M.block_accessibility = {
	/*
		Note: As of 29.04.2014. no duplicate CSS declaration in both module.js and userstyles.php
		CSS is now declared and generated based on user settings in a single point - userstyles.php
		module.js script updates user settings and fetch updated stylesheet over AJAX for each action
	*/

	ATBAR_SRC: 'https://core.atbar.org/atbar/en/latest/atbar.min.js',

	// font sizes in %, this is defined in changesize.php as well
	DEFAULT_FONTSIZE: 100,
	MAX_FONTSIZE: 197,
	MIN_FONTSIZE: 77,

	// only in JS-mode, because .getStyle('fontSize') will return computed style in px
	DAFAULT_PX_FONTSIZE: 13,
	MAX_PX_FONTSIZE: 26,
	MIN_PX_FONTSIZE: 10+1, // +1 because of unknown error...YUI for 77% returns style of 11px

	MAIN_SELECTOR : '#page', // userstyles.php applies CSS font-size to this element

	//stylesheet: '',

	sheetnode: '',

	instance_id: '',

	defaultsize: null,

	watch: null,

	debug: false,

	transactionsCount: 0, // AJAX transactions

	init: function(Y, autoload_atbar, instance_id) {
		// keep in mind that dynamic AJAX mode cannot work properly with IE <= 8 (for now), so this script will not even be loaded in block_accessibillity.php


		// TO-DO: determine if block is visible (for example in chat session is not)

		this.Y = Y;
		this.instance_id = instance_id;
		
		this.sheetnode = Y.one('link[href="'+M.cfg.wwwroot+
			'/blocks/accessibility/userstyles.php?instance_id='+instance_id+'"]');
		//this.stylesheet = Y.StyleSheet(this.sheetnode);

		// Set default font size
		//this.log('Initial size: '+Y.one('body').getStyle('fontSize'));
		//this.defaultsize = M.block_accessibility.get_current_fontsize('body'); // this is disabled because it gives false results...
		this.defaultsize = M.block_accessibility.DEFAULT_FONTSIZE; 

		// Attach the click handler
		Y.all('#block_accessibility_textresize a').on('click', function(e) {
			if (!e.target.hasClass('disabled')) {
				// If it is, and the button's not disabled, pass it's id to the changesize function
				M.block_accessibility.changesize(e.target);
			}
		});

		Y.all('#block_accessibility_changecolour a').on('click', function(e) {
			if (!e.target.hasClass('disabled')) {
				// If it is, and the button's not disabled, pass it's id to the changecolour function
				M.block_accessibility.changecolour(e.target);
			}
		});

		// Remove href attributes from anchors
		Y.all('#accessibility_controls a').each(function(node){
			node.removeAttribute('href');
		});

		// ATBar might be disabled in block's config
		if(Y.one('#atbar_auto') !== null){
			// checkbox for setting 'always' chackbox
		   Y.one('#atbar_auto').on('click', function(e) {
				if (e.target.get('checked')) {
					M.block_accessibility.atbar_autoload('on');
				} else {
					M.block_accessibility.atbar_autoload('off');
				}
			});
			
			// Create Bookmarklet-style link using code from ATbar site
			// http://access.ecs.soton.ac.uk/StudyBar/versions
			Y.one('#block_accessibility_launchtoolbar').on('click', function() {
				M.block_accessibility.load_atbar();

				// Do we really need it?
				// Hide block buttons until ATbar is closed
				Y.one('#block_accessibility_textresize').setStyle('display', 'none');
				Y.one('#block_accessibility_changecolour').setStyle('display', 'none');
				M.block_accessibility.watch_atbar_for_close();
			});

			if (autoload_atbar) {
				M.block_accessibility.load_atbar();
				// Hide block buttons until ATbar is closed
				Y.one('#block_accessibility_textresize').setStyle('display', 'none');
				Y.one('#block_accessibility_changecolour').setStyle('display', 'none');
				// Wait 1 second to give the bar a chance to load
				setTimeout("M.block_accessibility.watch_atbar_for_close();", 1000);
			}
		}



		// assign loader icon events
		// Y.on('io:start', M.block_accessibility.show_loading); // this triggers even for io actions outside block causing conflicts
		// Y.on('io:complete', M.block_accessibility.hide_loading);
	},


	/**
	 *  Code from ATbar bookmarklet to load bar into page
	 */
	load_atbar: function() {
		var jf = document.createElement('script');
		jf.src = M.block_accessibility.ATBAR_SRC;
		jf.type = 'text/javascript';
		jf.id = 'ToolBar';
		document.getElementsByTagName('head')[0].appendChild(jf);
	},

	/**
	 * Displays the specified message in the block's footer
	 *
	 * @param {String} msg the message to display
	 */
	show_message: function(msg) {
		//this.log('Message set to '+msg);
		this.Y.one('#block_accessibility_message').setContent(msg);

		// make message disappear after some time
		if(msg) setTimeout("M.block_accessibility.show_message('')", 5000);
	},

	/**
	 * Calls the database script on the server to save the current setting to
	 * the database. Displays a message on success, or an error on failure.
	 *
	 * @requires accessibility_show_message
	 * @requires webroot
	 *
	 */
	savesize: function() {
		this.Y.io(M.cfg.wwwroot+'/blocks/accessibility/database.php', {
			data: 'op=save&size=true&scheme=true',
			method: 'get',
			on: {
				success: function(id, o) {
					M.block_accessibility.show_message(M.util.get_string('saved', 'block_accessibility'));
					//setTimeout("M.block_accessibility.show_message('')", 5000);
				},
				failure: function(id, o) {
					alert(M.util.get_string('jsnosave', 'block_accessibility')+' '+o.status+' '+o.statusText);
				},
				start: M.block_accessibility.show_loading,
				end: M.block_accessibility.hide_loading
			}
		});
	},

	/**
	 * Enables or disables the buttons as specified
	 *
	 * @requires webroot
	 *
	 * @param {String} id the ID of the button to enable/disable
	 * @param {String} op the operation we're doing, either 'on' or 'off'.
	 *
	 */
	toggle_textsizer: function(id, op) {
		var button = this.Y.one('#block_accessibility_'+id);
		if (op == 'on') {
			if (button.hasClass('disabled')) {
				//this.log('Enabling '+button);
				button.removeClass('disabled');
			}
		} else if (op == 'off') {
			if(!button.hasClass('disabled')) {
				//this.log('Disabling '+button);
				button.addClass('disabled');
			}
		}
	},

	/**
	 * This handles clicks from the buttons. If increasing, decreasing or
	 * resetting size, it calls changesize.php via AJAX and sets the text
	 * size to the number returned from the server. If saving the size, it
	 * calls accessibility_savesize.
	 * Also enables/disables buttons as required when sizes are changed.
	 *
	 * @requires accessibility_toggle_textsizer
	 * @requires accessibility_savesize
	 * @requires accessibility_resetsize
	 * @requires stylesheet
	 * @requires webroot
	 *
	 * @param {Node} button the button that was pushed
	 *
	 */
	changesize: function(button) {

		Y = this.Y;

		switch (button.get('id')) {
			case "block_accessibility_inc":
				//this.log('Increasing size from '+this.defaultsize);
				Y.io(M.cfg.wwwroot+'/blocks/accessibility/changesize.php', {
					data: 'op=inc&cur='+this.defaultsize, // we need to find a default so we know where we're increasing/decreasing from, otherwise PHP will assume 100%
					method: 'get',
					on: {
						success: function(id, o) {
							
							// if redirected to login page, or some other error...
							if (!(o.response === undefined) && o.response.length > 0) {
								alert(M.util.get_string('jsnotloggedin', 'block_accessibility')+': '+o.status+' '+o.statusText);
							}

							// now that we updated user setting to the server, load updated stylesheet
							M.block_accessibility.reload_stylesheet();  
							var new_fontsize =  M.block_accessibility.get_current_fontsize(M.block_accessibility.MAIN_SELECTOR);
							M.block_accessibility.log('Increasing size to '+new_fontsize);

							// Disable/enable buttons as necessary
							var min_fontsize = M.block_accessibility.MIN_PX_FONTSIZE;
							var max_fontsize = M.block_accessibility.MAX_PX_FONTSIZE;
							if(new_fontsize == M.block_accessibility.defaultsize) {
								M.block_accessibility.toggle_textsizer('reset', 'off');
							} else {
								M.block_accessibility.toggle_textsizer('reset', 'on');
							}
							if (new_fontsize >= max_fontsize) {
								M.block_accessibility.toggle_textsizer('inc', 'off');
							}
							M.block_accessibility.toggle_textsizer('dec', 'on');
							M.block_accessibility.toggle_textsizer('save', 'on');
							
						},
						failure: function(o) {
							alert(M.util.get_string('jsnosize', 'block_accessibility')+': '+o.status+' '+o.statusText);
						},
						start: M.block_accessibility.show_loading,
						end: M.block_accessibility.hide_loading
				   }
				});
				break;
			case "block_accessibility_dec":
				//this.log('Decreasing size from '+this.defaultsize);
				Y.io(M.cfg.wwwroot+'/blocks/accessibility/changesize.php', {
					data: 'op=dec&cur='+this.defaultsize,
					method: 'get',
					on: {
						success: function(id, o) {

							// if redirected to login page, or some other error...
							if (!(o.response === undefined) && o.response.length > 0) {
								alert(M.util.get_string('jsnotloggedin', 'block_accessibility')+': '+o.status+' '+o.statusText);
							}

							// now that we updated user setting to the server, load updated stylesheet
							M.block_accessibility.reload_stylesheet();
							var new_fontsize =  M.block_accessibility.get_current_fontsize(M.block_accessibility.MAIN_SELECTOR);
							M.block_accessibility.log('Decreasing size to '+new_fontsize);

							// Disable/enable buttons as necessary
							var min_fontsize = M.block_accessibility.MIN_PX_FONTSIZE;
							var max_fontsize = M.block_accessibility.MAX_PX_FONTSIZE;
							if(new_fontsize == M.block_accessibility.defaultsize) {
								M.block_accessibility.toggle_textsizer('reset', 'off');
							} else {
								M.block_accessibility.toggle_textsizer('reset', 'on');
							}
							if (new_fontsize <= min_fontsize) {
								M.block_accessibility.toggle_textsizer('dec', 'off');
							} 
							M.block_accessibility.toggle_textsizer('inc', 'on');
							M.block_accessibility.toggle_textsizer('save', 'on');
							
						},
						failure: function(id, o) {
							alert(M.util.get_string('jsnosize', 'block_accessibility')+': '+o.status+' '+o.statusText);
						},
						start: M.block_accessibility.show_loading,
						end: M.block_accessibility.hide_loading
				   }
				});
				break;
			case "block_accessibility_reset":
				//this.log('Resetting size from '+this.defaultsize);
				Y.io(M.cfg.wwwroot+'/blocks/accessibility/changesize.php', {
					data: 'op=reset&cur='+this.defaultsize,
					method: 'get',
					on: {
						success: function(id, o) {

							// if redirected to login page, or some other error...
							if (!(o.response === undefined) && o.response.length > 0) {
								alert(M.util.get_string('jsnotloggedin', 'block_accessibility')+': '+o.status+' '+o.statusText);
							}

							// now that we updated user setting to the server, load updated stylesheet
							M.block_accessibility.reload_stylesheet();
							var new_fontsize =  M.block_accessibility.get_current_fontsize(M.block_accessibility.MAIN_SELECTOR);
							M.block_accessibility.log('Resetting size to '+new_fontsize);
  
							// Disable/enable buttons as necessary
							var min_fontsize = M.block_accessibility.MIN_PX_FONTSIZE;
							var max_fontsize = M.block_accessibility.MAX_PX_FONTSIZE;
							M.block_accessibility.toggle_textsizer('reset', 'off');
							if(new_fontsize <= min_fontsize) {
								M.block_accessibility.toggle_textsizer('dec', 'on');
							} else if (new_fontsize >= max_fontsize){
								M.block_accessibility.toggle_textsizer('inc', 'on');
							}
							M.block_accessibility.toggle_textsizer('save', 'off');
							//M.block_accessibility.resetsize();
							
						},
						failure: function(id, o) {
							alert(M.util.get_string('jsnosize', 'block_accessibility')+': '+o.status+' '+o.statusText);
						},
						start: M.block_accessibility.show_loading,
						end: M.block_accessibility.hide_loading
				   }
				});
				break;
			case "block_accessibility_save":
				//this.log('Saving Size');
				M.block_accessibility.savesize();
				break;
		}
	},

	/**
	 * This handles clicks from the colour scheme buttons.
	 * We start by getting the scheme number from the theme button's ID.
	 * We then get the elements that need dynamically re-styling via their
	 * CSS selectors and loop through the arrays to style them appropriately.
	 *
	 * @requires accessibility_toggle_textsizer
	 * @requires accessibility_resetscheme
	 * @requires stylesheet
	 * @requires webroot
	 *
	 * @param {String} button - the button that was clicked.
	 *
	 */

	changecolour: function(button) {
		Y = this.Y;
		scheme = button.get('id').substring(26);
		Y.io(M.cfg.wwwroot+'/blocks/accessibility/changecolour.php', {
			data: 'scheme='+scheme,
			method: 'get',
			on: {
				success: function (id, o) {
					// if redirected to login page, or some other error...
					if (!(o.response === undefined) && o.response.length > 0) {
						alert(M.util.get_string('jsnotloggedin', 'block_accessibility')+': '+o.status+' '+o.statusText);
					}
					
					M.block_accessibility.reload_stylesheet(); 
					if(scheme == 1){
						M.block_accessibility.toggle_textsizer('save', 'off'); // reset
						M.block_accessibility.toggle_textsizer('colour1', 'off');
					}
					else{
						M.block_accessibility.toggle_textsizer('save', 'on');
						M.block_accessibility.toggle_textsizer('colour1', 'on');
					} 
				},
				failure: function(id, o) {
					alert(get_string('jsnocolour', 'block_accessibility')+': '+o.status+' '+o.statusText);
				},
				start: M.block_accessibility.show_loading,
				end: M.block_accessibility.hide_loading
			}
		});
	},

	atbar_autoload: function(op) {
		if (op == 'on') {
			this.Y.io(M.cfg.wwwroot+'/blocks/accessibility/database.php', {
				data: 'op=save&atbar=true',
				method: 'get',
				on: {
					success: function(id, o) {
						M.block_accessibility.show_message(M.util.get_string('saved', 'block_accessibility'));
						//setTimeout("M.block_accessibility.show_message('')", 5000);
					},
					failure: function(id, o) {
						if (o.status != '404') {
							alert(M.util.get_string('jsnosave', 'block_accessibility')+': '+o.status+' '+o.statusText);
						}
					},
					start: M.block_accessibility.show_loading,
					end: M.block_accessibility.hide_loading
			   }
			});
		} else if (op == 'off') {
			this.Y.io(M.cfg.wwwroot+'/blocks/accessibility/database.php', {
				data: 'op=reset&atbar=true',
				method: 'get',
				on: {
					success: function(id, o) {
						M.block_accessibility.show_message(M.util.get_string('reset', 'block_accessibility'));
						//setTimeout("M.block_accessibility.show_message('')", 5000);
					},
					failure: function(id, o) {
						if (o.status != '404') {
							alert(M.util.get_string('jsnoreset', 'block_accessibility')+': '+o.status+' '+o.statusText);
						}
					},
					start: M.block_accessibility.show_loading,
					end: M.block_accessibility.hide_loading
			   }
			});
		}
	},

	watch_atbar_for_close: function() {
		Y = this.Y;
		this.watch = setInterval(function() {

			if (typeof AtKit !== 'undefined') {
				if (AtKit.isRendered()) {
					Y.one('#block_accessibility_textresize').setStyle('display', 'block');
					Y.one('#block_accessibility_changecolour').setStyle('display', 'block');
					clearInterval(M.block_accessibility.watch);
				}
			}
		}, 1000);
	},

	log: function(data) {
		if (this.debug) {
			console.log(data);
		}
	},

	/**
	 * Stylesheet is generated by userstyles.php based on user settings (e.g. font size)
	 * After settings are changed, the script should download and include updated stylesheet
	 *
	 */
	reload_stylesheet: function(){
		var cache_prevention_salt = new Date().getTime();
		var oldStylesheet = M.block_accessibility.sheetnode;
		var newStylesheet = null;
		var cssURL = M.cfg.wwwroot+
			'/blocks/accessibility/userstyles.php?instance_id='+
			M.block_accessibility.instance_id+
			'&v='+cache_prevention_salt
		
		if (document.createStyleSheet) // only for IE < 11 and IE > 8
		{
			/* 
				here we use href attribute change which makes some delay while reloading stylesheet

				1. one another idea would be to load stylesheet using this.Y.io(.. and create <style> element
				var styleSheet = document.createElement('STYLE');
				document.documentElement.firstChild.appendChild(styleSheet);

				2. initial idea was the same as for non-IE browsers but somehow doesn't work:
				oldStylesheet.remove(true);
				newStylesheet = document.createStyleSheet(cssURL);
				// also keep in mind that createStyleSheet can create up to 31 stylesheets	
				// http://msdn.microsoft.com/en-us/library/ie/ms531194(v=vs.85).aspx			
			*/
			
			oldStylesheet.set('href', cssURL);
		}
		else
		{
			// IE 11 and non-IE browsers:
			// creating new stylesheet and deleting old one makes more smooth transition
			// Why wouldn't we just set the href attribute insted of creating another stylesheet node? Because before the new stylesheet is loaded and while old one is deleted, the page will lose all the styles and all the elements get unstyled for a some time (poor user experience)

			newStylesheet = oldStylesheet.cloneNode(true);
			newStylesheet.set('href', cssURL); 
			this.Y.one('head').append(newStylesheet);
			// remove old stylesheet
			newStylesheet.getDOMNode().onload = function(){
				oldStylesheet.remove(true);
			};

			M.block_accessibility.sheetnode = newStylesheet;
		}


	},

	/**
	 * Stripes px or % and gives value only
	 * For improved user experience, only in JS-mode, we can set current font size as default font size
	 * We would initially put 100%, but it doesn't have to be true for all themes
	 * Also font-size value can be in % or in px, there is mapping defined in lib.php in the block
	 * The function needs to return percentage fontsize value as integer
	 *
	 * @param {String} root element to check font-size declaration (e.g. body or #page)
	 */
	get_current_fontsize: function(root_element){
		var currentsize = M.block_accessibility.DEFAULT_FONTSIZE;
		//var defaultsize = Y.one(root_element).getStyle('fontSize');
		var defaultsize = Y.one(root_element).getComputedStyle('fontSize');
		if (defaultsize.substr(-2) == 'px') {
			currentsize = defaultsize.substr(0, defaultsize.length-2);
		} else if (defaultsize.substr(-1) == '%') {
			currentsize = defaultsize.substr(0, defaultsize.length-1);
		}
		return currentsize;
	},

	show_loading: function(){
		this.transactionsCount++;
		Y.one('#loader-icon').setStyle('display', 'block');
		Y.one('#accessibility_controls').setStyle('opacity', '0.2');	
	},
	hide_loading: function(){
		if(this.transactionsCount < 0) this.transactionsCount--;
		else this.transactionsCount = 0; // prevention if count would end up to less than 0

		if(this.transactionsCount == 0){
			Y.one('#loader-icon').setStyle('display', 'none');
			Y.one('#accessibility_controls').setStyle('opacity', '1');	
		}
	},
}