/**
 * JSON + Object references wrapper
 *
 * @author Hunter Loftis <hunter@skookum.com>
 * @license The MIT license.
 * @copyright Copyright (c) 2010 Skookum, skookum.com
 */

;(function() {

  var CONTAINER_TYPES = 'object array date function'.split(' ');

  var REFERENCE_FLAG = '_CRYO_REF_';
  var INFINITY_FLAG = '_CRYO_INFINITY_';
  var FUNCTION_FLAG = '_CRYO_FUNCTION_';
  var UNDEFINED_FLAG = '_CRYO_UNDEFINED_';
  var DATE_FLAG = '_CRYO_DATE_';

  function typeOf(item) {
    if (typeof item === 'object') {
      if (item instanceof Array) return 'array';
      if (item instanceof Date) return 'date';
      return 'object';
    }
    return typeof item;
  }

  function stringify(item) {
    var references = [];
    var root = cloneWithReferences(item, references);

    return JSON.stringify({
      root: root,
      references: references
    });
  }

  function cloneWithReferences(item, references, savedItems) {
    savedItems = savedItems || [];
    var type = typeOf(item);

    // can this object contain its own properties?
    if (CONTAINER_TYPES.indexOf(type) !== -1) {
      var referenceIndex = savedItems.indexOf(item);
      // do we need to store a new reference to this object?
      if (referenceIndex === -1) {
        var clone = {};
        for (var key in item) {
          if (item.hasOwnProperty(key)) {
            clone[key] = cloneWithReferences(item[key], references, savedItems);
          }
        }
        referenceIndex = references.push({
          contents: clone,
          value: wrap(item)
        }) - 1;
        savedItems[referenceIndex] = item;
      }

      // return something like _CRYO_REF_22
      return REFERENCE_FLAG + referenceIndex;
    }

    // return a non-container object
    return wrap(item);
  }

  function parse(string) {
    var json = JSON.parse(string);

    return rebuildFromReferences(json.root, json.references);
  }

  function rebuildFromReferences(item, references, restoredItems) {
    restoredItems = restoredItems || [];
    if (starts(item, REFERENCE_FLAG)) {
      var referenceIndex = parseInt(item.slice(REFERENCE_FLAG.length), 10);
      if (!restoredItems.hasOwnProperty(referenceIndex)) {
        var ref = references[referenceIndex];
        var container = unwrap(ref.value);
        var contents = ref.contents;
        for (var key in contents) {
          container[key] = rebuildFromReferences(contents[key], references, restoredItems);
        }
        restoredItems[referenceIndex] = container;
      }
      return restoredItems[referenceIndex];
    }
    return unwrap(item);
  }

  function wrap(item) {
    var type = typeOf(item);
    if (type === 'undefined') return UNDEFINED_FLAG;
    if (type === 'function') return FUNCTION_FLAG + item.toString();
    if (type === 'date') return DATE_FLAG + item.getTime();
    if (item === Infinity) return INFINITY_FLAG;
    return item;
  }

  function unwrap(val) {
    if (typeOf(val) === 'string') {
      if (val === UNDEFINED_FLAG) return undefined;
      if (starts(val, FUNCTION_FLAG)) {
        var fn = val.slice(FUNCTION_FLAG.length);
        var argStart = fn.indexOf('(') + 1;
        var argEnd = fn.indexOf(')', argStart);
        var args = fn.slice(argStart, argEnd);
        var bodyStart = fn.indexOf('{') + 1;
        var bodyEnd = fn.lastIndexOf('}') - 1;
        var body = fn.slice(bodyStart, bodyEnd);
        return new Function(args, body);
      }
      if (starts(val, DATE_FLAG)) {
        var dateNum = parseInt(val.slice(DATE_FLAG.length), 10);
        return new Date(dateNum);
      }
      if (val === INFINITY_FLAG) return Infinity;
    }
    return val;
  }

  function starts(string, prefix) {
    return typeOf(string) === 'string' && string.slice(0, prefix.length) === prefix;
  }

  // Exported object
  var Cryo = {
    stringify: stringify,
    parse: parse
  };

  // global on server, window in browser
  var root = this;

  // AMD / RequireJS
  if (typeof define !== 'undefined' && define.amd) {
    define('Cryo', [], function () {
      return Cryo;
    });
  }

  // node.js
  else if (typeof module !== 'undefined' && module.exports) {
    module.exports = Cryo;
  }

  // included directly via <script> tag
  else {
    root.Cryo = Cryo;
  }

})();