text: /**
   * @license Copyright (c) 2003-2021, CKSource - Frederico Knabben. All rights reserved.
   * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
   */
  
  /**
   * @module engine/model/node
   */
  
  import toMap from '@ckeditor/ckeditor5-utils/src/tomap';
  import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
  import compareArrays from '@ckeditor/ckeditor5-utils/src/comparearrays';
  // To check if component is loaded more than once.
  import '@ckeditor/ckeditor5-utils/src/version';
  
  /**
   * Model node. Most basic structure of model tree.
   *
   * This is an abstract class that is a base for other classes representing different nodes in model.
   *
   * **Note:** If a node is detached from the model tree, you can manipulate it using it's API.
   * However, it is **very important** that nodes already attached to model tree should be only changed through
   * {@link module:engine/model/writer~Writer Writer API}.
   *
   * Changes done by `Node` methods, like {@link module:engine/model/element~Element#_insertChild _insertChild} or
   * {@link module:engine/model/node~Node#_setAttribute _setAttribute}
   * do not generate {@link module:engine/model/operation/operation~Operation operations}
   * which are essential for correct editor work if you modify nodes in {@link module:engine/model/document~Document document} root.
   *
   * The flow of working on `Node` (and classes that inherits from it) is as such:
   * 1. You can create a `Node` instance, modify it using it's API.
   * 2. Add `Node` to the model using `Batch` API.
   * 3. Change `Node` that was already added to the model using `Batch` API.
   *
   * Similarly, you cannot use `Batch` API on a node that has not been added to the model tree, with the exception
   * of {@link module:engine/model/writer~Writer#insert inserting} that node to the model tree.
   *
   * Be aware that using {@link module:engine/model/writer~Writer#remove remove from Batch API} does not allow to use `Node` API because
   * the information about `Node` is still kept in model document.
   *
   * In case of {@link module:engine/model/element~Element element node}, adding and removing children also counts as changing a node and
   * follows same rules.
   */
  export default class Node {
  	/**
  	 * Creates a model node.
  	 *
  	 * This is an abstract class, so this constructor should not be used directly.
  	 *
  	 * @abstract
  	 * @param {Object} [attrs] Node's attributes. See {@link module:utils/tomap~toMap} for a list of accepted values.
  	 */
  	constructor( attrs ) {
  		/**
  		 * Parent of this node. It could be {@link module:engine/model/element~Element}
  		 * or {@link module:engine/model/documentfragment~DocumentFragment}.
  		 * Equals to `null` if the node has no parent.
  		 *
  		 * @readonly
  		 * @member {module:engine/model/element~Element|module:engine/model/documentfragment~DocumentFragment|null}
  		 */
  		this.parent = null;
  
  		/**
  		 * Attributes set on this node.
  		 *
  		 * @private
  		 * @member {Map} module:engine/model/node~Node#_attrs
  		 */
  		this._attrs = toMap( attrs );
  	}
  
  	/**
  	 * Index of this node in it's parent or `null` if the node has no parent.
  	 *
  	 * Accessing this property throws an error if this node's parent element does not contain it.
  	 * This means that model tree got broken.
  	 *
  	 * @readonly
  	 * @type {Number|null}
  	 */
  	get index() {
  		let pos;
  
  		if ( !this.parent ) {
  			return null;
  		}
  
  		if ( ( pos = this.parent.getChildIndex( this ) ) === null ) {
  			throw new CKEditorError( 'model-node-not-found-in-parent', this );
  		}
  
  		return pos;
  	}
  
  	/**
  	 * Offset at which this node starts in it's parent. It is equal to the sum of {@link #offsetSize offsetSize}
  	 * of all it's previous siblings. Equals to `null` if node has no parent.
  	 *
  	 * Accessing this property throws an error if this node's parent element does not contain it.
  	 * This means that model tree got broken.
  	 *
  	 * @readonly
  	 * @type {Number|null}
  	 */
  	get startOffset() {
  		let pos;
  
  		if ( !this.parent ) {
  			return null;
  		}
  
  		if ( ( pos = this.parent.getChildStartOffset( this ) ) === null ) {
  			throw new CKEditorError( 'model-node-not-found-in-parent', this );
  		}
  
  		return pos;
  	}
  
  	/**
  	 * Offset size of this node. Represents how much "offset space" is occupied by the node in it's parent.
  	 * It is important for {@link module:engine/model/position~Position position}. When node has `offsetSize` greater than `1`, position
  	 * can be placed between that node start and end. `offsetSize` greater than `1` is for nodes that represents more
  	 * than one entity, i.e. {@link module:engine/model/text~Text text node}.
  	 *
  	 * @readonly
  	 * @type {Number}
  	 */
  	get offsetSize() {
  		return 1;
  	}
  
  	/**
  	 * Offset at which this node ends in it's parent. It is equal to the sum of this node's
  	 * {@link module:engine/model/node~Node#startOffset start offset} and {@link #offsetSize offset size}.
  	 * Equals to `null` if the node has no parent.
  	 *
  	 * @readonly
  	 * @type {Number|null}
  	 */
  	get endOffset() {
  		if ( !this.parent ) {
  			return null;
  		}
  
  		return this.startOffset + this.offsetSize;
  	}
  
  	/**
  	 * Node's next sibling or `null` if the node is a last child of it's parent or if the node has no parent.
  	 *
  	 * @readonly
  	 * @type {module:engine/model/node~Node|null}
  	 */
  	get nextSibling() {
  		const index = this.index;
  
  		return ( index !== null && this.parent.getChild( index + 1 ) ) || null;
  	}
  
  	/**
  	 * Node's previous sibling or `null` if the node is a first child of it's parent or if the node has no parent.
  	 *
  	 * @readonly
  	 * @type {module:engine/model/node~Node|null}
  	 */
  	get previousSibling() {
  		const index = this.index;
  
  		return ( index !== null && this.parent.getChild( index - 1 ) ) || null;
  	}
  
  	/**
  	 * The top-most ancestor of the node. If node has no parent it is the root itself. If the node is a part
  	 * of {@link module:engine/model/documentfragment~DocumentFragment}, it's `root` is equal to that `DocumentFragment`.
  	 *
  	 * @readonly
  	 * @type {module:engine/model/node~Node|module:engine/model/documentfragment~DocumentFragment}
  	 */
  	get root() {
  		let root = this; // eslint-disable-line consistent-this
  
  		while ( root.parent ) {
  			root = root.parent;
  		}
  
  		return root;
  	}
  
  	/**
  	 * Returns true if the node is in a tree rooted in the document (is a descendant of one of its roots).
  	 *
  	 * @returns {Boolean}
  	 */
  	isAttached() {
  		return this.root.is( 'rootElement' );
  	}
  
  	/**
  	 * Gets path to the node. The path is an array containing starting offsets of consecutive ancestors of this node,
  	 * beginning from {@link module:engine/model/node~Node#root root}, down to this node's starting offset. The path can be used to
  	 * create {@link module:engine/model/position~Position Position} instance.
  	 *
  	 *		const abc = new Text( 'abc' );
  	 *		const foo = new Text( 'foo' );
  	 *		const h1 = new Element( 'h1', null, new Text( 'header' ) );
  	 *		const p = new Element( 'p', null, [ abc, foo ] );
  	 *		const div = new Element( 'div', null, [ h1, p ] );
  	 *		foo.getPath(); // Returns [ 1, 3 ]. `foo` is in `p` which is in `div`. `p` starts at offset 1, while `foo` at 3.
  	 *		h1.getPath(); // Returns [ 0 ].
  	 *		div.getPath(); // Returns [].
  	 *
  	 * @returns {Array.<Number>} The path.
  	 */
  	getPath() {
  		const path = [];
  		let node = this; // eslint-disable-line consistent-this
  
  		while ( node.parent ) {
  			path.unshift( node.startOffset );
  			node = node.parent;
  		}
  
  		return path;
  	}
  
  	/**
  	 * Returns ancestors array of this node.
  	 *
  	 * @param {Object} options Options object.
  	 * @param {Boolean} [options.includeSelf=false] When set to `true` this node will be also included in parent's array.
  	 * @param {Boolean} [options.parentFirst=false] When set to `true`, array will be sorted from node's 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;
  	}
  
  	/**
  	 * Returns a {@link module:engine/model/element~Element} or {@link module:engine/model/documentfragment~DocumentFragment}
  	 * which is a common ancestor of both nodes.
  	 *
  	 * @param {module:engine/model/node~Node} node The second node.
  	 * @param {Object} options Options object.
  	 * @param {Boolean} [options.includeSelf=false] When set to `true` both nodes will be considered "ancestors" too.
  	 * Which means that if e.g. node A is inside B, then their common ancestor will be B.
  	 * @returns {module:engine/model/element~Element|module:engine/model/documentfragment~DocumentFragment|null}
  	 */
  	getCommonAncestor( node, options = {} ) {
  		const ancestorsA = this.getAncestors( options );
  		const ancestorsB = node.getAncestors( options );
  
  		let i = 0;
  
  		while ( ancestorsA[ i ] == ancestorsB[ i ] && ancestorsA[ i ] ) {
  			i++;
  		}
  
  		return i === 0 ? null : ancestorsA[ i - 1 ];
  	}
  
  	/**
  	 * Returns whether this node is before given node. `false` is returned if nodes are in different trees (for example,
  	 * in different {@link module:engine/model/documentfragment~DocumentFragment}s).
  	 *
  	 * @param {module:engine/model/node~Node} node Node to compare with.
  	 * @returns {Boolean}
  	 */
  	isBefore( node ) {
  		// Given node is not before this node if they are same.
  		if ( this == node ) {
  			return false;
  		}
  
  		// Return `false` if it is impossible to compare nodes.
  		if ( this.root !== node.root ) {
  			return false;
  		}
  
  		const thisPath = this.getPath();
  		const nodePath = node.getPath();
  
  		const result = compareArrays( thisPath, nodePath );
  
  		switch ( result ) {
  			case 'prefix':
  				return true;
  
  			case 'extension':
  				return false;
  
  			default:
  				return thisPath[ result ] < nodePath[ result ];
  		}
  	}
  
  	/**
  	 * Returns whether this node is after given node. `false` is returned if nodes are in different trees (for example,
  	 * in different {@link module:engine/model/documentfragment~DocumentFragment}s).
  	 *
  	 * @param {module:engine/model/node~Node} node Node to compare with.
  	 * @returns {Boolean}
  	 */
  	isAfter( node ) {
  		// Given node is not before this node if they are same.
  		if ( this == node ) {
  			return false;
  		}
  
  		// Return `false` if it is impossible to compare nodes.
  		if ( this.root !== node.root ) {
  			return false;
  		}
  
  		// In other cases, just check if the `node` is before, and return the opposite.
  		return !this.isBefore( node );
  	}
  
  	/**
  	 * Checks if the node has an attribute with given key.
  	 *
  	 * @param {String} key Key of attribute to check.
  	 * @returns {Boolean} `true` if attribute with given key is set on node, `false` otherwise.
  	 */
  	hasAttribute( key ) {
  		return this._attrs.has( key );
  	}
  
  	/**
  	 * Gets an attribute value for given key or `undefined` if that attribute is not set on node.
  	 *
  	 * @param {String} key Key of attribute to look for.
  	 * @returns {*} Attribute value or `undefined`.
  	 */
  	getAttribute( key ) {
  		return this._attrs.get( 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._attrs.entries();
  	}
  
  	/**
  	 * Returns iterator that iterates over this node's attribute keys.
  	 *
  	 * @returns {Iterable.<String>}
  	 */
  	getAttributeKeys() {
  		return this._attrs.keys();
  	}
  
  	/**
  	 * Converts `Node` to plain object and returns it.
  	 *
  	 * @returns {Object} `Node` converted to plain object.
  	 */
  	toJSON() {
  		const json = {};
  
  		// Serializes attributes to the object.
  		// attributes = { a: 'foo', b: 1, c: true }.
  		if ( this._attrs.size ) {
  			json.attributes = Array.from( this._attrs ).reduce( ( result, attr ) => {
  				result[ attr[ 0 ] ] = attr[ 1 ];
  
  				return result;
  			}, {} );
  		}
  
  		return json;
  	}
  
  	/**
  	 * Checks whether this object is of the given type.
  	 *
  	 * This method is useful when processing model objects that are of unknown type. For example, a function
  	 * may return a {@link module:engine/model/documentfragment~DocumentFragment} or a {@link module:engine/model/node~Node}
  	 * that can be either a text node or an element. This method can be used to check what kind of object is returned.
  	 *
  	 *		someObject.is( 'element' ); // -> true if this is an element
  	 *		someObject.is( 'node' ); // -> true if this is a node (a text node or an element)
  	 *		someObject.is( 'documentFragment' ); // -> true if this is a document fragment
  	 *
  	 * Since this method is also available on a range of view objects, you can prefix the type of the object with
  	 * `model:` or `view:` to check, for example, if this is the model's or view's element:
  	 *
  	 *		modelElement.is( 'model:element' ); // -> true
  	 *		modelElement.is( 'view:element' ); // -> false
  	 *
  	 * By using this method it is also possible to check a name of an element:
  	 *
  	 *		imageElement.is( 'element', 'image' ); // -> true
  	 *		imageElement.is( 'element', 'image' ); // -> same as above
  	 *		imageElement.is( 'model:element', 'image' ); // -> same as above, but more precise
  	 *
  	 * The list of model objects which implement the `is()` method:
  	 *
  	 * * {@link module:engine/model/node~Node#is `Node#is()`}
  	 * * {@link module:engine/model/text~Text#is `Text#is()`}
  	 * * {@link module:engine/model/element~Element#is `Element#is()`}
  	 * * {@link module:engine/model/rootelement~RootElement#is `RootElement#is()`}
  	 * * {@link module:engine/model/position~Position#is `Position#is()`}
  	 * * {@link module:engine/model/liveposition~LivePosition#is `LivePosition#is()`}
  	 * * {@link module:engine/model/range~Range#is `Range#is()`}
  	 * * {@link module:engine/model/liverange~LiveRange#is `LiveRange#is()`}
  	 * * {@link module:engine/model/documentfragment~DocumentFragment#is `DocumentFragment#is()`}
  	 * * {@link module:engine/model/selection~Selection#is `Selection#is()`}
  	 * * {@link module:engine/model/documentselection~DocumentSelection#is `DocumentSelection#is()`}
  	 * * {@link module:engine/model/markercollection~Marker#is `Marker#is()`}
  	 * * {@link module:engine/model/textproxy~TextProxy#is `TextProxy#is()`}
  	 *
  	 * @method #is
  	 * @param {String} type Type to check.
  	 * @returns {Boolean}
  	 */
  	is( type ) {
  		return type === 'node' || type === 'model:node';
  	}
  
  	/**
  	 * Creates a copy of this node, that is a node with exactly same attributes, and returns it.
  	 *
  	 * @protected
  	 * @returns {module:engine/model/node~Node} Node with same attributes as this node.
  	 */
  	_clone() {
  		return new Node( this._attrs );
  	}
  
  	/**
  	 * Removes this node from it's parent.
  	 *
  	 * @see module:engine/model/writer~Writer#remove
  	 * @protected
  	 */
  	_remove() {
  		this.parent._removeChildren( this.index );
  	}
  
  	/**
  	 * Sets attribute on the node. If attribute with the same key already is set, it's value is overwritten.
  	 *
  	 * @see module:engine/model/writer~Writer#setAttribute
  	 * @protected
  	 * @param {String} key Key of attribute to set.
  	 * @param {*} value Attribute value.
  	 */
  	_setAttribute( key, value ) {
  		this._attrs.set( key, value );
  	}
  
  	/**
  	 * Removes all attributes from the node and sets given attributes.
  	 *
  	 * @see module:engine/model/writer~Writer#setAttributes
  	 * @protected
  	 * @param {Object} [attrs] Attributes to set. See {@link module:utils/tomap~toMap} for a list of accepted values.
  	 */
  	_setAttributesTo( attrs ) {
  		this._attrs = toMap( attrs );
  	}
  
  	/**
  	 * Removes an attribute with given key from the node.
  	 *
  	 * @see module:engine/model/writer~Writer#removeAttribute
  	 * @protected
  	 * @param {String} key Key of attribute to remove.
  	 * @returns {Boolean} `true` if the attribute was set on the element, `false` otherwise.
  	 */
  	_removeAttribute( key ) {
  		return this._attrs.delete( key );
  	}
  
  	/**
  	 * Removes all attributes from the node.
  	 *
  	 * @see module:engine/model/writer~Writer#clearAttributes
  	 * @protected
  	 */
  	_clearAttributes() {
  		this._attrs.clear();
  	}
  }
  
  /**
   * The node's parent does not contain this node.
   *
   * @error model-node-not-found-in-parent
   */
  