/*
	Copyright (c) 2004-2008, The Dojo Foundation
	All Rights Reserved.

	Licensed under the Academic Free License version 2.1 or above OR the
	modified BSD license. For more information on Dojo licensing, see:

		http://dojotoolkit.org/book/dojo-book-0-9/introduction/licensing
*/


if(!dojo._hasResource["dojo.back"]){ //_hasResource checks added by build. Do not use _hasResource directly in your code.
dojo._hasResource["dojo.back"] = true;
dojo.provide("dojo.back");

/*=====
dojo.back = {
	// summary: Browser history management resources
}
=====*/


(function(){ 
	var back = dojo.back;

	// everyone deals with encoding the hash slightly differently

	function getHash(){ 
		var h = window.location.hash;
		if(h.charAt(0) == "#"){ h = h.substring(1); }
		return dojo.isMozilla ? h : decodeURIComponent(h); 
	}
	
	function setHash(h){
		if(!h){ h = ""; }
		window.location.hash = encodeURIComponent(h);
		historyCounter = history.length;
	}
	
	// if we're in the test for these methods, expose them on dojo.back. ok'd with alex.
	if(dojo.exists("tests.back-hash")){
		back.getHash = getHash;
		back.setHash = setHash;		
	}
	
	var initialHref = (typeof(window) !== "undefined") ? window.location.href : "";
	var initialHash = (typeof(window) !== "undefined") ? getHash() : "";
	var initialState = null;

	var locationTimer = null;
	var bookmarkAnchor = null;
	var historyIframe = null;
	var forwardStack = [];
	var historyStack = [];
	var moveForward = false;
	var changingUrl = false;
	var historyCounter;

	function handleBackButton(){
		//summary: private method. Do not call this directly.

		//The "current" page is always at the top of the history stack.
		//console.debug("handlingBackButton");
		var current = historyStack.pop();
		if(!current){ return; }
		var last = historyStack[historyStack.length-1];
		if(!last && historyStack.length == 0){
			last = initialState;
		}
		if(last){
			if(last.kwArgs["back"]){
				last.kwArgs["back"]();
			}else if(last.kwArgs["backButton"]){
				last.kwArgs["backButton"]();
			}else if(last.kwArgs["handle"]){
				last.kwArgs.handle("back");
			}
		}
		forwardStack.push(current);
		//console.debug("done handling back");
	}

	back.goBack = handleBackButton;

	function handleForwardButton(){
		//summary: private method. Do not call this directly.
		//console.debug("handling forward");
		var last = forwardStack.pop();
		if(!last){ return; }
		if(last.kwArgs["forward"]){
			last.kwArgs.forward();
		}else if(last.kwArgs["forwardButton"]){
			last.kwArgs.forwardButton();
		}else if(last.kwArgs["handle"]){
			last.kwArgs.handle("forward");
		}
		historyStack.push(last);
		//console.debug("done handling forward");
	}

	back.goForward = handleForwardButton;

	function createState(url, args, hash){
		//summary: private method. Do not call this directly.
		return {"url": url, "kwArgs": args, "urlHash": hash};	//Object
	}

	function getUrlQuery(url){
		//summary: private method. Do not call this directly.
		var segments = url.split("?");
		if(segments.length < 2){
			return null; //null
		}
		else{
			return segments[1]; //String
		}
	}
	
	function loadIframeHistory(){
		//summary: private method. Do not call this directly.
		var url = (dojo.config["dojoIframeHistoryUrl"] || dojo.moduleUrl("dojo", "resources/iframe_history.html")) + "?" + (new Date()).getTime();
		moveForward = true;
        if(historyIframe){
		    dojo.isSafari ? historyIframe.location = url : window.frames[historyIframe.name].location = url;
        }else{
            //console.warn("dojo.back: Not initialised. You need to call dojo.back.init() from a <script> block that lives inside the <body> tag.");
        }
		return url; //String
	}

	function checkLocation(){
		//console.debug("checking url");
		if(!changingUrl){
			var hsl = historyStack.length;
			
			var hash = getHash();

			if((hash === initialHash||window.location.href == initialHref)&&(hsl == 1)){
				// FIXME: could this ever be a forward button?
				// we can't clear it because we still need to check for forwards. Ugg.
				// clearInterval(this.locationTimer);
				handleBackButton();
				return;
			}
			
			// first check to see if we could have gone forward. We always halt on
			// a no-hash item.
			if(forwardStack.length > 0){
				if(forwardStack[forwardStack.length-1].urlHash === hash){
					handleForwardButton();
					return;
				}
			}
	
			// ok, that didn't work, try someplace back in the history stack
			if((hsl >= 2)&&(historyStack[hsl-2])){
				if(historyStack[hsl-2].urlHash === hash){
					handleBackButton();
					return;
				}
			}
			
			if(dojo.isSafari && dojo.isSafari < 3){
				var hisLen = history.length;
				if(hisLen > historyCounter) handleForwardButton();
				else if(hisLen < historyCounter) handleBackButton();
			  historyCounter = hisLen;
			}
		}
		//console.debug("done checking");
	};
	
	back.init = function(){
		//summary: Initializes the undo stack. This must be called from a <script> 
		//         block that lives inside the <body> tag to prevent bugs on IE.
		if(dojo.byId("dj_history")){ return; } // prevent reinit
		var src = dojo.config["dojoIframeHistoryUrl"] || dojo.moduleUrl("dojo", "resources/iframe_history.html");
		document.write('<iframe style="border:0;width:1px;height:1px;position:absolute;visibility:hidden;bottom:0;right:0;" name="dj_history" id="dj_history" src="' + src + '"></iframe>');
	};

	back.setInitialState = function(/*Object*/args){
		//summary: 
		//		Sets the state object and back callback for the very first page
		//		that is loaded.
		//description:
		//		It is recommended that you call this method as part of an event
		//		listener that is registered via dojo.addOnLoad().
		//args: Object
		//		See the addToHistory() function for the list of valid args properties.
		initialState = createState(initialHref, args, initialHash);
	};

	//FIXME: Make these doc comments not be awful. At least they're not wrong.
	//FIXME: Would like to support arbitrary back/forward jumps. Have to rework iframeLoaded among other things.
	//FIXME: is there a slight race condition in moz using change URL with the timer check and when
	//       the hash gets set? I think I have seen a back/forward call in quick succession, but not consistent.

	
	/*=====
	dojo.__backArgs = function(kwArgs){
		// back: Function?
		//		A function to be called when this state is reached via the user
		//		clicking the back button.
		//	forward: Function?
		//		Upon return to this state from the "back, forward" combination
		//		of navigation steps, this function will be called. Somewhat
		//		analgous to the semantic of an "onRedo" event handler.
		//	changeUrl: Boolean?|String?
		//		Boolean indicating whether or not to create a unique hash for
		//		this state. If a string is passed instead, it is used as the
		//		hash.
	}
	=====*/

	back.addToHistory = function(/*dojo.__backArgs*/ args){
		//	summary: 
		//		adds a state object (args) to the history list. 
		//	description:
		//		To support getting back button notifications, the object
		//		argument should implement a function called either "back",
		//		"backButton", or "handle". The string "back" will be passed as
		//		the first and only argument to this callback.
		//	
		//		To support getting forward button notifications, the object
		//		argument should implement a function called either "forward",
		//		"forwardButton", or "handle". The string "forward" will be
		//		passed as the first and only argument to this callback.
		//
		//		If you want the browser location string to change, define "changeUrl" on the object. If the
		//		value of "changeUrl" is true, then a unique number will be appended to the URL as a fragment
		//		identifier (http://some.domain.com/path#uniquenumber). If it is any other value that does
		//		not evaluate to false, that value will be used as the fragment identifier. For example,
		//		if changeUrl: 'page1', then the URL will look like: http://some.domain.com/path#page1
		//
	 	//	example:
		//		|	dojo.back.addToHistory({
		//		|		back: function(){ console.debug('back pressed'); },
		//		|		forward: function(){ console.debug('forward pressed'); },
		//		|		changeUrl: true
		//		|	});

		//	BROWSER NOTES:
		//  Safari 1.2: 
		//	back button "works" fine, however it's not possible to actually
		//	DETECT that you've moved backwards by inspecting window.location.
		//	Unless there is some other means of locating.
		//	FIXME: perhaps we can poll on history.length?
		//	Safari 2.0.3+ (and probably 1.3.2+):
		//	works fine, except when changeUrl is used. When changeUrl is used,
		//	Safari jumps all the way back to whatever page was shown before
		//	the page that uses dojo.undo.browser support.
		//	IE 5.5 SP2:
		//	back button behavior is macro. It does not move back to the
		//	previous hash value, but to the last full page load. This suggests
		//	that the iframe is the correct way to capture the back button in
		//	these cases.
		//	Don't test this page using local disk for MSIE. MSIE will not create 
		//	a history list for iframe_history.html if served from a file: URL. 
		//	The XML served back from the XHR tests will also not be properly 
		//	created if served from local disk. Serve the test pages from a web 
		//	server to test in that browser.
		//	IE 6.0:
		//	same behavior as IE 5.5 SP2
		//	Firefox 1.0+:
		//	the back button will return us to the previous hash on the same
		//	page, thereby not requiring an iframe hack, although we do then
		//	need to run a timer to detect inter-page movement.

		//If addToHistory is called, then that means we prune the
		//forward stack -- the user went back, then wanted to
		//start a new forward path.
		forwardStack = []; 

		var hash = null;
		var url = null;
		if(!historyIframe){
			if(dojo.config["useXDomain"] && !dojo.config["dojoIframeHistoryUrl"]){
				console.debug("dojo.back: When using cross-domain Dojo builds,"
					+ " please save iframe_history.html to your domain and set djConfig.dojoIframeHistoryUrl"
					+ " to the path on your domain to iframe_history.html");
			}
			historyIframe = window.frames["dj_history"];
		}
		if(!bookmarkAnchor){
			bookmarkAnchor = document.createElement("a");
			dojo.body().appendChild(bookmarkAnchor);
			bookmarkAnchor.style.display = "none";
		}
		if(args["changeUrl"]){
			hash = ""+ ((args["changeUrl"]!==true) ? args["changeUrl"] : (new Date()).getTime());
			
			//If the current hash matches the new one, just replace the history object with
			//this new one. It doesn't make sense to track different state objects for the same
			//logical URL. This matches the browser behavior of only putting in one history
			//item no matter how many times you click on the same #hash link, at least in Firefox
			//and Safari, and there is no reliable way in those browsers to know if a #hash link
			//has been clicked on multiple times. So making this the standard behavior in all browsers
			//so that dojo.back's behavior is the same in all browsers.
			if(historyStack.length == 0 && initialState.urlHash == hash){
				initialState = createState(url, args, hash);
				return;
			}else if(historyStack.length > 0 && historyStack[historyStack.length - 1].urlHash == hash){
				historyStack[historyStack.length - 1] = createState(url, args, hash);
				return;
			}

			changingUrl = true;
			setTimeout(function() { 
					setHash(hash); 
					changingUrl = false; 					
				}, 1);
			bookmarkAnchor.href = hash;
			
			if(dojo.isIE){
				url = loadIframeHistory();

				var oldCB = args["back"]||args["backButton"]||args["handle"];

				//The function takes handleName as a parameter, in case the
				//callback we are overriding was "handle". In that case,
				//we will need to pass the handle name to handle.
				var tcb = function(handleName){
					if(getHash() != ""){
						setTimeout(function() { setHash(hash); }, 1);
					}
					//Use apply to set "this" to args, and to try to avoid memory leaks.
					oldCB.apply(this, [handleName]);
				};
		
				//Set interceptor function in the right place.
				if(args["back"]){
					args.back = tcb;
				}else if(args["backButton"]){
					args.backButton = tcb;
				}else if(args["handle"]){
					args.handle = tcb;
				}
		
				var oldFW = args["forward"]||args["forwardButton"]||args["handle"];
		
				//The function takes handleName as a parameter, in case the
				//callback we are overriding was "handle". In that case,
				//we will need to pass the handle name to handle.
				var tfw = function(handleName){
					if(getHash() != ""){
						setHash(hash);
					}
					if(oldFW){ // we might not actually have one
						//Use apply to set "this" to args, and to try to avoid memory leaks.
						oldFW.apply(this, [handleName]);
					}
				};

				//Set interceptor function in the right place.
				if(args["forward"]){
					args.forward = tfw;
				}else if(args["forwardButton"]){
					args.forwardButton = tfw;
				}else if(args["handle"]){
					args.handle = tfw;
				}

			}else if(!dojo.isIE){
				// start the timer
				if(!locationTimer){
					locationTimer = setInterval(checkLocation, 200);
				}
				
			}
		}else{
			url = loadIframeHistory();
		}

		historyStack.push(createState(url, args, hash));
	};

	back._iframeLoaded = function(evt, ifrLoc){
		//summary: 
		//		private method. Do not call this directly.
		var query = getUrlQuery(ifrLoc.href);
		if(query == null){ 
			// alert("iframeLoaded");
			// we hit the end of the history, so we should go back
			if(historyStack.length == 1){
				handleBackButton();
			}
			return;
		}
		if(moveForward){
			// we were expecting it, so it's not either a forward or backward movement
			moveForward = false;
			return;
		}
	
		//Check the back stack first, since it is more likely.
		//Note that only one step back or forward is supported.
		if(historyStack.length >= 2 && query == getUrlQuery(historyStack[historyStack.length-2].url)){
			handleBackButton();
		}else if(forwardStack.length > 0 && query == getUrlQuery(forwardStack[forwardStack.length-1].url)){
			handleForwardButton();
		}
	};
 })();

}
