var $break = { };

var Enumerable = (function() {
  function each(iterator, context) {
    var index = 0;
    try {
      this._each(function(value) {
        iterator.call(context, value, index++);
      });
    } catch (e) {
      if (e != $break) throw e;
    }
    return this;
  }
  
  function eachSlice(number, iterator, context) {
    var index = -number, slices = [], array = this.toArray();
    if (number < 1) return array;
    while ((index += number) < array.length)
      slices.push(array.slice(index, index+number));
    return slices.collect(iterator, context);
  }

  function all(iterator, context) {
    iterator = iterator || Prototype.K;
    var result = true;
    this.each(function(value, index) {
      result = result && !!iterator.call(context, value, index);
      if (!result) throw $break;
    });
    return result;
  }

  function any(iterator, context) {
    iterator = iterator || Prototype.K;
    var result = false;
    this.each(function(value, index) {
      if (result = !!iterator.call(context, value, index))
        throw $break;
    });
    return result;
  }

  function collect(iterator, context) {
    iterator = iterator || Prototype.K;
    var results = [];
    this.each(function(value, index) {
      results.push(iterator.call(context, value, index));
    });
    return results;
  }
  
  function detect(iterator, context) {
    var result;
    this.each(function(value, index) {
      if (iterator.call(context, value, index)) {
        result = value;
        throw $break;
      }
    });
    return result;
  }
  
  function findAll(iterator, context) {
    var results = [];
    this.each(function(value, index) {
      if (iterator.call(context, value, index))
        results.push(value);
    });
    return results;
  }
  
  function grep(filter, iterator, context) {
    iterator = iterator || Prototype.K;
    var results = [];

    if (Object.isString(filter))
      filter = new RegExp(RegExp.escape(filter));
      
    this.each(function(value, index) {
      if (filter.match(value))
        results.push(iterator.call(context, value, index));
    });
    return results;
  }
  
  function include(object) {
    if (Object.isFunction(this.indexOf))
      if (this.indexOf(object) != -1) return true;

    var found = false;
    this.each(function(value) {
      if (value == object) {
        found = true;
        throw $break;
      }
    });
    return found;
  }
  
  function inGroupsOf(number, fillWith) {
    fillWith = Object.isUndefined(fillWith) ? null : fillWith;
    return this.eachSlice(number, function(slice) {
      while(slice.length < number) slice.push(fillWith);
      return slice;
    });
  }
  
  function inject(memo, iterator, context) {
    this.each(function(value, index) {
      memo = iterator.call(context, memo, value, index);
    });
    return memo;
  }
  
  function invoke(method) {
    var args = $A(arguments).slice(1);
    return this.map(function(value) {
      return value[method].apply(value, args);
    });
  }
  
  function max(iterator, context) {
    iterator = iterator || Prototype.K;
    var result;
    this.each(function(value, index) {
      value = iterator.call(context, value, index);
      if (result == null || value >= result)
        result = value;
    });
    return result;
  }
  
  function min(iterator, context) {
    iterator = iterator || Prototype.K;
    var result;
    this.each(function(value, index) {
      value = iterator.call(context, value, index);
      if (result == null || value < result)
        result = value;
    });
    return result;
  }
  
  function partition(iterator, context) {
    iterator = iterator || Prototype.K;
    var trues = [], falses = [];
    this.each(function(value, index) {
      (iterator.call(context, value, index) ?
        trues : falses).push(value);
    });
    return [trues, falses];
  }
  
  function pluck(property) {
    var results = [];
    this.each(function(value) {
      results.push(value[property]);
    });
    return results;
  }
  
  function reject(iterator, context) {
    var results = [];
    this.each(function(value, index) {
      if (!iterator.call(context, value, index))
        results.push(value);
    });
    return results;
  }
  
  function sortBy(iterator, context) {
    return this.map(function(value, index) {
      return {
        value: value,
        criteria: iterator.call(context, value, index)
      };
    }).sort(function(left, right) {
      var a = left.criteria, b = right.criteria;
      return a < b ? -1 : a > b ? 1 : 0;
    }).pluck('value');
  }
  
  function toArray() {
    return this.map();
  }
  
  function zip() {
    var iterator = Prototype.K, args = $A(arguments);
    if (Object.isFunction(args.last()))
      iterator = args.pop();

    var collections = [this].concat(args).map($A);
    return this.map(function(value, index) {
      return iterator(collections.pluck(index));
    });
  }
  
  function size() {
    return this.toArray().length;
  }
  
  function inspect() {
    return '#<Enumerable:' + this.toArray().inspect() + '>';
  }
  
  return {
    each:       each,
    eachSlice:  eachSlice,
    all:        all,
    every:      all,
    any:        any,
    some:       any,
    collect:    collect,
    map:        collect,
    detect:     detect,
    findAll:    findAll,
    select:     findAll,
    filter:     findAll,
    grep:       grep,
    include:    include,
    member:     include,
    inGroupsOf: inGroupsOf,
    inject:     inject,
    invoke:     invoke,
    max:        max,
    min:        min,
    partition:  partition,
    pluck:      pluck,
    reject:     reject,
    sortBy:     sortBy,
    toArray:    toArray,
    entries:    toArray,
    zip:        zip,
    size:       size,
    inspect:    inspect,
    find:       detect
  };
})();