/**
 * 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.
 *
 * @return {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 ) {
		obj.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 ) {

	let typeAheadID = 'typeahead-suggestions',
		typeAheadEl = document.getElementById( typeAheadID ), // Type-ahead DOM element.
		appendEl = document.getElementById( appendTo ),
		searchEl = document.getElementById( searchInput ),
		server = mw.config.get( 'wgServer' ),
		articleurl = server + mw.config.get( 'wgArticlePath' ).replace( '$1', '' ),
		thumbnailSize = getDevicePixelRatio() * 80,
		descriptionSource = mw.config.get( 'wgCitizenSearchDescriptionSource' ),
		maxSearchResults = mw.config.get( 'wgCitizenMaxSearchResults' ),
		searchString,
		typeAheadItems,
		activeItem,
		ssActiveIndex,
		api = new mw.Api();

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

	/**
	 * 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 ) {
			const index = this.incrementIndex();
			this.queue[ index ] = func( index );
			return index;
		},
		deleteSelfFromQueue: function ( i ) {
			delete this.queue[ i ];
		},
		deletePrevCallbacks: function ( j ) {
			let 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 );
		}
	};

	/**
	 * Removed the actual child nodes from typeAheadEl
	 * @see {typeAheadEl}
	 */
	function clearTypeAheadElements() {
		if ( typeof typeAheadEl === 'undefined' ) {
			return;
		}

		while ( typeAheadEl.firstChild !== null ) {
			typeAheadEl.removeChild( typeAheadEl.firstChild );
		}
	}

	/**
	 * 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 () {
			clearTypeAheadElements();
			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 ) {
		const el = e.relatedTarget;
		if ( el && /suggestion-link/.test( el.className ) ) {
			window.location = el.href;
		}
	}

	/**
	 * Card displayed while loading search results
	 * @return {string}
	 */
	function getLoadingIndicator() {
		return '<div class="suggestions-dropdown">' +
			'<div class="suggestion-link">' +
				'<div class="suggestion-text suggestion-placeholder">' +
					'<h3 class="suggestion-title"></h3>' +
					'<p class="suggestion-description"></p>' +
				'</div>' +
				'<div class="suggestion-thumbnail"></div>' +
			'</div>' +
		'</div>';
	}

	/**
	 * Card displayed if no results could be found
	 * @param {string} searchString - The search string.
	 * @return {string}
	 */
	function getNoResultsIndicator( searchString ) {
		const titlemsg = mw.message( 'citizen-search-no-results-title', searchString ).text(),
			descmsg = mw.message( 'citizen-search-no-results-desc', searchString ).text();

		return `
< div class = "suggestions-dropdown" >
	< div class = "suggestion-link" >
		< div class = "suggestion-text" >
			< h3 class = "suggestion-title" > ` + titlemsg + ` < / h3 >
			< p class = "suggestion-description" > ` + descmsg + ` < / p >
		< / div >
		< div class = "suggestion-thumbnail" > < / div >
	< / div >
< / div > `;
	}

	/**
	 * 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 ) {
		let callbackIndex,
			searchQuery;

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

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

		// Removed description prop
		// TODO: Use text extract or PCS for description
		searchQuery = {
			generator: 'prefixsearch',
			prop: 'pageprops|pageimages',
			redirects: '',
			ppprop: 'displaytitle',
			piprop: 'thumbnail',
			pithumbsize: thumbnailSize,
			pilimit: maxSearchResults,
			gpssearch: string,
			gpsnamespace: 0,
			gpslimit: maxSearchResults
		};

		switch ( descriptionSource ) {
			case 'wikidata':
				searchQuery.prop += '|description';
				break;
			case 'textextracts':
				searchQuery.prop += '|extracts';
				searchQuery.exchars = '60';
				searchQuery.exintro = '1';
				searchQuery.exlimit = maxSearchResults;
				searchQuery.explaintext = '1';
				break;
			case 'pagedescription':
				searchQuery.prop += '|pageprops';
				searchQuery.ppprop = 'description';
				break;
		}

		typeAheadEl.innerHTML = getLoadingIndicator();

		api.get( searchQuery )
			.done( ( data ) => {
				clearTypeAheadElements();
				window.callbackStack.queue[ callbackIndex ]( data, string );
			} );
	} // 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 ) {
		let 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 ) {
		let string = '<div class="suggestions-dropdown">',
			suggestionLink,
			suggestionThumbnail,
			suggestionText,
			suggestionTitle,
			suggestionDescription,
			page,
			sanitizedThumbURL = false,
			descriptionText = '',
			pageDescription = '',
			i;

		if ( suggestions.length === 0 ) {
			return getNoResultsIndicator( searchString );
		}

		for ( i = 0; i < suggestions.length; i++ ) {
			if ( !suggestions[ i ] ) {
				continue;
			}

			page = suggestions[ i ];

			switch ( descriptionSource ) {
				case 'wikidata':
					pageDescription = page.description || '';
					break;
				case 'textextracts':
					pageDescription = page.extract || '';
					break;
				case 'pagedescription':
					pageDescription = page.pageprops.description || '';
					break;
			}

			// 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: articleurl + 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 ) {
		let 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 ) {
		let callbackIndex = i,
			orderedResults = [],
			suggestions,
			item,
			result,
			templateDOMString,
			listEl;

		return function ( xhrResults, queryString ) {
			window.callbackStack.deletePrevCallbacks( callbackIndex );

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

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

			if ( suggestions.length === 0 ) {
				typeAheadEl.innerHTML = getNoResultsIndicator( queryString );
				return;
			}

			for ( item in suggestions ) {
				if ( Object.prototype.hasOwnProperty.call( suggestions, item ) ) {
					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 ) {
		let 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
	};
};