function $H(object) {
  return new Hash(object);
};

var Hash = Class.create(Enumerable, (function() {
  function initialize(object) {
    this._object = Object.isHash(object) ? object.toObject() : Object.clone(object);
  }

  function _each(iterator) {
    for (var key in this._object) {
      var value = this._object[key], pair = [key, value];
      pair.key = key;
      pair.value = value;
      iterator(pair);
    }
  }

  function set(key, value) {
    return this._object[key] = value;
  }

  function get(key) {
    // simulating poorly supported hasOwnProperty
    if (this._object[key] !== Object.prototype[key])
      return this._object[key];
  }

  function unset(key) {
    var value = this._object[key];
    delete this._object[key];
    return value;
  }

  function toObject() {
    return Object.clone(this._object);
  }

  function keys() {
    return this.pluck('key');
  }

  function values() {
    return this.pluck('value');
  }

  function index(value) {
    var match = this.detect(function(pair) { 
      return pair.value === value; 
    });
    return match && match.key;
  }

  function merge(object) {
    return this.clone().update(object);
  }

  function update(object) {
    return new Hash(object).inject(this, function(result, pair) {
      result.set(pair.key, pair.value);
      return result;
    });
  }

  function toQueryPair(key, value) {
    if (Object.isUndefined(value)) return key;
    return key + '=' + encodeURIComponent(String.interpret(value));
  }

  function toQueryString() {
    return this.inject([], function(results, pair) {
      var key = encodeURIComponent(pair.key), values = pair.value;
      
      if (values && typeof values == 'object') {
        if (Object.isArray(values))
          return results.concat(values.map(toQueryPair.curry(key)));
      } else results.push(toQueryPair(key, values));
      return results;
    }).join('&');
  }

  function inspect() {
    return '#<Hash:{' + this.map(function(pair) {
      return pair.map(Object.inspect).join(': ');
    }).join(', ') + '}>';
  }

  function toJSON() {
    return Object.toJSON(this.toObject());
  }

  function clone() {
    return new Hash(this);
  }
  
  return {
    initialize:             initialize,
    _each:                  _each,
    set:                    set,
    get:                    get,
    unset:                  unset,
    toObject:               toObject,
    toTemplateReplacements: toObject,
    keys:                   keys,
    values:                 values,
    index:                  index,
    merge:                  merge,
    update:                 update,
    toQueryString:          toQueryString,
    inspect:                inspect,
    toJSON:                 toJSON,
    clone:                  clone
  };
})());

Hash.from = $H;