overleaf/services/real-time/test/acceptance/libs/XMLHttpRequest.js

/**
 * Wrapper for built-in http.js to emulate the browser XMLHttpRequest object.
 *
 * This can be used with JS designed for browsers to improve reuse of code and
 * allow the use of existing libraries.
 *
 * Usage: include("XMLHttpRequest.js") and use XMLHttpRequest per W3C specs.
 *
 * @author Dan DeFelippi <dan@driverdan.com>
 * @contributor David Ellis <d.f.ellis@ieee.org>
 * @license MIT
 */

const { URL } = require('url')
const spawn = require('child_process').spawn
const fs = require('fs')

exports.XMLHttpRequest = function () {
  /**
   * Private variables
   */
  const self = this
  const http = require('http')
  const https = require('https')

  // Holds http.js objects
  let request
  let response

  // Request settings
  let settings = {}

  // Set some default headers
  const defaultHeaders = {
    'User-Agent': 'node-XMLHttpRequest',
    Accept: '*/*',
  }

  let headers = defaultHeaders

  // These headers are not user setable.
  // The following are allowed but banned in the spec:
  // * user-agent
  const forbiddenRequestHeaders = [
    'accept-charset',
    'accept-encoding',
    'access-control-request-headers',
    'access-control-request-method',
    'connection',
    'content-length',
    'content-transfer-encoding',
    // "cookie",
    'cookie2',
    'date',
    'expect',
    'host',
    'keep-alive',
    'origin',
    'referer',
    'te',
    'trailer',
    'transfer-encoding',
    'upgrade',
    'via',
  ]

  // These request methods are not allowed
  const forbiddenRequestMethods = ['TRACE', 'TRACK', 'CONNECT']

  // Send flag
  let sendFlag = false
  // Error flag, used when errors occur or abort is called
  let errorFlag = false

  // Event listeners
  const listeners = {}

  /**
   * Constants
   */

  this.UNSENT = 0
  this.OPENED = 1
  this.HEADERS_RECEIVED = 2
  this.LOADING = 3
  this.DONE = 4

  /**
   * Public vars
   */

  // Current state
  this.readyState = this.UNSENT

  // default ready state change handler in case one is not set or is set late
  this.onreadystatechange = null

  // Result & response
  this.responseText = ''
  this.responseXML = ''
  this.status = null
  this.statusText = null

  /**
   * Private methods
   */

  /**
   * Check if the specified header is allowed.
   *
   * @param string header Header to validate
   * @return boolean False if not allowed, otherwise true
   */
  const isAllowedHttpHeader = function (header) {
    return (
      header && forbiddenRequestHeaders.indexOf(header.toLowerCase()) === -1
    )
  }

  /**
   * Check if the specified method is allowed.
   *
   * @param string method Request method to validate
   * @return boolean False if not allowed, otherwise true
   */
  const isAllowedHttpMethod = function (method) {
    return method && forbiddenRequestMethods.indexOf(method) === -1
  }

  /**
   * Public methods
   */

  /**
   * Open the connection. Currently supports local server requests.
   *
   * @param string method Connection method (eg GET, POST)
   * @param string url URL for the connection.
   * @param boolean async Asynchronous connection. Default is true.
   * @param string user Username for basic authentication (optional)
   * @param string password Password for basic authentication (optional)
   */
  this.open = function (method, url, async, user, password) {
    this.abort()
    errorFlag = false

    // Check for valid request method
    if (!isAllowedHttpMethod(method)) {
      throw new Error('SecurityError: Request method not allowed')
    }

    settings = {
      method,
      url: url.toString(),
      async: typeof async !== 'boolean' ? true : async,
      user: user || null,
      password: password || null,
    }

    setState(this.OPENED)
  }

  /**
   * Sets a header for the request.
   *
   * @param string header Header name
   * @param string value Header value
   */
  this.setRequestHeader = function (header, value) {
    if (this.readyState !== this.OPENED) {
      throw new Error(
        'INVALID_STATE_ERR: setRequestHeader can only be called when state is OPEN'
      )
    }
    if (!isAllowedHttpHeader(header)) {
      console.warn('Refused to set unsafe header "' + header + '"')
      return
    }
    if (sendFlag) {
      throw new Error('INVALID_STATE_ERR: send flag is true')
    }
    headers[header] = value
  }

  /**
   * Gets a header from the server response.
   *
   * @param string header Name of header to get.
   * @return string Text of the header or null if it doesn't exist.
   */
  this.getResponseHeader = function (header) {
    if (
      typeof header === 'string' &&
      this.readyState > this.OPENED &&
      response.headers[header.toLowerCase()] &&
      !errorFlag
    ) {
      return response.headers[header.toLowerCase()]
    }

    return null
  }

  /**
   * Gets all the response headers.
   *
   * @return string A string with all response headers separated by CR+LF
   */
  this.getAllResponseHeaders = function () {
    if (this.readyState < this.HEADERS_RECEIVED || errorFlag) {
      return ''
    }
    let result = ''

    for (const i in response.headers) {
      // Cookie headers are excluded
      if (i !== 'set-cookie' && i !== 'set-cookie2') {
        result += i + ': ' + response.headers[i] + '\r\n'
      }
    }
    return result.substr(0, result.length - 2)
  }

  /**
   * Gets a request header
   *
   * @param string name Name of header to get
   * @return string Returns the request header or empty string if not set
   */
  this.getRequestHeader = function (name) {
    // @TODO Make this case insensitive
    if (typeof name === 'string' && headers[name]) {
      return headers[name]
    }

    return ''
  }

  /**
   * Sends the request to the server.
   *
   * @param string data Optional data to send as request body.
   */
  this.send = function (data) {
    if (this.readyState !== this.OPENED) {
      throw new Error(
        'INVALID_STATE_ERR: connection must be opened before send() is called'
      )
    }

    if (sendFlag) {
      throw new Error('INVALID_STATE_ERR: send has already been called')
    }

    let host
    let ssl = false
    let local = false
    const url = new URL(settings.url)

    // Determine the server
    switch (url.protocol) {
      case 'https:':
        ssl = true
        host = url.hostname
        break
      case 'http:':
        host = url.hostname
        break

      case 'file:':
        local = true
        break

      case undefined:
      case '':
        host = 'localhost'
        break

      default:
        throw new Error('Protocol not supported.')
    }

    // Load files off the local filesystem (file://)
    if (local) {
      if (settings.method !== 'GET') {
        throw new Error('XMLHttpRequest: Only GET method is supported')
      }

      if (settings.async) {
        fs.readFile(url.pathname, 'utf8', (error, data) => {
          if (error) {
            self.handleError(error)
          } else {
            self.status = 200
            self.responseText = data
            setState(self.DONE)
          }
        })
      } else {
        try {
          this.responseText = fs.readFileSync(url.pathname, 'utf8')
          this.status = 200
          setState(self.DONE)
        } catch (e) {
          this.handleError(e)
        }
      }

      return
    }

    // Default to port 80. If accessing localhost on another port be sure
    // to use http://localhost:port/path
    const port = url.port || (ssl ? 443 : 80)
    // Add query string if one is used
    const uri = url.pathname + (url.search ? url.search : '')

    // Set the Host header or the server may reject the request
    headers.Host = host
    if (!((ssl && port === 443) || port === 80)) {
      headers.Host += ':' + url.port
    }

    // Set Basic Auth if necessary
    if (settings.user) {
      if (typeof settings.password === 'undefined') {
        settings.password = ''
      }
      const authBuf = Buffer.from(settings.user + ':' + settings.password)
      headers.Authorization = 'Basic ' + authBuf.toString('base64')
    }

    // Set content length header
    if (settings.method === 'GET' || settings.method === 'HEAD') {
      data = null
    } else if (data) {
      headers['Content-Length'] = Buffer.byteLength(data)

      if (!headers['Content-Type']) {
        headers['Content-Type'] = 'text/plain;charset=UTF-8'
      }
    } else if (settings.method === 'POST') {
      // For a post with no data set Content-Length: 0.
      // This is required by buggy servers that don't meet the specs.
      headers['Content-Length'] = 0
    }

    const options = {
      host,
      port,
      path: uri,
      method: settings.method,
      headers,
    }

    // Reset error flag
    errorFlag = false

    // Handle async requests
    if (settings.async) {
      // Use the proper protocol
      const doRequest = ssl ? https.request : http.request

      // Request is being sent, set send flag
      sendFlag = true

      // As per spec, this is called here for historical reasons.
      self.dispatchEvent('readystatechange')

      // Create the request
      request = doRequest(options, resp => {
        response = resp
        response.setEncoding('utf8')

        setState(self.HEADERS_RECEIVED)
        self.status = response.statusCode

        response.on('data', chunk => {
          // Make sure there's some data
          if (chunk) {
            self.responseText += chunk
          }
          // Don't emit state changes if the connection has been aborted.
          if (sendFlag) {
            setState(self.LOADING)
          }
        })

        response.on('end', () => {
          if (sendFlag) {
            // Discard the 'end' event if the connection has been aborted
            setState(self.DONE)
            sendFlag = false
          }
        })

        response.on('error', error => {
          self.handleError(error)
        })
      }).on('error', error => {
        self.handleError(error)
      })

      // Node 0.4 and later won't accept empty data. Make sure it's needed.
      if (data) {
        request.write(data)
      }

      request.end()

      self.dispatchEvent('loadstart')
    } else {
      // Synchronous
      // Create a temporary file for communication with the other Node process
      const syncFile = '.node-xmlhttprequest-sync-' + process.pid
      fs.writeFileSync(syncFile, '', 'utf8')
      // The async request the other Node process executes
      const execString =
        "var http = require('http'), https = require('https'), fs = require('fs');" +
        'var doRequest = http' +
        (ssl ? 's' : '') +
        '.request;' +
        'var options = ' +
        JSON.stringify(options) +
        ';' +
        "var responseText = '';" +
        'var req = doRequest(options, function(response) {' +
        "response.setEncoding('utf8');" +
        "response.on('data', function(chunk) {" +
        'responseText += chunk;' +
        '});' +
        "response.on('end', function() {" +
        "fs.writeFileSync('" +
        syncFile +
        "', 'NODE-XMLHTTPREQUEST-STATUS:' + response.statusCode + ',' + responseText, 'utf8');" +
        '});' +
        "response.on('error', function(error) {" +
        "fs.writeFileSync('" +
        syncFile +
        "', 'NODE-XMLHTTPREQUEST-ERROR:' + JSON.stringify(error), 'utf8');" +
        '});' +
        "}).on('error', function(error) {" +
        "fs.writeFileSync('" +
        syncFile +
        "', 'NODE-XMLHTTPREQUEST-ERROR:' + JSON.stringify(error), 'utf8');" +
        '});' +
        (data ? "req.write('" + data.replace(/'/g, "\\'") + "');" : '') +
        'req.end();'
      // Start the other Node Process, executing this string
      const syncProc = spawn(process.argv[0], ['-e', execString])
      while ((self.responseText = fs.readFileSync(syncFile, 'utf8')) === '') {
        // Wait while the file is empty
      }
      // Kill the child process once the file has data
      syncProc.stdin.end()
      // Remove the temporary file
      fs.unlinkSync(syncFile)
      if (self.responseText.match(/^NODE-XMLHTTPREQUEST-ERROR:/)) {
        // If the file returned an error, handle it
        const errorObj = self.responseText.replace(
          /^NODE-XMLHTTPREQUEST-ERROR:/,
          ''
        )
        self.handleError(errorObj)
      } else {
        // If the file returned okay, parse its data and move to the DONE state
        self.status = self.responseText.replace(
          /^NODE-XMLHTTPREQUEST-STATUS:([0-9]*),.*/,
          '$1'
        )
        self.responseText = self.responseText.replace(
          /^NODE-XMLHTTPREQUEST-STATUS:[0-9]*,(.*)/,
          '$1'
        )
        setState(self.DONE)
      }
    }
  }

  /**
   * Called when an error is encountered to deal with it.
   */
  this.handleError = function (error) {
    this.status = 503
    this.statusText = error
    this.responseText = error.stack
    errorFlag = true
    setState(this.DONE)
  }

  /**
   * Aborts a request.
   */
  this.abort = function () {
    if (request) {
      request.abort()
      request = null
    }

    headers = defaultHeaders
    this.responseText = ''
    this.responseXML = ''

    errorFlag = true

    if (
      this.readyState !== this.UNSENT &&
      (this.readyState !== this.OPENED || sendFlag) &&
      this.readyState !== this.DONE
    ) {
      sendFlag = false
      setState(this.DONE)
    }
    this.readyState = this.UNSENT
  }

  /**
   * Adds an event listener. Preferred method of binding to events.
   */
  this.addEventListener = function (event, callback) {
    if (!(event in listeners)) {
      listeners[event] = []
    }
    // Currently allows duplicate callbacks. Should it?
    listeners[event].push(callback)
  }

  /**
   * Remove an event callback that has already been bound.
   * Only works on the matching funciton, cannot be a copy.
   */
  this.removeEventListener = function (event, callback) {
    if (event in listeners) {
      // Filter will return a new array with the callback removed
      listeners[event] = listeners[event].filter(ev => {
        return ev !== callback
      })
    }
  }

  /**
   * Dispatch any events, including both "on" methods and events attached using addEventListener.
   */
  this.dispatchEvent = function (event) {
    if (typeof self['on' + event] === 'function') {
      self['on' + event]()
    }
    if (event in listeners) {
      for (let i = 0, len = listeners[event].length; i < len; i++) {
        listeners[event][i].call(self)
      }
    }
  }

  /**
   * Changes readyState and calls onreadystatechange.
   *
   * @param int state New state
   */
  function setState(state) {
    if (self.readyState !== state) {
      self.readyState = state

      if (
        settings.async ||
        self.readyState < self.OPENED ||
        self.readyState === self.DONE
      ) {
        self.dispatchEvent('readystatechange')
      }

      if (self.readyState === self.DONE && !errorFlag) {
        self.dispatchEvent('load')
        // @TODO figure out InspectorInstrumentation::didLoadXHR(cookie)
        self.dispatchEvent('loadend')
      }
    }
  }
}