var Hash = function(object) {
  if (object instanceof Hash) this.merge(object);
  else Object.extend(this, object || { });
};

Object.extend(Hash, {
  toQueryString: function(obj) {
    var parts = [];
    parts.add = arguments.callee.addPair;
    
    this.prototype._each.call(obj, function(pair) {
      if (!pair.key) return;
      var value = pair.value;
      
      if (value && typeof value == 'object') {
        if (Object.isArray(value)) value.each(function(value) {
          parts.add(pair.key, value);
        });
        return;
      }
      parts.add(pair.key, value);
    });
    
    return parts.join('&');
  },
  
  toJSON: function(object) {
    var results = [];
    this.prototype._each.call(object, function(pair) {
      var value = Object.toJSON(pair.value);
      if (value !== undefined) results.push(pair.key.toJSON() + ': ' + value);
    });
    return '{' + results.join(', ') + '}';
  }
});

Hash.toQueryString.addPair = function(key, value, prefix) {
  key = encodeURIComponent(key);
  if (value === undefined) this.push(key);
  else this.push(key + '=' + (value == null ? '' : encodeURIComponent(value)));
};

Object.extend(Hash.prototype, Enumerable);
Object.extend(Hash.prototype, {
  _each: function(iterator) {
    for (var key in this) {
      var value = this[key];
      if (value && value == Hash.prototype[key]) continue;
      
      var pair = [key, value];
      pair.key = key;
      pair.value = value;
      iterator(pair);
    }
  },
  
  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(hash) {
    return $H(hash).inject(this, function(mergedHash, pair) {
      mergedHash[pair.key] = pair.value;
      return mergedHash;
    });
  },

  remove: function() {
    var result;
    for(var i = 0, length = arguments.length; i < length; i++) {
      var value = this[arguments[i]];
      if (value !== undefined){
        if (result === undefined) result = value;
        else {
          if (!Object.isArray(result)) result = [result];
          result.push(value);
        }
      }
      delete this[arguments[i]];
    }
    return result;
  },
  
  toQueryString: function() {
    return Hash.toQueryString(this);
  },
  
  inspect: function() {
    return '#<Hash:{' + this.map(function(pair) {
      return pair.map(Object.inspect).join(': ');
    }).join(', ') + '}>';
  },
  
  toJSON: function() {
    return Hash.toJSON(this);
  }
});

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

// Safari iterates over shadowed properties
if (function() {
  var i = 0, Test = function(value) { this.key = value };
  Test.prototype.key = 'foo';
  for (var property in new Test('bar')) i++;
  return i > 1;
}()) Hash.prototype._each = function(iterator) {
  var cache = [];
  for (var key in this) {
    var value = this[key];
    if ((value && value == Hash.prototype[key]) || cache.include(key)) continue;
    cache.push(key);
    var pair = [key, value];
    pair.key = key;
    pair.value = value;
    iterator(pair);
  }
};