text: /**
   * @license Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
   * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
   */
  
  /**
   * @module engine/model/textproxy
   */
  
  import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
  
  /**
   * `TextProxy` represents a part of {@link module:engine/model/text~Text text node}.
   *
   * Since {@link module:engine/model/position~Position positions} can be placed between characters of a text node,
   * {@link module:engine/model/range~Range ranges} may contain only parts of text nodes. When {@link module:engine/model/range~Range#getItems
   * getting items}
   * contained in such range, we need to represent a part of that text node, since returning the whole text node would be incorrect.
   * `TextProxy` solves this issue.
   *
   * `TextProxy` has an API similar to {@link module:engine/model/text~Text Text} and allows to do most of the common tasks performed
   * on model nodes.
   *
   * **Note:** Some `TextProxy` instances may represent whole text node, not just a part of it.
   * See {@link module:engine/model/textproxy~TextProxy#isPartial}.
   *
   * **Note:** `TextProxy` is not an instance of {@link module:engine/model/node~Node node}. Keep this in mind when using it as a
   * parameter of methods.
   *
   * **Note:** `TextProxy` is a readonly interface. If you want to perform changes on model data represented by a `TextProxy`
   * use {@link module:engine/model/writer~Writer model writer API}.
   *
   * **Note:** `TextProxy` instances are created on the fly, basing on the current state of model. Because of this, it is
   * highly unrecommended to store references to `TextProxy` instances. `TextProxy` instances are not refreshed when
   * model changes, so they might get invalidated. Instead, consider creating {@link module:engine/model/liveposition~LivePosition live
   * position}.
   *
   * `TextProxy` instances are created by {@link module:engine/model/treewalker~TreeWalker model 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/model/text~Text} textNode Text node which part is represented by this text proxy.
  	 * @param {Number} offsetInText Offset in {@link module:engine/model/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 ) {
  		/**
  		 * Text node which part is represented by this text proxy.
  		 *
  		 * @readonly
  		 * @member {module:engine/model/text~Text}
  		 */
  		this.textNode = textNode;
  
  		if ( offsetInText < 0 || offsetInText > textNode.offsetSize ) {
  			/**
  			 * Given `offsetInText` value is incorrect.
  			 *
  			 * @error model-textproxy-wrong-offsetintext
  			 */
  			throw new CKEditorError( 'model-textproxy-wrong-offsetintext: Given offsetInText value is incorrect.', this );
  		}
  
  		if ( length < 0 || offsetInText + length > textNode.offsetSize ) {
  			/**
  			 * Given `length` value is incorrect.
  			 *
  			 * @error model-textproxy-wrong-length
  			 */
  			throw new CKEditorError( 'model-textproxy-wrong-length: Given length value is incorrect.', this );
  		}
  
  		/**
  		 * Text data represented by this text proxy.
  		 *
  		 * @readonly
  		 * @member {String}
  		 */
  		this.data = textNode.data.substring( offsetInText, offsetInText + length );
  
  		/**
  		 * Offset in {@link module:engine/model/textproxy~TextProxy#textNode text node} from which the text proxy starts.
  		 *
  		 * @readonly
  		 * @member {Number}
  		 */
  		this.offsetInText = offsetInText;
  	}
  
  	/**
  	 * Offset at which this text proxy starts in it's parent.
  	 *
  	 * @see module:engine/model/node~Node#startOffset
  	 * @readonly
  	 * @type {Number}
  	 */
  	get startOffset() {
  		return this.textNode.startOffset !== null ? this.textNode.startOffset + this.offsetInText : null;
  	}
  
  	/**
  	 * Offset size of this text proxy. Equal to the number of characters represented by the text proxy.
  	 *
  	 * @see module:engine/model/node~Node#offsetSize
  	 * @readonly
  	 * @type {Number}
  	 */
  	get offsetSize() {
  		return this.data.length;
  	}
  
  	/**
  	 * Offset at which this text proxy ends in it's parent.
  	 *
  	 * @see module:engine/model/node~Node#endOffset
  	 * @readonly
  	 * @type {Number}
  	 */
  	get endOffset() {
  		return this.startOffset !== null ? this.startOffset + this.offsetSize : null;
  	}
  
  	/**
  	 * Flag indicating whether `TextProxy` instance covers only part of the original {@link module:engine/model/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/model/textproxy~TextProxy#textNode textNode}
  	 * ({@link module:engine/model/textproxy~TextProxy#offsetInText offsetInText} equals `0`) and text proxy sizes is equal to
  	 * text node size.
  	 *
  	 * @readonly
  	 * @type {Boolean}
  	 */
  	get isPartial() {
  		return this.offsetSize !== this.textNode.offsetSize;
  	}
  
  	/**
  	 * Parent of this text proxy, which is same as parent of text node represented by this text proxy.
  	 *
  	 * @readonly
  	 * @type {module:engine/model/element~Element|module:engine/model/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/model/node~Node|module:engine/model/documentfragment~DocumentFragment}
  	 */
  	get root() {
  		return this.textNode.root;
  	}
  
  	/**
  	 * {@link module:engine/model/document~Document Document} that owns text node represented by this text proxy or `null` if the text node
  	 * has no parent or is inside a {@link module:engine/model/documentfragment~DocumentFragment DocumentFragment}.
  	 *
  	 * @readonly
  	 * @type {module:engine/model/document~Document|null}
  	 */
  	get document() {
  		return this.textNode.document;
  	}
  
  	/**
  	 * Checks whether this object is of the given.
  	 *
  	 *		textProxy.is( 'textProxy' ); // -> true
  	 *		textProxy.is( 'model:textProxy' ); // -> true
  	 *
  	 *		textProxy.is( 'view:textProxy' ); // -> false
  	 *		textProxy.is( 'range' ); // -> false
  	 *
  	 * {@link module:engine/model/node~Node#is Check the entire list of model objects} which implement the `is()` method.
  	 *
  	 * @param {String} type
  	 * @returns {Boolean}
  	 */
  	is( type ) {
  		return type == 'textProxy' || type == 'model:textProxy';
  	}
  
  	/**
  	 * Gets path to this text proxy.
  	 *
  	 * @see module:engine/model/node~Node#getPath
  	 * @returns {Array.<Number>}
  	 */
  	getPath() {
  		const path = this.textNode.getPath();
  
  		if ( path.length > 0 ) {
  			path[ path.length - 1 ] += this.offsetInText;
  		}
  
  		return path;
  	}
  
  	/**
  	 * Returns ancestors array of this text proxy.
  	 *
  	 * @param {Object} options Options object.
  	 * @param {Boolean} [options.includeSelf=false] When set to `true` this text proxy 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 : this.parent;
  
  		while ( parent ) {
  			ancestors[ options.parentFirst ? 'push' : 'unshift' ]( parent );
  			parent = parent.parent;
  		}
  
  		return ancestors;
  	}
  
  	/**
  	 * Checks if this text proxy has an attribute for given key.
  	 *
  	 * @param {String} key Key of attribute to check.
  	 * @returns {Boolean} `true` if attribute with given key is set on text proxy, `false` otherwise.
  	 */
  	hasAttribute( key ) {
  		return this.textNode.hasAttribute( key );
  	}
  
  	/**
  	 * Gets an attribute value for given key or `undefined` if that attribute is not set on text proxy.
  	 *
  	 * @param {String} key Key of attribute to look for.
  	 * @returns {*} Attribute value or `undefined`.
  	 */
  	getAttribute( key ) {
  		return this.textNode.getAttribute( key );
  	}
  
  	/**
  	 * Returns iterator that iterates over this node's attributes. Attributes are returned as arrays containing two
  	 * items. First one is attribute key and second is attribute value.
  	 *
  	 * This format is accepted by native `Map` object and also can be passed in `Node` constructor.
  	 *
  	 * @returns {Iterable.<*>}
  	 */
  	getAttributes() {
  		return this.textNode.getAttributes();
  	}
  
  	/**
  	 * Returns iterator that iterates over this node's attribute keys.
  	 *
  	 * @returns {Iterable.<String>}
  	 */
  	getAttributeKeys() {
  		return this.textNode.getAttributeKeys();
  	}
  }
  