/**
 * Based on https://gerrit.wikimedia.org/g/wikimedia/portals/+/refs/heads/master
 * See T219590 for more details
 */

 /**
* Below are additional dependency extracted from polyfills.js
* TODO: Optimize and clear unneeded code
*/

/**
 * Detects reported or approximate device pixel ratio.
 * * 1.0 means 1 CSS pixel is 1 hardware pixel
 * * 2.0 means 1 CSS pixel is 2 hardware pixels
 * * etc.
 *
 * Uses window.devicePixelRatio if available, or CSS media queries on IE.
 *
 * @returns {number} Device pixel ratio
 */
function getDevicePixelRatio () {

	if ( window.devicePixelRatio !== undefined ) {
		// Most web browsers:
		// * WebKit (Safari, Chrome, Android browser, etc)
		// * Opera
		// * Firefox 18+
		return window.devicePixelRatio;
	} else if ( window.msMatchMedia !== undefined ) {
		// Windows 8 desktops / tablets, probably Windows Phone 8
		//
		// IE 10 doesn't report pixel ratio directly, but we can get the
		// screen DPI and divide by 96. We'll bracket to [1, 1.5, 2.0] for
		// simplicity, but you may get different values depending on zoom
		// factor, size of screen and orientation in Metro IE.
		if ( window.msMatchMedia( '(min-resolution: 192dpi)' ).matches ) {
			return 2;
		} else if ( window.msMatchMedia( '(min-resolution: 144dpi)' ).matches ) {
			return 1.5;
		} else {
			return 1;
		}
	} else {
		// Legacy browsers...
		// Assume 1 if unknown.
		return 1;
	}
}

function addEvent( obj, evt, fn ) {

	if ( !obj ) {
		return;
	}

	if ( obj.addEventListener ) {
		obj.addEventListener( evt, fn, false );
	} else if ( obj.attachEvent ) {
		attachedEvents.push( [ obj, evt, fn ] );
		obj.attachEvent( 'on' + evt, fn );
	}
}

/**
 * WMTypeAhead.
 * Displays search suggestions with thumbnail and description
 * as user types into an input field.
 *
 * @constructor
 * @param {string} appendTo  - ID of a container element that the suggestions will be appended to.
 * @param {string} searchInput - ID of a search input whose value will be used to generate
 *                               search suggestions.
 *
 * @return {Object} Returns an object with the following properties:
 * @return {HTMLElement} return.typeAheadEl The type-ahead DOM object.
 * @return {Function} return.query A function that loads the type-ahead suggestions.
 *
 * @example
 * var typeAhead = new WMTypeAhead('containerID', 'inputID');
 * typeAhead.query('search string', 'en');
 *
 */

window.WMTypeAhead = function(appendTo, searchInput) { // eslint-disable-line no-unused-vars

	var typeAheadID = 'typeahead-suggestions',
		typeAheadEl = document.getElementById(typeAheadID), // Type-ahead DOM element.
		appendEl = document.getElementById(appendTo),
		searchEl = document.getElementById(searchInput),
		thumbnailSize = getDevicePixelRatio() * 80,
		maxSearchResults = mw.config.get( 'wgCitizenMaxSearchResults' ),
		searchString,
		typeAheadItems,
		activeItem,
		ssActiveIndex;

	// Only create typeAheadEl once on page.
	if (!typeAheadEl) {
		typeAheadEl = document.createElement('div');
		typeAheadEl.id = typeAheadID;
		appendEl.appendChild(typeAheadEl);
	}

	/**
	 * Serializes a JS object into a URL parameter string.
	 *
	 * @param {Object} obj - object whose properties will be serialized
	 * @return {string}
	 */
	function serialize(obj) {
		var serialized = [],
			prop;

		for (prop in obj) {
			if (obj.hasOwnProperty(prop)) { // eslint-disable-line no-prototype-builtins
				serialized.push(prop + '=' + encodeURIComponent(obj[prop]));
			}
		}
		return serialized.join('&');
	}

	/**
	 * Keeps track of the search query callbacks. Consists of an array of
	 * callback functions and an index that keeps track of the order of requests.
	 * Callbacks are deleted by replacing the callback function with a no-op.
	 */
	window.callbackStack = {
		queue: {},
		index: -1,
		incrementIndex: function() {
			this.index += 1;
			return this.index;
		},
		addCallback: function(func) {
			var index = this.incrementIndex();
			this.queue[index] = func(index);
			return index;
		},
		deleteSelfFromQueue: function(i) {
			delete this.queue[i];
		},
		deletePrevCallbacks: function(j) {
			var callback;

			this.deleteSelfFromQueue(j);

			for (callback in this.queue) {
				if (callback < j) {
					this.queue[callback] = this.deleteSelfFromQueue.bind(
						window.callbackStack, callback
					);
				}
			}
		}
	};

	/**
	 * Maintains the 'active' state on search suggestions.
	 * Makes sure the 'active' element is synchronized between mouse and keyboard usage,
	 * and cleared when new search suggestions appear.
	 */
	ssActiveIndex = {
		index: -1,
		max: maxSearchResults,
		setMax: function(x) {
			this.max = x;
		},
		increment: function(i) {
			this.index += i;
			if (this.index < 0) {
				this.setIndex(this.max - 1);
			} // Index reaches top
			if (this.index === this.max) {
				this.setIndex(0);
			} // Index reaches bottom
			return this.index;
		},
		setIndex: function(i) {
			if (i <= this.max - 1) {
				this.index = i;
			}
			return this.index;
		},
		clear: function() {
			this.setIndex(-1);
		}
	};

	/**
	 * Removes the type-ahead suggestions from the DOM.
	 * Reason for timeout: The typeahead is set to clear on input blur.
	 * When a user clicks on a search suggestion, they triggers the input blur
	 * and remove the typeahead before a click event is registered.
	 * The timeout makes it so a click on the search suggestion is registered before
	 * an input blur.
	 * 300ms is used to account for the click delay on mobile devices.
	 *
	 */
	function clearTypeAhead() {
		setTimeout(function() {
			var searchScript = document.getElementById('api_opensearch');
			typeAheadEl.innerHTML = '';
			if (searchScript) {
				searchScript.src = false;
			}
			ssActiveIndex.clear();
		}, 300);
	}

	/**
	 * Manually redirects the page to the href of a given element.
	 *
	 * For Chrome on Android to solve T221628.
	 * When search suggestions below the fold are clicked, the blur event
	 * on the search input is triggered and the page scrolls the search input
	 * into view. However, the originating click event does not redirect
	 * the page.
	 *
	 * @param {Event} e
	 */
	function forceLinkFollow(e) {
		var el = e.relatedTarget;
		if (el && /suggestion-link/.test(el.className)) {
			window.location = el.href;
		}
	}

	/**
	 * Inserts script element containing the Search API results into document head.
	 * The script itself calls the 'portalOpensearchCallback' callback function,
	 *
	 * @param {string} string - query string to search.
	 * @param {string} lang - ISO code of language to search in.
	 */

	function loadQueryScript(string) {
		var script = document.getElementById('api_opensearch'),
			docHead = document.getElementsByTagName('head')[0],
			hostname,
			callbackIndex,
			searchQuery;

		// Variables declared in parent function.
		searchString = encodeURIComponent(string);
		if (searchString.length === 0) {
			clearTypeAhead();
			return;
		}

		// Change sitename here
		// TODO: Make it configurable from the skin
		hostname = mw.config.get('wgServer') + mw.config.get('wgScriptPath') + '/api.php?';

		// If script already exists, remove it.
		if (script) {
			docHead.removeChild(script);
		}

		script = document.createElement('script');
		script.id = 'api_opensearch';


		callbackIndex = window.callbackStack.addCallback(window.portalOpensearchCallback);

		// Removed description prop
		// TODO: Use text extract or PCS for description
		searchQuery = {
			action: 'query',
			format: 'json',
			generator: 'prefixsearch',
			prop: 'pageprops|pageimages|description|extracts',
			exlimit: mw.config.get( 'wgCitizenMaxSearchResults' ),
			exintro: 1,
			exchars: mw.config.get( 'wgCitizenSearchExchars' ),
			explaintext: 1,
			redirects: '',
			ppprop: 'displaytitle',
			piprop: 'thumbnail',
			pithumbsize: thumbnailSize,
			pilimit: maxSearchResults,
			gpssearch: string,
			gpsnamespace: 0,
			gpslimit: maxSearchResults,
			callback: 'callbackStack.queue[' + callbackIndex + ']'
		};

		script.src = hostname + serialize(searchQuery);
		docHead.appendChild(script);
	}

	// END loadQueryScript

	/**
	 * Highlights the part of the suggestion title that matches the search query.
	 * Used inside the generateTemplateString function.
	 *
	 * @param {string} title - The title of the search suggestion.
	 * @param {string} searchString - The string to highlight.
	 * @return {string} The title with highlighted part in an <em> tag.
	 */
	function highlightTitle(title, searchString) {

		var sanitizedSearchString = mw.html.escape(mw.RegExp.escape(searchString)),
			searchRegex = new RegExp(sanitizedSearchString, 'i'),
			startHighlightIndex = title.search(searchRegex),
			formattedTitle = mw.html.escape(title),
			endHighlightIndex,
			strong,
			beforeHighlight,
			aferHighlight;

		if (startHighlightIndex >= 0) {

			endHighlightIndex = startHighlightIndex + sanitizedSearchString.length;
			strong = title.substring(startHighlightIndex, endHighlightIndex);
			beforeHighlight = title.substring(0, startHighlightIndex);
			aferHighlight = title.substring(endHighlightIndex, title.length);
			formattedTitle = beforeHighlight + mw.html.element('em', { 'class': 'suggestion-highlight' }, strong) + aferHighlight;
		}

		return formattedTitle;
	} // END highlightTitle

	/**
	 * Generates a template string based on an array of search suggestions.
	 *
	 * @param {Array} suggestions - An array of search suggestion results.
	 * @return {string} A string representing the search suggestions DOM
	 */
	function generateTemplateString(suggestions) {
		var string = '<div class="suggestions-dropdown">',
			suggestionLink,
			suggestionThumbnail,
			suggestionText,
			suggestionTitle,
			suggestionDescription,
			page,
			sanitizedThumbURL = false,
			descriptionText = '',
			pageDescription = '',
			i;

		for (i = 0; i < suggestions.length; i++) {

			if (!suggestions[i]) {
				continue;
			}

			page = suggestions[i];
			// Description > TextExtracts
			pageDescription = page.description || page.extract || '';

			// Ensure that the value from the previous iteration isn't used
			sanitizedThumbURL = false;

			if (page.thumbnail && page.thumbnail.source) {
				sanitizedThumbURL = page.thumbnail.source.replace(/"/g, '%22');
				sanitizedThumbURL = sanitizedThumbURL.replace(/'/g, '%27');
			}

			// Ensure that the value from the previous iteration isn't used
			descriptionText = '';

			// Check if description exists
			if (pageDescription) {
				// If the description is an array, use the first item
				if (typeof pageDescription === 'object' && pageDescription[0]) {
					descriptionText = pageDescription[0].toString();
				} else {
					// Otherwise, use the description as is.
					descriptionText = pageDescription.toString();
				}
			}

			// Filter out no text from TextExtracts
			if (descriptionText == '...') {
				descriptionText = '';
			}

			suggestionDescription = mw.html.element('p', { 'class': 'suggestion-description' }, descriptionText);

			suggestionTitle = mw.html.element('h3', { 'class': 'suggestion-title' }, new mw.html.Raw(highlightTitle(page.title, searchString)));

			suggestionText = mw.html.element('div', { 'class': 'suggestion-text' }, new mw.html.Raw(suggestionTitle + suggestionDescription));

			suggestionThumbnail = mw.html.element('div', {
				'class': 'suggestion-thumbnail',
				style: (sanitizedThumbURL) ? 'background-image:url(' + sanitizedThumbURL + ')' : false
			}, '');

			// TODO: Make it configurable from the skin
			suggestionLink = mw.html.element('a', {
				'class': 'suggestion-link',
				href: mw.config.get('wgServer') + '/' + encodeURIComponent(page.title.replace(/ /gi, '_'))
			}, new mw.html.Raw(suggestionText + suggestionThumbnail));

			string += suggestionLink;

		}

		string += '</div>';

		return string;
	} // END generateTemplateString

	/**
	 * - Removes 'active' class from a collection of elements.
	 * - Adds 'active' class to an item if missing.
	 * - Removes 'active' class from item if present.
	 *
	 * @param {HTMLElement} item Item to add active class to.
	 * @param {NodeList} collection Sibling items.
	 */

	function toggleActiveClass(item, collection) {

		var activeClass = ' active', // Prefixed with space.
			colItem,
			i;

		for (i = 0; i < collection.length; i++) {

			colItem = collection[i];
			// Remove the class name from everything except item.
			if (colItem !== item) {
				colItem.className = colItem.className.replace(activeClass, '');
			} else {
				// If item has class name, remove it
				if (/ active/.test(item.className)) {
					item.className = item.className.replace(activeClass, '');
				} else {
					// It item doesn't have class name, add it.
					item.className += activeClass;
					ssActiveIndex.setIndex(i);
				}
			}
		}
	}

	/**
	 * Search API callback. Returns a closure that holds the index of the request.
	 * Deletes previous callbacks based on this index. This prevents callbacks for old
	 * requests from executing. Then:
	 *  - parses the search results
	 *  - generates the template String
	 *  - inserts the template string into the DOM
	 *  - attaches event listeners on each suggestion item.
	 *
	 * @param {number} i
	 * @return {Function}
	 */
	window.portalOpensearchCallback = function(i) {

		var callbackIndex = i,
			orderedResults = [],
			suggestions,
			item,
			result,
			templateDOMString,
			listEl;

		return function(xhrResults) {

			window.callbackStack.deletePrevCallbacks(callbackIndex);

			if (document.activeElement !== searchEl) {
				return;
			}

			suggestions = (xhrResults.query && xhrResults.query.pages) ?
				xhrResults.query.pages : [];

			for (item in suggestions) {
				result = suggestions[item];
				orderedResults[result.index - 1] = result;
			}

			templateDOMString = generateTemplateString(orderedResults);

			ssActiveIndex.setMax(orderedResults.length);
			ssActiveIndex.clear();

			typeAheadEl.innerHTML = templateDOMString;

			typeAheadItems = typeAheadEl.childNodes[0].childNodes;

			// Attaching hover events
			for (i = 0; i < typeAheadItems.length; i++) {
				listEl = typeAheadItems[i];
				// Requires the addEvent global polyfill
				addEvent(listEl, 'mouseenter', toggleActiveClass.bind(this, listEl, typeAheadItems));
				addEvent(listEl, 'mouseleave', toggleActiveClass.bind(this, listEl, typeAheadItems));
			}
		};
	};

	/**
	 * Keyboard events: up arrow, down arrow and enter.
	 * moves the 'active' suggestion up and down.
	 *
	 * @param {event} event
	 */
	function keyboardEvents(event) {

		var e = event || window.event,
			keycode = e.which || e.keyCode,
			suggestionItems,
			searchSuggestionIndex;

		if (!typeAheadEl.firstChild) {
			return;
		}

		if (keycode === 40 || keycode === 38) {
			suggestionItems = typeAheadEl.firstChild.childNodes;

			if (keycode === 40) {
				searchSuggestionIndex = ssActiveIndex.increment(1);
			} else {
				searchSuggestionIndex = ssActiveIndex.increment(-1);
			}

			activeItem = (suggestionItems) ? suggestionItems[searchSuggestionIndex] : false;

			toggleActiveClass(activeItem, suggestionItems);

		}
		if (keycode === 13 && activeItem) {

			if (e.preventDefault) {
				e.preventDefault();
			} else {
				(e.returnValue = false);
			}

			activeItem.children[0].click();
		}
	}

	addEvent(searchEl, 'keydown', keyboardEvents);

	addEvent(searchEl, 'blur', function(e) {
		clearTypeAhead();
		forceLinkFollow(e);
	});

	return {
		typeAheadEl: typeAheadEl,
		query: loadQueryScript
	};
};