const fs = require('fs').promises
const ytdl  = require('ytdl-core')
const Discord = require('discord.js')

const { Manager } = require('./manager')
const { Playlist } = require('./playlist');
const { youtube_instance } = require('../src/youtube');

/**
 * @extends Manager
 */
class PlaylistsManager extends Manager {
  #playlists
  #filepath

  constructor(gmanager, guild_id, { filepath = "playlists_manager.db", data = null } = {}) {
    return (async () => {
      super(...arguments)
      const playlists = data || await PlaylistsManager.readFile(filepath)
      Object.entries(playlists).forEach(([title, tracks]) => {
        playlists[title] = new Playlist({ tracks, name: title })
      })
      this.#playlists = playlists
      this.#filepath = filepath

      return this
    })()
  }

  static async readFile(filename) {
    try {
      return JSON.parse(await fs.readFile(filename, 'utf-8'))
    } catch (e) {
      console.warn(`> Impossible to read file "${filename}"`)
      return {}
    }
  }

  static async writeFile(filename, playlists) {
    return await fs.writeFile(filename, JSON.stringify(playlists, null, 2))
  }

  async register({ message, params }) {
    const player = this.get_manager('player')
    if (params[0] || player.get_playlist().is_named())  {
      const playlist_title = params[0] || player.get_playlist().get_name()
      this.#playlists[playlist_title] = player.get_playlist().clone()
      await PlaylistsManager.writeFile(this.#filepath, this.#playlists)
      message.channel.send(`:white_check_mark: Playlist \`${playlist_title}\` saved`)
      player.get_playlist().untouch()
      return true
    } else {
      message.channel.send(`:warning: Cannot save playlist without name`)
      return false
    }
  }

  async load({ message, params }) {
    const player = this.get_manager('player')
    const playlist_title = params[0] // TODO handle long names with spaces...
    const named_playlist = { title: playlist_title, playlist: this.#playlists[playlist_title] }
    // const playlist_id = params[0]
    // const named_playlist = this.#playlists[playlist_id - 1]
    if (named_playlist) {
      player.set_playlist(named_playlist.playlist.clone())
      message.channel.send(`:white_check_mark: Playlist \`${playlist_title}\` loaded`)
    } else {
      message.channel.send(`:warning: Cannot find playlist id \`${playlist_title}\``)
    }
  }

  async fork({ message, params }) {
    const [source, destination] = params
    if (!this.#playlists[source]) {
      message.channel.send(`:warning: Cannot find playlist source \`${source}\``)
    } else {
      this.#playlists[destination] = this.#playlists[source].clone()
      await PlaylistsManager.writeFile(this.#filepath, this.#playlists)
      message.channel.send(`:white_check_mark: Playlist \`${source}\` forked as \`${destination}\``)
    }
  }

  async list({ message, params }) {
    message.channel.send(
      "Playlists:\n" +
        "```json\n" +
        Object.entries(this.#playlists).map(([title, p], idx) => `${idx+1}: ${title} (${p.get_duration_as_string()})`).join("\n") +
        "```\n",
    )
  }

  async import({ message, params }) {
    const [playlist_title, query] = params
    const playlist = await youtube_instance.get_playlist(query)
    this.#playlists[playlist_title] = playlist
    await PlaylistsManager.writeFile(this.#filepath, this.#playlists)
    message.channel.send(`:white_check_mark: Playlist \`${playlist_title}\` imported`)
  }

  async export({ message, params }) {
    if (params.length === 0) params = ["db"]
    switch (params[0]) {
      case "db":
        const export_file = new Discord.MessageAttachment(this.#filepath);
        message.channel.send(export_file)
        break
      default:
        message.channel.send(`:warning: Cannot export this format.`)
    }
  }
}

module.exports = { PlaylistsManager }