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

var Hash = Class.create(Enumerable, (function() {

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

  return {
    initialize: function(object) {
      this._object = Object.isHash(object) ? object.toObject() : Object.clone(object);
    },

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

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

    get: function(key) {
      return this._object[key];
    },

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

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

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

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

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

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

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

    toQueryString: function() {
      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('&');
    },

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

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

    clone: function() {
      return new Hash(this);
    }
  }
})());

Hash.prototype.toTemplateReplacements = Hash.prototype.toObject;
Hash.from = $H;