Musare/backend/logic/songs.js

import async from "async";
import config from "config";
import mongoose from "mongoose";
import CoreClass from "../core";

let SongsModule;
let CacheModule;
let DBModule;
let UtilsModule;
let YouTubeModule;
let StationsModule;
let PlaylistsModule;

class ErrorWithData extends Error {
	/**
	 * @param {string} message - the error message
	 * @param {object} data - the error data
	 */
	constructor(message, data) {
		super(message);
		this.data = data;
	}
}

class _SongsModule extends CoreClass {
	// eslint-disable-next-line require-jsdoc
	constructor() {
		super("songs");

		SongsModule = this;
	}

	/**
	 * Initialises the songs module
	 *
	 * @returns {Promise} - returns promise (reject, resolve)
	 */
	async initialize() {
		this.setStage(1);

		CacheModule = this.moduleManager.modules.cache;
		DBModule = this.moduleManager.modules.db;
		UtilsModule = this.moduleManager.modules.utils;
		YouTubeModule = this.moduleManager.modules.youtube;
		StationsModule = this.moduleManager.modules.stations;
		PlaylistsModule = this.moduleManager.modules.playlists;

		this.SongModel = await DBModule.runJob("GET_MODEL", { modelName: "song" });
		this.SongSchemaCache = await CacheModule.runJob("GET_SCHEMA", { schemaName: "song" });

		this.setStage(2);

		return new Promise((resolve, reject) =>
			async.waterfall(
				[
					next => {
						this.setStage(2);
						CacheModule.runJob("HGETALL", { table: "songs" })
							.then(songs => {
								next(null, songs);
							})
							.catch(next);
					},

					(songs, next) => {
						this.setStage(3);

						if (!songs) return next();

						const youtubeIds = Object.keys(songs);

						return async.each(
							youtubeIds,
							(youtubeId, next) => {
								SongsModule.SongModel.findOne({ youtubeId }, (err, song) => {
									if (err) next(err);
									else if (!song)
										CacheModule.runJob("HDEL", {
											table: "songs",
											key: youtubeId
										})
											.then(() => next())
											.catch(next);
									else next();
								});
							},
							next
						);
					},

					next => {
						this.setStage(4);
						SongsModule.SongModel.find({}, next);
					},

					(songs, next) => {
						this.setStage(5);
						async.each(
							songs,
							(song, next) => {
								CacheModule.runJob("HSET", {
									table: "songs",
									key: song.youtubeId,
									value: SongsModule.SongSchemaCache(song)
								})
									.then(() => next())
									.catch(next);
							},
							next
						);
					}
				],
				async err => {
					if (err) {
						err = await UtilsModule.runJob("GET_ERROR", { error: err });
						reject(new Error(err));
					} else resolve();
				}
			)
		);
	}

	/**
	 * Gets a song by id from the cache or Mongo, and if it isn't in the cache yet, adds it the cache
	 *
	 * @param {object} payload - object containing the payload
	 * @param {string} payload.songId - the id of the song we are trying to get
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	GET_SONG(payload) {
		return new Promise((resolve, reject) =>
			async.waterfall(
				[
					next => {
						if (!mongoose.Types.ObjectId.isValid(payload.songId))
							return next("songId is not a valid ObjectId.");
						return CacheModule.runJob("HGET", { table: "songs", key: payload.songId }, this)
							.then(song => next(null, song))
							.catch(next);
					},

					(song, next) => {
						if (song) return next(true, song);
						return SongsModule.SongModel.findOne({ _id: payload.songId }, next);
					},

					(song, next) => {
						if (song) {
							CacheModule.runJob(
								"HSET",
								{
									table: "songs",
									key: payload.songId,
									value: song
								},
								this
							).then(song => next(null, song));
						} else next("Song not found.");
					}
				],
				(err, song) => {
					if (err && err !== true) return reject(new Error(err));
					return resolve({ song });
				}
			)
		);
	}

	/**
	 * Gets songs by id from Mongo
	 *
	 * @param {object} payload - object containing the payload
	 * @param {string} payload.songIds - the ids of the songs we are trying to get
	 * @param {string} payload.properties - the properties to return
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	GET_SONGS(payload) {
		return new Promise((resolve, reject) =>
			async.waterfall(
				[
					next => {
						if (!payload.songIds.every(songId => mongoose.Types.ObjectId.isValid(songId)))
							next("One or more songIds are not a valid ObjectId.");
						else next();
					},

					next => {
						const includeProperties = {};
						payload.properties.forEach(property => {
							includeProperties[property] = true;
						});
						return SongsModule.SongModel.find(
							{
								_id: { $in: payload.songIds }
							},
							includeProperties,
							next
						);
					}
				],
				(err, songs) => {
					if (err && err !== true) return reject(new Error(err));
					return resolve({ songs });
				}
			)
		);
	}

	/**
	 * Gets songs data
	 *
	 * @param {object} payload - object containing the payload
	 * @param {string} payload.page - the page
	 * @param {string} payload.pageSize - the page size
	 * @param {string} payload.properties - the properties to return for each song
	 * @param {string} payload.sort - the sort object
	 * @param {string} payload.queries - the queries array
	 * @param {string} payload.operator - the operator for queries
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	GET_DATA(payload) {
		return new Promise((resolve, reject) => {
			async.waterfall(
				[
					// Creates pipeline array
					next => next(null, []),

					// If a filter exists for requestedBy, add requestedByUsername property to all documents
					(pipeline, next) => {
						const { queries } = payload;

						// Check if a filter with the requestedBy property exists
						const requestedByFilterExists =
							queries.map(query => query.filter.property).indexOf("requestedBy") !== -1;
						// If no such filter exists, skip this function
						if (!requestedByFilterExists) return next(null, pipeline);

						// Adds requestedByOID field, which is an ObjectId version of requestedBy
						pipeline.push({
							$addFields: {
								requestedByOID: {
									$convert: {
										input: "$requestedBy",
										to: "objectId",
										onError: "unknown",
										onNull: "unknown"
									}
								}
							}
						});

						// Looks up user(s) with the same _id as the requestedByOID and puts the result in the requestedByUser field
						pipeline.push({
							$lookup: {
								from: "users",
								localField: "requestedByOID",
								foreignField: "_id",
								as: "requestedByUser"
							}
						});

						// Unwinds the requestedByUser array field into an object
						pipeline.push({
							$unwind: {
								path: "$requestedByUser",
								preserveNullAndEmptyArrays: true
							}
						});

						// Adds requestedByUsername field from the requestedByUser username, or unknown if it doesn't exist
						pipeline.push({
							$addFields: {
								requestedByUsername: {
									$ifNull: ["$requestedByUser.username", "unknown"]
								}
							}
						});

						// Removes the requestedByOID and requestedByUser property, just in case it doesn't get removed at a later stage
						pipeline.push({
							$project: {
								requestedByOID: 0,
								requestedByUser: 0
							}
						});

						return next(null, pipeline);
					},

					// If a filter exists for createdBy, add createdByUsername property to all documents
					(pipeline, next) => {
						const { queries } = payload;

						// Check if a filter with the createdBy property exists
						const createdByFilterExists =
							queries.map(query => query.filter.property).indexOf("createdBy") !== -1;
						// If no such filter exists, skip this function
						if (!createdByFilterExists) return next(null, pipeline);

						// Adds createdByOID field, which is an ObjectId version of createdBy
						pipeline.push({
							$addFields: {
								createdByOID: {
									$convert: {
										input: "$createdBy",
										to: "objectId",
										onError: "unknown",
										onNull: "unknown"
									}
								}
							}
						});

						// Looks up user(s) with the same _id as the createdByOID and puts the result in the createdByUser field
						pipeline.push({
							$lookup: {
								from: "users",
								localField: "createdByOID",
								foreignField: "_id",
								as: "createdByUser"
							}
						});

						// Unwinds the createdByUser array field into an object
						pipeline.push({
							$unwind: {
								path: "$createdByUser",
								preserveNullAndEmptyArrays: true
							}
						});

						// Adds createdByUsername field from the createdByUser username, or unknown if it doesn't exist
						pipeline.push({
							$addFields: {
								createdByUsername: {
									$ifNull: ["$createdByUser.username", "unknown"]
								}
							}
						});

						// Removes the createdByOID and createdByUser property, just in case it doesn't get removed at a later stage
						pipeline.push({
							$project: {
								createdByOID: 0,
								createdByUser: 0
							}
						});

						return next(null, pipeline);
					},

					// Adds the match stage to aggregation pipeline, which is responsible for filtering
					(pipeline, next) => {
						const { queries, operator } = payload;

						let queryError;
						const newQueries = queries.flatMap(query => {
							const { data, filter, filterType } = query;
							const newQuery = {};
							if (filterType === "regex") {
								newQuery[filter.property] = new RegExp(`${data.slice(1, data.length - 1)}`, "i");
							} else if (filterType === "contains") {
								newQuery[filter.property] = new RegExp(
									`${data.replaceAll(/[.*+?^${}()|[\]\\]/g, "\\$&")}`,
									"i"
								);
							} else if (filterType === "exact") {
								newQuery[filter.property] = data.toString();
							} else if (filterType === "datetimeBefore") {
								newQuery[filter.property] = { $lte: new Date(data) };
							} else if (filterType === "datetimeAfter") {
								newQuery[filter.property] = { $gte: new Date(data) };
							} else if (filterType === "numberLesserEqual") {
								newQuery[filter.property] = { $lte: data };
							} else if (filterType === "numberLesser") {
								newQuery[filter.property] = { $lt: data };
							} else if (filterType === "numberGreater") {
								newQuery[filter.property] = { $gt: data };
							} else if (filterType === "numberGreaterEqual") {
								newQuery[filter.property] = { $gte: data };
							} else if (filterType === "numberEquals") {
								newQuery[filter.property] = { $eq: data };
							}

							if (filter.property === "requestedBy")
								return { $or: [newQuery, { requestedByUsername: newQuery.requestedBy }] };
							if (filter.property === "createdBy")
								return { $or: [newQuery, { createdByUsername: newQuery.createdBy }] };

							return newQuery;
						});
						if (queryError) next(queryError);

						const queryObject = {};
						if (newQueries.length > 0) {
							if (operator === "and") queryObject.$and = newQueries;
							else if (operator === "or") queryObject.$or = newQueries;
							else if (operator === "nor") queryObject.$nor = newQueries;
						}

						pipeline.push({ $match: queryObject });

						next(null, pipeline);
					},

					// Adds sort stage to aggregation pipeline if there is at least one column being sorted, responsible for sorting data
					(pipeline, next) => {
						const { sort } = payload;
						const newSort = Object.fromEntries(
							Object.entries(sort).map(([property, direction]) => [
								property,
								direction === "ascending" ? 1 : -1
							])
						);
						if (Object.keys(newSort).length > 0) pipeline.push({ $sort: newSort });
						next(null, pipeline);
					},

					// Adds first project stage to aggregation pipeline, responsible for including only the requested properties
					(pipeline, next) => {
						const { properties } = payload;

						pipeline.push({ $project: Object.fromEntries(properties.map(property => [property, 1])) });

						next(null, pipeline);
					},

					// // Adds second project stage to aggregation pipeline, responsible for excluding some specific properties
					// (pipeline, next) => {
					// 	pipeline.push({
					// 		$project: {
					// 			title: 0
					// 		}
					// 	});

					// 	next(null, pipeline);
					// },

					// Adds the facet stage to aggregation pipeline, responsible for returning a total document count, skipping and limitting the documents that will be returned
					(pipeline, next) => {
						const { page, pageSize } = payload;

						pipeline.push({
							$facet: {
								count: [{ $count: "count" }],
								documents: [{ $skip: pageSize * (page - 1) }, { $limit: pageSize }]
							}
						});

						// console.dir(pipeline, { depth: 6 });

						next(null, pipeline);
					},

					// Executes the aggregation pipeline
					(pipeline, next) => {
						SongsModule.SongModel.aggregate(pipeline).exec((err, result) => {
							// console.dir(err);
							// console.dir(result, { depth: 6 });
							if (err) return next(err);
							if (result[0].count.length === 0) return next(null, 0, []);
							const { count } = result[0].count[0];
							const { documents } = result[0];
							// console.log(111, err, result, count, documents[0]);
							return next(null, count, documents);
						});
					}
				],
				(err, count, songs) => {
					if (err && err !== true) return reject(new Error(err));
					return resolve({ data: songs, count });
				}
			);
		});
	}

	/**
	 * Makes sure that if a song is not currently in the songs db, to add it
	 *
	 * @param {object} payload - an object containing the payload
	 * @param {string} payload.youtubeId - the youtube song id of the song we are trying to ensure is in the songs db
	 * @param {string} payload.userId - the youtube song id of the song we are trying to ensure is in the songs db
	 * @param {string} payload.automaticallyRequested - whether the song was automatically requested or not
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	ENSURE_SONG_EXISTS_BY_YOUTUBE_ID(payload) {
		return new Promise((resolve, reject) =>
			async.waterfall(
				[
					next => {
						SongsModule.SongModel.findOne({ youtubeId: payload.youtubeId }, next);
					},

					(song, next) => {
						if (song && song.duration > 0) next(true, song);
						else {
							YouTubeModule.runJob("GET_SONG", { youtubeId: payload.youtubeId }, this)
								.then(response => {
									next(null, song, response.song);
								})
								.catch(next);
						}
					},

					(song, youtubeSong, next) => {
						if (song && song.duration <= 0) {
							song.duration = youtubeSong.duration;
							song.save({ validateBeforeSave: true }, err => {
								if (err) return next(err, song);
								return next(null, song);
							});
						} else {
							const status =
								(!payload.userId && config.get("hideAnonymousSongs")) ||
								(payload.automaticallyRequested && config.get("hideAutomaticallyRequestedSongs"))
									? "hidden"
									: "unverified";

							const song = new SongsModule.SongModel({
								...youtubeSong,
								status,
								requestedBy: payload.userId,
								requestedAt: Date.now()
							});
							song.save({ validateBeforeSave: true }, err => {
								if (err) return next(err, song);
								return next(null, song);
							});
						}
					}
				],
				(err, song) => {
					if (err && err !== true) return reject(new Error(err));
					return resolve({ song });
				}
			)
		);
	}

	/**
	 * Gets a song by youtube id
	 *
	 * @param {object} payload - an object containing the payload
	 * @param {string} payload.youtubeId - the youtube id of the song we are trying to get
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	GET_SONG_FROM_YOUTUBE_ID(payload) {
		return new Promise((resolve, reject) =>
			async.waterfall(
				[
					next => {
						SongsModule.SongModel.findOne({ youtubeId: payload.youtubeId }, next);
					}
				],
				(err, song) => {
					if (err && err !== true) return reject(new Error(err));
					return resolve({ song });
				}
			)
		);
	}

	/**
	 * Gets a song from id from Mongo and updates the cache with it
	 *
	 * @param {object} payload - an object containing the payload
	 * @param {string} payload.songId - the id of the song we are trying to update
	 * @param {string} payload.oldStatus - old status of song being updated (optional)
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	UPDATE_SONG(payload) {
		return new Promise((resolve, reject) =>
			async.waterfall(
				[
					next => {
						SongsModule.SongModel.findOne({ _id: payload.songId }, next);
					},

					(song, next) => {
						if (!song) {
							CacheModule.runJob("HDEL", {
								table: "songs",
								key: payload.songId
							});
							return next("Song not found.");
						}

						return CacheModule.runJob(
							"HSET",
							{
								table: "songs",
								key: payload.songId,
								value: song
							},
							this
						)
							.then(song => {
								next(null, song);
							})
							.catch(next);
					},

					(song, next) => {
						const { _id, youtubeId, title, artists, thumbnail, duration, status } = song;
						const trimmedSong = {
							_id,
							youtubeId,
							title,
							artists,
							thumbnail,
							duration,
							status
						};
						this.log("INFO", `Going to update playlists now for song ${_id}`);
						DBModule.runJob("GET_MODEL", { modelName: "playlist" }, this)
							.then(playlistModel => {
								playlistModel.updateMany(
									{ "songs._id": song._id },
									{ $set: { "songs.$": trimmedSong } },
									err => {
										if (err) next(err);
										else
											playlistModel.find({ "songs._id": song._id }, (err, playlists) => {
												if (err) next(err);
												else {
													async.eachLimit(
														playlists,
														1,
														(playlist, next) => {
															PlaylistsModule.runJob(
																"UPDATE_PLAYLIST",
																{
																	playlistId: playlist._id
																},
																this
															)
																.then(() => {
																	next();
																})
																.catch(err => {
																	next(err);
																});
														},
														err => {
															if (err) next(err);
															else next(null, song);
														}
													);
												}
											});
									}
								);
							})
							.catch(err => {
								next(err);
							});
					},

					(song, next) => {
						const { _id, youtubeId, title, artists, thumbnail, duration, status } = song;
						this.log("INFO", `Going to update stations now for song ${_id}`);
						DBModule.runJob("GET_MODEL", { modelName: "station" }, this)
							.then(stationModel => {
								stationModel.updateMany(
									{ "queue._id": song._id },
									{
										$set: {
											"queue.$.youtubeId": youtubeId,
											"queue.$.title": title,
											"queue.$.artists": artists,
											"queue.$.thumbnail": thumbnail,
											"queue.$.duration": duration,
											"queue.$.status": status
										}
									},
									err => {
										if (err) this.log("ERROR", err);
										else
											stationModel.find({ "queue._id": song._id }, (err, stations) => {
												if (err) next(err);
												else {
													async.eachLimit(
														stations,
														1,
														(station, next) => {
															StationsModule.runJob(
																"UPDATE_STATION",
																{ stationId: station._id },
																this
															)
																.then(() => {
																	next();
																})
																.catch(err => {
																	next(err);
																});
														},
														err => {
															if (err) next(err);
															else next(null, song);
														}
													);
												}
											});
									}
								);
							})
							.catch(err => {
								next(err);
							});
					},

					(song, next) => {
						async.eachLimit(
							song.genres,
							1,
							(genre, next) => {
								PlaylistsModule.runJob("AUTOFILL_GENRE_PLAYLIST", { genre }, this)
									.then(() => {
										next();
									})
									.catch(err => next(err));
							},
							err => {
								next(err, song);
							}
						);
					}
				],
				(err, song) => {
					if (err && err !== true) return reject(new Error(err));

					if (!payload.oldStatus) payload.oldStatus = null;

					CacheModule.runJob("PUB", {
						channel: "song.updated",
						value: { songId: song._id, oldStatus: payload.oldStatus }
					});

					return resolve(song);
				}
			)
		);
	}

	/**
	 * Updates all songs
	 *
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	UPDATE_ALL_SONGS() {
		return new Promise((resolve, reject) =>
			async.waterfall(
				[
					next => {
						SongsModule.SongModel.find({}, next);
					},

					(songs, next) => {
						let index = 0;
						const { length } = songs;
						async.eachLimit(
							songs,
							2,
							(song, next) => {
								index += 1;
								console.log(`Updating song #${index} out of ${length}: ${song._id}`);
								SongsModule.runJob("UPDATE_SONG", { songId: song._id }, this)
									.then(() => {
										next();
									})
									.catch(err => {
										next(err);
									});
							},
							err => {
								next(err);
							}
						);
					}
				],
				err => {
					if (err && err !== true) return reject(new Error(err));
					return resolve();
				}
			)
		);
	}

	// /**
	//  * Deletes song from id from Mongo and cache
	//  *
	//  * @param {object} payload - returns an object containing the payload
	//  * @param {string} payload.songId - the song id of the song we are trying to delete
	//  * @returns {Promise} - returns a promise (resolve, reject)
	//  */
	// DELETE_SONG(payload) {
	// 	return new Promise((resolve, reject) =>
	// 		async.waterfall(
	// 			[
	// 				next => {
	// 					SongsModule.SongModel.deleteOne({ _id: payload.songId }, next);
	// 				},

	// 				next => {
	// 					CacheModule.runJob(
	// 						"HDEL",
	// 						{
	// 							table: "songs",
	// 							key: payload.songId
	// 						},
	// 						this
	// 					)
	// 						.then(() => next())
	// 						.catch(next);
	// 				},

	// 				next => {
	// 					this.log("INFO", `Going to update playlists and stations now for deleted song ${payload.songId}`);
	// 					DBModule.runJob("GET_MODEL", { modelName: "playlist" }).then(playlistModel => {
	// 						playlistModel.find({ "songs._id": song._id }, (err, playlists) => {
	// 							if (err) this.log("ERROR", err);
	// 							else {
	// 								playlistModel.updateMany(
	// 									{ "songs._id": payload.songId },
	// 									{ $pull: { "songs.$._id": payload.songId} },
	// 									err => {
	// 										if (err) this.log("ERROR", err);
	// 										else {
	// 											playlists.forEach(playlist => {
	// 												PlaylistsModule.runJob("UPDATE_PLAYLIST", {
	// 													playlistId: playlist._id
	// 												});
	// 											});
	// 										}
	// 									}
	// 								);

	// 							}
	// 						});
	// 					});
	// 					DBModule.runJob("GET_MODEL", { modelName: "station" }).then(stationModel => {
	// 						stationModel.find({ "queue._id": payload.songId }, (err, stations) => {
	// 							stationModel.updateMany(
	// 								{ "queue._id": payload.songId },
	// 								{
	// 									$pull: { "queue._id":  }
	// 								},
	// 								err => {
	// 									if (err) this.log("ERROR", err);
	// 									else {
	// 										stations.forEach(station => {
	// 											StationsModule.runJob("UPDATE_STATION", { stationId: station._id });
	// 										});
	// 									}
	// 								}
	// 							);
	// 						});
	// 					});
	// 				}
	// 			],
	// 			err => {
	// 				if (err && err !== true) return reject(new Error(err));
	// 				return resolve();
	// 			}
	// 		)
	// 	);
	// }

	/**
	 * Searches through songs
	 *
	 * @param {object} payload - object that contains the payload
	 * @param {string} payload.query - the query
	 * @param {string} payload.includeHidden - include hidden songs
	 * @param {string} payload.includeUnverified - include unverified songs
	 * @param {string} payload.includeVerified - include verified songs
	 * @param {string} payload.trimmed - include trimmed songs
	 * @param {string} payload.page - page (default 1)
	 * @returns {Promise} - returns promise (reject, resolve)
	 */
	SEARCH(payload) {
		return new Promise((resolve, reject) =>
			async.waterfall(
				[
					next => {
						const statuses = [];
						if (payload.includeHidden) statuses.push("hidden");
						if (payload.includeUnverified) statuses.push("unverified");
						if (payload.includeVerified) statuses.push("verified");
						if (statuses.length === 0) return next("No statuses have been included.");

						let { query } = payload;

						const isRegex =
							query.length > 2 && query.indexOf("/") === 0 && query.lastIndexOf("/") === query.length - 1;
						if (isRegex) query = query.slice(1, query.length - 1);
						else query = query.replaceAll(/[.*+?^${}()|[\]\\]/g, "\\$&");

						const filterArray = [
							{
								title: new RegExp(`${query}`, "i"),
								status: { $in: statuses }
							},
							{
								artists: new RegExp(`${query}`, "i"),
								status: { $in: statuses }
							}
						];

						return next(null, filterArray);
					},

					(filterArray, next) => {
						const page = payload.page ? payload.page : 1;
						const pageSize = 15;
						const skipAmount = pageSize * (page - 1);

						SongsModule.SongModel.find({ $or: filterArray }).count((err, count) => {
							if (err) next(err);
							else {
								SongsModule.SongModel.find({ $or: filterArray })
									.skip(skipAmount)
									.limit(pageSize)
									.exec((err, songs) => {
										if (err) next(err);
										else {
											next(null, {
												songs,
												page,
												pageSize,
												skipAmount,
												count
											});
										}
									});
							}
						});
					},

					(data, next) => {
						if (data.songs.length === 0) next("No songs found");
						else if (payload.trimmed) {
							next(null, {
								songs: data.songs.map(song => {
									const { _id, youtubeId, title, artists, thumbnail, duration, status } = song;
									return {
										_id,
										youtubeId,
										title,
										artists,
										thumbnail,
										duration,
										status
									};
								}),
								...data
							});
						} else next(null, data);
					}
				],
				(err, data) => {
					if (err && err !== true) return reject(new Error(err));
					return resolve(data);
				}
			)
		);
	}

	/**
	 * Recalculates dislikes and likes for a song
	 *
	 * @param {object} payload - returns an object containing the payload
	 * @param {string} payload.youtubeId - the youtube id of the song
	 * @param {string} payload.songId - the song id of the song
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	async RECALCULATE_SONG_RATINGS(payload) {
		const playlistModel = await DBModule.runJob("GET_MODEL", { modelName: "playlist" }, this);

		return new Promise((resolve, reject) => {
			async.waterfall(
				[
					next => {
						playlistModel.countDocuments(
							{ songs: { $elemMatch: { _id: payload.songId } }, type: "user-liked" },
							(err, likes) => {
								if (err) return next(err);
								return next(null, likes);
							}
						);
					},

					(likes, next) => {
						playlistModel.countDocuments(
							{ songs: { $elemMatch: { _id: payload.songId } }, type: "user-disliked" },
							(err, dislikes) => {
								if (err) return next(err);
								return next(err, { likes, dislikes });
							}
						);
					},

					({ likes, dislikes }, next) => {
						SongsModule.SongModel.updateOne(
							{ _id: payload.songId },
							{
								$set: {
									likes,
									dislikes
								}
							},
							err => next(err, { likes, dislikes })
						);
					}
				],
				(err, { likes, dislikes }) => {
					if (err) return reject(new Error(err));
					return resolve({ likes, dislikes });
				}
			);
		});
	}

	/**
	 * Recalculates dislikes and likes for all songs
	 *
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	RECALCULATE_ALL_SONG_RATINGS() {
		return new Promise((resolve, reject) => {
			async.waterfall(
				[
					next => {
						SongsModule.SongModel.find({}, { _id: true }, next);
					},

					(songs, next) => {
						async.eachLimit(
							songs,
							2,
							(song, next) => {
								SongsModule.runJob("RECALCULATE_SONG_RATINGS", { songId: song._id }, this)
									.then(() => {
										next();
									})
									.catch(err => {
										next(err);
									});
							},
							err => {
								next(err);
							}
						);
					}
				],
				err => {
					if (err) return reject(new Error(err));
					return resolve();
				}
			);
		});
	}

	/**
	 * Gets an array of all genres
	 *
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	GET_ALL_GENRES() {
		return new Promise((resolve, reject) =>
			async.waterfall(
				[
					next => {
						SongsModule.SongModel.find({ status: "verified" }, { genres: 1, _id: false }, next);
					},

					(songs, next) => {
						let allGenres = [];
						songs.forEach(song => {
							allGenres = allGenres.concat(song.genres);
						});

						const lowerCaseGenres = allGenres.map(genre => genre.toLowerCase());
						const uniqueGenres = lowerCaseGenres.filter(
							(value, index, self) => self.indexOf(value) === index
						);

						next(null, uniqueGenres);
					}
				],
				(err, genres) => {
					if (err && err !== true) return reject(new Error(err));
					return resolve({ genres });
				}
			)
		);
	}

	/**
	 * Gets an array of all songs with a specific genre
	 *
	 * @param {object} payload - returns an object containing the payload
	 * @param {string} payload.genre - the genre
	 * @returns {Promise} - returns a promise (resolve, reject)
	 */
	GET_ALL_SONGS_WITH_GENRE(payload) {
		return new Promise((resolve, reject) =>
			async.waterfall(
				[
					next => {
						SongsModule.SongModel.find(
							{
								status: "verified",
								genres: { $regex: new RegExp(`^${payload.genre.toLowerCase()}$`, "i") }
							},
							next
						);
					}
				],
				(err, songs) => {
					if (err && err !== true) return reject(new Error(err));
					return resolve({ songs });
				}
			)
		);
	}

	// runjob songs GET_ORPHANED_PLAYLIST_SONGS {}

	/**
	 * Gets a orphaned playlist songs
	 *
	 * @returns {Promise} - returns promise (reject, resolve)
	 */
	GET_ORPHANED_PLAYLIST_SONGS() {
		return new Promise((resolve, reject) => {
			DBModule.runJob("GET_MODEL", { modelName: "playlist" }, this).then(playlistModel => {
				playlistModel.find({}, (err, playlists) => {
					if (err) reject(new Error(err));
					else {
						SongsModule.SongModel.find({}, { _id: true, youtubeId: true }, (err, songs) => {
							if (err) reject(new Error(err));
							else {
								const songIds = songs.map(song => song._id.toString());
								const orphanedYoutubeIds = new Set();
								async.eachLimit(
									playlists,
									1,
									(playlist, next) => {
										playlist.songs.forEach(song => {
											if (
												(!song._id || songIds.indexOf(song._id.toString() === -1)) &&
												!orphanedYoutubeIds.has(song.youtubeId)
											) {
												orphanedYoutubeIds.add(song.youtubeId);
											}
										});
										next();
									},
									() => {
										resolve({ youtubeIds: Array.from(orphanedYoutubeIds) });
									}
								);
							}
						});
					}
				});
			});
		});
	}

	/**
	 * Requests a song, adding it to the DB
	 *
	 * @param {object} payload - The payload
	 * @param {string} payload.youtubeId - The YouTube song id of the song
	 * @param {string} payload.userId - The user id of the person requesting the song
	 * @returns {Promise} - returns promise (reject, resolve)
	 */
	REQUEST_SONG(payload) {
		return new Promise((resolve, reject) => {
			const { youtubeId, userId } = payload;
			const requestedAt = Date.now();

			async.waterfall(
				[
					next => {
						DBModule.runJob("GET_MODEL", { modelName: "user" }, this)
							.then(UserModel => {
								UserModel.findOne({ _id: userId }, { "preferences.anonymousSongRequests": 1 }, next);
							})
							.catch(next);
					},

					(user, next) => {
						SongsModule.SongModel.findOne({ youtubeId }, (err, song) => next(err, user, song));
					},

					// Get YouTube data from id
					(user, song, next) => {
						if (song) return next("This song is already in the database.", song);
						// TODO Add err object as first param of callback

						const requestedBy = user.preferences.anonymousSongRequests ? null : userId;
						const status = !requestedBy && config.get("hideAnonymousSongs") ? "hidden" : "unverified";

						return YouTubeModule.runJob("GET_SONG", { youtubeId }, this)
							.then(response => {
								const { song } = response;
								song.artists = [];
								song.genres = [];
								song.skipDuration = 0;
								song.explicit = false;
								song.requestedBy = user.preferences.anonymousSongRequests ? null : userId;
								song.requestedAt = requestedAt;
								song.status = status;
								next(null, song);
							})
							.catch(next);
					},
					(newSong, next) => {
						const song = new SongsModule.SongModel(newSong);
						song.save({ validateBeforeSave: false }, err => {
							if (err) return next(err, song);
							return next(null, song);
						});
					},
					(song, next) => {
						DBModule.runJob("GET_MODEL", { modelName: "user" }, this)
							.then(UserModel => {
								UserModel.findOne({ _id: userId }, (err, user) => {
									if (err) return next(err);
									if (!user) return next(null, song);

									user.statistics.songsRequested += 1;

									return user.save(err => {
										if (err) return next(err);
										return next(null, song);
									});
								});
							})
							.catch(next);
					}
				],
				async (err, song) => {
					if (err && err !== "This song is already in the database.") return reject(err);

					const { _id, youtubeId, title, artists, thumbnail, duration, status } = song;
					const trimmedSong = {
						_id,
						youtubeId,
						title,
						artists,
						thumbnail,
						duration,
						status
					};

					if (err && err === "This song is already in the database.")
						return reject(new ErrorWithData(err, { song: trimmedSong }));

					SongsModule.runJob("UPDATE_SONG", { songId: song._id });

					return resolve({ song: trimmedSong });
				}
			);
		});
	}

	/**
	 * Hides a song
	 *
	 * @param {object} payload - The payload
	 * @param {string} payload.songId - The song id of the song
	 * @returns {Promise} - returns promise (reject, resolve)
	 */
	HIDE_SONG(payload) {
		return new Promise((resolve, reject) => {
			const { songId } = payload;

			async.waterfall(
				[
					next => {
						SongsModule.SongModel.findOne({ _id: songId }, next);
					},

					// Get YouTube data from id
					(song, next) => {
						if (!song) return next("This song does not exist.");
						if (song.status === "hidden") return next("This song is already hidden.");
						// TODO Add err object as first param of callback
						return next(null, song.status);
					},

					(oldStatus, next) => {
						SongsModule.SongModel.updateOne({ _id: songId }, { status: "hidden" }, res =>
							next(null, res, oldStatus)
						);
					},

					(res, oldStatus, next) => {
						SongsModule.runJob("UPDATE_SONG", { songId, oldStatus });
						next();
					}
				],
				async err => {
					if (err) reject(err);
					resolve();
				}
			);
		});
	}

	/**
	 * Unhides a song
	 *
	 * @param {object} payload - The payload
	 * @param {string} payload.songId - The song id of the song
	 * @returns {Promise} - returns promise (reject, resolve)
	 */
	UNHIDE_SONG(payload) {
		return new Promise((resolve, reject) => {
			const { songId } = payload;

			async.waterfall(
				[
					next => {
						SongsModule.SongModel.findOne({ _id: songId }, next);
					},

					// Get YouTube data from id
					(song, next) => {
						if (!song) return next("This song does not exist.");
						if (song.status !== "hidden") return next("This song is not hidden.");
						// TODO Add err object as first param of callback
						return next();
					},

					next => {
						SongsModule.SongModel.updateOne({ _id: songId }, { status: "unverified" }, next);
					},

					(res, next) => {
						SongsModule.runJob("UPDATE_SONG", { songId, oldStatus: "hidden" });
						next();
					}
				],
				async err => {
					if (err) reject(err);
					resolve();
				}
			);
		});
	}

	// runjob songs REQUEST_ORPHANED_PLAYLIST_SONGS {}

	/**
	 * Requests all orphaned playlist songs, adding them to the database
	 *
	 * @returns {Promise} - returns promise (reject, resolve)
	 */
	REQUEST_ORPHANED_PLAYLIST_SONGS() {
		return new Promise((resolve, reject) => {
			DBModule.runJob("GET_MODEL", { modelName: "playlist" })
				.then(playlistModel => {
					SongsModule.runJob("GET_ORPHANED_PLAYLIST_SONGS", {}, this).then(response => {
						const { youtubeIds } = response;
						const playlistsToUpdate = new Set();

						async.eachLimit(
							youtubeIds,
							1,
							(youtubeId, next) => {
								async.waterfall(
									[
										next => {
											console.log(
												youtubeId,
												`this is song ${youtubeIds.indexOf(youtubeId) + 1}/${youtubeIds.length}`
											);
											setTimeout(next, 150);
										},

										next => {
											SongsModule.runJob(
												"ENSURE_SONG_EXISTS_BY_SONG_ID",
												{ youtubeId, automaticallyRequested: true },
												this
											)
												.then(() => next())
												.catch(next);
										},

										next => {
											console.log(444, youtubeId);

											SongsModule.SongModel.findOne({ youtubeId }, next);
										},

										(song, next) => {
											const { _id, title, artists, thumbnail, duration, status } = song;
											const trimmedSong = {
												_id,
												youtubeId,
												title,
												artists,
												thumbnail,
												duration,
												status
											};
											playlistModel.updateMany(
												{ "songs.youtubeId": song.youtubeId },
												{ $set: { "songs.$": trimmedSong } },
												err => {
													next(err, song);
												}
											);
										},

										(song, next) => {
											playlistModel.find({ "songs._id": song._id }, next);
										},

										(playlists, next) => {
											playlists.forEach(playlist => {
												playlistsToUpdate.add(playlist._id.toString());
											});

											next();
										}
									],
									next
								);
							},
							err => {
								if (err) reject(err);
								else {
									async.eachLimit(
										Array.from(playlistsToUpdate),
										1,
										(playlistId, next) => {
											PlaylistsModule.runJob(
												"UPDATE_PLAYLIST",
												{
													playlistId
												},
												this
											)
												.then(() => {
													next();
												})
												.catch(next);
										},
										err => {
											if (err) reject(err);
											else resolve();
										}
									);
								}
							}
						);
					});
				})
				.catch(reject);
		});
	}

	/**
	 * Gets a list of all genres
	 *
	 * @returns {Promise} - returns promise (reject, resolve)
	 */
	 GET_GENRES() {
		return new Promise((resolve, reject) => {
			async.waterfall(
				[
					next => {
						SongsModule.SongModel.distinct("genres", next);
					}
				],
				(err, genres) => {
					if (err) reject(err);
					resolve({ genres });
				}
			);
		});
	}

	/**
	 * Gets a list of all artists
	 *
	 * @returns {Promise} - returns promise (reject, resolve)
	 */
	 GET_ARTISTS() {
		return new Promise((resolve, reject) => {
			async.waterfall(
				[
					next => {
						SongsModule.SongModel.distinct("artists", next);
					}
				],
				(err, artists) => {
					if (err) reject(err);
					resolve({ artists });
				}
			);
		});
	}
}

export default new _SongsModule();