@workInProgress @ngdoc overview @name Developer Guide: DI: Understanding DI in Angular @description While DI is widely used in statically typed languages such as Java or C++, it has not been widely used in JavaScript. Angular brings the benefits of DI into JavaScript apps. In angular, DI is implemented as a subsystem that manages dependencies between services, controllers, widgets, and filters. The most important of these are {@link api/angular.service services}. Services are objects that handle common tasks in web applications. Angular provides several{@link api/angular.service built-in services}, and you can create your own custom services. The main job of angular's DI subsystem is to provide services to angular components that depend on them. The way the DI subsystem provides services is as follows: all services are registered with angular's {@link api/angular.service service API}, and all components that depend on services define those dependencies as a property (`$inject`). With this information, the DI subsystem manages the creation of service objects and the provision of those objects to the components that need them, at the time they need them. The following illustration steps through the sequence of events:

In the illustration above, the dependency injection sequence proceeds as follows: 1. Service factory functions are registered with angular's service factory repository. 2. `ng:autobind` triggers angular's bootstrap sequence, during which angular compiles the template, creates the root scope, and creates the dependency injector. 3. The `ng:controller` directive implicitly creates a new child scope, augmented by the application of the `PhoneListCtrl` controller function. 4. The Injector identifies the `$xhr` service as `PhoneListCtrl` controller's only dependency. 5. The Injector checks if the `$xhr` service has already been instantiated, and if not uses the factory function from the service factory repository to construct it. 6. DI provides the instance of $xhr service to the PhoneListCtrl controller constructor ## How Scope Relates to DI The {@link api/angular.injector injector} is responsible for resolving the service dependencies in the application. It gets created and configured with the creation of a root scope. The injector caches instances of services, with the services cache bound to the root scope. Different root scopes have different instances of the injector. While typical angular applications will only have one root scope (and hence the services will act like application singletons), in tests it is important to not share singletons across test invocations for isolation reasons. We achieve the necessary isolation by having each test create its own separate root scope.

// create a root scope
var rootScope = angular.scope();
// access the service locator
var myService = rootScope.$service('myService');

## Inferring dependencies from the signature of the factory function or constructor **EXPERIMENTAL FEATURE**: This is an experimental feature. See the important note at the end of this section for drawbacks. We resort to `$inject` and our own annotation because there is no way in JavaScript to get a list of arguments. Or is there? It turns out that calling `.toString()` on a function returns the function declaration along with the argument names as shown below:

function myFn(a,b){}
expect(myFn.toString()).toEqual('function myFn(a,b){}');

This means that angular can infer the function names after all and use that information to generate the `$inject` annotation automatically. Therefore the following two function definitions are equivalent:

// given a user defined service
angular.service('serviceA', ...);

// inject '$window', 'serviceA', curry 'name';
function fnA($window, serviceA, name){};
fnA.$inject = ['$window', 'serviceA'];

// inject '$window', 'serviceA', curry 'name';
function fnB($window, serviceA_, name){};
// implies: fnB.$inject = ['$window', 'serviceA'];

If angular does not find a `$inject` annotation on the function, then it calls the `.toString()` method and tries to infer what should be injected using the following rules: * Any argument starting with `$` is an angular service and will be added to the `$inject` property array * Any argument ending with `_` will be added to the `$inject` property array (angular strips the `_`) * All arguments following an argument which has neither `$` nor `_` , must not have `$` nor `_` (these are free arguments for {@link http://en.wikipedia.org/wiki/Currying currying}) **IMPORTANT** Minifiers/obfuscators change the names of function arguments and will therefore break the `$inject` inference. For this reason, either explicitly declare the `$inject` or do not use minifiers/obfuscators. In the future, we may provide a pre-processor which will scan the source code and insert the `$inject` into the source code so that it can be minified/obfuscated. ## Related Topics * {@link dev_guide.services Angular Services} ## Related API * {@link api/angular.service Services API} 7'>67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136

/**
 * @workInProgress
 * @ngdoc overview
 * @name angular.widget
 * @description
 *
 * Widgets are custom DOM elements.  An angular widget can be either a custom 
 * attribute that modifies an existing DOM elements or an entirely new DOM element.
 *
 * Following is the list of built-in angular widgets:
 *
 * * {@link angular.widget.@ng:format ng:format} - Formats data for display to user and for storage.
 * * {@link angular.widget.@ng:non-bindable ng:non-bindable} - Blocks angular from processing an
 *   HTML element.
 * * {@link angular.widget.@ng:repeat ng:repeat} - Creates and manages a collection of cloned HTML
 *   elements.
 * * {@link angular.widget.@ng:required ng:required} - Verifies presence of user input.
 * * {@link angular.widget.@ng:validate ng:validate} - Validates content of user input.
 * * {@link angular.widget.HTML HTML} - Standard HTML processed by angular.
 * * {@link angular.widget.ng:view ng:view} - Works with $route to "include" partial templates
 * * {@link angular.widget.ng:switch ng:switch} - Conditionally changes DOM structure
 * * {@link angular.widget.ng:include ng:include} - Includes an external HTML fragment
 *
 * For more information about angular widgets, see {@link guide/dev_guide.compiler.widgets
 * Understanding Angular Widgets} in the angular Developer Guide.
 */

/**
 * @workInProgress
 * @ngdoc widget
 * @name angular.widget.HTML
 *
 * @description
 * The most common widgets you will use will be in the form 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 html 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, null, function(code, response){
            element.html(response);
            childScope = useScope || createScope(scope);
            compiler.compile(element)(childScope);
            scope.$eval(onloadExp);
          }, false, true);
        } else {
          childScope = null;
          element.html('');
        }
      });
    }, {$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) {
    var hasNgHref = ((element.attr('ng:bind-attr') || '').indexOf('"href":') !== -1);

    // turn <a href ng:click="..">link</a> into a link in IE
    // but only if it doesn't have name attribute, in which case it's an anchor
    if (!hasNgHref && !element.attr('name') && !element.attr('href')) {
      element.attr('href', '');
    }

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


/**
 * @workInProgress
 * @ngdoc widget
 * @name angular.widget.@ng:repeat
 *
 * @description
 * The `ng:repeat` widget instantiates a template once per item from a collection. The collection is
 * enumerated with the `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 `$index`
 * is set to the item index or key.
 *
 * Special properties are exposed on the local scope of each template instance, including:
 *
 *   * `$index` – `{number}` – iterator offset of the repeated element (0..length-1)
 *   * `$position` – `{string}` – position of the repeated element in the iterator. One of:
 *        * `'first'`,
 *        * `'middle'`
 *        * `'last'`
 *
 * Note: Although `ng:repeat` looks like a directive, it is actually an attribute widget.
 *
 * @element ANY
 * @param {string} repeat_expression The expression indicating how to enumerate a collection. Two
 *   formats are currently supported:
 *
 *   * `variable in expression` – where variable is the user defined loop variable and `expression`
 *     is a scope expression giving the collection to enumerate.
 *
 *     For example: `track in cd.tracks`.
 *
 *   * `(key, value) in expression` – where `key` and `value` can be any user defined identifiers,
 *     and `expression` is the scope expression giving the collection to enumerate.
 *
 *     For example: `(name, age) in {'adam':10, 'amalie':12}`.
 *
 * @example
 * This example initializes the scope to a list of names and
 * then uses `ng:repeat` to display every person:
    <doc:example>
      <doc:source>
        <div ng:init="friends = [{name:'John', age:25}, {name:'Mary', age:28}]">
          I have {{friends.length}} friends. They are:
          <ul>
            <li ng:repeat="friend in friends">
              [{{$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),
          collectionLength = size(collection, true),
          fragment = (element[0].nodeName != 'OPTION') ? document.createDocumentFragment() : null,
          addFragment,
          childScope,
          key;

      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.$element;
            childScope.$eval();
          } 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);

              if (fragment) {
                fragment.appendChild(clone[0]);
                addFragment = true;
              } else {
                //temporarily preserve old way for option element
                lastIterElement.after(clone);
                lastIterElement = clone;
              }
            });
          }
          index ++;
        }
      }

      //attach new nodes buffered in doc fragment
      if (addFragment) {
        lastIterElement.after(jqLite(fragment));
      }

      // 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.widget.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's callback must be async, see commit history for more info
          $xhr('GET', src, function(code, response){
            element.html(response);
            compiler.compile(element)(childScope);
          });
        } else {
          element.html('');
        }
      })(); //initialize the state forcefully, it's possible that we missed the initial
            //$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);
  }
});