Started code review + some fixes (unfinished)

[vchess.git] / client / src / utils / ajax.js

import params from "../parameters"; //for server URL

// TODO: replace by fetch API ?
// https://www.sitepoint.com/xmlhttprequest-vs-the-fetch-api-whats-best-for-ajax-in-2019/
// Problem: fetch() does not set req.xhr... see access/ajax() security especially for /whoami

// From JSON (encoded string values!) to "arg1=...&arg2=..."
function toQueryString(data) {
  let data_str = "";
  Object.keys(data).forEach(k => {
    data_str += k + "=" + encodeURIComponent(data[k]) + "&";
  });
  return data_str.slice(0, -1); //remove last "&"
}

// data, error: optional
export function ajax(url, method, data, success, error) {
  let xhr = new XMLHttpRequest();
  if (data === undefined || typeof data === "function") {
    //no data
    error = success;
    success = data;
    data = {};
  }
  if (!success) success = () => {}; //by default, do nothing
  if (!error)
    error = errmsg => {
      alert(errmsg);
    };
  xhr.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
      let res_json = "";
      try {
        res_json = JSON.parse(xhr.responseText);
      } catch (e) {
        // Plain text (e.g. for rules retrieval) (TODO: no more plain text in current version)
        success(xhr.responseText);
      }
      if (res_json) {
        if (!res_json.errmsg && !res_json.errno) success(res_json);
        else {
          if (res_json.errmsg) error(res_json.errmsg);
          else error(res_json.code + ". errno = " + res_json.errno);
        }
      }
    }
  };

  if (["GET", "DELETE"].includes(method) && !!data) {
    // Append query params to URL
    url += "/?" + toQueryString(data);
  }
  xhr.open(method, params.serverUrl + url, true);
  xhr.setRequestHeader("X-Requested-With", "XMLHttpRequest");
  // Next line to allow cross-domain cookies in dev mode
  if (params.cors) xhr.withCredentials = true;
  if (["POST", "PUT"].includes(method)) {
    xhr.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
    xhr.send(JSON.stringify(data));
  } else xhr.send();
}