readmongo/node_modules/engine.io-client/lib/transports/polling-xhr.js

/* global attachEvent */

const XMLHttpRequest = require("xmlhttprequest-ssl");
const Polling = require("./polling");
const Emitter = require("component-emitter");
const { pick } = require("../util");
const globalThis = require("../globalThis");

const debug = require("debug")("engine.io-client:polling-xhr");

/**
 * Empty function
 */

function empty() {}

const hasXHR2 = (function() {
  const XMLHttpRequest = require("xmlhttprequest-ssl");
  const xhr = new XMLHttpRequest({ xdomain: false });
  return null != xhr.responseType;
})();

class XHR extends Polling {
  /**
   * XHR Polling constructor.
   *
   * @param {Object} opts
   * @api public
   */
  constructor(opts) {
    super(opts);

    if (typeof location !== "undefined") {
      const isSSL = "https:" === location.protocol;
      let port = location.port;

      // some user agents have empty `location.port`
      if (!port) {
        port = isSSL ? 443 : 80;
      }

      this.xd =
        (typeof location !== "undefined" &&
          opts.hostname !== location.hostname) ||
        port !== opts.port;
      this.xs = opts.secure !== isSSL;
    }
    /**
     * XHR supports binary
     */
    const forceBase64 = opts && opts.forceBase64;
    this.supportsBinary = hasXHR2 && !forceBase64;
  }

  /**
   * Creates a request.
   *
   * @param {String} method
   * @api private
   */
  request(opts = {}) {
    Object.assign(opts, { xd: this.xd, xs: this.xs }, this.opts);
    return new Request(this.uri(), opts);
  }

  /**
   * Sends data.
   *
   * @param {String} data to send.
   * @param {Function} called upon flush.
   * @api private
   */
  doWrite(data, fn) {
    const req = this.request({
      method: "POST",
      data: data
    });
    const self = this;
    req.on("success", fn);
    req.on("error", function(err) {
      self.onError("xhr post error", err);
    });
  }

  /**
   * Starts a poll cycle.
   *
   * @api private
   */
  doPoll() {
    debug("xhr poll");
    const req = this.request();
    const self = this;
    req.on("data", function(data) {
      self.onData(data);
    });
    req.on("error", function(err) {
      self.onError("xhr poll error", err);
    });
    this.pollXhr = req;
  }
}

class Request extends Emitter {
  /**
   * Request constructor
   *
   * @param {Object} options
   * @api public
   */
  constructor(uri, opts) {
    super();
    this.opts = opts;

    this.method = opts.method || "GET";
    this.uri = uri;
    this.async = false !== opts.async;
    this.data = undefined !== opts.data ? opts.data : null;

    this.create();
  }

  /**
   * Creates the XHR object and sends the request.
   *
   * @api private
   */
  create() {
    const opts = pick(
      this.opts,
      "agent",
      "enablesXDR",
      "pfx",
      "key",
      "passphrase",
      "cert",
      "ca",
      "ciphers",
      "rejectUnauthorized"
    );
    opts.xdomain = !!this.opts.xd;
    opts.xscheme = !!this.opts.xs;

    const xhr = (this.xhr = new XMLHttpRequest(opts));
    const self = this;

    try {
      debug("xhr open %s: %s", this.method, this.uri);
      xhr.open(this.method, this.uri, this.async);
      try {
        if (this.opts.extraHeaders) {
          xhr.setDisableHeaderCheck && xhr.setDisableHeaderCheck(true);
          for (let i in this.opts.extraHeaders) {
            if (this.opts.extraHeaders.hasOwnProperty(i)) {
              xhr.setRequestHeader(i, this.opts.extraHeaders[i]);
            }
          }
        }
      } catch (e) {}

      if ("POST" === this.method) {
        try {
          xhr.setRequestHeader("Content-type", "text/plain;charset=UTF-8");
        } catch (e) {}
      }

      try {
        xhr.setRequestHeader("Accept", "*/*");
      } catch (e) {}

      // ie6 check
      if ("withCredentials" in xhr) {
        xhr.withCredentials = this.opts.withCredentials;
      }

      if (this.opts.requestTimeout) {
        xhr.timeout = this.opts.requestTimeout;
      }

      if (this.hasXDR()) {
        xhr.onload = function() {
          self.onLoad();
        };
        xhr.onerror = function() {
          self.onError(xhr.responseText);
        };
      } else {
        xhr.onreadystatechange = function() {
          if (4 !== xhr.readyState) return;
          if (200 === xhr.status || 1223 === xhr.status) {
            self.onLoad();
          } else {
            // make sure the `error` event handler that's user-set
            // does not throw in the same tick and gets caught here
            setTimeout(function() {
              self.onError(typeof xhr.status === "number" ? xhr.status : 0);
            }, 0);
          }
        };
      }

      debug("xhr data %s", this.data);
      xhr.send(this.data);
    } catch (e) {
      // Need to defer since .create() is called directly from the constructor
      // and thus the 'error' event can only be only bound *after* this exception
      // occurs.  Therefore, also, we cannot throw here at all.
      setTimeout(function() {
        self.onError(e);
      }, 0);
      return;
    }

    if (typeof document !== "undefined") {
      this.index = Request.requestsCount++;
      Request.requests[this.index] = this;
    }
  }

  /**
   * Called upon successful response.
   *
   * @api private
   */
  onSuccess() {
    this.emit("success");
    this.cleanup();
  }

  /**
   * Called if we have data.
   *
   * @api private
   */
  onData(data) {
    this.emit("data", data);
    this.onSuccess();
  }

  /**
   * Called upon error.
   *
   * @api private
   */
  onError(err) {
    this.emit("error", err);
    this.cleanup(true);
  }

  /**
   * Cleans up house.
   *
   * @api private
   */
  cleanup(fromError) {
    if ("undefined" === typeof this.xhr || null === this.xhr) {
      return;
    }
    // xmlhttprequest
    if (this.hasXDR()) {
      this.xhr.onload = this.xhr.onerror = empty;
    } else {
      this.xhr.onreadystatechange = empty;
    }

    if (fromError) {
      try {
        this.xhr.abort();
      } catch (e) {}
    }

    if (typeof document !== "undefined") {
      delete Request.requests[this.index];
    }

    this.xhr = null;
  }

  /**
   * Called upon load.
   *
   * @api private
   */
  onLoad() {
    const data = this.xhr.responseText;
    if (data !== null) {
      this.onData(data);
    }
  }

  /**
   * Check if it has XDomainRequest.
   *
   * @api private
   */
  hasXDR() {
    return typeof XDomainRequest !== "undefined" && !this.xs && this.enablesXDR;
  }

  /**
   * Aborts the request.
   *
   * @api public
   */
  abort() {
    this.cleanup();
  }
}

/**
 * Aborts pending requests when unloading the window. This is needed to prevent
 * memory leaks (e.g. when using IE) and to ensure that no spurious error is
 * emitted.
 */

Request.requestsCount = 0;
Request.requests = {};

if (typeof document !== "undefined") {
  if (typeof attachEvent === "function") {
    attachEvent("onunload", unloadHandler);
  } else if (typeof addEventListener === "function") {
    const terminationEvent = "onpagehide" in globalThis ? "pagehide" : "unload";
    addEventListener(terminationEvent, unloadHandler, false);
  }
}

function unloadHandler() {
  for (let i in Request.requests) {
    if (Request.requests.hasOwnProperty(i)) {
      Request.requests[i].abort();
    }
  }
}

module.exports = XHR;
module.exports.Request = Request;