export interface Favorite {
  userId: string;
  trackId: string;
}

export const favorites = new Map<string, Favorite>();

export function favoriteKey(userId: string, trackId: string): string {
  return `${userId}:${trackId}`;
}

export function listFavorites(userId: string): Favorite[] {
  return [...favorites.values()].filter((favorite) => favorite.userId === userId);
}