/**
 * File navigation.js.
 *
 * Handles toggling the navigation menu for small screens and enables TAB key
 * navigation support for dropdown menus.
 */
(function () {
	var container, button, menu, links, subMenus, i, len;

	container = document.getElementById('site-navigation');
	if ( !container ) {
		return;
	}

	button = container.getElementsByTagName('button')[ 0 ];
	if ( 'undefined' === typeof button ) {
		return;
	}

	menu = container.getElementsByTagName('ul')[ 0 ];

	// Hide menu toggle button if menu is empty and return early.
	if ( 'undefined' === typeof menu ) {
		button.style.display = 'none';
		return;
	}

	menu.setAttribute('aria-expanded', 'false');
	if ( -1 === menu.className.indexOf('nav-menu') ) {
		menu.className += ' nav-menu';
	}

	button.onclick = function () {
		if ( -1 !== container.className.indexOf('toggled') ) {
			container.className = container.className.replace(' toggled', '');
			button.setAttribute('aria-expanded', 'false');
			menu.setAttribute('aria-expanded', 'false');
		} else {
			container.className += ' toggled';
			button.setAttribute('aria-expanded', 'true');
			menu.setAttribute('aria-expanded', 'true');
		}
	};

	window.addEventListener('resize', function () {
		var width = window.innerWidth;
		if ( width > 600 && -1 !== container.className.indexOf('toggled') ) {
			container.className = container.className.replace(' toggled', '');
			button.setAttribute('aria-expanded', 'false');
			menu.setAttribute('aria-expanded', 'false');
		}
	}, true);

	// Get all the link elements within the menu.
	links = menu.getElementsByTagName('a');
	subMenus = menu.getElementsByTagName('ul');

	// Set menu items with submenus to aria-haspopup="true".
	for ( i = 0, len = subMenus.length; i < len; i++ ) {
		subMenus[ i ].parentNode.setAttribute('aria-haspopup', 'true');
	}

	// Each time a menu link is focused or blurred, toggle focus.
	for ( i = 0, len = links.length; i < len; i++ ) {
		links[ i ].addEventListener('focus', toggleFocus, true);
		links[ i ].addEventListener('blur', toggleFocus, true);
	}

	/**
	 * Sets or removes .focus class on an element.
	 */
	function toggleFocus() {
		var self = this;

		// Move up through the ancestors of the current link until we hit .nav-menu.
		while ( -1 === self.className.indexOf('nav-menu') ) {

			// On li elements toggle the class .focus.
			if ( 'li' === self.tagName.toLowerCase() ) {
				if ( -1 !== self.className.indexOf('focus') ) {
					self.className = self.className.replace(' focus', '');
				} else {
					self.className += ' focus';
				}
			}

			self = self.parentElement;
		}
	}
})();