text: /**
   * @license Copyright (c) 2003-2018, CKSource - Frederico Knabben. All rights reserved.
   * For licensing, see LICENSE.md.
   */
  
  /**
   * @module engine/view/textproxy
   */
  
  import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
  
  /**
   * TextProxy is a wrapper for substring of {@link module:engine/view/text~Text}. Instance of this class is created by
   * {@link module:engine/view/treewalker~TreeWalker} when only a part of {@link module:engine/view/text~Text} needs to be returned.
   *
   * `TextProxy` has an API similar to {@link module:engine/view/text~Text Text} and allows to do most of the common tasks performed
   * on view nodes.
   *
   * **Note:** Some `TextProxy` instances may represent whole text node, not just a part of it.
   * See {@link module:engine/view/textproxy~TextProxy#isPartial}.
   *
   * **Note:** `TextProxy` is a readonly interface.
   *
   * **Note:** `TextProxy` instances are created on the fly basing on the current state of parent {@link module:engine/view/text~Text}.
   * Because of this it is highly unrecommended to store references to `TextProxy instances because they might get
   * invalidated due to operations on Document. Also TextProxy is not a {@link module:engine/view/node~Node} so it can not be
   * inserted as a child of {@link module:engine/view/element~Element}.
   *
   * `TextProxy` instances are created by {@link module:engine/view/treewalker~TreeWalker view tree walker}. You should not need to create
   * an instance of this class by your own.
   */
  export default class TextProxy {
  	/**
  	 * Creates a text proxy.
  	 *
  	 * @protected
  	 * @param {module:engine/view/text~Text} textNode Text node which part is represented by this text proxy.
  	 * @param {Number} offsetInText Offset in {@link module:engine/view/textproxy~TextProxy#textNode text node}
  	 * from which the text proxy starts.
  	 * @param {Number} length Text proxy length, that is how many text node's characters, starting from `offsetInText` it represents.
  	 * @constructor
  	 */
  	constructor( textNode, offsetInText, length ) {
  		/**
  		 * Reference to the {@link module:engine/view/text~Text} element which TextProxy is a substring.
  		 *
  		 * @readonly
  		 * @member {module:engine/view/text~Text} module:engine/view/textproxy~TextProxy#textNode
  		 */
  		this.textNode = textNode;
  
  		if ( offsetInText < 0 || offsetInText > textNode.data.length ) {
  			/**
  			 * Given offsetInText value is incorrect.
  			 *
  			 * @error view-textproxy-wrong-offsetintext
  			 */
  			throw new CKEditorError( 'view-textproxy-wrong-offsetintext: Given offsetInText value is incorrect.' );
  		}
  
  		if ( length < 0 || offsetInText + length > textNode.data.length ) {
  			/**
  			 * Given length value is incorrect.
  			 *
  			 * @error view-textproxy-wrong-length
  			 */
  			throw new CKEditorError( 'view-textproxy-wrong-length: Given length value is incorrect.' );
  		}
  
  		/**
  		 * Text data represented by this text proxy.
  		 *
  		 * @readonly
  		 * @member {String} module:engine/view/textproxy~TextProxy#data
  		 */
  		this.data = textNode.data.substring( offsetInText, offsetInText + length );
  
  		/**
  		 * Offset in the `textNode` where this `TextProxy` instance starts.
  		 *
  		 * @readonly
  		 * @member {Number} module:engine/view/textproxy~TextProxy#offsetInText
  		 */
  		this.offsetInText = offsetInText;
  	}
  
  	/**
  	 * @inheritDoc
  	 */
  	get offsetSize() {
  		return this.data.length;
  	}
  
  	/**
  	 * Flag indicating whether `TextProxy` instance covers only part of the original {@link module:engine/view/text~Text text node}
  	 * (`true`) or the whole text node (`false`).
  	 *
  	 * This is `false` when text proxy starts at the very beginning of {@link module:engine/view/textproxy~TextProxy#textNode textNode}
  	 * ({@link module:engine/view/textproxy~TextProxy#offsetInText offsetInText} equals `0`) and text proxy sizes is equal to
  	 * text node size.
  	 *
  	 * @readonly
  	 * @type {Boolean}
  	 */
  	get isPartial() {
  		return this.data.length !== this.textNode.data.length;
  	}
  
  	/**
  	 * Parent of this text proxy, which is same as parent of text node represented by this text proxy.
  	 *
  	 * @readonly
  	 * @type {module:engine/view/element~Element|module:engine/view/documentfragment~DocumentFragment|null}
  	 */
  	get parent() {
  		return this.textNode.parent;
  	}
  
  	/**
  	 * Root of this text proxy, which is same as root of text node represented by this text proxy.
  	 *
  	 * @readonly
  	 * @type {module:engine/view/node~Node|module:engine/view/documentfragment~DocumentFragment}
  	 */
  	get root() {
  		return this.textNode.root;
  	}
  
  	/**
  	 * {@link module:engine/view/document~Document View document} that owns this text proxy, or `null` if the text proxy is inside
  	 * {@link module:engine/view/documentfragment~DocumentFragment document fragment}.
  	 *
  	 * @readonly
  	 * @type {module:engine/view/document~Document|null}
  	 */
  	get document() {
  		return this.textNode.document;
  	}
  
  	/**
  	 * Checks whether given view tree object is of given type.
  	 *
  	 * Read more in {@link module:engine/view/node~Node#is}.
  	 *
  	 * @param {String} type
  	 * @returns {Boolean}
  	 */
  	is( type ) {
  		return type == 'textProxy';
  	}
  
  	/**
  	 * Returns ancestors array of this text proxy.
  	 *
  	 * @param {Object} options Options object.
  	 * @param {Boolean} [options.includeSelf=false] When set to `true` {#textNode} will be also included in parent's array.
  	 * @param {Boolean} [options.parentFirst=false] When set to `true`, array will be sorted from text proxy parent to
  	 * root element, otherwise root element will be the first item in the array.
  	 * @returns {Array} Array with ancestors.
  	 */
  	getAncestors( options = { includeSelf: false, parentFirst: false } ) {
  		const ancestors = [];
  		let parent = options.includeSelf ? this.textNode : this.parent;
  
  		while ( parent !== null ) {
  			ancestors[ options.parentFirst ? 'push' : 'unshift' ]( parent );
  			parent = parent.parent;
  		}
  
  		return ancestors;
  	}
  }
  