/**
 * @ngdoc module
 * @name material.components.icon
 * @description
 * Icon
 */
angular.module('material.components.icon', [
    'material.core'
  ])
  .directive('mdIcon', mdIconDirective);

/**
 * @ngdoc directive
 * @name mdIcon
 * @module material.components.icon
 *
 * @restrict E
 *
 * @description
 * The `md-icon` directive makes it easier to use vector-based icons in your app (as opposed to
 * raster-based icons types like PNG). The directive supports both icon fonts and SVG icons.
 *
 * Icons should be consider view-only elements that should not be used directly as buttons; instead nest a `<md-icon>`
 * inside a `md-button` to add hover and click features.
 *
 * ### Icon fonts
 * Icon fonts are a technique in which you use a font where the glyphs in the font are
 * your icons instead of text. Benefits include a straightforward way to bundle everything into a
 * single HTTP request, simple scaling, easy color changing, and more.
 *
 * `md-icon` let's you consume an icon font by letting you reference specific icons in that font
 * by name rather than character code.
 *
 * ### SVG
 * For SVGs, the problem with using `<img>` or a CSS `background-image` is that you can't take
 * advantage of some SVG features, such as styling specific parts of the icon with CSS or SVG
 * animation.
 *
 * `md-icon` makes it easier to use SVG icons by *inlining* the SVG into an `<svg>` element in the
 * document. The most straightforward way of referencing an SVG icon is via URL, just like a
 * traditional `<img>`. `$mdIconProvider`, as a convenience, let's you _name_ an icon so you can
 * reference it by name instead of URL throughout your templates.
 *
 * Additionally, you may not want to make separate HTTP requests for every icon, so you can bundle
 * your SVG icons together and pre-load them with $mdIconProvider as an icon set. An icon set can
 * also be given a name, which acts as a namespace for individual icons, so you can reference them
 * like `"social:cake"`.
 *
 * When using SVGs, both external SVGs (via URLs) or sets of SVGs [from icon sets] can be
 * easily loaded and used.When use font-icons, developers must following three (3) simple steps:
 *
 * <ol>
 * <li>Load the font library. e.g.<br/>
 *    &lt;link href="https://fonts.googleapis.com/icon?family=Material+Icons"
 *    rel="stylesheet"&gt;
 * </li>
 * <li> Use either (a) font-icon class names or (b) font ligatures to render the font glyph by using its textual name</li>
 * <li> Use &lt;md-icon md-font-icon="classname" /&gt; or <br/>
 *     use &lt;md-icon md-font-set="font library classname or alias"&gt; textual_name &lt;/md-icon&gt; or <br/>
 *     use &lt;md-icon md-font-set="font library classname or alias"&gt; numerical_character_reference &lt;/md-icon&gt;
 * </li>
 * </ol>
 *
 * Full details for these steps can be found:
 *
 * <ul>
 * <li>http://google.github.io/material-design-icons/</li>
 * <li>http://google.github.io/material-design-icons/#icon-font-for-the-web</li>
 * </ul>
 *
 * The Material Design icon style <code>.material-icons</code> and the icon font references are published in
 * Material Design Icons:
 *
 * <ul>
 * <li>http://www.google.com/design/icons/</li>
 * <li>https://www.google.com/design/icons/#ic_accessibility</li>
 * </ul>
 *
 * <h2 id="material_design_icons">Material Design Icons</h2>
 * Using the Material Design Icon-Selector, developers can easily and quickly search for a Material Design font-icon and
 * determine its textual name and character reference code. Click on any icon to see the slide-up information
 * panel with details regarding a SVG download or information on the font-icon usage.
 *
 * <a href="https://www.google.com/design/icons/#ic_accessibility" target="_blank" style="border-bottom:none;">
 * <img src="https://cloud.githubusercontent.com/assets/210413/7902490/fe8dd14c-0780-11e5-98fb-c821cc6475e6.png"
 *      aria-label="Material Design Icon-Selector" style="max-width:75%;padding-left:10%">
 * </a>
 *
 * <span class="image_caption">
 *  Click on the image above to link to the
 *  <a href="https://www.google.com/design/icons/#ic_accessibility" target="_blank">Material Design Icon-Selector</a>.
 * </span>
 *
 * @param {string} md-font-icon String name of CSS icon associated with the font-face will be used
 * to render the icon. Requires the fonts and the named CSS styles to be preloaded.
 * @param {string} md-font-set CSS style name associated with the font library; which will be assigned as
 * the class for the font-icon ligature. This value may also be an alias that is used to lookup the classname;
 * internally use `$mdIconProvider.fontSet(<alias>)` to determine the style name.
 * @param {string} md-svg-src String URL (or expression) used to load, cache, and display an
 *     external SVG.
 * @param {string} md-svg-icon md-svg-icon String name used for lookup of the icon from the internal cache;
 *     interpolated strings or expressions may also be used. Specific set names can be used with
 *     the syntax `<set name>:<icon name>`.<br/><br/>
 * To use icon sets, developers are required to pre-register the sets using the `$mdIconProvider` service.
 * @param {string=} aria-label Labels icon for accessibility. If an empty string is provided, icon
 * will be hidden from accessibility layer with `aria-hidden="true"`. If there's no aria-label on the icon
 * nor a label on the parent element, a warning will be logged to the console.
 * @param {string=} alt Labels icon for accessibility. If an empty string is provided, icon
 * will be hidden from accessibility layer with `aria-hidden="true"`. If there's no alt on the icon
 * nor a label on the parent element, a warning will be logged to the console. *
 * @usage
 * When using SVGs:
 * <hljs lang="html">
 *
 *  <!-- Icon ID; may contain optional icon set prefix; icons must registered using $mdIconProvider -->
 *  <md-icon md-svg-icon="social:android"    aria-label="android " ></md-icon>
 *
 *  <!-- Icon urls; may be preloaded in templateCache -->
 *  <md-icon md-svg-src="/android.svg"       aria-label="android " ></md-icon>
 *  <md-icon md-svg-src="{{ getAndroid() }}" aria-label="android " ></md-icon>
 *
 * </hljs>
 *
 * Use the <code>$mdIconProvider</code> to configure your application with
 * svg iconsets.
 *
 * <hljs lang="js">
 *  angular.module('appSvgIconSets', ['ngMaterial'])
 *    .controller('DemoCtrl', function($scope) {})
 *    .config(function($mdIconProvider) {
 *      $mdIconProvider
 *         .iconSet('social', 'img/icons/sets/social-icons.svg', 24)
 *         .defaultIconSet('img/icons/sets/core-icons.svg', 24);
 *     });
 * </hljs>
 *
 *
 * When using Font Icons with classnames:
 * <hljs lang="html">
 *
 *  <md-icon md-font-icon="android" aria-label="android" ></md-icon>
 *  <md-icon class="icon_home"      aria-label="Home"    ></md-icon>
 *
 * </hljs>
 *
 * When using Material Font Icons with ligatures:
 * <hljs lang="html">
 *  <!-- For Material Design Icons -->
 *  <!-- The class '.material-icons' is auto-added if a style has NOT been specified -->
 *  <md-icon> face </md-icon>
 *  <md-icon md-font-set="material-icons"> face </md-icon>
 *  <md-icon> #xE87C; </md-icon>
 *  <!-- The class '.material-icons' must be manually added if other styles are also specified-->
 *  <md-icon class="material-icons md-light md-48"> face </md-icon>
 * </hljs>
 *
 * When using other Font-Icon libraries:
 *
 * <hljs lang="js">
 *  // Specify a font-icon style alias
 *  angular.config(function($mdIconProvider) {
 *    $mdIconProvider.fontSet('fa', 'fontawesome');
 *  });
 * </hljs>
 *
 * <hljs lang="html">
 *  <md-icon md-font-set="fa">email</md-icon>
 * </hljs>
 *
 */
function mdIconDirective($mdIcon, $mdTheming, $mdAria ) {

  return {
    scope: {
      fontSet : '@mdFontSet',
      fontIcon: '@mdFontIcon',
      svgIcon : '@mdSvgIcon',
      svgSrc  : '@mdSvgSrc'
    },
    restrict: 'E',
    link : postLink
  };


  /**
   * Directive postLink
   * Supports embedded SVGs, font-icons, & external SVGs
   */
  function postLink(scope, element, attr) {
    $mdTheming(element);

    prepareForFontIcon();

    // If using a font-icon, then the textual name of the icon itself
    // provides the aria-label.

    var label = attr.alt || scope.fontIcon || scope.svgIcon || element.text();
    var attrName = attr.$normalize(attr.$attr.mdSvgIcon || attr.$attr.mdSvgSrc || '');

    if ( !attr['aria-label'] ) {

      if (label != '' && !parentsHaveText() ) {

        $mdAria.expect(element, 'aria-label', label);
        $mdAria.expect(element, 'role', 'img');

      } else if ( !element.text() ) {
        // If not a font-icon with ligature, then
        // hide from the accessibility layer.

        $mdAria.expect(element, 'aria-hidden', 'true');
      }
    }

    if (attrName) {
      // Use either pre-configured SVG or URL source, respectively.
      attr.$observe(attrName, function(attrVal) {

        element.empty();
        if (attrVal) {
          $mdIcon(attrVal).then(function(svg) {
            element.append(svg);
          });
        }

      });
    }

    function parentsHaveText() {
      var parent = element.parent();
      if (parent.attr('aria-label') || parent.text()) {
        return true;
      }
      else if(parent.parent().attr('aria-label') || parent.parent().text()) {
        return true;
      }
      return false;
    }

    function prepareForFontIcon () {
      if (!scope.svgIcon && !scope.svgSrc) {

        if (scope.fontIcon) {
          element.addClass('md-font');
          element.addClass(scope.fontIcon);
        }

        if (scope.fontSet) {
          element.addClass($mdIcon.fontSet(scope.fontSet));
        }

        // For Material Design font icons, the class '.material-icons'
        // is auto-added IF a style has not been specified

        if (!scope.fontIcon && !scope.fontSet && !angular.isDefined(attr.class)) {

            element.addClass('material-icons');
        }
      }

    }
  }
}
