src/conversion/modelconsumable.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/conversion/modelconsumable
*/
import TextProxy from '../model/textproxy';
/**
* Manages a list of consumable values for {@link module:engine/model/item~Item model items}.
*
* Consumables are various aspects of the model. A model item can be broken down into singular properties that might be
* taken into consideration when converting that item.
*
* `ModelConsumable` is used by {@link module:engine/conversion/downcastdispatcher~DowncastDispatcher} while analyzing changed
* parts of {@link module:engine/model/document~Document the document}. The added / changed / removed model items are broken down
* into singular properties (the item itself and it's attributes). All those parts are saved in `ModelConsumable`. Then,
* during conversion, when given part of model item is converted (i.e. the view element has been inserted into the view,
* but without attributes), consumable value is removed from `ModelConsumable`.
*
* For model items, `ModelConsumable` stores consumable values of one of following types: `insert`, `addattribute:<attributeKey>`,
* `changeattributes:<attributeKey>`, `removeattributes:<attributeKey>`.
*
* In most cases, it is enough to let {@link module:engine/conversion/downcastdispatcher~DowncastDispatcher}
* gather consumable values, so there is no need to use
* {@link module:engine/conversion/modelconsumable~ModelConsumable#add add method} directly.
* However, it is important to understand how consumable values can be
* {@link module:engine/conversion/modelconsumable~ModelConsumable#consume consumed}.
* See {@link module:engine/conversion/downcasthelpers default downcast converters} for more information.
*
* Keep in mind, that one conversion event may have multiple callbacks (converters) attached to it. Each of those is
* able to convert one or more parts of the model. However, when one of those callbacks actually converts
* something, other should not, because they would duplicate the results. Using `ModelConsumable` helps avoiding
* this situation, because callbacks should only convert those values, which were not yet consumed from `ModelConsumable`.
*
* Consuming multiple values in a single callback:
*
* // Converter for custom `image` element that might have a `caption` element inside which changes
* // how the image is displayed in the view:
* //
* // Model:
* //
* // [image]
* // └─ [caption]
* // └─ foo
* //
* // View:
* //
* // <figure>
* // ├─ <img />
* // └─ <caption>
* // └─ foo
* modelConversionDispatcher.on( 'insert:image', ( evt, data, conversionApi ) => {
* // First, consume the `image` element.
* conversionApi.consumable.consume( data.item, 'insert' );
*
* // Just create normal image element for the view.
* // Maybe it will be "decorated" later.
* const viewImage = new ViewElement( 'img' );
* const insertPosition = conversionApi.mapper.toViewPosition( data.range.start );
* const viewWriter = conversionApi.writer;
*
* // Check if the `image` element has children.
* if ( data.item.childCount > 0 ) {
* const modelCaption = data.item.getChild( 0 );
*
* // `modelCaption` insertion change is consumed from consumable values.
* // It will not be converted by other converters, but it's children (probably some text) will be.
* // Through mapping, converters for text will know where to insert contents of `modelCaption`.
* if ( conversionApi.consumable.consume( modelCaption, 'insert' ) ) {
* const viewCaption = new ViewElement( 'figcaption' );
*
* const viewImageHolder = new ViewElement( 'figure', null, [ viewImage, viewCaption ] );
*
* conversionApi.mapper.bindElements( modelCaption, viewCaption );
* conversionApi.mapper.bindElements( data.item, viewImageHolder );
* viewWriter.insert( insertPosition, viewImageHolder );
* }
* } else {
* conversionApi.mapper.bindElements( data.item, viewImage );
* viewWriter.insert( insertPosition, viewImage );
* }
*
* evt.stop();
* } );
*/
export default class ModelConsumable {
/**
* Creates an empty consumables list.
*/
constructor() {
/**
* Contains list of consumable values.
*
* @private
* @member {Map} module:engine/conversion/modelconsumable~ModelConsumable#_consumable
*/
this._consumable = new Map();
/**
* For each {@link module:engine/model/textproxy~TextProxy} added to `ModelConsumable`, this registry holds parent
* of that `TextProxy` and start and end indices of that `TextProxy`. This allows identification of `TextProxy`
* instances that points to the same part of the model but are different instances. Each distinct `TextProxy`
* is given unique `Symbol` which is then registered as consumable. This process is transparent for `ModelConsumable`
* API user because whenever `TextProxy` is added, tested, consumed or reverted, internal mechanisms of
* `ModelConsumable` translates `TextProxy` to that unique `Symbol`.
*
* @private
* @member {Map} module:engine/conversion/modelconsumable~ModelConsumable#_textProxyRegistry
*/
this._textProxyRegistry = new Map();
}
/**
* Adds a consumable value to the consumables list and links it with given model item.
*
* modelConsumable.add( modelElement, 'insert' ); // Add `modelElement` insertion change to consumable values.
* modelConsumable.add( modelElement, 'addAttribute:bold' ); // Add `bold` attribute insertion on `modelElement` change.
* modelConsumable.add( modelElement, 'removeAttribute:bold' ); // Add `bold` attribute removal on `modelElement` change.
* modelConsumable.add( modelSelection, 'selection' ); // Add `modelSelection` to consumable values.
* modelConsumable.add( modelRange, 'range' ); // Add `modelRange` to consumable values.
*
* @param {module:engine/model/item~Item|module:engine/model/selection~Selection|module:engine/model/range~Range} item
* Model item, range or selection that has the consumable.
* @param {String} type Consumable type. Will be normalized to a proper form, that is either `<word>` or `<part>:<part>`.
* Second colon and everything after will be cut. Passing event name is a safe and good practice.
*/
add( item, type ) {
type = _normalizeConsumableType( type );
if ( item instanceof TextProxy ) {
item = this._getSymbolForTextProxy( item );
}
if ( !this._consumable.has( item ) ) {
this._consumable.set( item, new Map() );
}
this._consumable.get( item ).set( type, true );
}
/**
* Removes given consumable value from given model item.
*
* modelConsumable.consume( modelElement, 'insert' ); // Remove `modelElement` insertion change from consumable values.
* modelConsumable.consume( modelElement, 'addAttribute:bold' ); // Remove `bold` attribute insertion on `modelElement` change.
* modelConsumable.consume( modelElement, 'removeAttribute:bold' ); // Remove `bold` attribute removal on `modelElement` change.
* modelConsumable.consume( modelSelection, 'selection' ); // Remove `modelSelection` from consumable values.
* modelConsumable.consume( modelRange, 'range' ); // Remove 'modelRange' from consumable values.
*
* @param {module:engine/model/item~Item|module:engine/model/selection~Selection|module:engine/model/range~Range} item
* Model item, range or selection from which consumable will be consumed.
* @param {String} type Consumable type. Will be normalized to a proper form, that is either `<word>` or `<part>:<part>`.
* Second colon and everything after will be cut. Passing event name is a safe and good practice.
* @returns {Boolean} `true` if consumable value was available and was consumed, `false` otherwise.
*/
consume( item, type ) {
type = _normalizeConsumableType( type );
if ( item instanceof TextProxy ) {
item = this._getSymbolForTextProxy( item );
}
if ( this.test( item, type ) ) {
this._consumable.get( item ).set( type, false );
return true;
} else {
return false;
}
}
/**
* Tests whether there is a consumable value of given type connected with given model item.
*
* modelConsumable.test( modelElement, 'insert' ); // Check for `modelElement` insertion change.
* modelConsumable.test( modelElement, 'addAttribute:bold' ); // Check for `bold` attribute insertion on `modelElement` change.
* modelConsumable.test( modelElement, 'removeAttribute:bold' ); // Check for `bold` attribute removal on `modelElement` change.
* modelConsumable.test( modelSelection, 'selection' ); // Check if `modelSelection` is consumable.
* modelConsumable.test( modelRange, 'range' ); // Check if `modelRange` is consumable.
*
* @param {module:engine/model/item~Item|module:engine/model/selection~Selection|module:engine/model/range~Range} item
* Model item, range or selection to be tested.
* @param {String} type Consumable type. Will be normalized to a proper form, that is either `<word>` or `<part>:<part>`.
* Second colon and everything after will be cut. Passing event name is a safe and good practice.
* @returns {null|Boolean} `null` if such consumable was never added, `false` if the consumable values was
* already consumed or `true` if it was added and not consumed yet.
*/
test( item, type ) {
type = _normalizeConsumableType( type );
if ( item instanceof TextProxy ) {
item = this._getSymbolForTextProxy( item );
}
const itemConsumables = this._consumable.get( item );
if ( itemConsumables === undefined ) {
return null;
}
const value = itemConsumables.get( type );
if ( value === undefined ) {
return null;
}
return value;
}
/**
* Reverts consuming of consumable value.
*
* modelConsumable.revert( modelElement, 'insert' ); // Revert consuming `modelElement` insertion change.
* modelConsumable.revert( modelElement, 'addAttribute:bold' ); // Revert consuming `bold` attribute insert from `modelElement`.
* modelConsumable.revert( modelElement, 'removeAttribute:bold' ); // Revert consuming `bold` attribute remove from `modelElement`.
* modelConsumable.revert( modelSelection, 'selection' ); // Revert consuming `modelSelection`.
* modelConsumable.revert( modelRange, 'range' ); // Revert consuming `modelRange`.
*
* @param {module:engine/model/item~Item|module:engine/model/selection~Selection|module:engine/model/range~Range} item
* Model item, range or selection to be reverted.
* @param {String} type Consumable type.
* @returns {null|Boolean} `true` if consumable has been reversed, `false` otherwise. `null` if the consumable has
* never been added.
*/
revert( item, type ) {
type = _normalizeConsumableType( type );
if ( item instanceof TextProxy ) {
item = this._getSymbolForTextProxy( item );
}
const test = this.test( item, type );
if ( test === false ) {
this._consumable.get( item ).set( type, true );
return true;
} else if ( test === true ) {
return false;
}
return null;
}
/**
* Gets a unique symbol for passed {@link module:engine/model/textproxy~TextProxy} instance. All `TextProxy` instances that
* have same parent, same start index and same end index will get the same symbol.
*
* Used internally to correctly consume `TextProxy` instances.
*
* @private
* @param {module:engine/model/textproxy~TextProxy} textProxy `TextProxy` instance to get a symbol for.
* @returns {Symbol} Symbol representing all equal instances of `TextProxy`.
*/
_getSymbolForTextProxy( textProxy ) {
let symbol = null;
const startMap = this._textProxyRegistry.get( textProxy.startOffset );
if ( startMap ) {
const endMap = startMap.get( textProxy.endOffset );
if ( endMap ) {
symbol = endMap.get( textProxy.parent );
}
}
if ( !symbol ) {
symbol = this._addSymbolForTextProxy( textProxy.startOffset, textProxy.endOffset, textProxy.parent );
}
return symbol;
}
/**
* Adds a symbol for given properties that characterizes a {@link module:engine/model/textproxy~TextProxy} instance.
*
* Used internally to correctly consume `TextProxy` instances.
*
* @private
* @param {Number} startIndex Text proxy start index in it's parent.
* @param {Number} endIndex Text proxy end index in it's parent.
* @param {module:engine/model/element~Element} parent Text proxy parent.
* @returns {Symbol} Symbol generated for given properties.
*/
_addSymbolForTextProxy( start, end, parent ) {
const symbol = Symbol( 'textProxySymbol' );
let startMap, endMap;
startMap = this._textProxyRegistry.get( start );
if ( !startMap ) {
startMap = new Map();
this._textProxyRegistry.set( start, startMap );
}
endMap = startMap.get( end );
if ( !endMap ) {
endMap = new Map();
startMap.set( end, endMap );
}
endMap.set( parent, symbol );
return symbol;
}
}
// Returns a normalized consumable type name from given string. A normalized consumable type name is a string that has
// at most one colon, for example: `insert` or `addMarker:highlight`. If string to normalize has more "parts" (more colons),
// the other parts are dropped, for example: `addattribute:bold:$text` -> `addattributes:bold`.
//
// @param {String} type Consumable type.
// @returns {String} Normalized consumable type.
function _normalizeConsumableType( type ) {
const parts = type.split( ':' );
return parts.length > 1 ? parts[ 0 ] + ':' + parts[ 1 ] : parts[ 0 ];
}