const {EventEmitter} = require('events')
const SquirrelUpdate = require('./squirrel-update')

class AutoUpdater extends EventEmitter {
  setFeedURL (updateUrl) {
    this.updateUrl = updateUrl
  }

  quitAndInstall () {
    if (SquirrelUpdate.existsSync()) {
      SquirrelUpdate.restartAtom(require('electron').app)
    } else {
      require('electron').autoUpdater.quitAndInstall()
    }
  }

  downloadUpdate (callback) {
    SquirrelUpdate.spawn(['--download', this.updateUrl], function (error, stdout) {
      let update
      if (error != null) return callback(error)

      try {
        // Last line of output is the JSON details about the releases
        const json = stdout.trim().split('\n').pop()
        const data = JSON.parse(json)
        const releasesToApply = data && data.releasesToApply
        if (releasesToApply.pop) update = releasesToApply.pop()
      } catch (error) {
        error.stdout = stdout
        return callback(error)
      }

      callback(null, update)
    })
  }

  installUpdate (callback) {
    SquirrelUpdate.spawn(['--update', this.updateUrl], callback)
  }

  supportsUpdates () {
    SquirrelUpdate.existsSync()
  }

  checkForUpdates () {
    if (!this.updateUrl) throw new Error('Update URL is not set')

    this.emit('checking-for-update')

    if (!SquirrelUpdate.existsSync()) {
      this.emit('update-not-available')
      return
    }

    this.downloadUpdate((error, update) => {
      if (error != null) {
        this.emit('update-not-available')
        return
      }

      if (update == null) {
        this.emit('update-not-available')
        return
      }

      this.emit('update-available')

      this.installUpdate(error => {
        if (error != null) {
          this.emit('update-not-available')
          return
        }

        this.emit(
          'update-downloaded',
          {},
          update.releaseNotes,
          update.version,
          new Date(),
          'https://atom.io',
          () => this.quitAndInstall()
        )
      })
    })
  }
}

module.exports = new AutoUpdater()
