jsan/lib/cycle.js

handle circular references when stringifying and parsing

var pathGetter = require('./path-getter');
var utils = require('./utils');

var WMap = typeof WeakMap !== 'undefined'?
  WeakMap:
  function() {
    var keys = [];
    var values = [];
    return {
      set: function(key, value) {
        keys.push(key);
        values.push(value);
      },
      get: function(key) {
        for (var i = 0; i < keys.length; i++) {
          if (keys[i] === key) {
            return values[i];
          }
        }
      }
    }
  };

// Based on https://github.com/douglascrockford/JSON-js/blob/master/cycle.js

exports.decycle = function decycle(object, options, replacer, map) {
  'use strict';

  map = map || new WMap();

  var noCircularOption = !Object.prototype.hasOwnProperty.call(options, 'circular');
  var withRefs = options.refs !== false;

  return (function derez(_value, path, key) {

    // The derez recurses through the object, producing the deep copy.

    var i,        // The loop counter
      name,       // Property name
      nu;         // The new object or array

    // typeof null === 'object', so go on if this value is really an object but not
    // one of the weird builtin objects.

    var value = typeof replacer === 'function' ? replacer(key || '', _value) : _value;

    if (options.date && value instanceof Date) {
      return {$jsan: 'd' + value.getTime()};
    }
    if (options.regex && value instanceof RegExp) {
      return {$jsan: 'r' + utils.getRegexFlags(value) + ',' + value.source};
    }
    if (options['function'] && typeof value === 'function') {
      return {$jsan: 'f' + utils.stringifyFunction(value, options['function'])}
    }
    if (options['nan'] && typeof value === 'number' && isNaN(value)) {
      return {$jsan: 'n'}
    }
    if (options['infinity']) {
      if (Number.POSITIVE_INFINITY === value) return {$jsan: 'i'}
      if (Number.NEGATIVE_INFINITY === value) return {$jsan: 'y'}
    }
    if (options['undefined'] && value === undefined) {
      return {$jsan: 'u'}
    }
    if (options['error'] && value instanceof Error) {
      return {$jsan: 'e' + value.message}
    }
    if (options['symbol'] && typeof value === 'symbol') {
      var symbolKey = Symbol.keyFor(value)
      if (symbolKey !== undefined) {
        return {$jsan: 'g' + symbolKey}
      }

      // 'Symbol(foo)'.slice(7, -1) === 'foo'
      return {$jsan: 's' + value.toString().slice(7, -1)}
    }

    if (options['map'] && typeof Map === 'function' && value instanceof Map && typeof Array.from === 'function') {
      return {$jsan: 'm' + JSON.stringify(decycle(Array.from(value), options, replacer, map))}
    }

    if (options['set'] && typeof Set === 'function' && value instanceof Set && typeof Array.from === 'function') {
      return {$jsan: 'l' + JSON.stringify(decycle(Array.from(value), options, replacer, map))}
    }

    if (value && typeof value.toJSON === 'function') {
      try {
        value = value.toJSON(key);
      } catch (error) {
        var keyString = (key || '$');
        return "toJSON failed for '" + (map.get(value) || keyString) + "'";
      }
    }

    if (typeof value === 'object' && value !== null &&
      !(value instanceof Boolean) &&
      !(value instanceof Date)    &&
      !(value instanceof Number)  &&
      !(value instanceof RegExp)  &&
      !(value instanceof String)  &&
      !(typeof value === 'symbol')  &&
      !(value instanceof Error)) {

        // If the value is an object or array, look to see if we have already
        // encountered it. If so, return a $ref/path object.

      if (typeof value === 'object') {
        var foundPath = map.get(value);
        if (foundPath) {
          if (noCircularOption && withRefs) {
            return {$jsan: foundPath};
          }
          
          // This is only a true circular reference if the parent path is inside of foundPath
          // drop the last component of the current path and check if it starts with foundPath
          var parentPath = path.split('.').slice(0, -1).join('.');
          if (parentPath.indexOf(foundPath) === 0) {
            if (!noCircularOption) {
              return typeof options.circular === 'function'?
              options.circular(value, path, foundPath):
              options.circular;
            }
            return {$jsan: foundPath};
          }
          if (withRefs) return {$jsan: foundPath};
        }
        map.set(value, path);
      }


      // If it is an array, replicate the array.

      if (Object.prototype.toString.apply(value) === '[object Array]') {
          nu = [];
          for (i = 0; i < value.length; i += 1) {
              nu[i] = derez(value[i], path + '[' + i + ']', i);
          }
      } else {

        // If it is an object, replicate the object.

        nu = {};
        for (name in value) {
          if (Object.prototype.hasOwnProperty.call(value, name)) {
            var nextPath = /^\w+$/.test(name) ?
              '.' + name :
              '[' + JSON.stringify(name) + ']';
            nu[name] = name === '$jsan' ? [derez(value[name], path + nextPath)] : derez(value[name], path + nextPath, name);
          }
        }
      }
      return nu;
    }
    return value;
  }(object, '$'));
};


exports.retrocycle = function retrocycle($) {
  'use strict';


  return (function rez(value) {

    // The rez function walks recursively through the object looking for $jsan
    // properties. When it finds one that has a value that is a path, then it
    // replaces the $jsan object with a reference to the value that is found by
    // the path.

    var i, item, name, path;

    if (value && typeof value === 'object') {
      if (Object.prototype.toString.apply(value) === '[object Array]') {
        for (i = 0; i < value.length; i += 1) {
          item = value[i];
          if (item && typeof item === 'object') {
            if (item.$jsan) {
              value[i] = utils.restore(item.$jsan, $);
            } else {
              rez(item);
            }
          }
        }
      } else {
        for (name in value) {
          // base case passed raw object
          if(typeof value[name] === 'string' && name === '$jsan'){
            return utils.restore(value.$jsan, $);
            break;
          }
          else {
            if (name === '$jsan') {
              value[name] = value[name][0];
            }
            if (typeof value[name] === 'object') {
              item = value[name];
              if (item && typeof item === 'object') {
                if (item.$jsan) {
                  value[name] = utils.restore(item.$jsan, $);
                } else {
                  rez(item);
                }
              }
            }
          }
        }
      }
    }
    return value;
  }($));
};