/**
 * @license Copyright (c) 2003-2020, CKSource - Frederico Knabben. All rights reserved.
 * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
 */

'use strict';

( function() {

	CKEDITOR._.mentions = {
		cache: {}
	};

	var MARKER = '@',
		MIN_CHARS = 2,
		cache = CKEDITOR._.mentions.cache;

	CKEDITOR.plugins.add( 'mentions', {
		requires: 'autocomplete,textmatch,ajax',
		instances: [],
		init: function( editor ) {
			var self = this;

			editor.on( 'instanceReady', function() {
				CKEDITOR.tools.array.forEach( editor.config.mentions || [], function( config ) {
					self.instances.push( new Mentions( editor, config ) );
				} );
			} );
		},
		isSupportedEnvironment: function( editor ) {
			return editor.plugins.autocomplete.isSupportedEnvironment( editor );
		}
	} );

	/**
	 * The [Mentions](https://ckeditor.com/cke4/addon/mentions) plugin allows you to type a marker character and get suggested values for the
	 * text matches so that you do not have to write it on your own.
	 *
	 * The recommended way to add the mentions feature to an editor is by setting the {@link CKEDITOR.config#mentions config.mentions} option:
	 *
	 * ```javascript
	 * // Passing mentions configuration when creating the editor.
	 * CKEDITOR.replace( 'editor', {
	 * 		mentions: [ { feed: ['Anna', 'Thomas', 'John'], minChars: 0 } ]
	 * } );
	 *
	 * // Simple usage with the CKEDITOR.config.mentions property.
	 * CKEDITOR.config.mentions = [ { feed: ['Anna', 'Thomas', 'John'], minChars: 0 } ];
	 * ```
	 *
	 * @class CKEDITOR.plugins.mentions
	 * @since 4.10.0
	 * @constructor Creates a new instance of mentions and attaches it to the editor.
	 * @param {CKEDITOR.editor} editor The editor to watch.
	 * @param {CKEDITOR.plugins.mentions.configDefinition} config Configuration object keeping information about how to instantiate the mentions plugin.
	 */
	function Mentions( editor, config ) {
		var feed = config.feed;

		/**
		 * Indicates that a mentions instance is case-sensitive for simple items feed, i.e. an array feed.
		 *
		 * **Note:** This will take no effect on feeds using a callback or URLs, as in this case the results are expected to
		 * be already filtered.
		 *
		 * @property {Boolean} [caseSensitive=false]
		 * @readonly
		 */
		this.caseSensitive = config.caseSensitive;

		/**
		 * The character that should trigger autocompletion.
		 *
		 * @property {String} [marker='@']
		 * @readonly
		 */
		this.marker = config.hasOwnProperty( 'marker' ) ? config.marker : MARKER;

		/**
		 * The number of characters that should follow the marker character in order to trigger the mentions feature.
		 *
		 * @property {Number} [minChars=2]
		 * @readonly
		 */
		this.minChars = config.minChars !== null && config.minChars !== undefined ? config.minChars : MIN_CHARS;

		/**
		 * The pattern used to match queries.
		 *
		 * The default pattern matches words with the query including the {@link #marker config.marker} and {@link #minChars config.minChars} properties.
		 *
		 * ```javascript
		 * // Match only words starting with "a".
		 * var pattern = /^a+\w*$/;
		 * ```
		 *
		 * @property {RegExp} pattern
		 * @readonly
		 */
		this.pattern = config.pattern || createPattern( this.marker, this.minChars );

		/**
		 * Indicates if the URL feed responses will be cached.
		 *
		 * The cache is based on the URL request and is shared between all mentions instances (including different editors).
		 *
		 * @property {Boolean} [cache=true]
		 * @readonly
		 */
		this.cache = config.cache !== undefined ? config.cache : true;

		/**
		 * @inheritdoc CKEDITOR.plugins.mentions.configDefinition#throttle
		 * @property {Number} [throttle=200]
		 * @readonly
		 */
		this.throttle = config.throttle !== undefined ? config.throttle : 200;

		/**
		 * {@link CKEDITOR.plugins.autocomplete Autocomplete} instance used by the mentions feature to implement autocompletion logic.
		 *
		 * @property {CKEDITOR.plugins.autocomplete}
		 * @private
		 */
		this._autocomplete = new CKEDITOR.plugins.autocomplete( editor, {
			textTestCallback: getTextTestCallback( this.marker, this.minChars, this.pattern ),
			dataCallback: getDataCallback( feed, this ),
			itemTemplate: config.itemTemplate,
			outputTemplate: config.outputTemplate,
			throttle: this.throttle,
			itemsLimit: config.itemsLimit
		} );
	}

	Mentions.prototype = {

		/**
		 * Destroys the mentions instance.
		 *
		 * The view element and event listeners will be removed from the DOM.
		 */
		destroy: function() {
			this._autocomplete.destroy();
		}
	};

	function createPattern( marker, minChars ) {
		// Match also diacritic characters (#2491).
		var pattern = '\\' + marker + '[_a-zA-Z0-9À-ž]';

		if ( minChars ) {
			pattern += '{' + minChars + ',}';
		} else {
			pattern += '*';
		}

		pattern += '$';

		return new RegExp( pattern );
	}

	function getTextTestCallback( marker, minChars, pattern ) {
		return function( range ) {
			if ( !range.collapsed ) {
				return null;
			}

			return CKEDITOR.plugins.textMatch.match( range, matchCallback );
		};

		function matchCallback( text, offset ) {
			var match = text.slice( 0, offset )
				.match( pattern );

			if ( !match ) {
				return null;
			}

			// Do not proceed if a query is a part of word.
			var prevChar = text[ match.index - 1];
			if ( prevChar !== undefined && !prevChar.match( /\s+/ ) ) {
				return null;
			}

			return {
				start: match.index,
				end: offset
			};
		}
	}

	function getDataCallback( feed, mentions ) {
		return function( matchInfo, callback ) {
			var query = matchInfo.query;

			// We are removing marker here to give clean query result for the endpoint callback.
			if ( mentions.marker ) {
				query = query.substring( mentions.marker.length );
			}

			if ( CKEDITOR.tools.array.isArray( feed ) ) {
				createArrayFeed();
			} else if ( typeof feed === 'string' ) {
				createUrlFeed();
			} else {
				feed( {
					query: query,
					marker: mentions.marker
				}, resolveCallbackData );
			}

			function createArrayFeed() {
				var data = indexArrayFeed( feed ).filter( function( item ) {
					var itemName = item.name;

					if ( !mentions.caseSensitive ) {
						itemName = itemName.toLowerCase();
						query = query.toLowerCase();
					}

					return itemName.indexOf( query ) === 0;
				} );

				resolveCallbackData( data );
			}

			function indexArrayFeed( feed ) {
				var index = 1;
				return CKEDITOR.tools.array.reduce( feed, function( current, name ) {
					current.push( { name: name, id: index++ } );
					return current;
				}, [] );
			}

			function createUrlFeed() {
				var encodedUrl = new CKEDITOR.template( feed )
					.output( { encodedQuery: encodeURIComponent( query ) } );

				if ( mentions.cache && cache[ encodedUrl ] ) {
					return resolveCallbackData( cache[ encodedUrl ] );
				}

				CKEDITOR.ajax.load( encodedUrl, function( data ) {
					var items = JSON.parse( data );

					// Cache URL responses for performance improvement (#1969).
					if ( mentions.cache && items !== null ) {
						cache[ encodedUrl ] = items;
					}

					resolveCallbackData( items );
				} );
			}

			function resolveCallbackData( data ) {
				if ( !data ) {
					return;
				}

				// We don't want to change item data, so lets create new one.
				var newData = CKEDITOR.tools.array.map( data, function( item ) {
					var name = mentions.marker + item.name;
					return CKEDITOR.tools.object.merge( item, { name: name } );
				} );

				callback( newData );
			}
		};
	}

	CKEDITOR.plugins.mentions = Mentions;

	/**
	 * A list of mentions configuration objects.
	 *
	 * For each configuration object a new {@link CKEDITOR.plugins.mentions mentions} plugin instance will be created and attached to the editor.
	 *
	 * ```javascript
	 * config.mentions = [
	 * 	{ feed: [ 'Anna', 'Thomas', 'Jack' ], minChars: 0 },
	 * 	{ feed: backendApiFunction, marker: '#' },
	 * 	{ feed: '/users?query={encodedQuery}', marker: '$' }
	 * ];
	 *
	 * ```
	 *
	 * @cfg {CKEDITOR.plugins.mentions.configDefinition[]} [mentions]
	 * @since 4.10.0
	 * @member CKEDITOR.config
	 */

	/**
	 * Abstract class describing the definition of a {@link CKEDITOR.plugins.mentions mentions} plugin configuration.
	 *
	 * This virtual class illustrates the properties that the developers can use to define and create
	 * a mentions configuration definition.
	 * The mentions definition object represents an object as a set of properties defining a mentions
	 * data feed and its optional parameters.
	 *
	 * Simple usage:
	 *
	 * ```javascript
	 * var definition = { feed: ['Anna', 'Thomas', 'John'], minChars: 0 };
	 * ```
	 *
	 * @class CKEDITOR.plugins.mentions.configDefinition
	 * @abstract
	 * @since 4.10.0
	 */

	/**
	 * The feed of items to be displayed in the mentions plugin.
	 *
	 * Essential option which should be configured to create a correct mentions configuration definition.
	 * There are three different ways to create a data feed:
	 *
	 * * A simple array of text matches as a synchronous data feed.
	 * * A backend URL string responding with a list of items in the JSON format. This method utilizes an asynchronous data feed.
	 * * A function allowing to use an asynchronous callback to customize the data source.
	 * Gives the freedom to use any data source depending on your implementation.
	 *
	 * # An array of text matches
	 * The easiest way to configure the data feed is to provide an array of text matches.
	 * The mentions plugin will use a synchronous data feed and create item IDs by itself.
	 * The biggest advantage of this method is its simplicity, although it is limited to a synchronous data feed.
	 * Please see two other methods if you require more complex techniques to fetch the text matches.
	 *
	 *```javascript
	 * var definition = { feed: ['Anna', 'Thomas', 'John'], minChars: 0 };
	 * ```
	 *
	 * By default query matching for an array feed is case insensitive.
	 * You can change this behavior by setting the {@link #caseSensitive caseSensitive} property to `true`.
	 *
	 * # A backend URL string
	 * You can provide a backend URL string which will be used to fetch text matches from a custom endpoint service.
	 * Each time the user types matching text into an editor, your backend service will be queried for text matches.
	 * An Ajax URL request should response with an array of matches in the JSON format. A URL response will appear in the mentions dropdown.
	 *
	 * A backend URL string features the special `encodedQuery` variable replaced with a mentions query.
	 * The `encodedQuery` variable allows you to create a customized URL which can be both RESTful API compliant or any other
	 * URL which suits your needs. E.g. for the query `@anna` and the given URL `/users?name={encodedQuery}` your endpoint
	 * service will be queried with `/users?name=anna`.
	 *
	 * ```javascript
	 * var definition = { feed: '/users?query={encodedQuery}' };
	 * ```
	 *
	 * To avoid multiple HTTP requests to your endpoint service, each HTTP response is cached by default and shared globally.
	 * See the {@link #cache cache} property for more details.
	 *
	 * # Function feed
	 * This method is recommended for advanced users who would like to take full control of the data feed.
	 * It allows you to provide the data feed as a function that accepts two parameters: `options` and `callback`.
	 * The provided function will be called every time the user types matching text into an editor.
	 *
	 * The `options` object contains information about the current query and a {@link #marker marker}.
	 *
	 * ```javascript
	 * { query: 'anna', marker: '@' }
	 * ```
	 *
	 * The `callback` argument should be used to pass an array of text match items into the mentions instance.
	 *
	 * ```javascript
	 * callback( [ { id: 1, name: 'anna' }, { id: 2, name: 'annabelle' } ] );
	 * ```
	 *
	 * Depending on your use case, you can use this code as an example boilerplate to create your own function feed:
	 *
	 * ```javascript
	 * var definition = {
	 *		feed: function( opts, callback ) {
	 *			var xhr = new XMLHttpRequest();
	 *
	 *			xhr.onreadystatechange = function() {
	 *				if ( xhr.readyState == 4 ) {
	 *					if ( xhr.status == 200 ) {
	 *						callback( JSON.parse( this.responseText ) );
	 *					} else {
	 *						callback( [] );
	 *					}
	 *				}
	 *			}
	 *
	 *			xhr.open( 'GET', '/users?name=' + opts.query );
	 *			xhr.send();
	 *		}
	 * };
	 * ```
	 *
	 * **Other details**
	 *
	 * When using the asynchronous method, i.e. a backend URL string or a function,
	 * you should provide correct object structure containing a unique item ID and a name.
	 *
	 * ```javascript
	 * // Example of expected results from the backend API.
	 * // The `firstName` and `lastName` properties are optional.
	 * [
	 * 		{ id: 1, name: 'anna87', firstName: 'Anna', lastName: 'Doe' },
	 * 		{ id: 2, name: 'tho-mass', firstName: 'Thomas', lastName: 'Doe' },
	 * 		{ id: 3, name: 'ozzy', firstName: 'John', lastName: 'Doe' }
	 * ]
	 * ```
	 *
	 * @property {String/String[]/Function} feed
	 */

	/**
	 * @inheritdoc CKEDITOR.plugins.autocomplete.configDefinition#itemTemplate
	 * @property {String} [itemTemplate]
	 */

	/**
	 * @inheritdoc CKEDITOR.plugins.autocomplete.configDefinition#outputTemplate
	 * @property {String} [outputTemplate]
	 */

	/**
	 * @inheritdoc CKEDITOR.plugins.autocomplete.configDefinition#throttle
	 * @property {Number} [throttle=200]
	 */

	/**
	 * @inheritdoc CKEDITOR.plugins.mentions#marker
	 * @property {String} [marker='@']
	 */

	/**
	 * @inheritdoc CKEDITOR.plugins.mentions#minChars
	 * @property {Number} [minChars=2]
	 */

	/**
	 * @inheritdoc CKEDITOR.plugins.mentions#caseSensitive
	 * @property {Boolean} [caseSensitive=false]
	 */

	/**
	 * @inheritdoc CKEDITOR.plugins.mentions#cache
	 * @property {Boolean} [cache=true]
	 */

	/**
	 * @inheritdoc CKEDITOR.plugins.mentions#pattern
	 * @property {RegExp} pattern
	 */

	/**
	 * @inheritdoc CKEDITOR.plugins.autocomplete.configDefinition#itemsLimit
	 * @property {Number} [itemsLimit]
	 */
} )();
