/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this file,

 * You can obtain one at http://mozilla.org/MPL/2.0/. */

var EXPORTED_SYMBOLS = ["CanonicalJSON"];

ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");

ChromeUtils.defineModuleGetter(this, "jsesc",

                               "resource://gre/modules/third_party/jsesc/jsesc.js");

var CanonicalJSON = {

  /**

   * Return the canonical JSON form of the passed source, sorting all the object

   * keys recursively. Note that this method will cause an infinite loop if

   * cycles exist in the source (bug 1265357).

   *

   * @param source

   *        The elements to be serialized.

   *

   * The output will have all unicode chars escaped with the unicode codepoint

   * as lowercase hexadecimal.

   *

   * @usage

   *        CanonicalJSON.stringify(listOfRecords);

   **/

  stringify: function stringify(source) {

    if (Array.isArray(source)) {

      const jsonArray = source.map(x => typeof x === "undefined" ? null : x);

      return `[${jsonArray.map(stringify).join(",")}]`;

    }

    if (typeof source === "number") {

      if (source === 0) {

        return (Object.is(source, -0)) ? "-0" : "0";

      }

    }

    // Leverage jsesc library, mainly for unicode escaping.

    const toJSON = (input) => jsesc(input, {lowercaseHex: true, json: true});

    if (typeof source !== "object" || source === null) {

      return toJSON(source);

    }

    // Dealing with objects, ordering keys.

    const sortedKeys = Object.keys(source).sort();

    const lastIndex = sortedKeys.length - 1;

    return sortedKeys.reduce((serial, key, index) => {

      const value = source[key];

      // JSON.stringify drops keys with an undefined value.

      if (typeof value === "undefined") {

        return serial;

      }

      const jsonValue = value && value.toJSON ? value.toJSON() : value;

      const suffix = index !== lastIndex ? "," : "";

      const escapedKey = toJSON(key);

      return serial + `${escapedKey}:${stringify(jsonValue)}${suffix}`;

    }, "{") + "}";

  },

};