
angular.module('material.core')
  .service('$mdAria', AriaService);

/*
 * @ngInject
 */
function AriaService($$rAF, $log, $window) {

  return {
    expect: expect,
    expectAsync: expectAsync,
    expectWithText: expectWithText
  };

  /**
   * Check if expected attribute has been specified on the target element or child
   * @param element
   * @param attrName
   * @param {optional} defaultValue What to set the attr to if no value is found
   */
  function expect(element, attrName, defaultValue) {
    var node = element[0] || element;

    // if node exists and neither it nor its children have the attribute
    if (node &&
       ((!node.hasAttribute(attrName) ||
        node.getAttribute(attrName).length === 0) &&
        !childHasAttribute(node, attrName))) {

      defaultValue = angular.isString(defaultValue) ? defaultValue.trim() : '';
      if (defaultValue.length) {
        element.attr(attrName, defaultValue);
      } else {
        $log.warn('ARIA: Attribute "', attrName, '", required for accessibility, is missing on node:', node);
      }

    }
  }

  function expectAsync(element, attrName, defaultValueGetter) {
    // Problem: when retrieving the element's contents synchronously to find the label,
    // the text may not be defined yet in the case of a binding.
    // There is a higher chance that a binding will be defined if we wait one frame.
    $$rAF(function() {
      expect(element, attrName, defaultValueGetter());
    });
  }

  function expectWithText(element, attrName) {
    expectAsync(element, attrName, function() {
      return getText(element);
    });
  }

  function getText(element) {
    return element.text().trim();
  }

  function childHasAttribute(node, attrName) {
    var hasChildren = node.hasChildNodes(),
        hasAttr = false;

    function isHidden(el) {
      var style = el.currentStyle ? el.currentStyle : $window.getComputedStyle(el);
      return (style.display === 'none');
    }

    if(hasChildren) {
      var children = node.childNodes;
      for(var i=0; i<children.length; i++){
        var child = children[i];
        if(child.nodeType === 1 && child.hasAttribute(attrName)) {
          if(!isHidden(child)){
            hasAttr = true;
          }
        }
      }
    }
    return hasAttr;
  }
}
