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- /**
- * @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 utils/fastdiff
- */
- /**
- * Finds positions of the first and last change in the given string/array and generates a set of changes:
- *
- * fastDiff( '12a', '12xyza' );
- * // [ { index: 2, type: 'insert', values: [ 'x', 'y', 'z' ] } ]
- *
- * fastDiff( '12a', '12aa' );
- * // [ { index: 3, type: 'insert', values: [ 'a' ] } ]
- *
- * fastDiff( '12xyza', '12a' );
- * // [ { index: 2, type: 'delete', howMany: 3 } ]
- *
- * fastDiff( [ '1', '2', 'a', 'a' ], [ '1', '2', 'a' ] );
- * // [ { index: 3, type: 'delete', howMany: 1 } ]
- *
- * fastDiff( [ '1', '2', 'a', 'b', 'c', '3' ], [ '2', 'a', 'b' ] );
- * // [ { index: 0, type: 'insert', values: [ '2', 'a', 'b' ] }, { index: 3, type: 'delete', howMany: 6 } ]
- *
- * Passed arrays can contain any type of data, however to compare them correctly custom comparator function
- * should be passed as a third parameter:
- *
- * fastDiff( [ { value: 1 }, { value: 2 } ], [ { value: 1 }, { value: 3 } ], ( a, b ) => {
- * return a.value === b.value;
- * } );
- * // [ { index: 1, type: 'insert', values: [ { value: 3 } ] }, { index: 2, type: 'delete', howMany: 1 } ]
- *
- * The resulted set of changes can be applied to the input in order to transform it into the output, for example:
- *
- * let input = '12abc3';
- * const output = '2ab';
- * const changes = fastDiff( input, output );
- *
- * changes.forEach( change => {
- * if ( change.type == 'insert' ) {
- * input = input.substring( 0, change.index ) + change.values.join( '' ) + input.substring( change.index );
- * } else if ( change.type == 'delete' ) {
- * input = input.substring( 0, change.index ) + input.substring( change.index + change.howMany );
- * }
- * } );
- *
- * // input equals output now
- *
- * or in case of arrays:
- *
- * let input = [ '1', '2', 'a', 'b', 'c', '3' ];
- * const output = [ '2', 'a', 'b' ];
- * const changes = fastDiff( input, output );
- *
- * changes.forEach( change => {
- * if ( change.type == 'insert' ) {
- * input = input.slice( 0, change.index ).concat( change.values, input.slice( change.index ) );
- * } else if ( change.type == 'delete' ) {
- * input = input.slice( 0, change.index ).concat( input.slice( change.index + change.howMany ) );
- * }
- * } );
- *
- * // input equals output now
- *
- * By passing `true` as the fourth parameter (`atomicChanges`) the output of this function will become compatible with
- * the {@link module:utils/diff~diff `diff()`} function:
- *
- * fastDiff( '12a', '12xyza' );
- * // [ 'equal', 'equal', 'insert', 'insert', 'insert', 'equal' ]
- *
- * The default output format of this function is compatible with the output format of
- * {@link module:utils/difftochanges~diffToChanges `diffToChanges()`}. The `diffToChanges()` input format is, in turn,
- * compatible with the output of {@link module:utils/diff~diff `diff()`}:
- *
- * const a = '1234';
- * const b = '12xyz34';
- *
- * // Both calls will return the same results (grouped changes format).
- * fastDiff( a, b );
- * diffToChanges( diff( a, b ) );
- *
- * // Again, both calls will return the same results (atomic changes format).
- * fastDiff( a, b, null, true );
- * diff( a, b );
- *
- *
- * @param {Array|String} a Input array or string.
- * @param {Array|String} b Input array or string.
- * @param {Function} [cmp] Optional function used to compare array values, by default `===` (strict equal operator) is used.
- * @param {Boolean} [atomicChanges=false] Whether an array of `inset|delete|equal` operations should
- * be returned instead of changes set. This makes this function compatible with {@link module:utils/diff~diff `diff()`}.
- * @returns {Array} Array of changes.
- */
- export default function fastDiff( a, b, cmp, atomicChanges = false ) {
- // Set the comparator function.
- cmp = cmp || function( a, b ) {
- return a === b;
- };
- // Convert the string (or any array-like object - eg. NodeList) to an array by using the slice() method because,
- // unlike Array.from(), it returns array of UTF-16 code units instead of the code points of a string.
- // One code point might be a surrogate pair of two code units. All text offsets are expected to be in code units.
- // See ckeditor/ckeditor5#3147.
- //
- // We need to make sure here that fastDiff() works identical to diff().
- if ( !Array.isArray( a ) ) {
- a = Array.prototype.slice.call( a );
- }
- if ( !Array.isArray( b ) ) {
- b = Array.prototype.slice.call( b );
- }
- // Find first and last change.
- const changeIndexes = findChangeBoundaryIndexes( a, b, cmp );
- // Transform into changes array.
- return atomicChanges ? changeIndexesToAtomicChanges( changeIndexes, b.length ) : changeIndexesToChanges( b, changeIndexes );
- }
- // Finds position of the first and last change in the given arrays. For example:
- //
- // const indexes = findChangeBoundaryIndexes( [ '1', '2', '3', '4' ], [ '1', '3', '4', '2', '4' ] );
- // console.log( indexes ); // { firstIndex: 1, lastIndexOld: 3, lastIndexNew: 4 }
- //
- // The above indexes means that in the first array the modified part is `1[23]4` and in the second array it is `1[342]4`.
- // Based on such indexes, array with `insert`/`delete` operations which allows transforming first value into the second one
- // can be generated.
- //
- // @param {Array} arr1
- // @param {Array} arr2
- // @param {Function} cmp Comparator function.
- // @returns {Object}
- // @returns {Number} return.firstIndex Index of the first change in both values (always the same for both).
- // @returns {Number} result.lastIndexOld Index of the last common value in `arr1`.
- // @returns {Number} result.lastIndexNew Index of the last common value in `arr2`.
- function findChangeBoundaryIndexes( arr1, arr2, cmp ) {
- // Find the first difference between passed values.
- const firstIndex = findFirstDifferenceIndex( arr1, arr2, cmp );
- // If arrays are equal return -1 indexes object.
- if ( firstIndex === -1 ) {
- return { firstIndex: -1, lastIndexOld: -1, lastIndexNew: -1 };
- }
- // Remove the common part of each value and reverse them to make it simpler to find the last difference between them.
- const oldArrayReversed = cutAndReverse( arr1, firstIndex );
- const newArrayReversed = cutAndReverse( arr2, firstIndex );
- // Find the first difference between reversed values.
- // It should be treated as "how many elements from the end the last difference occurred".
- //
- // For example:
- //
- // initial -> after cut -> reversed:
- // oldValue: '321ba' -> '21ba' -> 'ab12'
- // newValue: '31xba' -> '1xba' -> 'abx1'
- // lastIndex: -> 2
- //
- // So the last change occurred two characters from the end of the arrays.
- const lastIndex = findFirstDifferenceIndex( oldArrayReversed, newArrayReversed, cmp );
- // Use `lastIndex` to calculate proper offset, starting from the beginning (`lastIndex` kind of starts from the end).
- const lastIndexOld = arr1.length - lastIndex;
- const lastIndexNew = arr2.length - lastIndex;
- return { firstIndex, lastIndexOld, lastIndexNew };
- }
- // Returns a first index on which given arrays differ. If both arrays are the same, -1 is returned.
- //
- // @param {Array} arr1
- // @param {Array} arr2
- // @param {Function} cmp Comparator function.
- // @returns {Number}
- function findFirstDifferenceIndex( arr1, arr2, cmp ) {
- for ( let i = 0; i < Math.max( arr1.length, arr2.length ); i++ ) {
- if ( arr1[ i ] === undefined || arr2[ i ] === undefined || !cmp( arr1[ i ], arr2[ i ] ) ) {
- return i;
- }
- }
- return -1; // Return -1 if arrays are equal.
- }
- // Returns a copy of the given array with `howMany` elements removed starting from the beginning and in reversed order.
- //
- // @param {Array} arr Array to be processed.
- // @param {Number} howMany How many elements from array beginning to remove.
- // @returns {Array} Shortened and reversed array.
- function cutAndReverse( arr, howMany ) {
- return arr.slice( howMany ).reverse();
- }
- // Generates changes array based on change indexes from `findChangeBoundaryIndexes` function. This function will
- // generate array with 0 (no changes), 1 (deletion or insertion) or 2 records (insertion and deletion).
- //
- // @param {Array} newArray New array for which change indexes were calculated.
- // @param {Object} changeIndexes Change indexes object from `findChangeBoundaryIndexes` function.
- // @returns {Array.<Object>} Array of changes compatible with {@link module:utils/difftochanges~diffToChanges} format.
- function changeIndexesToChanges( newArray, changeIndexes ) {
- const result = [];
- const { firstIndex, lastIndexOld, lastIndexNew } = changeIndexes;
- // Order operations as 'insert', 'delete' array to keep compatibility with {@link module:utils/difftochanges~diffToChanges}
- // in most cases. However, 'diffToChanges' does not stick to any order so in some cases
- // (for example replacing '12345' with 'abcd') it will generate 'delete', 'insert' order.
- if ( lastIndexNew - firstIndex > 0 ) {
- result.push( {
- index: firstIndex,
- type: 'insert',
- values: newArray.slice( firstIndex, lastIndexNew )
- } );
- }
- if ( lastIndexOld - firstIndex > 0 ) {
- result.push( {
- index: firstIndex + ( lastIndexNew - firstIndex ), // Increase index of what was inserted.
- type: 'delete',
- howMany: lastIndexOld - firstIndex
- } );
- }
- return result;
- }
- // Generates array with set `equal|insert|delete` operations based on change indexes from `findChangeBoundaryIndexes` function.
- //
- // @param {Object} changeIndexes Change indexes object from `findChangeBoundaryIndexes` function.
- // @param {Number} newLength Length of the new array on which `findChangeBoundaryIndexes` calculated change indexes.
- // @returns {Array.<String>} Array of changes compatible with {@link module:utils/diff~diff} format.
- function changeIndexesToAtomicChanges( changeIndexes, newLength ) {
- const { firstIndex, lastIndexOld, lastIndexNew } = changeIndexes;
- // No changes.
- if ( firstIndex === -1 ) {
- return Array( newLength ).fill( 'equal' );
- }
- let result = [];
- if ( firstIndex > 0 ) {
- result = result.concat( Array( firstIndex ).fill( 'equal' ) );
- }
- if ( lastIndexNew - firstIndex > 0 ) {
- result = result.concat( Array( lastIndexNew - firstIndex ).fill( 'insert' ) );
- }
- if ( lastIndexOld - firstIndex > 0 ) {
- result = result.concat( Array( lastIndexOld - firstIndex ).fill( 'delete' ) );
- }
- if ( lastIndexNew < newLength ) {
- result = result.concat( Array( newLength - lastIndexNew ).fill( 'equal' ) );
- }
- return result;
- }
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