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* @license Copyright (c) 2003-2021, CKSource - Frederico Knabben. All rights reserved.\n * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license\n */\n\n/**\n * @module engine/view/treewalker\n */\n\nimport Element from './element';\nimport Text from './text';\nimport TextProxy from './textproxy';\nimport Position from './position';\nimport CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';\n\n/**\n * Position iterator class. It allows to iterate forward and backward over the document.\n */\nexport default class TreeWalker {\n\t/**\n\t * Creates a range iterator. All parameters are optional, but you have to specify either `boundaries` or `startPosition`.\n\t *\n\t * @constructor\n\t * @param {Object} options Object with configuration.\n\t * @param {module:engine/view/range~Range} [options.boundaries=null] Range to define boundaries of the iterator.\n\t * @param {module:engine/view/position~Position} [options.startPosition] Starting position.\n\t * @param {'forward'|'backward'} [options.direction='forward'] Walking direction.\n\t * @param {Boolean} [options.singleCharacters=false] Flag indicating whether all characters from\n\t * {@link module:engine/view/text~Text} should be returned as one {@link module:engine/view/text~Text} (`false`) ore one by one as\n\t * {@link module:engine/view/textproxy~TextProxy} (`true`).\n\t * @param {Boolean} [options.shallow=false] Flag indicating whether iterator should enter elements or not. If the\n\t * iterator is shallow child nodes of any iterated node will not be returned along with `elementEnd` tag.\n\t * @param {Boolean} [options.ignoreElementEnd=false] Flag indicating whether iterator should ignore `elementEnd`\n\t * tags. If the option is true walker will not return a parent node of start position. If this option is `true`\n\t * each {@link module:engine/view/element~Element} will be returned once, while if the option is `false` they might be returned\n\t * twice: for `'elementStart'` and `'elementEnd'`.\n\t */\n\tconstructor( options = {} ) {\n\t\tif ( !options.boundaries && !options.startPosition ) {\n\t\t\t/**\n\t\t\t * Neither boundaries nor starting position have been defined.\n\t\t\t *\n\t\t\t * @error view-tree-walker-no-start-position\n\t\t\t */\n\t\t\tthrow new CKEditorError(\n\t\t\t\t'view-tree-walker-no-start-position',\n\t\t\t\tnull\n\t\t\t);\n\t\t}\n\n\t\tif ( options.direction && options.direction != 'forward' && options.direction != 'backward' ) {\n\t\t\t/**\n\t\t\t * Only `backward` and `forward` direction allowed.\n\t\t\t *\n\t\t\t * @error view-tree-walker-unknown-direction\n\t\t\t */\n\t\t\tthrow new CKEditorError( 'view-tree-walker-unknown-direction', options.startPosition, { direction: options.direction } );\n\t\t}\n\n\t\t/**\n\t\t * Iterator boundaries.\n\t\t *\n\t\t * When the iterator is walking `'forward'` on the end of boundary or is walking `'backward'`\n\t\t * on the start of boundary, then `{ done: true }` is returned.\n\t\t *\n\t\t * If boundaries are not defined they are set before first and after last child of the root node.\n\t\t *\n\t\t * @readonly\n\t\t * @member {module:engine/view/range~Range} module:engine/view/treewalker~TreeWalker#boundaries\n\t\t */\n\t\tthis.boundaries = options.boundaries || null;\n\n\t\t/**\n\t\t * Iterator position. If start position is not defined then position depends on {@link #direction}. If direction is\n\t\t * `'forward'` position starts form the beginning, when direction is `'backward'` position starts from the end.\n\t\t *\n\t\t * @readonly\n\t\t * @member {module:engine/view/position~Position} module:engine/view/treewalker~TreeWalker#position\n\t\t */\n\t\tif ( options.startPosition ) {\n\t\t\tthis.position = Position._createAt( options.startPosition );\n\t\t} else {\n\t\t\tthis.position = Position._createAt( options.boundaries[ options.direction == 'backward' ? 'end' : 'start' ] );\n\t\t}\n\n\t\t/**\n\t\t * Walking direction. Defaults `'forward'`.\n\t\t *\n\t\t * @readonly\n\t\t * @member {'backward'|'forward'} module:engine/view/treewalker~TreeWalker#direction\n\t\t */\n\t\tthis.direction = options.direction || 'forward';\n\n\t\t/**\n\t\t * Flag indicating whether all characters from {@link module:engine/view/text~Text} should be returned as one\n\t\t * {@link module:engine/view/text~Text} or one by one as {@link module:engine/view/textproxy~TextProxy}.\n\t\t *\n\t\t * @readonly\n\t\t * @member {Boolean} module:engine/view/treewalker~TreeWalker#singleCharacters\n\t\t */\n\t\tthis.singleCharacters = !!options.singleCharacters;\n\n\t\t/**\n\t\t * Flag indicating whether iterator should enter elements or not. If the iterator is shallow child nodes of any\n\t\t * iterated node will not be returned along with `elementEnd` tag.\n\t\t *\n\t\t * @readonly\n\t\t * @member {Boolean} module:engine/view/treewalker~TreeWalker#shallow\n\t\t */\n\t\tthis.shallow = !!options.shallow;\n\n\t\t/**\n\t\t * Flag indicating whether iterator should ignore `elementEnd` tags. If set to `true`, walker will not\n\t\t * return a parent node of the start position. Each {@link module:engine/view/element~Element} will be returned once.\n\t\t * When set to `false` each element might be returned twice: for `'elementStart'` and `'elementEnd'`.\n\t\t *\n\t\t * @readonly\n\t\t * @member {Boolean} module:engine/view/treewalker~TreeWalker#ignoreElementEnd\n\t\t */\n\t\tthis.ignoreElementEnd = !!options.ignoreElementEnd;\n\n\t\t/**\n\t\t * Start boundary parent.\n\t\t *\n\t\t * @private\n\t\t * @member {module:engine/view/node~Node} module:engine/view/treewalker~TreeWalker#_boundaryStartParent\n\t\t */\n\t\tthis._boundaryStartParent = this.boundaries ? this.boundaries.start.parent : null;\n\n\t\t/**\n\t\t * End boundary parent.\n\t\t *\n\t\t * @private\n\t\t * @member {module:engine/view/node~Node} module:engine/view/treewalker~TreeWalker#_boundaryEndParent\n\t\t */\n\t\tthis._boundaryEndParent = this.boundaries ? this.boundaries.end.parent : null;\n\t}\n\n\t/**\n\t * Iterable interface.\n\t *\n\t * @returns {Iterable.<module:engine/view/treewalker~TreeWalkerValue>}\n\t */\n\t[ Symbol.iterator ]() {\n\t\treturn this;\n\t}\n\n\t/**\n\t * Moves {@link #position} in the {@link #direction} skipping values as long as the callback function returns `true`.\n\t *\n\t * For example:\n\t *\n\t * \t\twalker.skip( value => value.type == 'text' ); // <p>{}foo</p> -> <p>foo[]</p>\n\t * \t\twalker.skip( value => true ); // Move the position to the end: <p>{}foo</p> -> <p>foo</p>[]\n\t * \t\twalker.skip( value => false ); // Do not move the position.\n\t *\n\t * @param {Function} skip Callback function. Gets {@link module:engine/view/treewalker~TreeWalkerValue} and should\n\t * return `true` if the value should be skipped or `false` if not.\n\t */\n\tskip( skip ) {\n\t\tlet done, value, prevPosition;\n\n\t\tdo {\n\t\t\tprevPosition = this.position;\n\n\t\t\t( { done, value } = this.next() );\n\t\t} while ( !done && skip( value ) );\n\n\t\tif ( !done ) {\n\t\t\tthis.position = prevPosition;\n\t\t}\n\t}\n\n\t/**\n\t * Gets the next tree walker's value.\n\t *\n\t * @returns {module:engine/view/treewalker~TreeWalkerValue} Object implementing iterator interface, returning\n\t * information about taken step.\n\t */\n\tnext() {\n\t\tif ( this.direction == 'forward' ) {\n\t\t\treturn this._next();\n\t\t} else {\n\t\t\treturn this._previous();\n\t\t}\n\t}\n\n\t/**\n\t * Makes a step forward in view. Moves the {@link #position} to the next position and returns the encountered value.\n\t *\n\t * @private\n\t * @returns {Object}\n\t * @returns {Boolean} return.done `true` if iterator is done, `false` otherwise.\n\t * @returns {module:engine/view/treewalker~TreeWalkerValue} return.value Information about taken step.\n\t */\n\t_next() {\n\t\tlet position = this.position.clone();\n\t\tconst previousPosition = this.position;\n\t\tconst parent = position.parent;\n\n\t\t// We are at the end of the root.\n\t\tif ( parent.parent === null && position.offset === parent.childCount ) {\n\t\t\treturn { done: true };\n\t\t}\n\n\t\t// We reached the walker boundary.\n\t\tif ( parent === this._boundaryEndParent && position.offset == this.boundaries.end.offset ) {\n\t\t\treturn { done: true };\n\t\t}\n\n\t\t// Get node just after current position.\n\t\tlet node;\n\n\t\t// Text is a specific parent because it contains string instead of child nodes.\n\t\tif ( parent instanceof Text ) {\n\t\t\tif ( position.isAtEnd ) {\n\t\t\t\t// Prevent returning \"elementEnd\" for Text node. Skip that value and return the next walker step.\n\t\t\t\tthis.position = Position._createAfter( parent );\n\n\t\t\t\treturn this._next();\n\t\t\t}\n\n\t\t\tnode = parent.data[ position.offset ];\n\t\t} else {\n\t\t\tnode = parent.getChild( position.offset );\n\t\t}\n\n\t\tif ( node instanceof Element ) {\n\t\t\tif ( !this.shallow ) {\n\t\t\t\tposition = new Position( node, 0 );\n\t\t\t} else {\n\t\t\t\tposition.offset++;\n\t\t\t}\n\n\t\t\tthis.position = position;\n\n\t\t\treturn this._formatReturnValue( 'elementStart', node, previousPosition, position, 1 );\n\t\t} else if ( node instanceof Text ) {\n\t\t\tif ( this.singleCharacters ) {\n\t\t\t\tposition = new Position( node, 0 );\n\t\t\t\tthis.position = position;\n\n\t\t\t\treturn this._next();\n\t\t\t} else {\n\t\t\t\tlet charactersCount = node.data.length;\n\t\t\t\tlet item;\n\n\t\t\t\t// If text stick out of walker range, we need to cut it and wrap in TextProxy.\n\t\t\t\tif ( node == this._boundaryEndParent ) {\n\t\t\t\t\tcharactersCount = this.boundaries.end.offset;\n\t\t\t\t\titem = new TextProxy( node, 0, charactersCount );\n\t\t\t\t\tposition = Position._createAfter( item );\n\t\t\t\t} else {\n\t\t\t\t\titem = new TextProxy( node, 0, node.data.length );\n\t\t\t\t\t// If not just keep moving forward.\n\t\t\t\t\tposition.offset++;\n\t\t\t\t}\n\n\t\t\t\tthis.position = position;\n\n\t\t\t\treturn this._formatReturnValue( 'text', item, previousPosition, position, charactersCount );\n\t\t\t}\n\t\t} else if ( typeof node == 'string' ) {\n\t\t\tlet textLength;\n\n\t\t\tif ( this.singleCharacters ) {\n\t\t\t\ttextLength = 1;\n\t\t\t} else {\n\t\t\t\t// Check if text stick out of walker range.\n\t\t\t\tconst endOffset = parent === this._boundaryEndParent ? this.boundaries.end.offset : parent.data.length;\n\n\t\t\t\ttextLength = endOffset - position.offset;\n\t\t\t}\n\n\t\t\tconst textProxy = new TextProxy( parent, position.offset, textLength );\n\n\t\t\tposition.offset += textLength;\n\t\t\tthis.position = position;\n\n\t\t\treturn this._formatReturnValue( 'text', textProxy, previousPosition, position, textLength );\n\t\t} else {\n\t\t\t// `node` is not set, we reached the end of current `parent`.\n\t\t\tposition = Position._createAfter( parent );\n\t\t\tthis.position = position;\n\n\t\t\tif ( this.ignoreElementEnd ) {\n\t\t\t\treturn this._next();\n\t\t\t} else {\n\t\t\t\treturn this._formatReturnValue( 'elementEnd', parent, previousPosition, position );\n\t\t\t}\n\t\t}\n\t}\n\n\t/**\n\t * Makes a step backward in view. Moves the {@link #position} to the previous position and returns the encountered value.\n\t *\n\t * @private\n\t * @returns {Object}\n\t * @returns {Boolean} return.done True if iterator is done.\n\t * @returns {module:engine/view/treewalker~TreeWalkerValue} return.value Information about taken step.\n\t */\n\t_previous() {\n\t\tlet position = this.position.clone();\n\t\tconst previousPosition = this.position;\n\t\tconst parent = position.parent;\n\n\t\t// We are at the beginning of the root.\n\t\tif ( parent.parent === null && position.offset === 0 ) {\n\t\t\treturn { done: true };\n\t\t}\n\n\t\t// We reached the walker boundary.\n\t\tif ( parent == this._boundaryStartParent && position.offset == this.boundaries.start.offset ) {\n\t\t\treturn { done: true };\n\t\t}\n\n\t\t// Get node just before current position.\n\t\tlet node;\n\n\t\t// Text {@link module:engine/view/text~Text} element is a specific parent because contains string instead of child nodes.\n\t\tif ( parent instanceof Text ) {\n\t\t\tif ( position.isAtStart ) {\n\t\t\t\t// Prevent returning \"elementStart\" for Text node. Skip that value and return the next walker step.\n\t\t\t\tthis.position = Position._createBefore( parent );\n\n\t\t\t\treturn this._previous();\n\t\t\t}\n\n\t\t\tnode = parent.data[ position.offset - 1 ];\n\t\t} else {\n\t\t\tnode = parent.getChild( position.offset - 1 );\n\t\t}\n\n\t\tif ( node instanceof Element ) {\n\t\t\tif ( !this.shallow ) {\n\t\t\t\tposition = new Position( node, node.childCount );\n\t\t\t\tthis.position = position;\n\n\t\t\t\tif ( this.ignoreElementEnd ) {\n\t\t\t\t\treturn this._previous();\n\t\t\t\t} else {\n\t\t\t\t\treturn this._formatReturnValue( 'elementEnd', node, previousPosition, position );\n\t\t\t\t}\n\t\t\t} else {\n\t\t\t\tposition.offset--;\n\t\t\t\tthis.position = position;\n\n\t\t\t\treturn this._formatReturnValue( 'elementStart', node, previousPosition, position, 1 );\n\t\t\t}\n\t\t} else if ( node instanceof Text ) {\n\t\t\tif ( this.singleCharacters ) {\n\t\t\t\tposition = new Position( node, node.data.length );\n\t\t\t\tthis.position = position;\n\n\t\t\t\treturn this._previous();\n\t\t\t} else {\n\t\t\t\tlet charactersCount = node.data.length;\n\t\t\t\tlet item;\n\n\t\t\t\t// If text stick out of walker range, we need to cut it and wrap in TextProxy.\n\t\t\t\tif ( node == this._boundaryStartParent ) {\n\t\t\t\t\tconst offset = this.boundaries.start.offset;\n\n\t\t\t\t\titem = new TextProxy( node, offset, node.data.length - offset );\n\t\t\t\t\tcharactersCount = item.data.length;\n\t\t\t\t\tposition = Position._createBefore( item );\n\t\t\t\t} else {\n\t\t\t\t\titem = new TextProxy( node, 0, node.data.length );\n\t\t\t\t\t// If not just keep moving backward.\n\t\t\t\t\tposition.offset--;\n\t\t\t\t}\n\n\t\t\t\tthis.position = position;\n\n\t\t\t\treturn this._formatReturnValue( 'text', item, previousPosition, position, charactersCount );\n\t\t\t}\n\t\t} else if ( typeof node == 'string' ) {\n\t\t\tlet textLength;\n\n\t\t\tif ( !this.singleCharacters ) {\n\t\t\t\t// Check if text stick out of walker range.\n\t\t\t\tconst startOffset = parent === this._boundaryStartParent ? this.boundaries.start.offset : 0;\n\n\t\t\t\ttextLength = position.offset - startOffset;\n\t\t\t} else {\n\t\t\t\ttextLength = 1;\n\t\t\t}\n\n\t\t\tposition.offset -= textLength;\n\n\t\t\tconst textProxy = new TextProxy( parent, position.offset, textLength );\n\n\t\t\tthis.position = position;\n\n\t\t\treturn this._formatReturnValue( 'text', textProxy, previousPosition, position, textLength );\n\t\t} else {\n\t\t\t// `node` is not set, we reached the beginning of current `parent`.\n\t\t\tposition = Position._createBefore( parent );\n\t\t\tthis.position = position;\n\n\t\t\treturn this._formatReturnValue( 'elementStart', parent, previousPosition, position, 1 );\n\t\t}\n\t}\n\n\t/**\n\t * Format returned data and adjust `previousPosition` and `nextPosition` if reach the bound of the {@link module:engine/view/text~Text}.\n\t *\n\t * @private\n\t * @param {module:engine/view/treewalker~TreeWalkerValueType} type Type of step.\n\t * @param {module:engine/view/item~Item} item Item between old and new position.\n\t * @param {module:engine/view/position~Position} previousPosition Previous position of iterator.\n\t * @param {module:engine/view/position~Position} nextPosition Next position of iterator.\n\t * @param {Number} [length] Length of the item.\n\t * @returns {module:engine/view/treewalker~TreeWalkerValue}\n\t */\n\t_formatReturnValue( type, item, previousPosition, nextPosition, length ) {\n\t\t// Text is a specific parent, because contains string instead of children.\n\t\t// Walker doesn't enter to the Text except situations when walker is iterating over every single character,\n\t\t// or the bound starts/ends inside the Text. So when the position is at the beginning or at the end of the Text\n\t\t// we move it just before or just after Text.\n\t\tif ( item instanceof TextProxy ) {\n\t\t\t// Position is at the end of Text.\n\t\t\tif ( item.offsetInText + item.data.length == item.textNode.data.length ) {\n\t\t\t\tif ( this.direction == 'forward' && !( this.boundaries && this.boundaries.end.isEqual( this.position ) ) ) {\n\t\t\t\t\tnextPosition = Position._createAfter( item.textNode );\n\t\t\t\t\t// When we change nextPosition of returned value we need also update walker current position.\n\t\t\t\t\tthis.position = nextPosition;\n\t\t\t\t} else {\n\t\t\t\t\tpreviousPosition = Position._createAfter( item.textNode );\n\t\t\t\t}\n\t\t\t}\n\n\t\t\t// Position is at the begining ot the text.\n\t\t\tif ( item.offsetInText === 0 ) {\n\t\t\t\tif ( this.direction == 'backward' && !( this.boundaries && this.boundaries.start.isEqual( this.position ) ) ) {\n\t\t\t\t\tnextPosition = Position._createBefore( item.textNode );\n\t\t\t\t\t// When we change nextPosition of returned value we need also update walker current position.\n\t\t\t\t\tthis.position = nextPosition;\n\t\t\t\t} else {\n\t\t\t\t\tpreviousPosition = Position._createBefore( item.textNode );\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\treturn {\n\t\t\tdone: false,\n\t\t\tvalue: {\n\t\t\t\ttype,\n\t\t\t\titem,\n\t\t\t\tpreviousPosition,\n\t\t\t\tnextPosition,\n\t\t\t\tlength\n\t\t\t}\n\t\t};\n\t}\n}\n\n/**\n * Type of the step made by {@link module:engine/view/treewalker~TreeWalker}.\n * Possible values: `'elementStart'` if walker is at the beginning of a node, `'elementEnd'` if walker is at the end\n * of node, or `'text'` if walker traversed over single and multiple characters.\n * For {@link module:engine/view/text~Text} `elementStart` and `elementEnd` is not returned.\n *\n * @typedef {String} module:engine/view/treewalker~TreeWalkerValueType\n */\n\n/**\n * Object returned by {@link module:engine/view/treewalker~TreeWalker} when traversing tree view.\n *\n * @typedef {Object} module:engine/view/treewalker~TreeWalkerValue\n * @property {module:engine/view/treewalker~TreeWalkerValueType} type\n * @property {module:engine/view/item~Item} item Item between the old and the new positions\n * of the tree walker.\n * @property {module:engine/view/position~Position} previousPosition Previous position of the iterator.\n * * Forward iteration: For `'elementEnd'` it is the last position inside the element. For all other types it is the\n * position before the item.\n * * Backward iteration: For `'elementStart'` it is the first position inside the element. For all other types it is\n * the position after item.\n * * If the position is at the beginning or at the end of the {@link module:engine/view/text~Text} it is always moved from the\n * inside of the text to its parent just before or just after that text.\n * @property {module:engine/view/position~Position} nextPosition Next position of the iterator.\n * * Forward iteration: For `'elementStart'` it is the first position inside the element. For all other types it is\n * the position after the item.\n * * Backward iteration: For `'elementEnd'` it is last position inside element. For all other types it is the position\n * before the item.\n * * If the position is at the beginning or at the end of the {@link module:engine/view/text~Text} it is always moved from the\n * inside of the text to its parent just before or just after that text.\n * @property {Number} [length] Length of the item. For `'elementStart'` it is `1`. For `'text'` it is\n * the length of that text. For `'elementEnd'` it is `undefined`.\n */\n\n/**\n * Tree walking directions.\n *\n * @typedef {'forward'|'backward'} module:engine/view/treewalker~TreeWalkerDirection\n */\n"],"sourceRoot":""}