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

import config from '../config';
import stub from '../stubs/artist';
import albumStore from './album';

const UNKNOWN_ARTIST_ID = 1;
const VARIOUS_ARTISTS_ID = 2;

export default {
    stub,

    state: {
        artists: [],
    },

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

        albumStore.init(this.all);

        // 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) {
        this.getImage(artist);
        Vue.set(artist, 'playCount', 0);

        // Here we build a list of songs performed by the artist, so that we don't need to traverse
        // down the "artist > albums > items" route later.
        // This also makes sure songs in compilation albums are counted as well.
        Vue.set(artist, 'songs', reduce(artist.albums, (songs, album) => {
            // If the album is compilation, we cater for the songs contributed by this artist only.
            if (album.is_compilation) {
                return songs.concat(filter(album.songs, { contributing_artist_id: artist.id }));
            }

            // Otherwise, just use all songs in the album.
            return songs.concat(album.songs);
        }, []));

        Vue.set(artist, 'songCount', artist.songs.length);

        Vue.set(artist, 'info', null);

        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 find(this.all, { id });
    },

    /**
     * Adds an artist/artists into the current collection.
     *
     * @param  {Array.<Object>|Object} artists
     */
    add(artists) {
        artists = [].concat(artists);
        each(artists, a => this.setupArtist(a));

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

    /**
     * Remove artist(s) from the store.
     *
     * @param  {Array.<Object>|Object} artists
     */
    remove(artists) {
        this.all = difference(this.all, [].concat(artists));
    },

    /**
     * Add album(s) into an artist.
     *
     * @param {Object} artist
     * @param {Array.<Object>|Object} albums
     *
     */
    addAlbumsIntoArtist(artist, albums) {
        albums = [].concat(albums);

        artist.albums = union(artist.albums ? artist.albums : [], albums);

        each(albums, album => {
            album.artist_id = artist.id;
            album.artist = artist;
            artist.playCount += album.playCount;
        });
    },

    /**
     * Remove album(s) from an artist.
     *
     * @param  {Object} artist
     * @param  {Array.<Object>|Object} albums
     */
    removeAlbumsFromArtist(artist, albums) {
        albums = [].concat(albums);
        artist.albums = difference(artist.albums, albums);
        each(albums, album => artist.playCount -= album.playCount);
    },

    /**
     * Checks if an artist is empty.
     *
     * @param  {Object}  artist
     *
     * @return {boolean}
     */
    isArtistEmpty(artist) {
        return !artist.albums.length;
    },

    /**
     * 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 the artist's image.
     *
     * @param {Object} artist
     *
     * @return {String}
     */
    getImage(artist) {
        if (!artist.image) {
            // Try to get an image from one of the albums.
            artist.image = config.unknownCover;

            artist.albums.every(album => {
                // If there's a "real" cover, use it.
                if (album.image !== config.unknownCover) {
                    artist.image = album.cover;

                    // I want to break free.
                    return false;
                }
            });
        }

        return artist.image;
    },

    /**
     * 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);
    },
};