@@ -49,6 +49,7 @@ class Uppy {
         youCanOnlyUploadFileTypes: 'You can only upload: %{types}',
         companionError: 'Connection with Companion failed',
         companionAuthError: 'Authorization required',
+        companionUnauthorizeHint: 'To unauthorize to your %{provider} account, please go to %{url}',
         failedToUpload: 'Failed to upload %{file}',
         noInternetConnection: 'No Internet connection',
         connectedToInternet: 'Connected to the Internet',
const Translator = require('@uppy/utils/lib/Translator')
const ee = require('namespace-emitter')
const cuid = require('cuid')
const throttle = require('lodash.throttle')
const prettyBytes = require('@uppy/utils/lib/prettyBytes')
const match = require('mime-match')
const DefaultStore = require('@uppy/store-default')
const getFileType = require('@uppy/utils/lib/getFileType')
const getFileNameAndExtension = require('@uppy/utils/lib/getFileNameAndExtension')
const generateFileID = require('@uppy/utils/lib/generateFileID')
const supportsUploadProgress = require('./supportsUploadProgress')
const { nullLogger, debugLogger } = require('./loggers')
const Plugin = require('./Plugin') // Exported from here.

class RestrictionError extends Error {
  constructor (...args) {
    super(...args)
    this.isRestriction = true
  }
}

/**
 * Uppy Core module.
 * Manages plugins, state updates, acts as an event bus,
 * adds/removes files and metadata.
 */
class Uppy {
  static VERSION = require('../package.json').version

  /**
   * Instantiate Uppy
   *
   * @param {object} opts — Uppy options
   */
  constructor (opts) {
    this.defaultLocale = {
      strings: {
        youCanOnlyUploadX: {
          0: 'You can only upload %{smart_count} file',
          1: 'You can only upload %{smart_count} files',
          2: 'You can only upload %{smart_count} files'
        },
        youHaveToAtLeastSelectX: {
          0: 'You have to select at least %{smart_count} file',
          1: 'You have to select at least %{smart_count} files',
          2: 'You have to select at least %{smart_count} files'
        },
        exceedsSize: 'This file exceeds maximum allowed size of',
        youCanOnlyUploadFileTypes: 'You can only upload: %{types}',
        companionError: 'Connection with Companion failed',
        companionAuthError: 'Authorization required',
        failedToUpload: 'Failed to upload %{file}',
        noInternetConnection: 'No Internet connection',
        connectedToInternet: 'Connected to the Internet',
        // Strings for remote providers
        noFilesFound: 'You have no files or folders here',
        selectX: {
          0: 'Select %{smart_count}',
          1: 'Select %{smart_count}',
          2: 'Select %{smart_count}'
        },
        selectAllFilesFromFolderNamed: 'Select all files from folder %{name}',
        unselectAllFilesFromFolderNamed: 'Unselect all files from folder %{name}',
        selectFileNamed: 'Select file %{name}',
        unselectFileNamed: 'Unselect file %{name}',
        openFolderNamed: 'Open folder %{name}',
        cancel: 'Cancel',
        logOut: 'Log out',
        filter: 'Filter',
        resetFilter: 'Reset filter',
        loading: 'Loading...',
        authenticateWithTitle: 'Please authenticate with %{pluginName} to select files',
        authenticateWith: 'Connect to %{pluginName}',
        emptyFolderAdded: 'No files were added from empty folder',
        folderAdded: {
          0: 'Added %{smart_count} file from %{folder}',
          1: 'Added %{smart_count} files from %{folder}',
          2: 'Added %{smart_count} files from %{folder}'
        }
      }
    }

    // set default options
    const defaultOptions = {
      id: 'uppy',
      autoProceed: false,
      allowMultipleUploads: true,
      debug: false,
      restrictions: {
        maxFileSize: null,
        maxNumberOfFiles: null,
        minNumberOfFiles: null,
        allowedFileTypes: null
      },
      meta: {},
      onBeforeFileAdded: (currentFile, files) => currentFile,
      onBeforeUpload: (files) => files,
      store: DefaultStore(),
      logger: nullLogger
    }

    // Merge default options with the ones set by user
    this.opts = Object.assign({}, defaultOptions, opts)
    this.opts.restrictions = Object.assign({}, defaultOptions.restrictions, this.opts.restrictions)

    // Support debug: true for backwards-compatability, unless logger is set in opts
    // opts instead of this.opts to avoid comparing objects — we set logger: nullLogger in defaultOptions
    if (opts && opts.logger && opts.debug) {
      this.log('You are using a custom `logger`, but also set `debug: true`, which uses built-in logger to output logs to console. Ignoring `debug: true` and using your custom `logger`.', 'warning')
    } else if (opts && opts.debug) {
      this.opts.logger = debugLogger
    }

    this.log(`Using Core v${this.constructor.VERSION}`)

    if (this.opts.restrictions.allowedFileTypes &&
        this.opts.restrictions.allowedFileTypes !== null &&
        !Array.isArray(this.opts.restrictions.allowedFileTypes)) {
      throw new TypeError(`'restrictions.allowedFileTypes' must be an array`)
    }

    // i18n
    this.translator = new Translator([this.defaultLocale, this.opts.locale])
    this.locale = this.translator.locale
    this.i18n = this.translator.translate.bind(this.translator)
    this.i18nArray = this.translator.translateArray.bind(this.translator)

    // Container for different types of plugins
    this.plugins = {}

    this.getState = this.getState.bind(this)
    this.getPlugin = this.getPlugin.bind(this)
    this.setFileMeta = this.setFileMeta.bind(this)
    this.setFileState = this.setFileState.bind(this)
    this.log = this.log.bind(this)
    this.info = this.info.bind(this)
    this.hideInfo = this.hideInfo.bind(this)
    this.addFile = this.addFile.bind(this)
    this.removeFile = this.removeFile.bind(this)
    this.pauseResume = this.pauseResume.bind(this)

    // ___Why throttle at 500ms?
    //    - We must throttle at >250ms for superfocus in Dashboard to work well (because animation takes 0.25s, and we want to wait for all animations to be over before refocusing).
    //    [Practical Check]: if thottle is at 100ms, then if you are uploading a file, and click 'ADD MORE FILES', - focus won't activate in Firefox.
    //    - We must throttle at around >500ms to avoid performance lags.
    //    [Practical Check] Firefox, try to upload a big file for a prolonged period of time. Laptop will start to heat up.
    this._calculateProgress = throttle(this._calculateProgress.bind(this), 500, { leading: true, trailing: true })

    this.updateOnlineStatus = this.updateOnlineStatus.bind(this)
    this.resetProgress = this.resetProgress.bind(this)

    this.pauseAll = this.pauseAll.bind(this)
    this.resumeAll = this.resumeAll.bind(this)
    this.retryAll = this.retryAll.bind(this)
    this.cancelAll = this.cancelAll.bind(this)
    this.retryUpload = this.retryUpload.bind(this)
    this.upload = this.upload.bind(this)

    this.emitter = ee()
    this.on = this.on.bind(this)
    this.off = this.off.bind(this)
    this.once = this.emitter.once.bind(this.emitter)
    this.emit = this.emitter.emit.bind(this.emitter)

    this.preProcessors = []
    this.uploaders = []
    this.postProcessors = []

    this.store = this.opts.store
    this.setState({
      plugins: {},
      files: {},
      currentUploads: {},
      allowNewUpload: true,
      capabilities: {
        uploadProgress: supportsUploadProgress(),
        individualCancellation: true,
        resumableUploads: false
      },
      totalProgress: 0,
      meta: { ...this.opts.meta },
      info: {
        isHidden: true,
        type: 'info',
        message: ''
      }
    })

    this._storeUnsubscribe = this.store.subscribe((prevState, nextState, patch) => {
      this.emit('state-update', prevState, nextState, patch)
      this.updateAll(nextState)
    })

    // Exposing uppy object on window for debugging and testing
    if (this.opts.debug && typeof window !== 'undefined') {
      window[this.opts.id] = this
    }

    this._addListeners()
  }

  on (event, callback) {
    this.emitter.on(event, callback)
    return this
  }

  off (event, callback) {
    this.emitter.off(event, callback)
    return this
  }

  /**
   * Iterate on all plugins and run `update` on them.
   * Called each time state changes.
   *
   */
  updateAll (state) {
    this.iteratePlugins(plugin => {
      plugin.update(state)
    })
  }

  /**
   * Updates state with a patch
   *
   * @param {object} patch {foo: 'bar'}
   */
  setState (patch) {
    this.store.setState(patch)
  }

  /**
   * Returns current state.
   *
   * @returns {object}
   */
  getState () {
    return this.store.getState()
  }

  /**
   * Back compat for when uppy.state is used instead of uppy.getState().
   */
  get state () {
    return this.getState()
  }

  /**
   * Shorthand to set state for a specific file.
   */
  setFileState (fileID, state) {
    if (!this.getState().files[fileID]) {
      throw new Error(`Can’t set state for ${fileID} (the file could have been removed)`)
    }

    this.setState({
      files: Object.assign({}, this.getState().files, {
        [fileID]: Object.assign({}, this.getState().files[fileID], state)
      })
    })
  }

  resetProgress () {
    const defaultProgress = {
      percentage: 0,
      bytesUploaded: 0,
      uploadComplete: false,
      uploadStarted: null
    }
    const files = Object.assign({}, this.getState().files)
    const updatedFiles = {}
    Object.keys(files).forEach(fileID => {
      const updatedFile = Object.assign({}, files[fileID])
      updatedFile.progress = Object.assign({}, updatedFile.progress, defaultProgress)
      updatedFiles[fileID] = updatedFile
    })

    this.setState({
      files: updatedFiles,
      totalProgress: 0
    })

    // TODO Document on the website
    this.emit('reset-progress')
  }

  addPreProcessor (fn) {
    this.preProcessors.push(fn)
  }

  removePreProcessor (fn) {
    const i = this.preProcessors.indexOf(fn)
    if (i !== -1) {
      this.preProcessors.splice(i, 1)
    }
  }

  addPostProcessor (fn) {
    this.postProcessors.push(fn)
  }

  removePostProcessor (fn) {
    const i = this.postProcessors.indexOf(fn)
    if (i !== -1) {
      this.postProcessors.splice(i, 1)
    }
  }

  addUploader (fn) {
    this.uploaders.push(fn)
  }

  removeUploader (fn) {
    const i = this.uploaders.indexOf(fn)
    if (i !== -1) {
      this.uploaders.splice(i, 1)
    }
  }

  setMeta (data) {
    const updatedMeta = Object.assign({}, this.getState().meta, data)
    const updatedFiles = Object.assign({}, this.getState().files)

    Object.keys(updatedFiles).forEach((fileID) => {
      updatedFiles[fileID] = Object.assign({}, updatedFiles[fileID], {
        meta: Object.assign({}, updatedFiles[fileID].meta, data)
      })
    })

    this.log('Adding metadata:')
    this.log(data)

    this.setState({
      meta: updatedMeta,
      files: updatedFiles
    })
  }

  setFileMeta (fileID, data) {
    const updatedFiles = Object.assign({}, this.getState().files)
    if (!updatedFiles[fileID]) {
      this.log('Was trying to set metadata for a file that has been removed: ', fileID)
      return
    }
    const newMeta = Object.assign({}, updatedFiles[fileID].meta, data)
    updatedFiles[fileID] = Object.assign({}, updatedFiles[fileID], {
      meta: newMeta
    })
    this.setState({ files: updatedFiles })
  }

  /**
   * Get a file object.
   *
   * @param {string} fileID The ID of the file object to return.
   */
  getFile (fileID) {
    return this.getState().files[fileID]
  }

  /**
   * Get all files in an array.
   */
  getFiles () {
    const { files } = this.getState()
    return Object.keys(files).map((fileID) => files[fileID])
  }

  /**
   * Check if minNumberOfFiles restriction is reached before uploading.
   *
   * @private
   */
  _checkMinNumberOfFiles (files) {
    const { minNumberOfFiles } = this.opts.restrictions
    if (Object.keys(files).length < minNumberOfFiles) {
      throw new RestrictionError(`${this.i18n('youHaveToAtLeastSelectX', { smart_count: minNumberOfFiles })}`)
    }
  }

  /**
   * Check if file passes a set of restrictions set in options: maxFileSize,
   * maxNumberOfFiles and allowedFileTypes.
   *
   * @param {object} file object to check
   * @private
   */
  _checkRestrictions (file) {
    const { maxFileSize, maxNumberOfFiles, allowedFileTypes } = this.opts.restrictions

    if (maxNumberOfFiles) {
      if (Object.keys(this.getState().files).length + 1 > maxNumberOfFiles) {
        throw new RestrictionError(`${this.i18n('youCanOnlyUploadX', { smart_count: maxNumberOfFiles })}`)
      }
    }

    if (allowedFileTypes) {
      const isCorrectFileType = allowedFileTypes.some((type) => {
        // is this is a mime-type
        if (type.indexOf('/') > -1) {
          if (!file.type) return false
          return match(file.type, type)
        }

        // otherwise this is likely an extension
        if (type[0] === '.') {
          return file.extension.toLowerCase() === type.substr(1).toLowerCase()
        }
        return false
      })

      if (!isCorrectFileType) {
        const allowedFileTypesString = allowedFileTypes.join(', ')
        throw new RestrictionError(this.i18n('youCanOnlyUploadFileTypes', { types: allowedFileTypesString }))
      }
    }

    // We can't check maxFileSize if the size is unknown.
    if (maxFileSize && file.data.size != null) {
      if (file.data.size > maxFileSize) {
        throw new RestrictionError(`${this.i18n('exceedsSize')} ${prettyBytes(maxFileSize)}`)
      }
    }
  }

  _showOrLogErrorAndThrow (err, { showInformer = true, file = null } = {}) {
    const message = typeof err === 'object' ? err.message : err
    const details = (typeof err === 'object' && err.details) ? err.details : ''

    // Restriction errors should be logged, but not as errors,
    // as they are expected and shown in the UI.
    if (err.isRestriction) {
      this.log(`${message} ${details}`)
      this.emit('restriction-failed', file, err)
    } else {
      this.log(`${message} ${details}`, 'error')
    }

    // Sometimes informer has to be shown manually by the developer,
    // for example, in `onBeforeFileAdded`.
    if (showInformer) {
      this.info({ message: message, details: details }, 'error', 5000)
    }

    throw (typeof err === 'object' ? err : new Error(err))
  }

  /**
   * Add a new file to `state.files`. This will run `onBeforeFileAdded`,
   * try to guess file type in a clever way, check file against restrictions,
   * and start an upload if `autoProceed === true`.
   *
   * @param {object} file object to add
   * @returns {string} id for the added file
   */
  addFile (file) {
    const { files, allowNewUpload } = this.getState()

    if (allowNewUpload === false) {
      this._showOrLogErrorAndThrow(new RestrictionError('Cannot add new files: already uploading.'), { file })
    }

    const fileType = getFileType(file)
    file.type = fileType

    const onBeforeFileAddedResult = this.opts.onBeforeFileAdded(file, files)

    if (onBeforeFileAddedResult === false) {
      // Don’t show UI info for this error, as it should be done by the developer
      this._showOrLogErrorAndThrow(new RestrictionError('Cannot add the file because onBeforeFileAdded returned false.'), { showInformer: false, file })
    }

    if (typeof onBeforeFileAddedResult === 'object' && onBeforeFileAddedResult) {
      file = onBeforeFileAddedResult
    }

    let fileName
    if (file.name) {
      fileName = file.name
    } else if (fileType.split('/')[0] === 'image') {
      fileName = fileType.split('/')[0] + '.' + fileType.split('/')[1]
    } else {
      fileName = 'noname'
    }
    const fileExtension = getFileNameAndExtension(fileName).extension
    const isRemote = file.isRemote || false

    const fileID = generateFileID(file)

    if (files[fileID]) {
      this._showOrLogErrorAndThrow(new RestrictionError(`Cannot add the duplicate file '${fileName}', it already exists.`), { file })
    }

    const meta = file.meta || {}
    meta.name = fileName
    meta.type = fileType

    // `null` means the size is unknown.
    const size = isFinite(file.data.size) ? file.data.size : null
    const newFile = {
      source: file.source || '',
      id: fileID,
      name: fileName,
      extension: fileExtension || '',
      meta: Object.assign({}, this.getState().meta, meta),
      type: fileType,
      data: file.data,
      progress: {
        percentage: 0,
        bytesUploaded: 0,
        bytesTotal: size,
        uploadComplete: false,
        uploadStarted: null
      },
      size: size,
      isRemote: isRemote,
      remote: file.remote || '',
      preview: file.preview
    }

    try {
      this._checkRestrictions(newFile)
    } catch (err) {
      this._showOrLogErrorAndThrow(err, { file: newFile })
    }

    this.setState({
      files: Object.assign({}, files, {
        [fileID]: newFile
      })
    })

    this.emit('file-added', newFile)
    this.log(`Added file: ${fileName}, ${fileID}, mime type: ${fileType}`)

    if (this.opts.autoProceed && !this.scheduledAutoProceed) {
      this.scheduledAutoProceed = setTimeout(() => {
        this.scheduledAutoProceed = null
        this.upload().catch((err) => {
          if (!err.isRestriction) {
            this.log(err.stack || err.message || err)
          }
        })
      }, 4)
    }

    return fileID
  }

  removeFile (fileID) {
    const { files, currentUploads } = this.getState()
    const updatedFiles = Object.assign({}, files)
    const removedFile = updatedFiles[fileID]
    delete updatedFiles[fileID]

    // Remove this file from its `currentUpload`.
    const updatedUploads = Object.assign({}, currentUploads)
    const removeUploads = []
    Object.keys(updatedUploads).forEach((uploadID) => {
      const newFileIDs = currentUploads[uploadID].fileIDs.filter((uploadFileID) => uploadFileID !== fileID)
      // Remove the upload if no files are associated with it anymore.
      if (newFileIDs.length === 0) {
        removeUploads.push(uploadID)
        return
      }

      updatedUploads[uploadID] = Object.assign({}, currentUploads[uploadID], {
        fileIDs: newFileIDs
      })
    })

    this.setState({
      currentUploads: updatedUploads,
      files: updatedFiles,
      ...(
        // If this is the last file we just removed - allow new uploads!
        Object.keys(updatedFiles).length === 0 &&
        { allowNewUpload: true }
      )
    })

    removeUploads.forEach((uploadID) => {
      this._removeUpload(uploadID)
    })

    this._calculateTotalProgress()
    this.emit('file-removed', removedFile)
    this.log(`File removed: ${removedFile.id}`)
  }

  pauseResume (fileID) {
    if (!this.getState().capabilities.resumableUploads ||
         this.getFile(fileID).uploadComplete) {
      return
    }

    const wasPaused = this.getFile(fileID).isPaused || false
    const isPaused = !wasPaused

    this.setFileState(fileID, {
      isPaused: isPaused
    })

    this.emit('upload-pause', fileID, isPaused)

    return isPaused
  }

  pauseAll () {
    const updatedFiles = Object.assign({}, this.getState().files)
    const inProgressUpdatedFiles = Object.keys(updatedFiles).filter((file) => {
      return !updatedFiles[file].progress.uploadComplete &&
             updatedFiles[file].progress.uploadStarted
    })

    inProgressUpdatedFiles.forEach((file) => {
      const updatedFile = Object.assign({}, updatedFiles[file], {
        isPaused: true
      })
      updatedFiles[file] = updatedFile
    })
    this.setState({ files: updatedFiles })

    this.emit('pause-all')
  }

  resumeAll () {
    const updatedFiles = Object.assign({}, this.getState().files)
    const inProgressUpdatedFiles = Object.keys(updatedFiles).filter((file) => {
      return !updatedFiles[file].progress.uploadComplete &&
             updatedFiles[file].progress.uploadStarted
    })

    inProgressUpdatedFiles.forEach((file) => {
      const updatedFile = Object.assign({}, updatedFiles[file], {
        isPaused: false,
        error: null
      })
      updatedFiles[file] = updatedFile
    })
    this.setState({ files: updatedFiles })

    this.emit('resume-all')
  }

  retryAll () {
    const updatedFiles = Object.assign({}, this.getState().files)
    const filesToRetry = Object.keys(updatedFiles).filter(file => {
      return updatedFiles[file].error
    })

    filesToRetry.forEach((file) => {
      const updatedFile = Object.assign({}, updatedFiles[file], {
        isPaused: false,
        error: null
      })
      updatedFiles[file] = updatedFile
    })
    this.setState({
      files: updatedFiles,
      error: null
    })

    this.emit('retry-all', filesToRetry)

    const uploadID = this._createUpload(filesToRetry)
    return this._runUpload(uploadID)
  }

  cancelAll () {
    this.emit('cancel-all')

    const files = Object.keys(this.getState().files)
    files.forEach((fileID) => {
      this.removeFile(fileID)
    })

    this.setState({
      totalProgress: 0,
      error: null
    })
  }

  retryUpload (fileID) {
    this.setFileState(fileID, {
      error: null,
      isPaused: false
    })

    this.emit('upload-retry', fileID)

    const uploadID = this._createUpload([fileID])
    return this._runUpload(uploadID)
  }

  reset () {
    this.cancelAll()
  }

  _calculateProgress (file, data) {
    if (!this.getFile(file.id)) {
      this.log(`Not setting progress for a file that has been removed: ${file.id}`)
      return
    }

    // bytesTotal may be null or zero; in that case we can't divide by it
    const canHavePercentage = isFinite(data.bytesTotal) && data.bytesTotal > 0
    this.setFileState(file.id, {
      progress: Object.assign({}, this.getFile(file.id).progress, {
        bytesUploaded: data.bytesUploaded,
        bytesTotal: data.bytesTotal,
        percentage: canHavePercentage
          // TODO(goto-bus-stop) flooring this should probably be the choice of the UI?
          // we get more accurate calculations if we don't round this at all.
          ? Math.round(data.bytesUploaded / data.bytesTotal * 100)
          : 0
      })
    })

    this._calculateTotalProgress()
  }

  _calculateTotalProgress () {
    // calculate total progress, using the number of files currently uploading,
    // multiplied by 100 and the summ of individual progress of each file
    const files = this.getFiles()

    const inProgress = files.filter((file) => {
      return file.progress.uploadStarted
    })

    if (inProgress.length === 0) {
      this.emit('progress', 0)
      this.setState({ totalProgress: 0 })
      return
    }

    const sizedFiles = inProgress.filter((file) => file.progress.bytesTotal != null)
    const unsizedFiles = inProgress.filter((file) => file.progress.bytesTotal == null)

    if (sizedFiles.length === 0) {
      const progressMax = inProgress.length * 100
      const currentProgress = unsizedFiles.reduce((acc, file) => {
        return acc + file.progress.percentage
      }, 0)
      const totalProgress = Math.round(currentProgress / progressMax * 100)
      this.setState({ totalProgress })
      return
    }

    let totalSize = sizedFiles.reduce((acc, file) => {
      return acc + file.progress.bytesTotal
    }, 0)
    const averageSize = totalSize / sizedFiles.length
    totalSize += averageSize * unsizedFiles.length

    let uploadedSize = 0
    sizedFiles.forEach((file) => {
      uploadedSize += file.progress.bytesUploaded
    })
    unsizedFiles.forEach((file) => {
      uploadedSize += averageSize * (file.progress.percentage || 0) / 100
    })

    let totalProgress = totalSize === 0
      ? 0
      : Math.round(uploadedSize / totalSize * 100)

    // hot fix, because:
    // uploadedSize ended up larger than totalSize, resulting in 1325% total
    if (totalProgress > 100) {
      totalProgress = 100
    }

    this.setState({ totalProgress })
    this.emit('progress', totalProgress)
  }

  /**
   * Registers listeners for all global actions, like:
   * `error`, `file-removed`, `upload-progress`
   */
  _addListeners () {
    this.on('error', (error) => {
      this.setState({ error: error.message })
    })

    this.on('upload-error', (file, error, response) => {
      this.setFileState(file.id, {
        error: error.message,
        response
      })

      this.setState({ error: error.message })

      let message = this.i18n('failedToUpload', { file: file.name })
      if (typeof error === 'object' && error.message) {
        message = { message: message, details: error.message }
      }
      this.info(message, 'error', 5000)
    })

    this.on('upload', () => {
      this.setState({ error: null })
    })

    this.on('upload-started', (file, upload) => {
      if (!this.getFile(file.id)) {
        this.log(`Not setting progress for a file that has been removed: ${file.id}`)
        return
      }
      this.setFileState(file.id, {
        progress: {
          uploadStarted: Date.now(),
          uploadComplete: false,
          percentage: 0,
          bytesUploaded: 0,
          bytesTotal: file.size
        }
      })
    })

    this.on('upload-progress', this._calculateProgress)

    this.on('upload-success', (file, uploadResp) => {
      const currentProgress = this.getFile(file.id).progress
      this.setFileState(file.id, {
        progress: Object.assign({}, currentProgress, {
          uploadComplete: true,
          percentage: 100,
          bytesUploaded: currentProgress.bytesTotal
        }),
        response: uploadResp,
        uploadURL: uploadResp.uploadURL,
        isPaused: false
      })

      this._calculateTotalProgress()
    })

    this.on('preprocess-progress', (file, progress) => {
      if (!this.getFile(file.id)) {
        this.log(`Not setting progress for a file that has been removed: ${file.id}`)
        return
      }
      this.setFileState(file.id, {
        progress: Object.assign({}, this.getFile(file.id).progress, {
          preprocess: progress
        })
      })
    })

    this.on('preprocess-complete', (file) => {
      if (!this.getFile(file.id)) {
        this.log(`Not setting progress for a file that has been removed: ${file.id}`)
        return
      }
      const files = Object.assign({}, this.getState().files)
      files[file.id] = Object.assign({}, files[file.id], {
        progress: Object.assign({}, files[file.id].progress)
      })
      delete files[file.id].progress.preprocess

      this.setState({ files: files })
    })

    this.on('postprocess-progress', (file, progress) => {
      if (!this.getFile(file.id)) {
        this.log(`Not setting progress for a file that has been removed: ${file.id}`)
        return
      }
      this.setFileState(file.id, {
        progress: Object.assign({}, this.getState().files[file.id].progress, {
          postprocess: progress
        })
      })
    })

    this.on('postprocess-complete', (file) => {
      if (!this.getFile(file.id)) {
        this.log(`Not setting progress for a file that has been removed: ${file.id}`)
        return
      }
      const files = Object.assign({}, this.getState().files)
      files[file.id] = Object.assign({}, files[file.id], {
        progress: Object.assign({}, files[file.id].progress)
      })
      delete files[file.id].progress.postprocess
      // TODO should we set some kind of `fullyComplete` property on the file object
      // so it's easier to see that the file is upload…fully complete…rather than
      // what we have to do now (`uploadComplete && !postprocess`)

      this.setState({ files: files })
    })

    this.on('restored', () => {
      // Files may have changed--ensure progress is still accurate.
      this._calculateTotalProgress()
    })

    // show informer if offline
    if (typeof window !== 'undefined' && window.addEventListener) {
      window.addEventListener('online', () => this.updateOnlineStatus())
      window.addEventListener('offline', () => this.updateOnlineStatus())
      setTimeout(() => this.updateOnlineStatus(), 3000)
    }
  }

  updateOnlineStatus () {
    const online =
      typeof window.navigator.onLine !== 'undefined'
        ? window.navigator.onLine
        : true
    if (!online) {
      this.emit('is-offline')
      this.info(this.i18n('noInternetConnection'), 'error', 0)
      this.wasOffline = true
    } else {
      this.emit('is-online')
      if (this.wasOffline) {
        this.emit('back-online')
        this.info(this.i18n('connectedToInternet'), 'success', 3000)
        this.wasOffline = false
      }
    }
  }

  getID () {
    return this.opts.id
  }

  /**
   * Registers a plugin with Core.
   *
   * @param {object} Plugin object
   * @param {object} [opts] object with options to be passed to Plugin
   * @returns {object} self for chaining
   */
  use (Plugin, opts) {
    if (typeof Plugin !== 'function') {
      const msg = `Expected a plugin class, but got ${Plugin === null ? 'null' : typeof Plugin}.` +
        ' Please verify that the plugin was imported and spelled correctly.'
      throw new TypeError(msg)
    }

    // Instantiate
    const plugin = new Plugin(this, opts)
    const pluginId = plugin.id
    this.plugins[plugin.type] = this.plugins[plugin.type] || []

    if (!pluginId) {
      throw new Error('Your plugin must have an id')
    }

    if (!plugin.type) {
      throw new Error('Your plugin must have a type')
    }

    const existsPluginAlready = this.getPlugin(pluginId)
    if (existsPluginAlready) {
      const msg = `Already found a plugin named '${existsPluginAlready.id}'. ` +
        `Tried to use: '${pluginId}'.\n` +
        `Uppy plugins must have unique 'id' options. See https://uppy.io/docs/plugins/#id.`
      throw new Error(msg)
    }

    if (Plugin.VERSION) {
      this.log(`Using ${pluginId} v${Plugin.VERSION}`)
    }

    this.plugins[plugin.type].push(plugin)
    plugin.install()

    return this
  }

  /**
   * Find one Plugin by name.
   *
   * @param {string} id plugin id
   * @returns {object|boolean}
   */
  getPlugin (id) {
    let foundPlugin = null
    this.iteratePlugins((plugin) => {
      if (plugin.id === id) {
        foundPlugin = plugin
        return false
      }
    })
    return foundPlugin
  }

  /**
   * Iterate through all `use`d plugins.
   *
   * @param {Function} method that will be run on each plugin
   */
  iteratePlugins (method) {
    Object.keys(this.plugins).forEach(pluginType => {
      this.plugins[pluginType].forEach(method)
    })
  }

  /**
   * Uninstall and remove a plugin.
   *
   * @param {object} instance The plugin instance to remove.
   */
  removePlugin (instance) {
    this.log(`Removing plugin ${instance.id}`)
    this.emit('plugin-remove', instance)

    if (instance.uninstall) {
      instance.uninstall()
    }

    const list = this.plugins[instance.type].slice()
    const index = list.indexOf(instance)
    if (index !== -1) {
      list.splice(index, 1)
      this.plugins[instance.type] = list
    }

    const updatedState = this.getState()
    delete updatedState.plugins[instance.id]
    this.setState(updatedState)
  }

  /**
   * Uninstall all plugins and close down this Uppy instance.
   */
  close () {
    this.log(`Closing Uppy instance ${this.opts.id}: removing all files and uninstalling plugins`)

    this.reset()

    this._storeUnsubscribe()

    this.iteratePlugins((plugin) => {
      this.removePlugin(plugin)
    })
  }

  /**
   * Set info message in `state.info`, so that UI plugins like `Informer`
   * can display the message.
   *
   * @param {string | object} message Message to be displayed by the informer
   * @param {string} [type]
   * @param {number} [duration]
   */

  info (message, type = 'info', duration = 3000) {
    const isComplexMessage = typeof message === 'object'

    this.setState({
      info: {
        isHidden: false,
        type: type,
        message: isComplexMessage ? message.message : message,
        details: isComplexMessage ? message.details : null
      }
    })

    this.emit('info-visible')

    clearTimeout(this.infoTimeoutID)
    if (duration === 0) {
      this.infoTimeoutID = undefined
      return
    }

    // hide the informer after `duration` milliseconds
    this.infoTimeoutID = setTimeout(this.hideInfo, duration)
  }

  hideInfo () {
    const newInfo = Object.assign({}, this.getState().info, {
      isHidden: true
    })
    this.setState({
      info: newInfo
    })
    this.emit('info-hidden')
  }

  /**
   * Passes messages to a function, provided in `opts.logger`.
   * If `opts.logger: Uppy.debugLogger` or `opts.debug: true`, logs to the browser console.
   *
   * @param {string|object} message to log
   * @param {string} [type] optional `error` or `warning`
   */
  log (message, type) {
    const { logger } = this.opts
    switch (type) {
      case 'error': logger.error(message); break
      case 'warning': logger.warn(message); break
      default: logger.debug(message); break
    }
  }

  /**
   * Obsolete, event listeners are now added in the constructor.
   */
  run () {
    this.log('Calling run() is no longer necessary.', 'warning')
    return this
  }

  /**
   * Restore an upload by its ID.
   */
  restore (uploadID) {
    this.log(`Core: attempting to restore upload "${uploadID}"`)

    if (!this.getState().currentUploads[uploadID]) {
      this._removeUpload(uploadID)
      return Promise.reject(new Error('Nonexistent upload'))
    }

    return this._runUpload(uploadID)
  }

  /**
   * Create an upload for a bunch of files.
   *
   * @param {Array<string>} fileIDs File IDs to include in this upload.
   * @returns {string} ID of this upload.
   */
  _createUpload (fileIDs) {
    const { allowNewUpload, currentUploads } = this.getState()
    if (!allowNewUpload) {
      throw new Error('Cannot create a new upload: already uploading.')
    }

    const uploadID = cuid()

    this.emit('upload', {
      id: uploadID,
      fileIDs: fileIDs
    })

    this.setState({
      allowNewUpload: this.opts.allowMultipleUploads !== false,

      currentUploads: {
        ...currentUploads,
        [uploadID]: {
          fileIDs: fileIDs,
          step: 0,
          result: {}
        }
      }
    })

    return uploadID
  }

  _getUpload (uploadID) {
    const { currentUploads } = this.getState()

    return currentUploads[uploadID]
  }

  /**
   * Add data to an upload's result object.
   *
   * @param {string} uploadID The ID of the upload.
   * @param {object} data Data properties to add to the result object.
   */
  addResultData (uploadID, data) {
    if (!this._getUpload(uploadID)) {
      this.log(`Not setting result for an upload that has been removed: ${uploadID}`)
      return
    }
    const currentUploads = this.getState().currentUploads
    const currentUpload = Object.assign({}, currentUploads[uploadID], {
      result: Object.assign({}, currentUploads[uploadID].result, data)
    })
    this.setState({
      currentUploads: Object.assign({}, currentUploads, {
        [uploadID]: currentUpload
      })
    })
  }

  /**
   * Remove an upload, eg. if it has been canceled or completed.
   *
   * @param {string} uploadID The ID of the upload.
   */
  _removeUpload (uploadID) {
    const currentUploads = Object.assign({}, this.getState().currentUploads)
    delete currentUploads[uploadID]

    this.setState({
      currentUploads: currentUploads
    })
  }

  /**
   * Run an upload. This picks up where it left off in case the upload is being restored.
   *
   * @private
   */
  _runUpload (uploadID) {
    const uploadData = this.getState().currentUploads[uploadID]
    const restoreStep = uploadData.step

    const steps = [
      ...this.preProcessors,
      ...this.uploaders,
      ...this.postProcessors
    ]
    let lastStep = Promise.resolve()
    steps.forEach((fn, step) => {
      // Skip this step if we are restoring and have already completed this step before.
      if (step < restoreStep) {
        return
      }

      lastStep = lastStep.then(() => {
        const { currentUploads } = this.getState()
        const currentUpload = currentUploads[uploadID]
        if (!currentUpload) {
          return
        }

        const updatedUpload = Object.assign({}, currentUpload, {
          step: step
        })
        this.setState({
          currentUploads: Object.assign({}, currentUploads, {
            [uploadID]: updatedUpload
          })
        })

        // TODO give this the `updatedUpload` object as its only parameter maybe?
        // Otherwise when more metadata may be added to the upload this would keep getting more parameters
        return fn(updatedUpload.fileIDs, uploadID)
      }).then((result) => {
        return null
      })
    })

    // Not returning the `catch`ed promise, because we still want to return a rejected
    // promise from this method if the upload failed.
    lastStep.catch((err) => {
      this.emit('error', err, uploadID)
      this._removeUpload(uploadID)
    })

    return lastStep.then(() => {
      // Set result data.
      const { currentUploads } = this.getState()
      const currentUpload = currentUploads[uploadID]
      if (!currentUpload) {
        return
      }

      const files = currentUpload.fileIDs
        .map((fileID) => this.getFile(fileID))
      const successful = files.filter((file) => !file.error)
      const failed = files.filter((file) => file.error)
      this.addResultData(uploadID, { successful, failed, uploadID })
    }).then(() => {
      // Emit completion events.
      // This is in a separate function so that the `currentUploads` variable
      // always refers to the latest state. In the handler right above it refers
      // to an outdated object without the `.result` property.
      const { currentUploads } = this.getState()
      if (!currentUploads[uploadID]) {
        return
      }
      const currentUpload = currentUploads[uploadID]
      const result = currentUpload.result
      this.emit('complete', result)

      this._removeUpload(uploadID)

      return result
    }).then((result) => {
      if (result == null) {
        this.log(`Not setting result for an upload that has been removed: ${uploadID}`)
      }
      return result
    })
  }

  /**
   * Start an upload for all the files that are not currently being uploaded.
   *
   * @returns {Promise}
   */
  upload () {
    if (!this.plugins.uploader) {
      this.log('No uploader type plugins are used', 'warning')
    }

    let files = this.getState().files

    const onBeforeUploadResult = this.opts.onBeforeUpload(files)

    if (onBeforeUploadResult === false) {
      return Promise.reject(new Error('Not starting the upload because onBeforeUpload returned false'))
    }

    if (onBeforeUploadResult && typeof onBeforeUploadResult === 'object') {
      files = onBeforeUploadResult
    }

    return Promise.resolve()
      .then(() => this._checkMinNumberOfFiles(files))
      .then(() => {
        const { currentUploads } = this.getState()
        // get a list of files that are currently assigned to uploads
        const currentlyUploadingFiles = Object.keys(currentUploads).reduce((prev, curr) => prev.concat(currentUploads[curr].fileIDs), [])

        const waitingFileIDs = []
        Object.keys(files).forEach((fileID) => {
          const file = this.getFile(fileID)
          // if the file hasn't started uploading and hasn't already been assigned to an upload..
          if ((!file.progress.uploadStarted) && (currentlyUploadingFiles.indexOf(fileID) === -1)) {
            waitingFileIDs.push(file.id)
          }
        })

        const uploadID = this._createUpload(waitingFileIDs)
        return this._runUpload(uploadID)
      })
      .catch((err) => {
        this._showOrLogErrorAndThrow(err)
      })
  }
}

module.exports = function (opts) {
  return new Uppy(opts)
}

// Expose class constructor.
module.exports.Uppy = Uppy
module.exports.Plugin = Plugin
module.exports.debugLogger = debugLogger

The link is not clickable and users won't be able to copy it before the bubble disappears, so I'm not sure if this is super useful. Maybe we could make it say something like "You can now remove the authorization in %{provider}'s settings panel"? Would be nice to actually link to the page but that would require some changes in the info bubbles...