'use strict';

/**
 * @ngdoc directive
 * @name ng.directive:ngRepeat
 *
 * @description
 * The `ngRepeat` directive instantiates a template once per item from a collection. Each template
 * instance gets its own scope, where the given loop variable is set to the current collection item,
 * and `$index` is set to the item index or key.
 *
 * Special properties are exposed on the local scope of each template instance, including:
 *
 *   * `$index` – `{number}` – iterator offset of the repeated element (0..length-1)
 *   * `$first` – `{boolean}` – true if the repeated element is first in the iterator.
 *   * `$middle` – `{boolean}` – true if the repeated element is between the first and last in the iterator.
 *   * `$last` – `{boolean}` – true if the repeated element is last in the iterator.
 *
 *
 * @element ANY
 * @scope
 * @priority 1000
 * @param {repeat_expression} ngRepeat The expression indicating how to enumerate a collection. These
 *   formats are currently supported:
 *
 *   * `variable in expression` – where variable is the user defined loop variable and `expression`
 *     is a scope expression giving the collection to enumerate.
 *
 *     For example: `track in cd.tracks`.
 *
 *   * `(key, value) in expression` – where `key` and `value` can be any user defined identifiers,
 *     and `expression` is the scope expression giving the collection to enumerate.
 *
 *     For example: `(name, age) in {'adam':10, 'amalie':12}`.
 *
 *   * `variable in expression track by tracking_expression` – You can also provide an optional tracking function
 *     which can be used to associate the objects in the collection with the DOM elements. If no tractking function
 *     is specified the ng-repeat associates elements by identity in the collection. It is an error to have
 *     more then one tractking function to  resolve to the same key. (This would mean that two distinct objects are
 *     mapped to the same DOM element, which is not possible.)
 *
 *     For example: `item in items` is equivalent to `item in items track by $id(item)'. This implies that the DOM elements
 *     will be associated by item identity in the array.
 *
 *     For example: `item in items track by $id(item)`. A built in `$id()` function can be used to assign a unique
 *     `$$hashKey` property to each item in the array. This property is then used as a key to associated DOM elements
 *     with the corresponding item in the array by identity. Moving the same object in array would move the DOM
 *     element in the same way ian the DOM.
 *
 *     For example: `item in items track by item.id` Is a typical pattern when the items come from the database. In this
 *     case the object identity does not matter. Two objects are considered equivalent as long as their `id`
 *     property is same.
 *
 * @example
 * This example initializes the scope to a list of names and
 * then uses `ngRepeat` to display every person:
    <doc:example>
      <doc:source>
        <div ng-init="friends = [{name:'John', age:25}, {name:'Mary', age:28}]">
          I have {{friends.length}} friends. They are:
          <ul>
            <li ng-repeat="friend in friends">
              [{{$index + 1}}] {{friend.name}} who is {{friend.age}} years old.
            </li>
          </ul>
        </div>
      </doc:source>
      <doc:scenario>
         it('should check ng-repeat', function() {
           var r = using('.doc-example-live').repeater('ul li');
           expect(r.count()).toBe(2);
           expect(r.row(0)).toEqual(["1","John","25"]);
           expect(r.row(1)).toEqual(["2","Mary","28"]);
         });
      </doc:scenario>
    </doc:example>
 */
var ngRepeatDirective = ['$parse', function($parse) {
  return {
    transclude: 'element',
    priority: 1000,
    terminal: true,
    compile: function(element, attr, linker) {
      return function($scope, $element, $attr){
        var expression = $attr.ngRepeat;
        var match = expression.match(/^\s*(.+)\s+in\s+(.*?)\s*(\s+track\s+by\s+(.+)\s*)?$/),
          trackByExp, hashExpFn, trackByIdFn, lhs, rhs, valueIdentifier, keyIdentifier,
          hashFnLocals = {$id: hashKey};

        if (!match) {
          throw Error("Expected ngRepeat in form of '_item_ in _collection_[ track by _id_]' but got '" +
            expression + "'.");
        }

        lhs = match[1];
        rhs = match[2];
        trackByExp = match[4];

        if (trackByExp) {
          hashExpFn = $parse(trackByExp);
          trackByIdFn = function(key, value, index) {
            // assign key, value, and $index to the locals so that they can be used in hash functions
            if (keyIdentifier) hashFnLocals[keyIdentifier] = key;
            hashFnLocals[valueIdentifier] = value;
            hashFnLocals.$index = index;
            return hashExpFn($scope, hashFnLocals);
          };
        } else {
          trackByIdFn = function(key, value) {
            return hashKey(value);
          }
        }
        
        match = lhs.match(/^(?:([\$\w]+)|\(([\$\w]+)\s*,\s*([\$\w]+)\))$/);
        if (!match) {
          throw Error("'item' in 'item in collection' should be identifier or (key, value) but got '" +
              lhs + "'.");
        }
        valueIdentifier = match[3] || match[1];
        keyIdentifier = match[2];

        // Store a list of elements from previous run. This is a hash where key is the item from the
        // iterator, and the value is objects with following properties.
        //   - scope: bound scope
        //   - element: previous element.
        //   - index: position
        var lastBlockMap = {};

        //watch props
        $scope.$watchCollection(rhs, function ngRepeatAction(collection){
          var index, length,
              cursor = $element,     // current position of the node
              // Same as lastBlockMap but it has the current state. It will become the
              // lastBlockMap on the next iteration.
              nextBlockMap = {},
              arrayLength,
              childScope,
              key, value, // key/value of iteration
              trackById,
              collectionKeys,
              block,       // last object information {scope, element, id}
              nextBlockOrder = [];


          if (isArray(collection)) {
            collectionKeys = collection;
          } else {
            // if object, extract keys, sort them and use to determine order of iteration over obj props
            collectionKeys = [];
            for (key in collection) {
              if (collection.hasOwnProperty(key) && key.charAt(0) != '$') {
                collectionKeys.push(key);
              }
            }
            collectionKeys.sort();
          }

          arrayLength = collectionKeys.length;

          // locate existing items
          length = nextBlockOrder.length = collectionKeys.length;
          for(index = 0; index < length; index++) {
           key = (collection === collectionKeys) ? index : collectionKeys[index];
           value = collection[key];
           trackById = trackByIdFn(key, value, index);
           if((block = lastBlockMap[trackById])) {
             delete lastBlockMap[trackById];
             nextBlockMap[trackById] = block;
             nextBlockOrder[index] = block;
           } else if (nextBlockMap.hasOwnProperty(trackById)) {
             // restore lastBlockMap
             forEach(nextBlockOrder, function(block) {
               if (block && block.element) lastBlockMap[block.id] = block;
             });
             // This is a duplicate and we need to throw an error
             throw new Error('Duplicates in a repeater are not allowed. Repeater: ' + expression);
           } else {
             // new never before seen block
             nextBlockOrder[index] = { id: trackById };
           }
         }

          // remove existing items
          for (key in lastBlockMap) {
            if (lastBlockMap.hasOwnProperty(key)) {
              block = lastBlockMap[key];
              block.element.remove();
              block.scope.$destroy();
            }
          }

          // we are not using forEach for perf reasons (trying to avoid #call)
          for (index = 0, length = collectionKeys.length; index < length; index++) {
            key = (collection === collectionKeys) ? index : collectionKeys[index];
            value = collection[key];
            block = nextBlockOrder[index];

            if (block.element) {
              // if we have already seen this object, then we need to reuse the
              // associated scope/element
              childScope = block.scope;

              if (block.element == cursor) {
                // do nothing
                cursor = block.element;
              } else {
                // existing item which got moved
                cursor.after(block.element);
                cursor = block.element;
              }
            } else {
              // new item which we don't know about
              childScope = $scope.$new();
            }

            childScope[valueIdentifier] = value;
            if (keyIdentifier) childScope[keyIdentifier] = key;
            childScope.$index = index;
            childScope.$first = (index === 0);
            childScope.$last = (index === (arrayLength - 1));
            childScope.$middle = !(childScope.$first || childScope.$last);

            if (!block.element) {
              linker(childScope, function(clone){
                cursor.after(clone);
                cursor = clone;
                block.scope = childScope;
                block.element = clone;
                nextBlockMap[block.id] = block;
              });
            }
          }
          lastBlockMap = nextBlockMap;
        });
      };
    }
  };
}];