
type Service struct {
	pool    *pgxpool.Pool
	logger  *slog.Logger
	dataDir string
}

// NewService constructs a Service. logger may be nil (defaults to
// slog.Default). dataDir is the on-disk root for cached artifacts; used to
// clean up artist-art on artist delete. Empty string disables the cleanup.
func NewService(pool *pgxpool.Pool, logger *slog.Logger, dataDir string) *Service {
	if logger == nil {
		logger = slog.Default()
	}
	return &Service{pool: pool, logger: logger, dataDir: dataDir}
}

// RemoveTrack deletes the track's file and then its row, and tidies away an
// album or artist the delete empties.
//
// Returns:
//   - deletedAlbumID: non-nil when removing the track left the album
//     empty and the album row was deleted.
//   - deletedArtistID: non-nil when both album AND artist were left
//     empty (only set if deletedAlbumID is also set).
//   - err: ErrNotFound, or a failure before anything was deleted. When the
//     file cannot be removed it is a *library.FileRemoveError and NOTHING was
//     deleted — see library.DeleteTrackFile for why that order is the contract
//     (#3918).
//
// adminID is currently unused — the cascade audit-log line that would
// reference it isn't wired in this slice. It's threaded through the
// signature so the upcoming admin_tracks handler doesn't have to
// re-plumb when audit logging lands.
func (s *Service) RemoveTrack(
	ctx context.Context,
	trackID, adminID pgtype.UUID, //nolint:revive // adminID reserved for audit-log wiring in a follow-up
) (deletedAlbumID *pgtype.UUID, deletedArtistID *pgtype.UUID, err error) {
	deleted, err := library.DeleteTrackFile(ctx, s.pool, s.logger, s.dataDir, trackID)
	if err != nil {
		if errors.Is(err, library.ErrTrackNotFound) {
			return nil, nil, ErrNotFound
		}
		return nil, nil, fmt.Errorf("delete track: %w", err)
	}
	return deleted.AlbumID, deleted.ArtistID, nil
}

// MergeDuplicates merges a duplicate group into the copy to keep
// (library.MergeDuplicateGroup) and records the merge in the audit log.
func (s *Service) MergeDuplicates(
	ctx context.Context, groupID, survivorID, actorID pgtype.UUID,
) (library.MergeResult, error) {
	res, err := library.MergeDuplicateGroup(ctx, s.pool, s.logger, s.dataDir, groupID, survivorID)
	if err != nil {
		return res, err
	}

	removed := make([]map[string]string, 0, len(res.Removed))
	for _, c := range res.Removed {
		removed = append(removed, map[string]string{"track_id": syncpkg.FormatUUID(c.TrackID), "file_path": c.FilePath})
	}
	audit.WriteOrLog(ctx, s.pool, s.logger, actorID, pgtype.UUID{}, audit.ActionDuplicateMerge, map[string]any{
		"group_id":          syncpkg.FormatUUID(groupID),
		"tier":              res.Tier,
		"survivor_track_id": syncpkg.FormatUUID(res.Survivor.TrackID),
		"survivor_path":     res.Survivor.FilePath,
		"removed":           removed,
		"moved": map[string]any{
			"play_events": res.PlayEvents, "skip_events": res.SkipEvents,
			"likes": res.Likes, "playlist_entries": res.PlaylistEntries,
		},
	})
	return res, nil
}