/*eslint camelcase: ["error", {properties: "never"}]*/

import Vue from 'vue'
import { reduce, each, union, difference, take, filter, orderBy } from 'lodash'

import stub from '../stubs/artist'

const UNKNOWN_ARTIST_ID = 1
const VARIOUS_ARTISTS_ID = 2

export const artistStore = {
  stub,
  cache: [],

  state: {
    artists: []
  },

  /**
   * Init the store.
   *
   * @param  {Array.<Object>} artists The array of artists we got from the server.
   */
  init (artists) {
    this.all = artists

    // Traverse through artists array to get the cover and number of songs for each.
    each(this.all, artist => this.setupArtist(artist))
  },

  /**
   * Set up the (reactive) properties of an artist.
   *
   * @param  {Object} artist
   */
  setupArtist (artist) {
    Vue.set(artist, 'playCount', 0)
    Vue.set(artist, 'info', null)
    Vue.set(artist, 'albums', [])
    Vue.set(artist, 'songs', [])

    this.cache[artist.id] = artist

    return artist
  },

  /**
   * Get all artists.
   *
   * @return {Array.<Object>}
   */
  get all () {
    return this.state.artists
  },

  /**
   * Set all artists.
   *
   * @param  {Array.<Object>} value
   */
  set all (value) {
    this.state.artists = value
  },

  /**
   * Get an artist object by its ID.
   *
   * @param  {Number} id
   */
  byId (id) {
    return this.cache[id]
  },

  /**
   * Adds an artist/artists into the current collection.
   *
   * @param  {Array.<Object>|Object} artists
   */
  add (artists) {
    artists = [].concat(artists)
    each(artists, artist => {
      this.setupArtist(artist)
      artist.playCount = reduce(artist.songs, (count, song) => count + song.playCount, 0)
    })

    this.all = union(this.all, artists)
  },

  purify () {
    this.compact()
  },

  /**
   * Remove empty artists from the store.
   */
  compact () {
    const emptyArtists = filter(this.all, artist => artist.songs.length === 0)
    if (!emptyArtists.length) {
      return
    }

    this.all = difference(this.all, emptyArtists)
    each(emptyArtists, artist => delete this.cache[artist.id])
  },

  /**
   * Determine if the artist is the special "Various Artists".
   *
   * @param  {Object}  artist
   *
   * @return {Boolean}
   */
  isVariousArtists (artist) {
    return artist.id === VARIOUS_ARTISTS_ID
  },

  /**
   * Determine if the artist is the special "Unknown Artist".
   *
   * @param  {Object}  artist [description]
   *
   * @return {Boolean}
   */
  isUnknownArtist (artist) {
    return artist.id === UNKNOWN_ARTIST_ID
  },

  /**
   * Get all songs performed by an artist.
   *
   * @param {Object} artist
   *
   * @return {Array.<Object>}
   */
  getSongsByArtist (artist) {
    return artist.songs
  },

  /**
   * Get top n most-played artists.
   *
   * @param  {Number} n
   *
   * @return {Array.<Object>}
   */
  getMostPlayed (n = 6) {
    // Only non-unknown artists with actually play count are applicable.
    // Also, "Various Artists" doesn't count.
    const applicable = filter(this.all, artist => {
      return artist.playCount &&
        !this.isUnknownArtist(artist) &&
        !this.isVariousArtists(artist)
    })

    return take(orderBy(applicable, 'playCount', 'desc'), n)
  }
}