//
// "menu.js"
// A Menu Enhancement Library
//
(function(){
	
	var items = {};
	var domImpl = document.implementation;
	var hasMouseEnter = domImpl.hasFeature("Events.mouseenter", "3.0");
	var hasMouseLeave = domImpl.hasFeature("Events.mouseleave", "3.0");
	var started = false;
	
	// Abstraction layer for event registration differences
	function addListener(obj, event, handler) {
		if (obj.addEventListener) {
			// Code for IE9, Firefox, Chrome, Safari, etc.
			obj.addEventListener(event, handler, false);
		} else {
			// Code for IE8 and lower
			obj.attachEvent("on" + event, function(){handler.call(obj, arguments)});
		}
	}

	// Initialize menu summaries
	function init() {
		if(started) return;
		started = true;
		var summaries = document.querySelectorAll(".menu .summary");
		for(var i = 0; i < summaries.length; i++) {
			initSummary(summaries[i]);
		}
		addListener(window, "keydown", seek);
	}
	
	// Retrieve the character associated with an event
	function getChar(e) {
		if(e.key) {
			if(e.key.length == 1) return e.key.toLowerCase();
		} else if (e.keyCode && e.keyCode >= 65 && e.keyCode <= 90) {
			return String.fromCharCode(e.keyCode).toLowerCase();
		}
	}
	
	//
	// Menu Event Handlers
	//

	// Seek out typing of menu item names
	var name = "", timeout;
	function seek(e) {
		clearTimeout(timeout);
		name += getChar(e) || "";
		if(items[name]) items[name].focus();
		timeout = setTimeout(function(){name=""}, 750);
	}

	// Display a single summary
	function showSummary(e) {
		var elm = this;
		elm.summary.style.display = "block";
	}

	// Hide a single summary
	function hideSummary(e) {
		var elm = this;
		elm.summary.style.display = "none";
	}

	//
	// Initialization Methods
	//

	// Add listeners to show/hide summaries when needed
	function initSummary(summary) {
		// Link menu item with summary
		var menuitem = summary.parentNode;
		var name = menuitem.querySelector(".name").firstChild.nodeValue.toLowerCase();
		menuitem.summary = summary;
		items[name] = menuitem;
		
		// Hide summary
		summary.style.display = "none";
		
		// Hook show/hide focus listeners
		addListener(menuitem, "focus", showSummary);
		addListener(menuitem, "blur", hideSummary);
		
		// Hook show/hide mouse listeners
		if(hasMouseEnter && hasMouseLeave) {
			addListener(menuitem, "mouseenter", showSummary);
			addListener(menuitem, "mouseleave", hideSummary);
		} else {
			addListener(menuitem, "mouseover", showSummary);
			addListener(menuitem, "mouseout", hideSummary);
		}
	}

    // DON'T USE THIS: 
    // Simulate known compatibility patterns.
    // In the real-world, this typically happens after an "if IE" check.    
    var write = document.write;
    write("Menu framework loaded.");
    
	addListener(window, "load", init);
	addListener(document, "DOMContentLoaded", init);
})()