/** * Diff Match and Patch * Copyright 2018 The diff-match-patch Authors. * https://github.com/google/diff-match-patch * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /** * @fileoverview Computes the difference between two texts to create a patch. * Applies the patch onto another text, allowing for errors. * @author fraser@google.com (Neil Fraser) */ /** * CHANGES by pedrottimark to diff_match_patch_uncompressed.ts file: * * 1. Delete anything not needed to use diff_cleanupSemantic method * 2. Convert from prototype properties to var declarations * 3. Convert Diff to class from constructor and prototype * 4. Add type annotations for arguments and return values * 5. Add exports */ /** * The data structure representing a diff is an array of tuples: * [[DIFF_DELETE, 'Hello'], [DIFF_INSERT, 'Goodbye'], [DIFF_EQUAL, ' world.']] * which means: delete 'Hello', add 'Goodbye' and keep ' world.' */ const DIFF_DELETE = -1 const DIFF_INSERT = 1 const DIFF_EQUAL = 0 /** * Class representing one diff tuple. * Attempts to look like a two-element array (which is what this used to be). * @param {number} op Operation, one of: DIFF_DELETE, DIFF_INSERT, DIFF_EQUAL. * @param {string} text Text to be deleted, inserted, or retained. * @constructor */ class Diff { 0: number 1: string constructor(op: number, text: string) { this[0] = op this[1] = text } } /** * Determine the common prefix of two strings. * @param {string} text1 First string. * @param {string} text2 Second string. * @return {number} The number of characters common to the start of each * string. */ function diff_commonPrefix(text1: string, text2: string): number { // Quick check for common null cases. if (!text1 || !text2 || text1.charAt(0) !== text2.charAt(0)) { return 0 } // Binary search. // Performance analysis: https://neil.fraser.name/news/2007/10/09/ let pointermin = 0 let pointermax = Math.min(text1.length, text2.length) let pointermid = pointermax let pointerstart = 0 while (pointermin < pointermid) { if (text1.substring(pointerstart, pointermid) === text2.substring(pointerstart, pointermid)) { pointermin = pointermid pointerstart = pointermin } else { pointermax = pointermid } pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin) } return pointermid } /** * Determine the common suffix of two strings. * @param {string} text1 First string. * @param {string} text2 Second string. * @return {number} The number of characters common to the end of each string. */ function diff_commonSuffix(text1: string, text2: string): number { // Quick check for common null cases. if (!text1 || !text2 || text1.charAt(text1.length - 1) !== text2.charAt(text2.length - 1)) { return 0 } // Binary search. // Performance analysis: https://neil.fraser.name/news/2007/10/09/ let pointermin = 0 let pointermax = Math.min(text1.length, text2.length) let pointermid = pointermax let pointerend = 0 while (pointermin < pointermid) { if ( text1.substring(text1.length - pointermid, text1.length - pointerend) === text2.substring(text2.length - pointermid, text2.length - pointerend) ) { pointermin = pointermid pointerend = pointermin } else { pointermax = pointermid } pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin) } return pointermid } /** * Determine if the suffix of one string is the prefix of another. * @param {string} text1 First string. * @param {string} text2 Second string. * @return {number} The number of characters common to the end of the first * string and the start of the second string. * @private */ function diff_commonOverlap_(text1: string, text2: string): number { // Cache the text lengths to prevent multiple calls. const text1_length = text1.length const text2_length = text2.length // Eliminate the null case. if (text1_length === 0 || text2_length === 0) { return 0 } // Truncate the longer string. if (text1_length > text2_length) { text1 = text1.substring(text1_length - text2_length) } else if (text1_length < text2_length) { text2 = text2.substring(0, text1_length) } const text_length = Math.min(text1_length, text2_length) // Quick check for the worst case. if (text1 === text2) { return text_length } // Start by looking for a single character match // and increase length until no match is found. // Performance analysis: https://neil.fraser.name/news/2010/11/04/ let best = 0 let length = 1 while (true) { const pattern = text1.substring(text_length - length) const found = text2.indexOf(pattern) if (found === -1) { return best } length += found if (found === 0 || text1.substring(text_length - length) === text2.substring(0, length)) { best = length length++ } } } /** * Reduce the number of edits by eliminating semantically trivial equalities. * @param {!Array.} diffs Array of diff tuples. */ function diff_cleanupSemantic(diffs: Array): void { let changes = false const equalities = [] // Stack of indices where equalities are found. let equalitiesLength = 0 // Keeping our own length var is faster in JS. /** @type {?string} */ let lastEquality = null // Always equal to diffs[equalities[equalitiesLength - 1]][1] let pointer = 0 // Index of current position. // Number of characters that changed prior to the equality. let length_insertions1 = 0 let length_deletions1 = 0 // Number of characters that changed after the equality. let length_insertions2 = 0 let length_deletions2 = 0 while (pointer < diffs.length) { if (diffs[pointer][0] === DIFF_EQUAL) { // Equality found. equalities[equalitiesLength++] = pointer length_insertions1 = length_insertions2 length_deletions1 = length_deletions2 length_insertions2 = 0 length_deletions2 = 0 lastEquality = diffs[pointer][1] } else { // An insertion or deletion. if (diffs[pointer][0] === DIFF_INSERT) { length_insertions2 += diffs[pointer][1].length } else { length_deletions2 += diffs[pointer][1].length } // Eliminate an equality that is smaller or equal to the edits on both // sides of it. if ( lastEquality && lastEquality.length <= Math.max(length_insertions1, length_deletions1) && lastEquality.length <= Math.max(length_insertions2, length_deletions2) ) { // Duplicate record. diffs.splice(equalities[equalitiesLength - 1], 0, new Diff(DIFF_DELETE, lastEquality)) // Change second copy to insert. diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT // Throw away the equality we just deleted. equalitiesLength-- // Throw away the previous equality (it needs to be reevaluated). equalitiesLength-- pointer = equalitiesLength > 0 ? equalities[equalitiesLength - 1] : -1 length_insertions1 = 0 // Reset the counters. length_deletions1 = 0 length_insertions2 = 0 length_deletions2 = 0 lastEquality = null changes = true } } pointer++ } // Normalize the diff. if (changes) { diff_cleanupMerge(diffs) } diff_cleanupSemanticLossless(diffs) // Find any overlaps between deletions and insertions. // e.g: abcxxxxxxdef // -> abcxxxdef // e.g: xxxabcdefxxx // -> defxxxabc // Only extract an overlap if it is as big as the edit ahead or behind it. pointer = 1 while (pointer < diffs.length) { if (diffs[pointer - 1][0] === DIFF_DELETE && diffs[pointer][0] === DIFF_INSERT) { const deletion = diffs[pointer - 1][1] const insertion = diffs[pointer][1] const overlap_length1 = diff_commonOverlap_(deletion, insertion) const overlap_length2 = diff_commonOverlap_(insertion, deletion) if (overlap_length1 >= overlap_length2) { if (overlap_length1 >= deletion.length / 2 || overlap_length1 >= insertion.length / 2) { // Overlap found. Insert an equality and trim the surrounding edits. diffs.splice(pointer, 0, new Diff(DIFF_EQUAL, insertion.substring(0, overlap_length1))) diffs[pointer - 1][1] = deletion.substring(0, deletion.length - overlap_length1) diffs[pointer + 1][1] = insertion.substring(overlap_length1) pointer++ } } else { if (overlap_length2 >= deletion.length / 2 || overlap_length2 >= insertion.length / 2) { // Reverse overlap found. // Insert an equality and swap and trim the surrounding edits. diffs.splice(pointer, 0, new Diff(DIFF_EQUAL, deletion.substring(0, overlap_length2))) diffs[pointer - 1][0] = DIFF_INSERT diffs[pointer - 1][1] = insertion.substring(0, insertion.length - overlap_length2) diffs[pointer + 1][0] = DIFF_DELETE diffs[pointer + 1][1] = deletion.substring(overlap_length2) pointer++ } } pointer++ } pointer++ } } // Define some regex patterns for matching boundaries. const nonAlphaNumericRegex_ = /[^a-z0-9]/i const whitespaceRegex_ = /\s/ const linebreakRegex_ = /[\r\n]/ const blanklineEndRegex_ = /\n\r?\n$/ const blanklineStartRegex_ = /^\r?\n\r?\n/ /** * Look for single edits surrounded on both sides by equalities * which can be shifted sideways to align the edit to a word boundary. * e.g: The cat came. -> The cat came. * @param {!Array.} diffs Array of diff tuples. */ function diff_cleanupSemanticLossless(diffs: Array) { let pointer = 1 // Intentionally ignore the first and last element (don't need checking). while (pointer < diffs.length - 1) { if (diffs[pointer - 1][0] === DIFF_EQUAL && diffs[pointer + 1][0] === DIFF_EQUAL) { // This is a single edit surrounded by equalities. let equality1 = diffs[pointer - 1][1] let edit = diffs[pointer][1] let equality2 = diffs[pointer + 1][1] // First, shift the edit as far left as possible. const commonOffset = diff_commonSuffix(equality1, edit) if (commonOffset) { const commonString = edit.substring(edit.length - commonOffset) equality1 = equality1.substring(0, equality1.length - commonOffset) edit = commonString + edit.substring(0, edit.length - commonOffset) equality2 = commonString + equality2 } // Second, step character by character right, looking for the best fit. let bestEquality1 = equality1 let bestEdit = edit let bestEquality2 = equality2 let bestScore = diff_cleanupSemanticScore_(equality1, edit) + diff_cleanupSemanticScore_(edit, equality2) while (edit.charAt(0) === equality2.charAt(0)) { equality1 += edit.charAt(0) edit = edit.substring(1) + equality2.charAt(0) equality2 = equality2.substring(1) const score = diff_cleanupSemanticScore_(equality1, edit) + diff_cleanupSemanticScore_(edit, equality2) // The >= encourages trailing rather than leading whitespace on edits. if (score >= bestScore) { bestScore = score bestEquality1 = equality1 bestEdit = edit bestEquality2 = equality2 } } if (diffs[pointer - 1][1] !== bestEquality1) { // We have an improvement, save it back to the diff. if (bestEquality1) { diffs[pointer - 1][1] = bestEquality1 } else { diffs.splice(pointer - 1, 1) pointer-- } diffs[pointer][1] = bestEdit if (bestEquality2) { diffs[pointer + 1][1] = bestEquality2 } else { diffs.splice(pointer + 1, 1) pointer-- } } } pointer++ } } /** * Reorder and merge like edit sections. Merge equalities. * Any edit section can move as long as it doesn't cross an equality. * @param {!Array.} diffs Array of diff tuples. */ function diff_cleanupMerge(diffs: Array) { // Add a dummy entry at the end. diffs.push(new Diff(DIFF_EQUAL, '')) let pointer = 0 let count_delete = 0 let count_insert = 0 let text_delete = '' let text_insert = '' let commonlength while (pointer < diffs.length) { switch (diffs[pointer][0]) { case DIFF_INSERT: count_insert++ text_insert += diffs[pointer][1] pointer++ break case DIFF_DELETE: count_delete++ text_delete += diffs[pointer][1] pointer++ break case DIFF_EQUAL: // Upon reaching an equality, check for prior redundancies. if (count_delete + count_insert > 1) { if (count_delete !== 0 && count_insert !== 0) { // Factor out any common prefixes. commonlength = diff_commonPrefix(text_insert, text_delete) if (commonlength !== 0) { if ( pointer - count_delete - count_insert > 0 && diffs[pointer - count_delete - count_insert - 1][0] === DIFF_EQUAL ) { diffs[pointer - count_delete - count_insert - 1][1] += text_insert.substring( 0, commonlength, ) } else { diffs.splice(0, 0, new Diff(DIFF_EQUAL, text_insert.substring(0, commonlength))) pointer++ } text_insert = text_insert.substring(commonlength) text_delete = text_delete.substring(commonlength) } // Factor out any common suffixes. commonlength = diff_commonSuffix(text_insert, text_delete) if (commonlength !== 0) { diffs[pointer][1] = text_insert.substring(text_insert.length - commonlength) + diffs[pointer][1] text_insert = text_insert.substring(0, text_insert.length - commonlength) text_delete = text_delete.substring(0, text_delete.length - commonlength) } } // Delete the offending records and add the merged ones. pointer -= count_delete + count_insert diffs.splice(pointer, count_delete + count_insert) if (text_delete.length) { diffs.splice(pointer, 0, new Diff(DIFF_DELETE, text_delete)) pointer++ } if (text_insert.length) { diffs.splice(pointer, 0, new Diff(DIFF_INSERT, text_insert)) pointer++ } pointer++ } else if (pointer !== 0 && diffs[pointer - 1][0] === DIFF_EQUAL) { // Merge this equality with the previous one. diffs[pointer - 1][1] += diffs[pointer][1] diffs.splice(pointer, 1) } else { pointer++ } count_insert = 0 count_delete = 0 text_delete = '' text_insert = '' break } } if (diffs.at(-1)?.[1] === '') { diffs.pop() } // Remove the dummy entry at the end. // Second pass: look for single edits surrounded on both sides by equalities // which can be shifted sideways to eliminate an equality. // e.g: ABAC -> ABAC let changes = false pointer = 1 // Intentionally ignore the first and last element (don't need checking). while (pointer < diffs.length - 1) { if (diffs[pointer - 1][0] === DIFF_EQUAL && diffs[pointer + 1][0] === DIFF_EQUAL) { // This is a single edit surrounded by equalities. if ( diffs[pointer][1].substring(diffs[pointer][1].length - diffs[pointer - 1][1].length) === diffs[pointer - 1][1] ) { // Shift the edit over the previous equality. diffs[pointer][1] = diffs[pointer - 1][1] + diffs[pointer][1].substring(0, diffs[pointer][1].length - diffs[pointer - 1][1].length) diffs[pointer + 1][1] = diffs[pointer - 1][1] + diffs[pointer + 1][1] diffs.splice(pointer - 1, 1) changes = true } else if ( diffs[pointer][1].substring(0, diffs[pointer + 1][1].length) === diffs[pointer + 1][1] ) { // Shift the edit over the next equality. diffs[pointer - 1][1] += diffs[pointer + 1][1] diffs[pointer][1] = diffs[pointer][1].substring(diffs[pointer + 1][1].length) + diffs[pointer + 1][1] diffs.splice(pointer + 1, 1) changes = true } } pointer++ } // If shifts were made, the diff needs reordering and another shift sweep. if (changes) { diff_cleanupMerge(diffs) } } /** * Given two strings, compute a score representing whether the internal * boundary falls on logical boundaries. * Scores range from 6 (best) to 0 (worst). * Closure, but does not reference any external variables. * @param {string} one First string. * @param {string} two Second string. * @return {number} The score. * @private */ function diff_cleanupSemanticScore_(one: string, two: string): number { if (!one || !two) { // Edges are the best. return 6 } // Each port of this function behaves slightly differently due to // subtle differences in each language's definition of things like // 'whitespace'. Since this function's purpose is largely cosmetic, // the choice has been made to use each language's native features // rather than force total conformity. const char1 = one.charAt(one.length - 1) const char2 = two.charAt(0) const nonAlphaNumeric1 = char1.match(nonAlphaNumericRegex_) const nonAlphaNumeric2 = char2.match(nonAlphaNumericRegex_) const whitespace1 = nonAlphaNumeric1 && char1.match(whitespaceRegex_) const whitespace2 = nonAlphaNumeric2 && char2.match(whitespaceRegex_) const lineBreak1 = whitespace1 && char1.match(linebreakRegex_) const lineBreak2 = whitespace2 && char2.match(linebreakRegex_) const blankLine1 = lineBreak1 && one.match(blanklineEndRegex_) const blankLine2 = lineBreak2 && two.match(blanklineStartRegex_) if (blankLine1 || blankLine2) { // Five points for blank lines. return 5 } else if (lineBreak1 || lineBreak2) { // Four points for line breaks. return 4 } else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) { // Three points for end of sentences. return 3 } else if (whitespace1 || whitespace2) { // Two points for whitespace. return 2 } else if (nonAlphaNumeric1 || nonAlphaNumeric2) { // One point for non-alphanumeric. return 1 } return 0 } export { diff_cleanupSemantic as cleanupSemantic, Diff, DIFF_DELETE, DIFF_EQUAL, DIFF_INSERT }