/**
 * @workInProgress
 * @ngdoc widget
 * @name angular.widget.HTML
 *
 * @description
 * The most common widgets you will use will be in the from of the
 * standard HTML set. These widgets are bound using the name attribute
 * to an expression. In addition they can have `ng:validate`, `ng:required`,
 * `ng:format`, `ng:change` attribute to further control their behavior.
 *
 * @usageContent
 *   see example below for usage
 *
 *   <input type="text|checkbox|..." ... />
 *   <textarea ... />
 *   <select ...>
 *     <option>...</option>
 *   </select>
 *
 * @example
    <doc:example>
      <doc:source>
        <table style="font-size:.9em;">
          <tr>
            <th>Name</th>
            <th>Format</th>
            <th>HTML</th>
            <th>UI</th>
            <th ng:non-bindable>{{input#}}</th>
          </tr>
          <tr>
            <th>text</th>
            <td>String</td>
            <td><tt>&lt;input type="text" name="input1"&gt;</tt></td>
            <td><input type="text" name="input1" size="4"></td>
            <td><tt>{{input1|json}}</tt></td>
          </tr>
          <tr>
            <th>textarea</th>
            <td>String</td>
            <td><tt>&lt;textarea name="input2"&gt;&lt;/textarea&gt;</tt></td>
            <td><textarea name="input2" cols='6'></textarea></td>
            <td><tt>{{input2|json}}</tt></td>
          </tr>
          <tr>
            <th>radio</th>
            <td>String</td>
            <td><tt>
              &lt;input type="radio" name="input3" value="A"&gt;<br>
              &lt;input type="radio" name="input3" value="B"&gt;
            </tt></td>
            <td>
              <input type="radio" name="input3" value="A">
              <input type="radio" name="input3" value="B">
            </td>
            <td><tt>{{input3|json}}</tt></td>
          </tr>
          <tr>
            <th>checkbox</th>
            <td>Boolean</td>
            <td><tt>&lt;input type="checkbox" name="input4" value="checked"&gt;</tt></td>
            <td><input type="checkbox" name="input4" value="checked"></td>
            <td><tt>{{input4|json}}</tt></td>
          </tr>
          <tr>
            <th>pulldown</th>
            <td>String</td>
            <td><tt>
              &lt;select name="input5"&gt;<br>
              &nbsp;&nbsp;&lt;option value="c"&gt;C&lt;/option&gt;<br>
              &nbsp;&nbsp;&lt;option value="d"&gt;D&lt;/option&gt;<br>
              &lt;/select&gt;<br>
            </tt></td>
            <td>
              <select name="input5">
                <option value="c">C</option>
                <option value="d">D</option>
              </select>
            </td>
            <td><tt>{{input5|json}}</tt></td>
          </tr>
          <tr>
            <th>multiselect</th>
            <td>Array</td>
            <td><tt>
              &lt;select name="input6" multiple size="4"&gt;<br>
              &nbsp;&nbsp;&lt;option value="e"&gt;E&lt;/option&gt;<br>
              &nbsp;&nbsp;&lt;option value="f"&gt;F&lt;/option&gt;<br>
              &lt;/select&gt;<br>
            </tt></td>
            <td>
              <select name="input6" multiple size="4">
                <option value="e">E</option>
                <option value="f">F</option>
              </select>
            </td>
            <td><tt>{{input6|json}}</tt></td>
          </tr>
        </table>
      </doc:source>
      <doc:scenario>

        it('should exercise text', function(){
         input('input1').enter('Carlos');
         expect(binding('input1')).toEqual('"Carlos"');
        });
        it('should exercise textarea', function(){
         input('input2').enter('Carlos');
         expect(binding('input2')).toEqual('"Carlos"');
        });
        it('should exercise radio', function(){
         expect(binding('input3')).toEqual('null');
         input('input3').select('A');
         expect(binding('input3')).toEqual('"A"');
         input('input3').select('B');
         expect(binding('input3')).toEqual('"B"');
        });
        it('should exercise checkbox', function(){
         expect(binding('input4')).toEqual('false');
         input('input4').check();
         expect(binding('input4')).toEqual('true');
        });
        it('should exercise pulldown', function(){
         expect(binding('input5')).toEqual('"c"');
         select('input5').option('d');
         expect(binding('input5')).toEqual('"d"');
        });
        it('should exercise multiselect', function(){
         expect(binding('input6')).toEqual('[]');
         select('input6').options('e');
         expect(binding('input6')).toEqual('["e"]');
         select('input6').options('e', 'f');
         expect(binding('input6')).toEqual('["e","f"]');
        });
      </doc:scenario>
    </doc:example>
 */

function modelAccessor(scope, element) {
  var expr = element.attr('name');
  var assign;
  if (expr) {
    assign = parser(expr).assignable().assign;
    if (!assign) throw new Error("Expression '" + expr + "' is not assignable.");
    return {
      get: function() {
        return scope.$eval(expr);
      },
      set: function(value) {
        if (value !== _undefined) {
          return scope.$tryEval(function(){
            assign(scope, value);
          }, element);
        }
      }
    };
  }
}

function modelFormattedAccessor(scope, element) {
  var accessor = modelAccessor(scope, element),
      formatterName = element.attr('ng:format') || NOOP,
      formatter = compileFormatter(formatterName);
  if (accessor) {
    return {
      get: function() {
        return formatter.format(scope, accessor.get());
      },
      set: function(value) {
        return accessor.set(formatter.parse(scope, value));
      }
    };
  }
}

function compileValidator(expr) {
  return parser(expr).validator()();
}

function compileFormatter(expr) {
  return parser(expr).formatter()();
}

/**
 * @workInProgress
 * @ngdoc widget
 * @name angular.widget.@ng:validate
 *
 * @description
 * The `ng:validate` attribute widget validates the user input. If the input does not pass
 * validation, the `ng-validation-error` CSS class and the `ng:error` attribute are set on the input
 * element. Check out {@link angular.validator validators} to find out more.
 *
 * @param {string} validator The name of a built-in or custom {@link angular.validator validator} to
 *     to be used.
 *
 * @element INPUT
 * @css ng-validation-error
 *
 * @example
 * This example shows how the input element becomes red when it contains invalid input. Correct
 * the input to make the error disappear.
 *
    <doc:example>
      <doc:source>
        I don't validate:
        <input type="text" name="value" value="NotANumber"><br/>

        I need an integer or nothing:
        <input type="text" name="value" ng:validate="integer"><br/>
      </doc:source>
      <doc:scenario>
         it('should check ng:validate', function(){
           expect(element('.doc-example-live :input:last').attr('className')).
             toMatch(/ng-validation-error/);

           input('value').enter('123');
           expect(element('.doc-example-live :input:last').attr('className')).
             not().toMatch(/ng-validation-error/);
         });
      </doc:scenario>
    </doc:example>
 */
/**
 * @workInProgress
 * @ngdoc widget
 * @name angular.widget.@ng:required
 *
 * @description
 * The `ng:required` attribute widget validates that the user input is present. It is a special case
 * of the {@link angular.widget.@ng:validate ng:validate} attribute widget.
 *
 * @element INPUT
 * @css ng-validation-error
 *
 * @example
 * This example shows how the input element becomes red when it contains invalid input. Correct
 * the input to make the error disappear.
 *
    <doc:example>
      <doc:source>
        I cannot be blank: <input type="text" name="value" ng:required><br/>
      </doc:source>
      <doc:scenario>
       it('should check ng:required', function(){
         expect(element('.doc-example-live :input').attr('className')).toMatch(/ng-validation-error/);
         input('value').enter('123');
         expect(element('.doc-example-live :input').attr('className')).not().toMatch(/ng-validation-error/);
       });
      </doc:scenario>
    </doc:example>
 */
/**
 * @workInProgress
 * @ngdoc widget
 * @name angular.widget.@ng:format
 *
 * @description
 * The `ng:format` attribute widget formats stored data to user-readable text and parses the text
 * back to the stored form. You might find this useful for example if you collect user input in a
 * text field but need to store the data in the model as a list. Check out
 * {@link angular.formatter formatters} to learn more.
 *
 * @param {string} formatter The name of the built-in or custom {@link angular.formatter formatter}
 *     to be used.
 *
 * @element INPUT
 *
 * @example
 * This example shows how the user input is converted from a string and internally represented as an
 * array.
 *
    <doc:example>
      <doc:source>
        Enter a comma separated list of items:
        <input type="text" name="list" ng:format="list" value="table, chairs, plate">
        <pre>list={{list}}</pre>
      </doc:source>
      <doc:scenario>
       it('should check ng:format', function(){
         expect(binding('list')).toBe('list=["table","chairs","plate"]');
         input('list').enter(',,, a ,,,');
         expect(binding('list')).toBe('list=["a"]');
       });
      </doc:scenario>
    </doc:example>
 */
function valueAccessor(scope, element) {
  var validatorName = element.attr('ng:validate') || NOOP,
      validator = compileValidator(validatorName),
      requiredExpr = element.attr('ng:required'),
      formatterName = element.attr('ng:format') || NOOP,
      formatter = compileFormatter(formatterName),
      format, parse, lastError, required,
      invalidWidgets = scope.$service('$invalidWidgets') || {markValid:noop, markInvalid:noop};
  if (!validator) throw "Validator named '" + validatorName + "' not found.";
  format = formatter.format;
  parse = formatter.parse;
  if (requiredExpr) {
    scope.$watch(requiredExpr, function(newValue) {
      required = newValue;
      validate();
    });
  } else {
    required = requiredExpr === '';
  }

  element.data($$validate, validate);
  return {
    get: function(){
      if (lastError)
        elementError(element, NG_VALIDATION_ERROR, _null);
      try {
        var value = parse(scope, element.val());
        validate();
        return value;
      } catch (e) {
        lastError = e;
        elementError(element, NG_VALIDATION_ERROR, e);
      }
    },
    set: function(value) {
      var oldValue = element.val(),
          newValue = format(scope, value);
      if (oldValue != newValue) {
        element.val(newValue || ''); // needed for ie
      }
      validate();
    }
  };

  function validate() {
    var value = trim(element.val());
    if (element[0].disabled || element[0].readOnly) {
      elementError(element, NG_VALIDATION_ERROR, _null);
      invalidWidgets.markValid(element);
    } else {
      var error, validateScope = inherit(scope, {$element:element});
      error = required && !value
              ? 'Required'
              : (value ? validator(validateScope, value) : _null);
      elementError(element, NG_VALIDATION_ERROR, error);
      lastError = error;
      if (error) {
        invalidWidgets.markInvalid(element);
      } else {
        invalidWidgets.markValid(element);
      }
    }
  }
}

function checkedAccessor(scope, element) {
  var domElement = element[0], elementValue = domElement.value;
  return {
    get: function(){
      return !!domElement.checked;
    },
    set: function(value){
      domElement.checked = toBoolean(value);
    }
  };
}

function radioAccessor(scope, element) {
  var domElement = element[0];
  return {
    get: function(){
      return domElement.checked ? domElement.value : _null;
    },
    set: function(value){
      domElement.checked = value == domElement.value;
    }
  };
}

function optionsAccessor(scope, element) {
  var formatterName = element.attr('ng:format') || NOOP,
      formatter = compileFormatter(formatterName);
  return {
    get: function(){
      var values = [];
      forEach(element[0].options, function(option){
        if (option.selected) values.push(formatter.parse(scope, option.value));
      });
      return values;
    },
    set: function(values){
      var keys = {};
      forEach(values, function(value){
        keys[formatter.format(scope, value)] = true;
      });
      forEach(element[0].options, function(option){
        option.selected = keys[option.value];
      });
    }
  };
}

function noopAccessor() { return { get: noop, set: noop }; }

/*
 * TODO: refactor
 *
 * The table bellow is not quite right. In some cases the formatter is on the model side
 * and in some cases it is on the view side. This is a historical artifact
 *
 * The concept of model/view accessor is useful for anyone who is trying to develop UI, and
 * so it should be exposed to others. There should be a form object which keeps track of the
 * accessors and also acts as their factory. It should expose it as an object and allow
 * the validator to publish errors to it, so that the the error messages can be bound to it.
 *
 */
var textWidget = inputWidget('keydown change', modelAccessor, valueAccessor, initWidgetValue(), true),
    buttonWidget = inputWidget('click', noopAccessor, noopAccessor, noop),
    INPUT_TYPE = {
      'text':            textWidget,
      'textarea':        textWidget,
      'hidden':          textWidget,
      'password':        textWidget,
      'button':          buttonWidget,
      'submit':          buttonWidget,
      'reset':           buttonWidget,
      'image':           buttonWidget,
      'checkbox':        inputWidget('click', modelFormattedAccessor, checkedAccessor, initWidgetValue(false)),
      'radio':           inputWidget('click', modelFormattedAccessor, radioAccessor, radioInit),
      'select-one':      inputWidget('change', modelAccessor, valueAccessor, initWidgetValue(_null)),
      'select-multiple': inputWidget('change', modelAccessor, optionsAccessor, initWidgetValue([]))
//      'file':            fileWidget???
    };


function initWidgetValue(initValue) {
  return function (model, view) {
    var value = view.get();
    if (!value && isDefined(initValue)) {
      value = copy(initValue);
    }
    if (isUndefined(model.get()) && isDefined(value)) {
      model.set(value);
    }
  };
}

function radioInit(model, view, element) {
 var modelValue = model.get(), viewValue = view.get(), input = element[0];
 input.checked = false;
 input.name = this.$id + '@' + input.name;
 if (isUndefined(modelValue)) {
   model.set(modelValue = _null);
 }
 if (modelValue == _null && viewValue !== _null) {
   model.set(viewValue);
 }
 view.set(modelValue);
}

/**
 * @workInProgress
 * @ngdoc directive
 * @name angular.directive.ng:change
 *
 * @description
 * The directive executes an expression whenever the input widget changes.
 *
 * @element INPUT
 * @param {expression} expression to execute.
 *
 * @example
 * @example
    <doc:example>
      <doc:source>
        <div ng:init="checkboxCount=0; textCount=0"></div>
        <input type="text" name="text" ng:change="textCount = 1 + textCount">
           changeCount {{textCount}}<br/>
        <input type="checkbox" name="checkbox" ng:change="checkboxCount = 1 + checkboxCount">
           changeCount {{checkboxCount}}<br/>
      </doc:source>
      <doc:scenario>
         it('should check ng:change', function(){
           expect(binding('textCount')).toBe('0');
           expect(binding('checkboxCount')).toBe('0');

           using('.doc-example-live').input('text').enter('abc');
           expect(binding('textCount')).toBe('1');
           expect(binding('checkboxCount')).toBe('0');


           using('.doc-example-live').input('checkbox').check();
           expect(binding('textCount')).toBe('1');
           expect(binding('checkboxCount')).toBe('1');
         });
      </doc:scenario>
    </doc:example>
 */
function inputWidget(events, modelAccessor, viewAccessor, initFn, textBox) {
  return injectService(['$updateView', '$defer'], function($updateView, $defer, element) {
    var scope = this,
        model = modelAccessor(scope, element),
        view = viewAccessor(scope, element),
        action = element.attr('ng:change') || '',
        lastValue;
    if (model) {
      initFn.call(scope, model, view, element);
      this.$eval(element.attr('ng:init')||'');
      element.bind(events, function(event){
        function handler(){
          var value = view.get();
          if (!textBox || value != lastValue) {
            model.set(value);
            lastValue = model.get();
            scope.$tryEval(action, element);
            $updateView();
          }
        }
        event.type == 'keydown' ? $defer(handler) : handler();
      });
      scope.$watch(model.get, function(value){
        if (lastValue !== value) {
          view.set(lastValue = value);
        }
      });
    }
  });
}

function inputWidgetSelector(element){
  this.directives(true);
  this.descend(true);
  return INPUT_TYPE[lowercase(element[0].type)] || noop;
}

angularWidget('input', inputWidgetSelector);
angularWidget('textarea', inputWidgetSelector);
angularWidget('button', inputWidgetSelector);
angularWidget('select', function(element){
  this.descend(true);
  return inputWidgetSelector.call(this, element);
});


/*
 * Consider this:
 * <select name="selection">
 *   <option ng:repeat="x in [1,2]">{{x}}</option>
 * </select>
 *
 * The issue is that the select gets evaluated before option is unrolled.
 * This means that the selection is undefined, but the browser
 * default behavior is to show the top selection in the list.
 * To fix that we register a $update function on the select element
 * and the option creation then calls the $update function when it is
 * unrolled. The $update function then calls this update function, which
 * then tries to determine if the model is unassigned, and if so it tries to
 * chose one of the options from the list.
 */
angularWidget('option', function(){
  this.descend(true);
  this.directives(true);
  return function(option) {
    var select = option.parent();
    var isMultiple = select[0].type == 'select-multiple';
    var scope = select.scope();
    var model = modelAccessor(scope, select);

    //if parent select doesn't have a name, don't bother doing anything any more
    if (!model) return;

    var formattedModel = modelFormattedAccessor(scope, select);
    var view = isMultiple
      ? optionsAccessor(scope, select)
      : valueAccessor(scope, select);
    var lastValue = option.attr($value);
    var wasSelected = option.attr('ng-' + $selected);
    option.data($$update, isMultiple
      ? function(){
          view.set(model.get());
        }
      : function(){
          var currentValue = option.attr($value);
          var isSelected = option.attr('ng-' + $selected);
          var modelValue = model.get();
          if (wasSelected != isSelected || lastValue != currentValue) {
            wasSelected = isSelected;
            lastValue = currentValue;
            if (isSelected || !modelValue == null || modelValue == undefined )
              formattedModel.set(currentValue);
            if (currentValue == modelValue) {
              view.set(lastValue);
            }
          }
        }
    );
  };
});

/**
 * @workInProgress
 * @ngdoc widget
 * @name angular.widget.ng:include
 *
 * @description
 * Include external HTML fragment.
 *
 * Keep in mind that Same Origin Policy applies to included resources
 * (e.g. ng:include won't work for file:// access).
 *
 * @param {string} src expression evaluating to URL.
 * @param {Scope=} [scope=new_child_scope] optional expression which evaluates to an
 *                 instance of angular.scope to set the HTML fragment to.
 * @param {string=} onload Expression to evaluate when a new partial is loaded.
 *
 * @example
    <doc:example>
      <doc:source>
       <select name="url">
        <option value="angular.filter.date.html">date filter</option>
        <option value="angular.filter.html.html">html filter</option>
        <option value="">(blank)</option>
       </select>
       <tt>url = <a href="{{url}}">{{url}}</a></tt>
       <hr/>
       <ng:include src="url"></ng:include>
      </doc:source>
      <doc:scenario>
        it('should load date filter', function(){
         expect(element('.doc-example-live ng\\:include').text()).toMatch(/angular\.filter\.date/);
        });
        it('should change to hmtl filter', function(){
         select('url').option('angular.filter.html.html');
         expect(element('.doc-example-live ng\\:include').text()).toMatch(/angular\.filter\.html/);
        });
        it('should change to blank', function(){
         select('url').option('');
         expect(element('.doc-example-live ng\\:include').text()).toEqual('');
        });
      </doc:scenario>
    </doc:example>
 */
angularWidget('ng:include', function(element){
  var compiler = this,
      srcExp = element.attr("src"),
      scopeExp = element.attr("scope") || '',
      onloadExp = element[0].getAttribute('onload') || ''; //workaround for jquery bug #7537
  if (element[0]['ng:compiled']) {
    this.descend(true);
    this.directives(true);
  } else {
    element[0]['ng:compiled'] = true;
    return extend(function(xhr, element){
      var scope = this, childScope;
      var changeCounter = 0;
      var preventRecursion = false;
      function incrementChange(){ changeCounter++;}
      this.$watch(srcExp, incrementChange);
      this.$watch(scopeExp, incrementChange);

      // note that this propagates eval to the current childScope, where childScope is dynamically
      // bound (via $route.onChange callback) to the current scope created by $route
      scope.$onEval(function(){
        if (childScope && !preventRecursion) {
          preventRecursion = true;
          try {
            childScope.$eval();
          } finally {
            preventRecursion = false;
          }
        }
      });
      this.$watch(function(){return changeCounter;}, function(){
        var src = this.$eval(srcExp),
            useScope = this.$eval(scopeExp);

        if (src) {
          xhr('GET', src, function(code, response){
            element.html(response);
            childScope = useScope || createScope(scope);
            compiler.compile(element)(childScope);
            scope.$eval(onloadExp);
          });
        } else {
          childScope = null;
          element.html('');
        }
      });
    }, {$inject:['$xhr.cache']});
  }
});

/**
 * @workInProgress
 * @ngdoc widget
 * @name angular.widget.ng:switch
 *
 * @description
 * Conditionally change the DOM structure.
 *
 * @usageContent
 * <any ng:switch-when="matchValue1">...</any>
 *   <any ng:switch-when="matchValue2">...</any>
 *   ...
 *   <any ng:switch-default>...</any>
 *
 * @param {*} on expression to match against <tt>ng:switch-when</tt>.
 * @paramDescription
 * On child elments add:
 *
 * * `ng:switch-when`: the case statement to match against. If match then this
 *   case will be displayed.
 * * `ng:switch-default`: the default case when no other casses match.
 *
 * @example
    <doc:example>
      <doc:source>
        <select name="switch">
          <option>settings</option>
          <option>home</option>
          <option>other</option>
        </select>
        <tt>switch={{switch}}</tt>
        </hr>
        <ng:switch on="switch" >
          <div ng:switch-when="settings">Settings Div</div>
          <span ng:switch-when="home">Home Span</span>
          <span ng:switch-default>default</span>
        </ng:switch>
        </code>
      </doc:source>
      <doc:scenario>
        it('should start in settings', function(){
         expect(element('.doc-example-live ng\\:switch').text()).toEqual('Settings Div');
        });
        it('should change to home', function(){
         select('switch').option('home');
         expect(element('.doc-example-live ng\\:switch').text()).toEqual('Home Span');
        });
        it('should select deafault', function(){
         select('switch').option('other');
         expect(element('.doc-example-live ng\\:switch').text()).toEqual('default');
        });
      </doc:scenario>
    </doc:example>
 */
//TODO(im): remove all the code related to using and inline equals
var ngSwitch = angularWidget('ng:switch', function (element){
  var compiler = this,
      watchExpr = element.attr("on"),
      usingExpr = (element.attr("using") || 'equals'),
      usingExprParams = usingExpr.split(":"),
      usingFn = ngSwitch[usingExprParams.shift()],
      changeExpr = element.attr('change') || '',
      cases = [];
  if (!usingFn) throw "Using expression '" + usingExpr + "' unknown.";
  if (!watchExpr) throw "Missing 'on' attribute.";
  eachNode(element, function(caseElement){
    var when = caseElement.attr('ng:switch-when');
    var switchCase = {
        change: changeExpr,
        element: caseElement,
        template: compiler.compile(caseElement)
      };
    if (isString(when)) {
      switchCase.when = function(scope, value){
        var args = [value, when];
        forEach(usingExprParams, function(arg){
          args.push(arg);
        });
        return usingFn.apply(scope, args);
      };
      cases.unshift(switchCase);
    } else if (isString(caseElement.attr('ng:switch-default'))) {
      switchCase.when = valueFn(true);
      cases.push(switchCase);
    }
  });

  // this needs to be here for IE
  forEach(cases, function(_case){
    _case.element.remove();
  });

  element.html('');
  return function(element){
    var scope = this, childScope;
    this.$watch(watchExpr, function(value){
      var found = false;
      element.html('');
      childScope = createScope(scope);
      forEach(cases, function(switchCase){
        if (!found && switchCase.when(childScope, value)) {
          found = true;
          childScope.$tryEval(switchCase.change, element);
          switchCase.template(childScope, function(caseElement){
            element.append(caseElement);
          });
        }
      });
    });
    scope.$onEval(function(){
      if (childScope) childScope.$eval();
    });
  };
}, {
  equals: function(on, when) {
    return ''+on == when;
  }
});


/*
 * Modifies the default behavior of html A tag, so that the default action is prevented when href
 * attribute is empty.
 *
 * The reasoning for this change is to allow easy creation of action links with ng:click without
 * changing the location or causing page reloads, e.g.:
 * <a href="" ng:click="model.$save()">Save</a>
 */
angularWidget('a', function() {
  this.descend(true);
  this.directives(true);

  return function(element) {
    if (element.attr('href') === '') {
      element.bind('click', function(event){
        event.preventDefault();
      });
    }
  };
});


/**
 * @workInProgress
 * @ngdoc widget
 * @name angular.widget.@ng:repeat
 *
 * @description
 * `ng:repeat` instantiates a template once per item from a collection. The collection is enumerated
 * with `ng:repeat-index` attribute starting from 0. Each template instance gets its own scope where
 * the given loop variable is set to the current collection item and `$index` is set to the item
 * index or key.
 *
 * There are special properties exposed on the local scope of each template instance:
 *
 *   * `$index` – `{number}` – iterator offset of the repeated element (0..length-1)
 *   * `$position` – {string} – position of the repeated element in the iterator. One of: `'first'`,
 *     `'middle'` or `'last'`.
 *
 * NOTE: `ng:repeat` looks like a directive, but is actually an attribute widget.
 *
 * @element ANY
 * @param {string} repeat_expression The expression indicating how to enumerate a collection. Two
 *   formats are currently supported:
 *
 *   * `variable in expression` – where variable is the user defined loop variable and `expression`
 *     is a scope expression giving the collection to enumerate.
 *
 *     For example: `track in cd.tracks`.
 *   * `(key, value) in expression` – where `key` and `value` can be any user defined identifiers,
 *     and `expression` is the scope expression giving the collection to enumerate.
 *
 *     For example: `(name, age) in {'adam':10, 'amalie':12}`.
 *
 * @example
 * This example initializes the scope to a list of names and
 * than uses `ng:repeat` to display every person.
    <doc:example>
      <doc:source>
        <div ng:init="friends = [{name:'John', age:25}, {name:'Mary', age:28}]">
          I have {{friends.length}} friends. They are:
          <ul>
            <li ng:repeat="friend in friends">
              [{{$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>
 */
angularWidget('@ng:repeat', function(expression, element){
  element.removeAttr('ng:repeat');
  element.replaceWith(jqLite('<!-- ng:repeat: ' + expression + ' --!>'));
  var linker = this.compile(element);
  return function(iterStartElement){
    var match = expression.match(/^\s*(.+)\s+in\s+(.*)\s*$/),
        lhs, rhs, valueIdent, keyIdent;
    if (! match) {
      throw Error("Expected ng:repeat in form of 'item in collection' but got '" +
      expression + "'.");
    }
    lhs = match[1];
    rhs = match[2];
    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 '" +
      keyValue + "'.");
    }
    valueIdent = match[3] || match[1];
    keyIdent = match[2];

    var children = [], currentScope = this;
    this.$onEval(function(){
      var index = 0,
          childCount = children.length,
          lastIterElement = iterStartElement,
          collection = this.$tryEval(rhs, iterStartElement),
          is_array = isArray(collection),
          collectionLength = 0,
          childScope,
          key;

      if (is_array) {
        collectionLength = collection.length;
      } else {
        for (key in collection)
          if (collection.hasOwnProperty(key))
            collectionLength++;
      }

      for (key in collection) {
        if (collection.hasOwnProperty(key)) {
          if (index < childCount) {
            // reuse existing child
            childScope = children[index];
            childScope[valueIdent] = collection[key];
            if (keyIdent) childScope[keyIdent] = key;
            lastIterElement = childScope.$element;
          } else {
            // grow children
            childScope = createScope(currentScope);
            childScope[valueIdent] = collection[key];
            if (keyIdent) childScope[keyIdent] = key;
            childScope.$index = index;
            childScope.$position = index == 0
                ? 'first'
                : (index == collectionLength - 1 ? 'last' : 'middle');
            children.push(childScope);
            linker(childScope, function(clone){
              clone.attr('ng:repeat-index', index);
              lastIterElement.after(clone);
              lastIterElement = clone;
            });
          }
          childScope.$eval();
          index ++;
        }
      }
      // shrink children
      while(children.length > index) {
        children.pop().$element.remove();
      }
    }, iterStartElement);
  };
});


/**
 * @workInProgress
 * @ngdoc widget
 * @name angular.widget.@ng:non-bindable
 *
 * @description
 * Sometimes it is necessary to write code which looks like bindings but which should be left alone
 * by angular. Use `ng:non-bindable` to make angular ignore a chunk of HTML.
 *
 * NOTE: `ng:non-bindable` looks like a directive, but is actually an attribute widget.
 *
 * @element ANY
 *
 * @example
 * In this example there are two location where a siple binding (`{{}}`) is present, but the one
 * wrapped in `ng:non-bindable` is left alone.
 *
 * @example
    <doc:example>
      <doc:source>
        <div>Normal: {{1 + 2}}</div>
        <div ng:non-bindable>Ignored: {{1 + 2}}</div>
      </doc:source>
      <doc:scenario>
       it('should check ng:non-bindable', function(){
         expect(using('.doc-example-live').binding('1 + 2')).toBe('3');
         expect(using('.doc-example-live').element('div:last').text()).
           toMatch(/1 \+ 2/);
       });
      </doc:scenario>
    </doc:example>
 */
angularWidget("@ng:non-bindable", noop);


/**
 * @ngdoc widget
 * @name angular.widget.ng:view
 *
 * @description
 * # Overview
 * `ng:view` is a widget that complements the {@link angular.service.$route $route} service by
 * including the rendered template of the current route into the main layout (`index.html`) file.
 * Every time the current route changes, the included view changes with it according to the
 * configuration of the `$route` service.
 *
 * This widget provides functionality similar to {@link angular.service.ng:include ng:include} when
 * used like this:
 *
 *     <ng:include src="$route.current.template" scope="$route.current.scope"></ng:include>
 *
 *
 * # Advantages
 * Compared to `ng:include`, `ng:view` offers these advantages:
 *
 * - shorter syntax
 * - more efficient execution
 * - doesn't require `$route` service to be available on the root scope
 *
 *
 * @example
    <doc:example>
      <doc:source>
         <script>
           function MyCtrl($route) {
             $route.when('/overview', {controller: OverviewCtrl, template: 'guide.overview.html'});
             $route.when('/bootstrap', {controller: BootstrapCtrl, template: 'guide.bootstrap.html'});
             console.log(window.$route = $route);
           };
           MyCtrl.$inject = ['$route'];

           function BootstrapCtrl(){}
           function OverviewCtrl(){}
         </script>
         <div ng:controller="MyCtrl">
           <a href="#/overview">overview</a> | <a href="#/bootstrap">bootstrap</a> | <a href="#/undefined">undefined</a><br/>
           The view is included below:
           <hr/>
           <ng:view></ng:view>
         </div>
      </doc:source>
      <doc:scenario>
      </doc:scenario>
    </doc:example>
 */
angularWidget('ng:view', function(element) {
  var compiler = this;

  if (!element[0]['ng:compiled']) {
    element[0]['ng:compiled'] = true;
    return injectService(['$xhr.cache', '$route'], function($xhr, $route, element){
      var parentScope = this,
          childScope;

      $route.onChange(function(){
        var src;

        if ($route.current) {
          src = $route.current.template;
          childScope = $route.current.scope;
        }

        if (src) {
          $xhr('GET', src, function(code, response){
            element.html(response);
            compiler.compile(element)(childScope);
          });
        } else {
          element.html('');
        }
      })(); //initialize the state forcefully, it's possible that we missed the initial
            //$route#onChange already

      // note that this propagates eval to the current childScope, where childScope is dynamically
      // bound (via $route.onChange callback) to the current scope created by $route
      parentScope.$onEval(function() {
        if (childScope) {
          childScope.$eval();
        }
      });
    });
  } else {
    this.descend(true);
    this.directives(true);
  }
});