/**
 * History.js HTML4 Support
 * Depends on the HTML5 Support
 * @author Benjamin Arthur Lupton <contact@balupton.com>
 * @copyright 2010-2011 Benjamin Arthur Lupton <contact@balupton.com>
 * @license New BSD License <http://creativecommons.org/licenses/BSD/>
 */

(function(window,undefined){
	"use strict";

	// ========================================================================
	// Initialise

	// Localise Globals
	var
		document = window.document, // Make sure we are using the correct document
		setTimeout = window.setTimeout||setTimeout,
		clearTimeout = window.clearTimeout||clearTimeout,
		setInterval = window.setInterval||setInterval,
		History = window.History = window.History||{}; // Public History Object

	// Check Existence
	if ( typeof History.initHtml4 !== 'undefined' ) {
		throw new Error('History.js HTML4 Support has already been loaded...');
	}


	// ========================================================================
	// Initialise HTML4 Support

	// Initialise HTML4 Support
	History.initHtml4 = function(){
		// Initialise
		if ( typeof History.initHtml4.initialized !== 'undefined' ) {
			// Already Loaded
			return false;
		}
		else {
			History.initHtml4.initialized = true;
		}


		// ====================================================================
		// Properties

		/**
		 * History.enabled
		 * Is History enabled?
		 */
		History.enabled = true;


		// ====================================================================
		// Hash Storage

		/**
		 * History.savedHashes
		 * Store the hashes in an array
		 */
		History.savedHashes = [];

		/**
		 * History.isLastHash(newHash)
		 * Checks if the hash is the last hash
		 * @param {string} newHash
		 * @return {boolean} true
		 */
		History.isLastHash = function(newHash){
			// Prepare
			var oldHash = History.getHashByIndex(),
				isLast;

			// Check
			isLast = newHash === oldHash;

			// Return isLast
			return isLast;
		};

		/**
		 * History.saveHash(newHash)
		 * Push a Hash
		 * @param {string} newHash
		 * @return {boolean} true
		 */
		History.saveHash = function(newHash){
			// Check Hash
			if ( History.isLastHash(newHash) ) {
				return false;
			}

			// Push the Hash
			History.savedHashes.push(newHash);

			// Return true
			return true;
		};

		/**
		 * History.getHashByIndex()
		 * Gets a hash by the index
		 * @param {integer} index
		 * @return {string}
		 */
		History.getHashByIndex = function(index){
			// Prepare
			var hash = null;

			// Handle
			if ( typeof index === 'undefined' ) {
				// Get the last inserted
				hash = History.savedHashes[History.savedHashes.length-1];
			}
			else if ( index < 0 ) {
				// Get from the end
				hash = History.savedHashes[History.savedHashes.length+index];
			}
			else {
				// Get from the beginning
				hash = History.savedHashes[index];
			}

			// Return hash
			return hash;
		};


		// ====================================================================
		// Discarded States

		/**
		 * History.discardedHashes
		 * A hashed array of discarded hashes
		 */
		History.discardedHashes = {};

		/**
		 * History.discardedStates
		 * A hashed array of discarded states
		 */
		History.discardedStates = {};

		/**
		 * History.discardState(State)
		 * Discards the state by ignoring it through History
		 * @param {object} State
		 * @return {true}
		 */
		History.discardState = function(discardedState,forwardState,backState){
			//History.debug('History.discardState', arguments);
			// Prepare
			var discardedStateHash = History.getHashByState(discardedState),
				discardObject;

			// Create Discard Object
			discardObject = {
				'discardedState': discardedState,
				'backState': backState,
				'forwardState': forwardState
			};

			// Add to DiscardedStates
			History.discardedStates[discardedStateHash] = discardObject;

			// Return true
			return true;
		};

		/**
		 * History.discardHash(hash)
		 * Discards the hash by ignoring it through History
		 * @param {string} hash
		 * @return {true}
		 */
		History.discardHash = function(discardedHash,forwardState,backState){
			//History.debug('History.discardState', arguments);
			// Create Discard Object
			var discardObject = {
				'discardedHash': discardedHash,
				'backState': backState,
				'forwardState': forwardState
			};

			// Add to discardedHash
			History.discardedHashes[discardedHash] = discardObject;

			// Return true
			return true;
		};

		/**
		 * History.discardState(State)
		 * Checks to see if the state is discarded
		 * @param {object} State
		 * @return {bool}
		 */
		History.discardedState = function(State){
			// Prepare
			var StateHash = History.getHashByState(State),
				discarded;

			// Check
			discarded = History.discardedStates[StateHash]||false;

			// Return true
			return discarded;
		};

		/**
		 * History.discardedHash(hash)
		 * Checks to see if the state is discarded
		 * @param {string} State
		 * @return {bool}
		 */
		History.discardedHash = function(hash){
			// Check
			var discarded = History.discardedHashes[hash]||false;

			// Return true
			return discarded;
		};

		/**
		 * History.recycleState(State)
		 * Allows a discarded state to be used again
		 * @param {object} data
		 * @param {string} title
		 * @param {string} url
		 * @return {true}
		 */
		History.recycleState = function(State){
			//History.debug('History.recycleState', arguments);
			// Prepare
			var StateHash = History.getHashByState(State);

			// Remove from DiscardedStates
			if ( History.discardedState(State) ) {
				delete History.discardedStates[StateHash];
			}

			// Return true
			return true;
		};


		// ====================================================================
		// HTML4 HashChange Support

		if ( History.emulated.hashChange ) {
			/*
			 * We must emulate the HTML4 HashChange Support by manually checking for hash changes
			 */

			/**
			 * History.hashChangeInit()
			 * Init the HashChange Emulation
			 */
			History.hashChangeInit = function(){
				// Define our Checker Function
				History.checkerFunction = null;

				// Define some variables that will help in our checker function
				var lastDocumentHash = '',
					iframeId, iframe,
					lastIframeHash, checkerRunning;

				// Handle depending on the browser
				if ( History.isInternetExplorer() ) {
					// IE6 and IE7
					// We need to use an iframe to emulate the back and forward buttons

					// Create iFrame
					iframeId = 'historyjs-iframe';
					iframe = document.createElement('iframe');

					// Adjust iFarme
					iframe.setAttribute('id', iframeId);
					iframe.style.display = 'none';

					// Append iFrame
					document.body.appendChild(iframe);

					// Create initial history entry
					iframe.contentWindow.document.open();
					iframe.contentWindow.document.close();

					// Define some variables that will help in our checker function
					lastIframeHash = '';
					checkerRunning = false;

					// Define the checker function
					History.checkerFunction = function(){
						// Check Running
						if ( checkerRunning ) {
							return false;
						}

						// Update Running
						checkerRunning = true;

						// Fetch
						var documentHash = History.getHash()||'',
							iframeHash = History.unescapeHash(iframe.contentWindow.document.location.hash)||'';

						// The Document Hash has changed (application caused)
						if ( documentHash !== lastDocumentHash ) {
							// Equalise
							lastDocumentHash = documentHash;

							// Create a history entry in the iframe
							if ( iframeHash !== documentHash ) {
								//History.debug('hashchange.checker: iframe hash change', 'documentHash (new):', documentHash, 'iframeHash (old):', iframeHash);

								// Equalise
								lastIframeHash = iframeHash = documentHash;

								// Create History Entry
								iframe.contentWindow.document.open();
								iframe.contentWindow.document.close();

								// Update the iframe's hash
								iframe.contentWindow.document.location.hash = History.escapeHash(documentHash);
							}

							// Trigger Hashchange Event
							History.Adapter.trigger(window,'hashchange');
						}

						// The iFrame Hash has changed (back button caused)
						else if ( iframeHash !== lastIframeHash ) {
							//History.debug('hashchange.checker: iframe hash out of sync', 'iframeHash (new):', iframeHash, 'documentHash (old):', documentHash);

							// Equalise
							lastIframeHash = iframeHash;

							// Update the Hash
							History.setHash(iframeHash,false);
						}

						// Reset Running
						checkerRunning = false;

						// Return true
						return true;
					};
				}
				else {
					// We are not IE
					// Firefox 1 or 2, Opera

					// Define the checker function
					History.checkerFunction = function(){
						// Prepare
						var documentHash = History.getHash();

						// The Document Hash has changed (application caused)
						if ( documentHash !== lastDocumentHash ) {
							// Equalise
							lastDocumentHash = documentHash;

							// Trigger Hashchange Event
							History.Adapter.trigger(window,'hashchange');
						}

						// Return true
						return true;
					};
				}

				// Apply the checker function
				History.intervalList.push(setInterval(History.checkerFunction, History.options.hashChangeInterval));

				// Done
				return true;
			}; // History.hashChangeInit

			// Bind hashChangeInit
			History.Adapter.onDomLoad(History.hashChangeInit);

		} // History.emulated.hashChange


		// ====================================================================
		// HTML5 State Support

		// Non-Native pushState Implementation
		if ( History.emulated.pushState ) {
			/*
			 * We must emulate the HTML5 State Management by using HTML4 HashChange
			 */

			/**
			 * History.onHashChange(event)
			 * Trigger HTML5's window.onpopstate via HTML4 HashChange Support
			 */
			History.onHashChange = function(event){
				//History.debug('History.onHashChange', arguments);

				// Prepare
				var currentUrl = ((event && event.newURL) || document.location.href),
					currentHash = History.getHashByUrl(currentUrl),
					currentState = null,
					currentStateHash = null,
					currentStateHashExits = null,
					discardObject;

				// Check if we are the same state
				if ( History.isLastHash(currentHash) ) {
					// There has been no change (just the page's hash has finally propagated)
					//History.debug('History.onHashChange: no change');
					History.busy(false);
					return false;
				}

				// Reset the double check
				History.doubleCheckComplete();

				// Store our location for use in detecting back/forward direction
				History.saveHash(currentHash);

				// Expand Hash
				if ( currentHash && History.isTraditionalAnchor(currentHash) ) {
					//History.debug('History.onHashChange: traditional anchor', currentHash);
					// Traditional Anchor Hash
					History.Adapter.trigger(window,'anchorchange');
					History.busy(false);
					return false;
				}

				// Create State
				currentState = History.extractState(History.getFullUrl(currentHash||document.location.href,false),true);

				// Check if we are the same state
				if ( History.isLastSavedState(currentState) ) {
					//History.debug('History.onHashChange: no change');
					// There has been no change (just the page's hash has finally propagated)
					History.busy(false);
					return false;
				}

				// Create the state Hash
				currentStateHash = History.getHashByState(currentState);

				// Check if we are DiscardedState
				discardObject = History.discardedState(currentState);
				if ( discardObject ) {
					// Ignore this state as it has been discarded and go back to the state before it
					if ( History.getHashByIndex(-2) === History.getHashByState(discardObject.forwardState) ) {
						// We are going backwards
						//History.debug('History.onHashChange: go backwards');
						History.back(false);
					} else {
						// We are going forwards
						//History.debug('History.onHashChange: go forwards');
						History.forward(false);
					}
					return false;
				}

				// Push the new HTML5 State
				//History.debug('History.onHashChange: success hashchange');
				History.pushState(currentState.data,currentState.title,currentState.url,false);

				// End onHashChange closure
				return true;
			};
			History.Adapter.bind(window,'hashchange',History.onHashChange);

			/**
			 * History.pushState(data,title,url)
			 * Add a new State to the history object, become it, and trigger onpopstate
			 * We have to trigger for HTML4 compatibility
			 * @param {object} data
			 * @param {string} title
			 * @param {string} url
			 * @return {true}
			 */
			History.pushState = function(data,title,url,queue){
				//History.debug('History.pushState: called', arguments);

				// Check the State
				if ( History.getHashByUrl(url) ) {
					throw new Error('History.js does not support states with fragement-identifiers (hashes/anchors).');
				}

				// Handle Queueing
				if ( queue !== false && History.busy() ) {
					// Wait + Push to Queue
					//History.debug('History.pushState: we must wait', arguments);
					History.pushQueue({
						scope: History,
						callback: History.pushState,
						args: arguments,
						queue: queue
					});
					return false;
				}

				// Make Busy
				History.busy(true);

				// Fetch the State Object
				var newState = History.createStateObject(data,title,url),
					newStateHash = History.getHashByState(newState),
					oldState = History.getState(false),
					oldStateHash = History.getHashByState(oldState),
					html4Hash = History.getHash();

				// Store the newState
				History.storeState(newState);
				History.expectedStateId = newState.id;

				// Recycle the State
				History.recycleState(newState);

				// Force update of the title
				History.setTitle(newState);

				// Check if we are the same State
				if ( newStateHash === oldStateHash ) {
					//History.debug('History.pushState: no change', newStateHash);
					History.busy(false);
					return false;
				}

				// Update HTML4 Hash
				if ( newStateHash !== html4Hash && newStateHash !== History.getShortUrl(document.location.href) ) {
					//History.debug('History.pushState: update hash', newStateHash, html4Hash);
					History.setHash(newStateHash,false);
					return false;
				}

				// Update HTML5 State
				History.saveState(newState);

				// Fire HTML5 Event
				//History.debug('History.pushState: trigger popstate');
				History.Adapter.trigger(window,'statechange');
				History.busy(false);

				// End pushState closure
				return true;
			};

			/**
			 * History.replaceState(data,title,url)
			 * Replace the State and trigger onpopstate
			 * We have to trigger for HTML4 compatibility
			 * @param {object} data
			 * @param {string} title
			 * @param {string} url
			 * @return {true}
			 */
			History.replaceState = function(data,title,url,queue){
				//History.debug('History.replaceState: called', arguments);

				// Check the State
				if ( History.getHashByUrl(url) ) {
					throw new Error('History.js does not support states with fragement-identifiers (hashes/anchors).');
				}

				// Handle Queueing
				if ( queue !== false && History.busy() ) {
					// Wait + Push to Queue
					//History.debug('History.replaceState: we must wait', arguments);
					History.pushQueue({
						scope: History,
						callback: History.replaceState,
						args: arguments,
						queue: queue
					});
					return false;
				}

				// Make Busy
				History.busy(true);

				// Fetch the State Objects
				var newState        = History.createStateObject(data,title,url),
					oldState        = History.getState(false),
					previousState   = History.getStateByIndex(-2);

				// Discard Old State
				History.discardState(oldState,newState,previousState);

				// Alias to PushState
				History.pushState(newState.data,newState.title,newState.url,false);

				// End replaceState closure
				return true;
			};

		} // History.emulated.pushState



		// ====================================================================
		// Initialise

		// Non-Native pushState Implementation
		if ( History.emulated.pushState ) {
			/**
			 * Ensure initial state is handled correctly
			 */
			if ( History.getHash() && !History.emulated.hashChange ) {
				History.Adapter.onDomLoad(function(){
					History.Adapter.trigger(window,'hashchange');
				});
			}

		} // History.emulated.pushState

	}; // History.initHtml4

	// Try and Initialise History
	if ( typeof History.init !== 'undefined' ) {
		History.init();
	}

})(window);
