react-native-background-downloader/lib/downloadTask.js

import { NativeModules } from 'react-native'
const { RNBackgroundDownloader } = NativeModules

function validateHandler (handler) {
  if (!(typeof handler === 'function'))
    throw new TypeError(`[RNBackgroundDownloader] expected argument to be a function, got: ${typeof handler}`)
}
export default class DownloadTask {
    state = 'PENDING'
    percent = 0
    bytesWritten = 0
    totalBytes = 0
    metadata = {}

    constructor (taskInfo, originalTask) {
      this.id = taskInfo.id
      this.percent = taskInfo.percent ?? 0
      this.bytesWritten = taskInfo.bytesWritten ?? 0
      this.totalBytes = taskInfo.totalBytes ?? 0

      if (this.#parseable(taskInfo.metadata))
        this.metadata = JSON.parse(taskInfo.metadata)

      if (originalTask) {
        this._beginHandler = originalTask._beginHandler
        this._progressHandler = originalTask._progressHandler
        this._doneHandler = originalTask._doneHandler
        this._errorHandler = originalTask._errorHandler
      }
    }

    begin (handler) {
      validateHandler(handler)
      this._beginHandler = handler
      return this
    }

    progress (handler) {
      validateHandler(handler)
      this._progressHandler = handler
      return this
    }

    done (handler) {
      validateHandler(handler)
      this._doneHandler = handler
      return this
    }

    error (handler) {
      validateHandler(handler)
      this._errorHandler = handler
      return this
    }

    _onBegin ({ expectedBytes, headers }) {
      this.state = 'DOWNLOADING'
      if (this._beginHandler)
        this._beginHandler({ expectedBytes, headers })
    }

    _onProgress (percent, bytesWritten, totalBytes) {
      this.percent = percent
      this.bytesWritten = bytesWritten
      this.totalBytes = totalBytes
      if (this._progressHandler)
        this._progressHandler(percent, bytesWritten, totalBytes)
    }

    _onDone ({ location }) {
      this.state = 'DONE'
      if (this._doneHandler)
        this._doneHandler({ location })
    }

    _onError (error, errorCode) {
      this.state = 'FAILED'
      if (this._errorHandler)
        this._errorHandler(error, errorCode)
    }

    pause () {
      this.state = 'PAUSED'
      RNBackgroundDownloader.pauseTask(this.id)
    }

    resume () {
      this.state = 'DOWNLOADING'
      RNBackgroundDownloader.resumeTask(this.id)
    }

    stop () {
      this.state = 'STOPPED'
      RNBackgroundDownloader.stopTask(this.id)
    }

    #parseable = (element) => {
      try {
        JSON.parse(element)
        return true
      } catch (err) {
        return false
      }
    }
}