src/view/treewalker.js
/**
* @license Copyright (c) 2003-2020, CKSource - Frederico Knabben. All rights reserved.
* For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
*/
/**
* @module engine/view/treewalker
*/
import Element from './element';
import Text from './text';
import TextProxy from './textproxy';
import Position from './position';
import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
/**
* Position iterator class. It allows to iterate forward and backward over the document.
*/
export default class TreeWalker {
/**
* Creates a range iterator. All parameters are optional, but you have to specify either `boundaries` or `startPosition`.
*
* @constructor
* @param {Object} options Object with configuration.
* @param {module:engine/view/range~Range} [options.boundaries=null] Range to define boundaries of the iterator.
* @param {module:engine/view/position~Position} [options.startPosition] Starting position.
* @param {'forward'|'backward'} [options.direction='forward'] Walking direction.
* @param {Boolean} [options.singleCharacters=false] Flag indicating whether all characters from
* {@link module:engine/view/text~Text} should be returned as one {@link module:engine/view/text~Text} (`false`) ore one by one as
* {@link module:engine/view/textproxy~TextProxy} (`true`).
* @param {Boolean} [options.shallow=false] Flag indicating whether iterator should enter elements or not. If the
* iterator is shallow child nodes of any iterated node will not be returned along with `elementEnd` tag.
* @param {Boolean} [options.ignoreElementEnd=false] Flag indicating whether iterator should ignore `elementEnd`
* tags. If the option is true walker will not return a parent node of start position. If this option is `true`
* each {@link module:engine/view/element~Element} will be returned once, while if the option is `false` they might be returned
* twice: for `'elementStart'` and `'elementEnd'`.
*/
constructor( options = {} ) {
if ( !options.boundaries && !options.startPosition ) {
/**
* Neither boundaries nor starting position have been defined.
*
* @error view-tree-walker-no-start-position
*/
throw new CKEditorError(
'view-tree-walker-no-start-position: Neither boundaries nor starting position have been defined.',
null
);
}
if ( options.direction && options.direction != 'forward' && options.direction != 'backward' ) {
throw new CKEditorError(
'view-tree-walker-unknown-direction: Only `backward` and `forward` direction allowed.',
options.startPosition,
{ direction: options.direction }
);
}
/**
* Iterator boundaries.
*
* When the iterator is walking `'forward'` on the end of boundary or is walking `'backward'`
* on the start of boundary, then `{ done: true }` is returned.
*
* If boundaries are not defined they are set before first and after last child of the root node.
*
* @readonly
* @member {module:engine/view/range~Range} module:engine/view/treewalker~TreeWalker#boundaries
*/
this.boundaries = options.boundaries || null;
/**
* Iterator position. If start position is not defined then position depends on {@link #direction}. If direction is
* `'forward'` position starts form the beginning, when direction is `'backward'` position starts from the end.
*
* @readonly
* @member {module:engine/view/position~Position} module:engine/view/treewalker~TreeWalker#position
*/
if ( options.startPosition ) {
this.position = Position._createAt( options.startPosition );
} else {
this.position = Position._createAt( options.boundaries[ options.direction == 'backward' ? 'end' : 'start' ] );
}
/**
* Walking direction. Defaults `'forward'`.
*
* @readonly
* @member {'backward'|'forward'} module:engine/view/treewalker~TreeWalker#direction
*/
this.direction = options.direction || 'forward';
/**
* Flag indicating whether all characters from {@link module:engine/view/text~Text} should be returned as one
* {@link module:engine/view/text~Text} or one by one as {@link module:engine/view/textproxy~TextProxy}.
*
* @readonly
* @member {Boolean} module:engine/view/treewalker~TreeWalker#singleCharacters
*/
this.singleCharacters = !!options.singleCharacters;
/**
* Flag indicating whether iterator should enter elements or not. If the iterator is shallow child nodes of any
* iterated node will not be returned along with `elementEnd` tag.
*
* @readonly
* @member {Boolean} module:engine/view/treewalker~TreeWalker#shallow
*/
this.shallow = !!options.shallow;
/**
* Flag indicating whether iterator should ignore `elementEnd` tags. If set to `true`, walker will not
* return a parent node of the start position. Each {@link module:engine/view/element~Element} will be returned once.
* When set to `false` each element might be returned twice: for `'elementStart'` and `'elementEnd'`.
*
* @readonly
* @member {Boolean} module:engine/view/treewalker~TreeWalker#ignoreElementEnd
*/
this.ignoreElementEnd = !!options.ignoreElementEnd;
/**
* Start boundary parent.
*
* @private
* @member {module:engine/view/node~Node} module:engine/view/treewalker~TreeWalker#_boundaryStartParent
*/
this._boundaryStartParent = this.boundaries ? this.boundaries.start.parent : null;
/**
* End boundary parent.
*
* @private
* @member {module:engine/view/node~Node} module:engine/view/treewalker~TreeWalker#_boundaryEndParent
*/
this._boundaryEndParent = this.boundaries ? this.boundaries.end.parent : null;
}
/**
* Iterable interface.
*
* @returns {Iterable.<module:engine/view/treewalker~TreeWalkerValue>}
*/
[ Symbol.iterator ]() {
return this;
}
/**
* Moves {@link #position} in the {@link #direction} skipping values as long as the callback function returns `true`.
*
* For example:
*
* walker.skip( value => value.type == 'text' ); // <p>{}foo</p> -> <p>foo[]</p>
* walker.skip( value => true ); // Move the position to the end: <p>{}foo</p> -> <p>foo</p>[]
* walker.skip( value => false ); // Do not move the position.
*
* @param {Function} skip Callback function. Gets {@link module:engine/view/treewalker~TreeWalkerValue} and should
* return `true` if the value should be skipped or `false` if not.
*/
skip( skip ) {
let done, value, prevPosition;
do {
prevPosition = this.position;
( { done, value } = this.next() );
} while ( !done && skip( value ) );
if ( !done ) {
this.position = prevPosition;
}
}
/**
* Gets the next tree walker's value.
*
* @returns {module:engine/view/treewalker~TreeWalkerValue} Object implementing iterator interface, returning
* information about taken step.
*/
next() {
if ( this.direction == 'forward' ) {
return this._next();
} else {
return this._previous();
}
}
/**
* Makes a step forward in view. Moves the {@link #position} to the next position and returns the encountered value.
*
* @private
* @returns {Object}
* @returns {Boolean} return.done `true` if iterator is done, `false` otherwise.
* @returns {module:engine/view/treewalker~TreeWalkerValue} return.value Information about taken step.
*/
_next() {
let position = this.position.clone();
const previousPosition = this.position;
const parent = position.parent;
// We are at the end of the root.
if ( parent.parent === null && position.offset === parent.childCount ) {
return { done: true };
}
// We reached the walker boundary.
if ( parent === this._boundaryEndParent && position.offset == this.boundaries.end.offset ) {
return { done: true };
}
// Get node just after current position.
let node;
// Text is a specific parent because it contains string instead of child nodes.
if ( parent instanceof Text ) {
if ( position.isAtEnd ) {
// Prevent returning "elementEnd" for Text node. Skip that value and return the next walker step.
this.position = Position._createAfter( parent );
return this._next();
}
node = parent.data[ position.offset ];
} else {
node = parent.getChild( position.offset );
}
if ( node instanceof Element ) {
if ( !this.shallow ) {
position = new Position( node, 0 );
} else {
position.offset++;
}
this.position = position;
return this._formatReturnValue( 'elementStart', node, previousPosition, position, 1 );
} else if ( node instanceof Text ) {
if ( this.singleCharacters ) {
position = new Position( node, 0 );
this.position = position;
return this._next();
} else {
let charactersCount = node.data.length;
let item;
// If text stick out of walker range, we need to cut it and wrap in TextProxy.
if ( node == this._boundaryEndParent ) {
charactersCount = this.boundaries.end.offset;
item = new TextProxy( node, 0, charactersCount );
position = Position._createAfter( item );
} else {
item = new TextProxy( node, 0, node.data.length );
// If not just keep moving forward.
position.offset++;
}
this.position = position;
return this._formatReturnValue( 'text', item, previousPosition, position, charactersCount );
}
} else if ( typeof node == 'string' ) {
let textLength;
if ( this.singleCharacters ) {
textLength = 1;
} else {
// Check if text stick out of walker range.
const endOffset = parent === this._boundaryEndParent ? this.boundaries.end.offset : parent.data.length;
textLength = endOffset - position.offset;
}
const textProxy = new TextProxy( parent, position.offset, textLength );
position.offset += textLength;
this.position = position;
return this._formatReturnValue( 'text', textProxy, previousPosition, position, textLength );
} else {
// `node` is not set, we reached the end of current `parent`.
position = Position._createAfter( parent );
this.position = position;
if ( this.ignoreElementEnd ) {
return this._next();
} else {
return this._formatReturnValue( 'elementEnd', parent, previousPosition, position );
}
}
}
/**
* Makes a step backward in view. Moves the {@link #position} to the previous position and returns the encountered value.
*
* @private
* @returns {Object}
* @returns {Boolean} return.done True if iterator is done.
* @returns {module:engine/view/treewalker~TreeWalkerValue} return.value Information about taken step.
*/
_previous() {
let position = this.position.clone();
const previousPosition = this.position;
const parent = position.parent;
// We are at the beginning of the root.
if ( parent.parent === null && position.offset === 0 ) {
return { done: true };
}
// We reached the walker boundary.
if ( parent == this._boundaryStartParent && position.offset == this.boundaries.start.offset ) {
return { done: true };
}
// Get node just before current position.
let node;
// Text {@link module:engine/view/text~Text} element is a specific parent because contains string instead of child nodes.
if ( parent instanceof Text ) {
if ( position.isAtStart ) {
// Prevent returning "elementStart" for Text node. Skip that value and return the next walker step.
this.position = Position._createBefore( parent );
return this._previous();
}
node = parent.data[ position.offset - 1 ];
} else {
node = parent.getChild( position.offset - 1 );
}
if ( node instanceof Element ) {
if ( !this.shallow ) {
position = new Position( node, node.childCount );
this.position = position;
if ( this.ignoreElementEnd ) {
return this._previous();
} else {
return this._formatReturnValue( 'elementEnd', node, previousPosition, position );
}
} else {
position.offset--;
this.position = position;
return this._formatReturnValue( 'elementStart', node, previousPosition, position, 1 );
}
} else if ( node instanceof Text ) {
if ( this.singleCharacters ) {
position = new Position( node, node.data.length );
this.position = position;
return this._previous();
} else {
let charactersCount = node.data.length;
let item;
// If text stick out of walker range, we need to cut it and wrap in TextProxy.
if ( node == this._boundaryStartParent ) {
const offset = this.boundaries.start.offset;
item = new TextProxy( node, offset, node.data.length - offset );
charactersCount = item.data.length;
position = Position._createBefore( item );
} else {
item = new TextProxy( node, 0, node.data.length );
// If not just keep moving backward.
position.offset--;
}
this.position = position;
return this._formatReturnValue( 'text', item, previousPosition, position, charactersCount );
}
} else if ( typeof node == 'string' ) {
let textLength;
if ( !this.singleCharacters ) {
// Check if text stick out of walker range.
const startOffset = parent === this._boundaryStartParent ? this.boundaries.start.offset : 0;
textLength = position.offset - startOffset;
} else {
textLength = 1;
}
position.offset -= textLength;
const textProxy = new TextProxy( parent, position.offset, textLength );
this.position = position;
return this._formatReturnValue( 'text', textProxy, previousPosition, position, textLength );
} else {
// `node` is not set, we reached the beginning of current `parent`.
position = Position._createBefore( parent );
this.position = position;
return this._formatReturnValue( 'elementStart', parent, previousPosition, position, 1 );
}
}
/**
* Format returned data and adjust `previousPosition` and `nextPosition` if reach the bound of the {@link module:engine/view/text~Text}.
*
* @private
* @param {module:engine/view/treewalker~TreeWalkerValueType} type Type of step.
* @param {module:engine/view/item~Item} item Item between old and new position.
* @param {module:engine/view/position~Position} previousPosition Previous position of iterator.
* @param {module:engine/view/position~Position} nextPosition Next position of iterator.
* @param {Number} [length] Length of the item.
* @returns {module:engine/view/treewalker~TreeWalkerValue}
*/
_formatReturnValue( type, item, previousPosition, nextPosition, length ) {
// Text is a specific parent, because contains string instead of children.
// Walker doesn't enter to the Text except situations when walker is iterating over every single character,
// or the bound starts/ends inside the Text. So when the position is at the beginning or at the end of the Text
// we move it just before or just after Text.
if ( item instanceof TextProxy ) {
// Position is at the end of Text.
if ( item.offsetInText + item.data.length == item.textNode.data.length ) {
if ( this.direction == 'forward' && !( this.boundaries && this.boundaries.end.isEqual( this.position ) ) ) {
nextPosition = Position._createAfter( item.textNode );
// When we change nextPosition of returned value we need also update walker current position.
this.position = nextPosition;
} else {
previousPosition = Position._createAfter( item.textNode );
}
}
// Position is at the begining ot the text.
if ( item.offsetInText === 0 ) {
if ( this.direction == 'backward' && !( this.boundaries && this.boundaries.start.isEqual( this.position ) ) ) {
nextPosition = Position._createBefore( item.textNode );
// When we change nextPosition of returned value we need also update walker current position.
this.position = nextPosition;
} else {
previousPosition = Position._createBefore( item.textNode );
}
}
}
return {
done: false,
value: {
type,
item,
previousPosition,
nextPosition,
length
}
};
}
}
/**
* Type of the step made by {@link module:engine/view/treewalker~TreeWalker}.
* Possible values: `'elementStart'` if walker is at the beginning of a node, `'elementEnd'` if walker is at the end
* of node, or `'text'` if walker traversed over single and multiple characters.
* For {@link module:engine/view/text~Text} `elementStart` and `elementEnd` is not returned.
*
* @typedef {String} module:engine/view/treewalker~TreeWalkerValueType
*/
/**
* Object returned by {@link module:engine/view/treewalker~TreeWalker} when traversing tree view.
*
* @typedef {Object} module:engine/view/treewalker~TreeWalkerValue
* @property {module:engine/view/treewalker~TreeWalkerValueType} type
* @property {module:engine/view/item~Item} item Item between the old and the new positions
* of the tree walker.
* @property {module:engine/view/position~Position} previousPosition Previous position of the iterator.
* * Forward iteration: For `'elementEnd'` it is the last position inside the element. For all other types it is the
* position before the item.
* * Backward iteration: For `'elementStart'` it is the first position inside the element. For all other types it is
* the position after item.
* * 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
* inside of the text to its parent just before or just after that text.
* @property {module:engine/view/position~Position} nextPosition Next position of the iterator.
* * Forward iteration: For `'elementStart'` it is the first position inside the element. For all other types it is
* the position after the item.
* * Backward iteration: For `'elementEnd'` it is last position inside element. For all other types it is the position
* before the item.
* * 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
* inside of the text to its parent just before or just after that text.
* @property {Number} [length] Length of the item. For `'elementStart'` it is `1`. For `'text'` it is
* the length of that text. For `'elementEnd'` it is `undefined`.
*/
/**
* Tree walking directions.
*
* @typedef {'forward'|'backward'} module:engine/view/treewalker~TreeWalkerDirection
*/