(function (root, factory) {
	if ( typeof define === 'function' && define.amd ) {
		define([], function () {
			return factory(root);
		});
	} else if ( typeof exports === 'object' ) {
		module.exports = factory(root);
	} else {
		root.Tabby = factory(root);
	}
})(typeof global !== 'undefined' ? global : typeof window !== 'undefined' ? window : this, function (window) {

	'use strict';

	//
	// Variables
	//

	var defaults = {
		idPrefix: 'tabby-toggle_',
		default: '[data-tabby-default]'
	};


	//
	// Methods
	//

	/**
	 * Merge two or more objects together.
	 * @param   {Object}   objects  The objects to merge together
	 * @returns {Object}            Merged values of defaults and options
	 */
	var extend = function () {
		var merged = {};
		Array.prototype.forEach.call(arguments, function (obj) {
			for (var key in obj) {
				if (!obj.hasOwnProperty(key)) return;
				merged[key] = obj[key];
			}
		});
		return merged;
	};

	/**
	 * Emit a custom event
	 * @param  {String} type    The event type
	 * @param  {Node}   tab     The tab to attach the event to
	 * @param  {Node}   details Details about the event
	 */
	var emitEvent = function (tab, details) {

		// Create a new event
		var event;
		if (typeof window.CustomEvent === 'function') {
			event = new CustomEvent('tabby', {
				bubbles: true,
				cancelable: true,
				detail: details
			});
		} else {
			event = document.createEvent('CustomEvent');
			event.initCustomEvent('tabby', true, true, details);
		}

		// Dispatch the event
		tab.dispatchEvent(event);

	};

	/**
	 * Remove roles and attributes from a tab and its content
	 * @param  {Node}   tab      The tab
	 * @param  {Node}   content  The tab content
	 * @param  {Object} settings User settings and options
	 */
	var destroyTab = function (tab, content, settings) {

		// Remove the generated ID
		if (tab.id.slice(0, settings.idPrefix.length) === settings.idPrefix) {
			tab.id = '';
		}

		// Remove roles
		tab.removeAttribute('role');
		tab.removeAttribute('aria-controls');
		tab.removeAttribute('aria-selected');
		tab.removeAttribute('tabindex');
		tab.closest('li').removeAttribute('role');
		content.removeAttribute('role');
		content.removeAttribute('aria-labelledby');
		content.removeAttribute('hidden');

	};

	/**
	 * Add the required roles and attributes to a tab and its content
	 * @param  {Node}   tab      The tab
	 * @param  {Node}   content  The tab content
	 * @param  {Object} settings User settings and options
	 */
	var setupTab = function (tab, content, settings) {

		// Give tab an ID if it doesn't already have one
		if (!tab.id) {
			tab.id = settings.idPrefix + content.id;
		}

		// Add roles
		tab.setAttribute('role', 'tab');
		tab.setAttribute('aria-controls', content.id);
		tab.closest('li').setAttribute('role', 'presentation');
		content.setAttribute('role', 'tabpanel');
		content.setAttribute('aria-labelledby', tab.id);

		// Add selected state
		if (tab.matches(settings.default)) {
			tab.setAttribute('aria-selected', 'true');
		} else {
			tab.setAttribute('aria-selected', 'false');
			tab.setAttribute('tabindex', '-1');
			content.setAttribute('hidden', 'hidden');
		}

	};

	/**
	 * Hide a tab and its content
	 * @param  {Node} newTab The new tab that's replacing it
	 */
	var hide = function (newTab) {

		// Variables
		var tabGroup = newTab.closest('[role="tablist"]');
		if (!tabGroup) return {};
		var tab = tabGroup.querySelector('[role="tab"][aria-selected="true"]');
		if (!tab) return {};
		var content = document.querySelector(tab.hash);

		// Hide the tab
		tab.setAttribute('aria-selected', 'false');
		tab.setAttribute('tabindex', '-1');

		// Hide the content
		if (!content) return {previousTab: tab};
		content.setAttribute('hidden', 'hidden');

		// Return the hidden tab and content
		return {
			previousTab: tab,
			previousContent: content
		};

	};

	/**
	 * Show a tab and its content
	 * @param  {Node} tab      The tab
	 * @param  {Node} content  The tab content
	 */
	var show = function (tab, content) {
		tab.setAttribute('aria-selected', 'true');
		tab.setAttribute('tabindex', '0');
		content.removeAttribute('hidden');
		tab.focus();
	};

	/**
	 * Toggle a new tab
	 * @param  {Node} tab The tab to show
	 */
	var toggle = function (tab) {

		// Make sure there's a tab to toggle and it's not already active
		if (!tab || tab.getAttribute('aria-selected') == 'true') return;

		// Variables
		var content = document.querySelector(tab.hash);
		if (!content) return;

		// Hide active tab and content
		var details = hide(tab);

		// Show new tab and content
		show(tab, content);

		// Add event details
		details.tab = tab;
		details.content = content;

		// Emit a custom event
		emitEvent(tab, details);

	};

	/**
	 * Get all of the tabs in a tablist
	 * @param  {Node}   tab  A tab from the list
	 * @return {Object}      The tabs and the index of the currently active one
	 */
	var getTabsMap = function (tab) {
		var tabGroup = tab.closest('[role="tablist"]');
		var tabs = tabGroup ? tabGroup.querySelectorAll('[role="tab"]') : null;
		if (!tabs) return;
		return {
			tabs: tabs,
			index: Array.prototype.indexOf.call(tabs, tab)
		};
	};

	/**
	 * Switch the active tab based on keyboard activity
	 * @param  {Node} tab The currently active tab
	 * @param  {Key}  key The key that was pressed
	 */
	var switchTabs = function (tab, key) {

		// Get a map of tabs
		var map = getTabsMap(tab);
		if (!map) return;
		var length = map.tabs.length - 1;
		var index;

		// Go to previous tab
		if (['ArrowUp', 'ArrowLeft', 'Up', 'Left'].indexOf(key) > -1) {
			index = map.index < 1 ? length : map.index - 1;
		}

		// Go to next tab
		else if (['ArrowDown', 'ArrowRight', 'Down', 'Right'].indexOf(key) > -1) {
			index = map.index === length ? 0 : map.index + 1;
		}

		// Go to home
		else if (key === 'Home') {
			index = 0;

		}

		// Go to end
		else if (key === 'End') {
			index = length;
		}

		// Toggle the tab
		toggle(map.tabs[index]);

	};

	/**
	 * Activate a tab based on the URL
	 * @param  {String} selector The selector for this instantiation
	 */
	var loadFromURL = function (selector) {
		if (window.location.hash.length < 1) return;
		var tab = document.querySelector(selector + ' [role="tab"][href*="' + window.location.hash + '"]');
		toggle(tab);
	};

	/**
	 * Create the Constructor object
	 */
	var Constructor = function (selector, options) {

		//
		// Variables
		//

		var publicAPIs = {};
		var settings, tabWrapper;


		//
		// Methods
		//

		publicAPIs.destroy = function () {

			// Get all tabs
			var tabs = tabWrapper.querySelectorAll('a');

			// Add roles to tabs
			Array.prototype.forEach.call(tabs, function (tab) {

				// Get the tab content
				var content = document.querySelector(tab.hash);
				if (!content) return;

				// Setup the tab
				destroyTab(tab, content, settings);

			});

			// Remove role from wrapper
			tabWrapper.removeAttribute('role');

			// Remove event listeners
			document.documentElement.removeEventListener('click', clickHandler, true);
			tabWrapper.removeEventListener('keydown', keyHandler, true);

			// Reset variables
			settings = null;
			tabWrapper = null;

		};

		/**
		 * Setup the DOM with the proper attributes
		 */
		publicAPIs.setup = function () {

			// Variables
			tabWrapper = document.querySelector(selector);
			if (!tabWrapper) return;
			var tabs = tabWrapper.querySelectorAll('a');

			// Add role to wrapper
			tabWrapper.setAttribute('role', 'tablist');

			// Add roles to tabs
			Array.prototype.forEach.call(tabs, function (tab) {

				// Get the tab content
				var content = document.querySelector(tab.hash);
				if (!content) return;

				// Setup the tab
				setupTab(tab, content, settings);

			});

		};

		/**
		 * Toggle a tab based on an ID
		 * @param  {String|Node} id The tab to toggle
		 */
		publicAPIs.toggle = function (id) {

			// Get the tab
			var tab = id;
			if (typeof id === 'string') {
				tab = document.querySelector(selector + ' [role="tab"][href*="' + id + '"]');
			}

			// Toggle the tab
			toggle(tab);

		};

		/**
		 * Handle click events
		 */
		var clickHandler = function (event) {

			// Only run on toggles
			var tab = event.target.closest(selector + ' [role="tab"]');
			if (!tab) return;

			// Prevent link behavior
			event.preventDefault();

			// Toggle the tab
			toggle(tab);

		};

		/**
		 * Handle keydown events
		 */
		var keyHandler = function (event) {

			// Only run if a tab is in focus
			var tab = document.activeElement;
			if (!tab.matches(selector + ' [role="tab"]')) return;

			// Only run for specific keys
			if (['ArrowUp', 'ArrowDown', 'ArrowLeft', 'ArrowRight', 'Up', 'Down', 'Left', 'Right', 'Home', 'End'].indexOf(event.key) < 0) return;

			// Switch tabs
			switchTabs(tab, event.key);

		};

		/**
		 * Initialize the instance
		 */
		var init = function () {

			// Merge user options with defaults
			settings = extend(defaults, options || {});

			// Setup the DOM
			publicAPIs.setup();

			// Load a tab from the URL
			loadFromURL(selector);

			// Add event listeners
			document.documentElement.addEventListener('click', clickHandler, true);
			tabWrapper.addEventListener('keydown', keyHandler, true);

		};


		//
		// Initialize and return the Public APIs
		//

		init();
		return publicAPIs;

	};


	//
	// Return the Constructor
	//

	return Constructor;

});