/** * @license Copyright (c) 2003-2015, CKSource - Frederico Knabben. All rights reserved. * For licensing, see LICENSE.md. */ 'use strict'; /** * Transforms given {document.operation.Operation} by another {document.operation.Operation} and returns the result of * that transformation as an array containing one or more {document.operation.Operation} elements. * * Operations work on specified positions, passed to them when they are created. Whenever {@link document.Document document} * changes, we have to reflect those modifications by updating or "transforming" operations which are not yet applied. * When an operation is transformed, its parameters may change based on the operation by which it is transformed. * If the transform-by operation applied any modifications to the Tree Data Model which affect positions or nodes * connected with transformed operation, those changes will be reflected in the parameters of the returned operation(s). * * Whenever the {@link document.Document document} has different {@link document.Document#baseVersion} * than the operation you want to {@link document.Document#applyOperation apply}, you need to transform that * operation by all operations which were already applied to the {@link document.Document document} and have greater * {@link document.Document#baseVersion} than the operation being applied. Transform them in the same order as those * operations which were applied. This way all modifications done to the Tree Data Model will be reflected * in the operation parameters and the operation will "operate" on "up-to-date" version of the Tree Data Model. * This is mostly the case with Operational Transformations but it might be needed in particular features as well. * * In some cases, when given operation apply changes to the same nodes as this operation, two or more operations need * to be created as one would not be able to reflect the combination of these operations. * This is why an array is returned instead of a single object. All returned operations have to be applied * (or further transformed) to get an effect which was intended in pre-transformed operation. * * Sometimes two operations are in conflict. This happens when they modify the same node in a different way, i.e. * set different value for the same attribute or move the node into different positions. When this happens, * we need to decide which operation is more important. We can't assume that operation `a` or operation `b` is always * more important. In Operational Transformations algorithms we often need to get a result of transforming * `a` by `b` and also `b` by `a`. In both transformations the same operation has to be the important one. If we assume * that first or the second passed operation is always more important we won't be able to solve this case. * * @function document.operation.transform * @param {document.operation.Operation} a Operation that will be transformed. * @param {document.operation.Operation} b Operation to transform by. * @param {Boolean} isAMoreImportantThanB Flag indicating whether the operation which will be transformed (`a`) should be treated * as more important when resolving conflicts. * @returns {Array.} Result of the transformation. */ CKEDITOR.define( [ 'document/operation/insertoperation', 'document/operation/changeoperation', 'document/operation/moveoperation', 'document/operation/nooperation', 'document/range', 'utils' ], ( InsertOperation, ChangeOperation, MoveOperation, NoOperation, Range, utils ) => { const ot = { InsertOperation: { // Transforms InsertOperation `a` by InsertOperation `b`. Accepts a flag stating whether `a` is more important // than `b` when it comes to resolving conflicts. Returns results as an array of operations. InsertOperation( a, b, isStrong ) { // Transformed operations are always new instances, not references to the original operations. const transformed = a.clone(); // Transform insert position by the other operation position. transformed.position = transformed.position.getTransformedByInsertion( b.position, b.nodeList.length, !isStrong ); return [ transformed ]; }, ChangeOperation: doNotUpdate, // Transforms InsertOperation `a` by MoveOperation `b`. Accepts a flag stating whether `a` is more important // than `b` when it comes to resolving conflicts. Returns results as an array of operations. MoveOperation( a, b, isStrong ) { const transformed = a.clone(); // Transform insert position by the other operation parameters. transformed.position = a.position.getTransformedByMove( b.sourcePosition, b.targetPosition, b.howMany, !isStrong ); return [ transformed ]; } }, ChangeOperation: { // Transforms ChangeOperation `a` by InsertOperation `b`. Returns results as an array of operations. InsertOperation( a, b ) { // Transform this operation's range. const ranges = a.range.getTransformedByInsertion( b.position, b.nodeList.length ); // Map transformed range(s) to operations and return them. return ranges.reverse().map( ( range ) => { return new ChangeOperation( range, a.oldAttr, a.newAttr, a.baseVersion ); } ); }, // Transforms ChangeOperation `a` by ChangeOperation `b`. Accepts a flag stating whether `a` is more important // than `b` when it comes to resolving conflicts. Returns results as an array of operations. ChangeOperation( a, b, isStrong ) { if ( haveConflictingAttributes( a, b ) ) { // If operations attributes are in conflict, check if their ranges intersect and manage them properly. let operations = []; // First, we want to apply change to the part of a range that has not been changed by the other operation. operations = operations.concat( a.range.getDifference( b.range ).map( ( range ) => { return new ChangeOperation( range, a.oldAttr, a.newAttr, a.baseVersion ); } ) ); if ( isStrong ) { // If this operation is more important, we want also want to apply change to the part of the // original range that has already been changed by the other operation. Since that range // got changed we have to update oldAttr. const common = a.range.getIntersection( b.range ); if ( common !== null ) { operations.push( new ChangeOperation( common, b.oldAttr, a.newAttr, a.baseVersion ) ); } } // If no operations has been added nothing should get updated, but since we need to return // an instance of Operation we add NoOperation to the array. if ( operations.length === 0 ) { operations.push( new NoOperation( a.baseVersion ) ); } return operations; } else { // If operations don't conflict simply, return an array containing just a clone of this operation. return [ a.clone() ]; } }, // Transforms ChangeOperation `a` by MoveOperation `b`. Returns results as an array of operations. MoveOperation( a, b ) { // Convert MoveOperation properties into a range. const rangeB = Range.createFromPositionAndOffset( b.sourcePosition, b.howMany ); // Get target position from the state "after" nodes specified by MoveOperation are "detached". const newTargetPosition = b.targetPosition.getTransformedByDeletion( b.sourcePosition, b.howMany ); // This will aggregate transformed ranges. let ranges = []; // Difference is a part of changed range that is modified by ChangeOperation but are not affected // by MoveOperation. This can be zero, one or two ranges (if moved range is inside changed range). // If two ranges were returned it means that rangeB was inside rangeA. We will cover rangeB later. // Right now we will make a simplification and join difference ranges and transform them as one. const difference = joinRanges( a.range.getDifference( rangeB ) ); // Common is a range of nodes that is affected by MoveOperation. So it got moved to other place. const common = a.range.getIntersection( rangeB ); if ( difference !== null ) { // MoveOperation removes nodes from their original position. We acknowledge this by proper transformation. // Take the start and the end of the range and transform them by deletion of moved nodes. // Note that if rangeB was inside ChangeOperation range, only difference.end will be transformed. // This nicely covers the joining simplification we did in the previous step. difference.start = difference.start.getTransformedByDeletion( b.sourcePosition, b.howMany ); difference.end = difference.end.getTransformedByDeletion( b.sourcePosition, b.howMany ); // MoveOperation pastes nodes into target position. We acknowledge this by proper transformation. // Note that since we operate on transformed difference range, we should transform by // previously transformed target position. // Note that we do not use Position.getTransformedByMove on range boundaries because we need to // transform by insertion a range as a whole, since newTargetPosition might be inside that range. ranges = difference.getTransformedByInsertion( newTargetPosition, b.howMany, false ).reverse(); } if ( common !== null ) { // Here we do not need to worry that newTargetPosition is inside moved range, because that // would mean that the MoveOperation targets into itself, and that is incorrect operation. // Instead, we calculate the new position of that part of original range. common.start = common.start._getCombined( b.sourcePosition, newTargetPosition ); common.end = common.end._getCombined( b.sourcePosition, newTargetPosition ); ranges.push( common ); } // Map transformed range(s) to operations and return them. return ranges.map( ( range ) => { return new ChangeOperation( range, a.oldAttr, a.newAttr, a.baseVersion ); } ); } }, MoveOperation: { // Transforms MoveOperation `a` by InsertOperation `b`. Accepts a flag stating whether `a` is more important // than `b` when it comes to resolving conflicts. Returns results as an array of operations. InsertOperation( a, b, isStrong ) { // Get target position from the state "after" nodes are inserted by InsertOperation. const newTargetPosition = a.targetPosition.getTransformedByInsertion( b.position, b.nodeList.length, !isStrong ); // Create range from MoveOperation properties and transform it by insertion as well. const rangeB = Range.createFromPositionAndOffset( a.sourcePosition, a.howMany ); const ranges = rangeB.getTransformedByInsertion( b.position, b.nodeList.length, true ); // Map transformed range(s) to operations and return them. return ranges.reverse().map( ( range ) => { return new MoveOperation( range.start, newTargetPosition.clone(), range.end.offset - range.start.offset, a.baseVersion ); } ); }, ChangeOperation: doNotUpdate, // Transforms MoveOperation `a` by MoveOperation `b`. Accepts a flag stating whether `a` is more important // than `b` when it comes to resolving conflicts. Returns results as an array of operations. MoveOperation( a, b, isStrong ) { // Special case when both move operations' target positions are inside nodes that are // being moved by the other move operation. So in other words, we move ranges into inside of each other. // This case can't be solved reasonably (on the other hand, it should not happen often). if ( moveTargetIntoMovedRange( a, b ) && moveTargetIntoMovedRange( b, a ) ) { // Instead of transforming operation, we return a reverse of the operation that we transform by. // So when the results of this "transformation" will be applied, `b` MoveOperation will get reversed. return [ b.getReversed() ]; } // Create ranges from MoveOperations properties. const rangeA = Range.createFromPositionAndOffset( a.sourcePosition, a.howMany ); const rangeB = Range.createFromPositionAndOffset( b.sourcePosition, b.howMany ); // Special case when transformed range contains both the other operation's whole range and target. // In such case, operations are not really conflicting and we should leave transformed operation as it is. // Without this we would have 3 or 4 operations and the transformation result would probably be not intuitive. if ( rangeA.containsRange( rangeB ) && rangeA.containsPosition( b.targetPosition ) ) { return [ a.clone() ]; } // Mirror situation for the case above - now transformed range is wholly contained in the other // operation's range and also targets to that range. Without this special treatment we would // transform this operation into NoOperation, but this would not be compatible with the result // generated by the special case above. else if ( rangeB.containsRange( rangeA ) && rangeB.containsPosition( a.targetPosition ) ) { return [ new MoveOperation( a.sourcePosition._getCombined( b.sourcePosition, b.targetPosition ), a.targetPosition._getCombined( b.sourcePosition, b.targetPosition ), a.howMany, a.baseVersion ) ]; } // All the other non-special cases are treated by generic algorithm below. const differenceSet = rangeA.getDifference( rangeB ); const common = rangeA.getIntersection( rangeB ); // This will aggregate transformed ranges. let ranges = []; // Get target position from the state "after" nodes specified by other MoveOperation are "detached". const moveTargetPosition = b.targetPosition.getTransformedByDeletion( b.sourcePosition, b.howMany ); // First, we take care of that part of the range that is only modified by transformed operation. for ( let i = 0; i < differenceSet.length; i++ ) { // MoveOperation removes nodes from their original position. We acknowledge this by proper transformation. // Take the start and the end of the range and transform them by deletion of moved nodes. differenceSet[ i ].start = differenceSet[ i ].start.getTransformedByDeletion( b.sourcePosition, b.howMany ); differenceSet[ i ].end = differenceSet[ i ].end.getTransformedByDeletion( b.sourcePosition, b.howMany ); // MoveOperation pastes nodes into target position. We acknowledge this by proper transformation. // Note that since we operate on transformed difference range, we should transform by // previously transformed target position. // Note that we do not use Position.getTransformedByMove on range boundaries because we need to // transform by insertion a range as a whole, since newTargetPosition might be inside that range. ranges = ranges.concat( differenceSet[ i ].getTransformedByInsertion( moveTargetPosition, b.howMany, true ) ); } // Then, we have to manage the common part of both move ranges. // If MoveOperations has common range it can be one of two: // * on the same tree level - it means that we move the same nodes into different places // * on deeper tree level - it means that we move nodes that are inside moved nodes // The operations are conflicting only if they try to move exactly same nodes, so only in the first case. // So, we will handle common range if it is "deeper" or if transformed operation is more important. let isDeeper = utils.compareArrays( b.sourcePosition.getParentPath(), a.sourcePosition.getParentPath() ) == utils.compareArrays.PREFIX; if ( common !== null && ( isDeeper || isStrong ) ) { // Here we do not need to worry that newTargetPosition is inside moved range, because that // would mean that the MoveOperation targets into itself, and that is incorrect operation. // Instead, we calculate the new position of that part of original range. common.start = common.start._getCombined( b.sourcePosition, moveTargetPosition ); common.end = common.end._getCombined( b.sourcePosition, moveTargetPosition ); // We have to take care of proper range order. // Note that both push, splice and unshift do the same if there are no ranges in the array. if ( rangeB.end.isAfter( rangeA.end ) ) { ranges.push( common ); } else if ( rangeB.start.isBefore( rangeA.start ) ) { ranges.unshift( common ); } else { ranges.splice( 1, 0, common ); } } // At this point we transformed this operation's source ranges it means that nothing should be changed. // But since we need to return an instance of Operation we return an array with NoOperation. if ( ranges.length === 0 ) { return [ new NoOperation( a.baseVersion ) ]; } // Target position also could be affected by the other MoveOperation. We will transform it. let newTargetPosition = a.targetPosition.getTransformedByMove( b.sourcePosition, moveTargetPosition, b.howMany, !isStrong ); // Map transformed range(s) to operations and return them. return ranges.reverse().map( ( range ) => { return new MoveOperation( range.start, newTargetPosition, range.end.offset - range.start.offset, a.baseVersion ); } ); } } }; return ( a, b, isStrong ) => { let group; let algorithm; if ( a instanceof InsertOperation ) { group = ot.InsertOperation; } else if ( a instanceof ChangeOperation ) { group = ot.ChangeOperation; } else if ( a instanceof MoveOperation ) { group = ot.MoveOperation; } else { algorithm = doNotUpdate; } if ( group ) { if ( b instanceof InsertOperation ) { algorithm = group.InsertOperation; } else if ( b instanceof ChangeOperation ) { algorithm = group.ChangeOperation; } else if ( b instanceof MoveOperation ) { algorithm = group.MoveOperation; } else { algorithm = doNotUpdate; } } let transformed = algorithm( a, b, isStrong ); return updateBaseVersions( a.baseVersion, transformed ); }; // When we don't want to update an operation, we create and return a clone of it. // Returns the operation in "unified format" - wrapped in an Array. function doNotUpdate( operation ) { return [ operation.clone() ]; } // Takes an Array of operations and sets consecutive base versions for them, starting from given base version. // Returns the passed array. function updateBaseVersions( baseVersion, operations ) { for ( let i = 0; i < operations.length; i++ ) { operations[ i ].baseVersion = baseVersion + i + 1; } return operations; } // Checks whether MoveOperation targetPosition is inside a node from the moved range of the other MoveOperation. function moveTargetIntoMovedRange( a, b ) { return a.targetPosition.getTransformedByDeletion( b.sourcePosition, b.howMany ) === null; } // Takes two ChangeOperations and checks whether their attributes are in conflict. // This happens when both operations changes an attribute with the same key and they either set different // values for this attribute or one of them removes it while the other one sets it. // Returns true if attributes are in conflict. function haveConflictingAttributes( a, b ) { // Keeping in mind that newAttr or oldAttr might be null. // We will retrieve the key from whichever parameter is set. const keyA = ( a.newAttr || a.oldAttr ).key; const keyB = ( b.newAttr || b.oldAttr ).key; if ( keyA != keyB ) { // Different keys - not conflicting. return false; } if ( a.newAttr === null && b.newAttr === null ) { // Both remove the attribute - not conflicting. return false; } // Check if they set different value or one of them removes the attribute. return ( a.newAttr === null && b.newAttr !== null ) || ( a.newAttr !== null && b.newAttr === null ) || ( !a.newAttr.isEqual( b.newAttr ) ); } // Gets an array of Ranges and produces one Range out of it. The root of a new range will be same as // the root of the first range in the array. If any of given ranges has different root than the first range, // it will be discarded. function joinRanges( ranges ) { if ( ranges.length === 0 ) { return null; } else if ( ranges.length == 1 ) { return ranges[ 0 ]; } else { ranges[ 0 ].end = ranges[ ranges.length - 1 ].end; return ranges[ 0 ]; } } } );