HackMD/public/js/google-drive-upload.js

/* eslint-env browser, jquery */
/**
 * Helper for implementing retries with backoff. Initial retry
 * delay is 1 second, increasing by 2x (+jitter) for subsequent retries
 *
 * @constructor
 */
var RetryHandler = function () {
  this.interval = 1000 // Start at one second
  this.maxInterval = 60 * 1000 // Don't wait longer than a minute
}

/**
 * Invoke the function after waiting
 *
 * @param {function} fn Function to invoke
 */
RetryHandler.prototype.retry = function (fn) {
  setTimeout(fn, this.interval)
  this.interval = this.nextInterval_()
}

/**
 * Reset the counter (e.g. after successful request.)
 */
RetryHandler.prototype.reset = function () {
  this.interval = 1000
}

/**
 * Calculate the next wait time.
 * @return {number} Next wait interval, in milliseconds
 *
 * @private
 */
RetryHandler.prototype.nextInterval_ = function () {
  var interval = this.interval * 2 + this.getRandomInt_(0, 1000)
  return Math.min(interval, this.maxInterval)
}

/**
 * Get a random int in the range of min to max. Used to add jitter to wait times.
 *
 * @param {number} min Lower bounds
 * @param {number} max Upper bounds
 * @private
 */
RetryHandler.prototype.getRandomInt_ = function (min, max) {
  return Math.floor(Math.random() * (max - min + 1) + min)
}

/**
 * Helper class for resumable uploads using XHR/CORS. Can upload any Blob-like item, whether
 * files or in-memory constructs.
 *
 * @example
 * var content = new Blob(["Hello world"], {"type": "text/plain"});
 * var uploader = new MediaUploader({
 *   file: content,
 *   token: accessToken,
 *   onComplete: function(data) { ... }
 *   onError: function(data) { ... }
 * });
 * uploader.upload();
 *
 * @constructor
 * @param {object} options Hash of options
 * @param {string} options.token Access token
 * @param {blob} options.file Blob-like item to upload
 * @param {string} [options.fileId] ID of file if replacing
 * @param {object} [options.params] Additional query parameters
 * @param {string} [options.contentType] Content-type, if overriding the type of the blob.
 * @param {object} [options.metadata] File metadata
 * @param {function} [options.onComplete] Callback for when upload is complete
 * @param {function} [options.onProgress] Callback for status for the in-progress upload
 * @param {function} [options.onError] Callback if upload fails
 */
var MediaUploader = function (options) {
  var noop = function () {}
  this.file = options.file
  this.contentType = options.contentType || this.file.type || 'application/octet-stream'
  this.metadata = options.metadata || {
    'title': this.file.name,
    'mimeType': this.contentType
  }
  this.token = options.token
  this.onComplete = options.onComplete || noop
  this.onProgress = options.onProgress || noop
  this.onError = options.onError || noop
  this.offset = options.offset || 0
  this.chunkSize = options.chunkSize || 0
  this.retryHandler = new RetryHandler()

  this.url = options.url
  if (!this.url) {
    var params = options.params || {}
    params.uploadType = 'resumable'
    this.url = this.buildUrl_(options.fileId, params, options.baseUrl)
  }
  this.httpMethod = options.fileId ? 'PUT' : 'POST'
}

/**
 * Initiate the upload.
 */
MediaUploader.prototype.upload = function () {
  var xhr = new XMLHttpRequest()

  xhr.open(this.httpMethod, this.url, true)
  xhr.setRequestHeader('Authorization', 'Bearer ' + this.token)
  xhr.setRequestHeader('Content-Type', 'application/json')
  xhr.setRequestHeader('X-Upload-Content-Length', this.file.size)
  xhr.setRequestHeader('X-Upload-Content-Type', this.contentType)

  xhr.onload = function (e) {
    if (e.target.status < 400) {
      var location = e.target.getResponseHeader('Location')
      this.url = location
      this.sendFile_()
    } else {
      this.onUploadError_(e)
    }
  }.bind(this)
  xhr.onerror = this.onUploadError_.bind(this)
  xhr.send(JSON.stringify(this.metadata))
}

/**
 * Send the actual file content.
 *
 * @private
 */
MediaUploader.prototype.sendFile_ = function () {
  var content = this.file
  var end = this.file.size

  if (this.offset || this.chunkSize) {
    // Only bother to slice the file if we're either resuming or uploading in chunks
    if (this.chunkSize) {
      end = Math.min(this.offset + this.chunkSize, this.file.size)
    }
    content = content.slice(this.offset, end)
  }

  var xhr = new XMLHttpRequest()
  xhr.open('PUT', this.url, true)
  xhr.setRequestHeader('Content-Type', this.contentType)
  xhr.setRequestHeader('Content-Range', 'bytes ' + this.offset + '-' + (end - 1) + '/' + this.file.size)
  xhr.setRequestHeader('X-Upload-Content-Type', this.file.type)
  if (xhr.upload) {
    xhr.upload.addEventListener('progress', this.onProgress)
  }
  xhr.onload = this.onContentUploadSuccess_.bind(this)
  xhr.onerror = this.onContentUploadError_.bind(this)
  xhr.send(content)
}

/**
 * Query for the state of the file for resumption.
 *
 * @private
 */
MediaUploader.prototype.resume_ = function () {
  var xhr = new XMLHttpRequest()
  xhr.open('PUT', this.url, true)
  xhr.setRequestHeader('Content-Range', 'bytes */' + this.file.size)
  xhr.setRequestHeader('X-Upload-Content-Type', this.file.type)
  if (xhr.upload) {
    xhr.upload.addEventListener('progress', this.onProgress)
  }
  xhr.onload = this.onContentUploadSuccess_.bind(this)
  xhr.onerror = this.onContentUploadError_.bind(this)
  xhr.send()
}

/**
 * Extract the last saved range if available in the request.
 *
 * @param {XMLHttpRequest} xhr Request object
 */
MediaUploader.prototype.extractRange_ = function (xhr) {
  var range = xhr.getResponseHeader('Range')
  if (range) {
    this.offset = parseInt(range.match(/\d+/g).pop(), 10) + 1
  }
}

/**
 * Handle successful responses for uploads. Depending on the context,
 * may continue with uploading the next chunk of the file or, if complete,
 * invokes the caller's callback.
 *
 * @private
 * @param {object} e XHR event
 */
MediaUploader.prototype.onContentUploadSuccess_ = function (e) {
  if (e.target.status === 200 || e.target.status === 201) {
    this.onComplete(e.target.response)
  } else if (e.target.status === 308) {
    this.extractRange_(e.target)
    this.retryHandler.reset()
    this.sendFile_()
  } else {
    this.onContentUploadError_(e)
  }
}

/**
 * Handles errors for uploads. Either retries or aborts depending
 * on the error.
 *
 * @private
 * @param {object} e XHR event
 */
MediaUploader.prototype.onContentUploadError_ = function (e) {
  if (e.target.status && e.target.status < 500) {
    this.onError(e.target.response)
  } else {
    this.retryHandler.retry(this.resume_.bind(this))
  }
}

/**
 * Handles errors for the initial request.
 *
 * @private
 * @param {object} e XHR event
 */
MediaUploader.prototype.onUploadError_ = function (e) {
  this.onError(e.target.response) // TODO - Retries for initial upload
}

/**
 * Construct a query string from a hash/object
 *
 * @private
 * @param {object} [params] Key/value pairs for query string
 * @return {string} query string
 */
MediaUploader.prototype.buildQuery_ = function (params) {
  params = params || {}
  return Object.keys(params).map(function (key) {
    return encodeURIComponent(key) + '=' + encodeURIComponent(params[key])
  }).join('&')
}

/**
 * Build the drive upload URL
 *
 * @private
 * @param {string} [id] File ID if replacing
 * @param {object} [params] Query parameters
 * @return {string} URL
 */
MediaUploader.prototype.buildUrl_ = function (id, params, baseUrl) {
  var url = baseUrl || 'https://www.googleapis.com/upload/drive/v2/files/'
  if (id) {
    url += id
  }
  var query = this.buildQuery_(params)
  if (query) {
    url += '?' + query
  }
  return url
}

window.MediaUploader = MediaUploader