Use a centralized diff-match-patch package

We use our own fork of the diff-match-patch npm package, which adds an
optimization for the semantic alignment loop.

services/document-updater/app/js/DiffCodec.js

@@ -1,4 +1,4 @@
-const { diff_match_patch: DMP } = require('../lib/diff_match_patch')
+const DMP = require('diff-match-patch')
 const dmp = new DMP()
 
 module.exports = {

services/document-updater/app/lib/diff_match_patch.js

@@ -1,2341 +0,0 @@
-/* eslint-disable */
-/**
- * Diff Match and Patch
- *
- * Copyright 2006 Google Inc.
- * http://code.google.com/p/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)
- */
-
-/**
- * Class containing the diff, match and patch methods.
- * @constructor
- */
-function diff_match_patch() {
-  // Defaults.
-  // Redefine these in your program to override the defaults.
-
-  // Number of seconds to map a diff before giving up (0 for infinity).
-  this.Diff_Timeout = 1.0
-  // Cost of an empty edit operation in terms of edit characters.
-  this.Diff_EditCost = 4
-  // At what point is no match declared (0.0 = perfection, 1.0 = very loose).
-  this.Match_Threshold = 0.5
-  // How far to search for a match (0 = exact location, 1000+ = broad match).
-  // A match this many characters away from the expected location will add
-  // 1.0 to the score (0.0 is a perfect match).
-  this.Match_Distance = 1000
-  // When deleting a large block of text (over ~64 characters), how close do
-  // the contents have to be to match the expected contents. (0.0 = perfection,
-  // 1.0 = very loose).  Note that Match_Threshold controls how closely the
-  // end points of a delete need to match.
-  this.Patch_DeleteThreshold = 0.5
-  // Chunk size for context length.
-  this.Patch_Margin = 4
-
-  // The number of bits in an int.
-  this.Match_MaxBits = 32
-}
-
-//  DIFF FUNCTIONS
-
-/**
- * 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.'
- */
-var DIFF_DELETE = -1
-var DIFF_INSERT = 1
-var DIFF_EQUAL = 0
-
-/** @typedef {{0: number, 1: string}} */
-diff_match_patch.Diff
-
-/**
- * Find the differences between two texts.  Simplifies the problem by stripping
- * any common prefix or suffix off the texts before diffing.
- * @param {string} text1 Old string to be diffed.
- * @param {string} text2 New string to be diffed.
- * @param {boolean=} opt_checklines Optional speedup flag. If present and false,
- *     then don't run a line-level diff first to identify the changed areas.
- *     Defaults to true, which does a faster, slightly less optimal diff.
- * @param {number} opt_deadline Optional time when the diff should be complete
- *     by.  Used internally for recursive calls.  Users should set DiffTimeout
- *     instead.
- * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
- */
-diff_match_patch.prototype.diff_main = function (
-  text1,
-  text2,
-  opt_checklines,
-  opt_deadline
-) {
-  // Set a deadline by which time the diff must be complete.
-  if (typeof opt_deadline == 'undefined') {
-    if (this.Diff_Timeout <= 0) {
-      opt_deadline = Number.MAX_VALUE
-    } else {
-      opt_deadline = new Date().getTime() + this.Diff_Timeout * 1000
-    }
-  }
-  var deadline = opt_deadline
-
-  // Check for null inputs.
-  if (text1 == null || text2 == null) {
-    throw new Error('Null input. (diff_main)')
-  }
-
-  // Check for equality (speedup).
-  if (text1 == text2) {
-    if (text1) {
-      return [[DIFF_EQUAL, text1]]
-    }
-    return []
-  }
-
-  if (typeof opt_checklines == 'undefined') {
-    opt_checklines = true
-  }
-  var checklines = opt_checklines
-
-  // Trim off common prefix (speedup).
-  var commonlength = this.diff_commonPrefix(text1, text2)
-  var commonprefix = text1.substring(0, commonlength)
-  text1 = text1.substring(commonlength)
-  text2 = text2.substring(commonlength)
-
-  // Trim off common suffix (speedup).
-  commonlength = this.diff_commonSuffix(text1, text2)
-  var commonsuffix = text1.substring(text1.length - commonlength)
-  text1 = text1.substring(0, text1.length - commonlength)
-  text2 = text2.substring(0, text2.length - commonlength)
-
-  // Compute the diff on the middle block.
-  var diffs = this.diff_compute_(text1, text2, checklines, deadline)
-
-  // Restore the prefix and suffix.
-  if (commonprefix) {
-    diffs.unshift([DIFF_EQUAL, commonprefix])
-  }
-  if (commonsuffix) {
-    diffs.push([DIFF_EQUAL, commonsuffix])
-  }
-  this.diff_cleanupMerge(diffs)
-  return diffs
-}
-
-/**
- * Find the differences between two texts.  Assumes that the texts do not
- * have any common prefix or suffix.
- * @param {string} text1 Old string to be diffed.
- * @param {string} text2 New string to be diffed.
- * @param {boolean} checklines Speedup flag.  If false, then don't run a
- *     line-level diff first to identify the changed areas.
- *     If true, then run a faster, slightly less optimal diff.
- * @param {number} deadline Time when the diff should be complete by.
- * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
- * @private
- */
-diff_match_patch.prototype.diff_compute_ = function (
-  text1,
-  text2,
-  checklines,
-  deadline
-) {
-  var diffs
-
-  if (!text1) {
-    // Just add some text (speedup).
-    return [[DIFF_INSERT, text2]]
-  }
-
-  if (!text2) {
-    // Just delete some text (speedup).
-    return [[DIFF_DELETE, text1]]
-  }
-
-  var longtext = text1.length > text2.length ? text1 : text2
-  var shorttext = text1.length > text2.length ? text2 : text1
-  var i = longtext.indexOf(shorttext)
-  if (i != -1) {
-    // Shorter text is inside the longer text (speedup).
-    diffs = [
-      [DIFF_INSERT, longtext.substring(0, i)],
-      [DIFF_EQUAL, shorttext],
-      [DIFF_INSERT, longtext.substring(i + shorttext.length)]
-    ]
-    // Swap insertions for deletions if diff is reversed.
-    if (text1.length > text2.length) {
-      diffs[0][0] = diffs[2][0] = DIFF_DELETE
-    }
-    return diffs
-  }
-
-  if (shorttext.length == 1) {
-    // Single character string.
-    // After the previous speedup, the character can't be an equality.
-    return [
-      [DIFF_DELETE, text1],
-      [DIFF_INSERT, text2]
-    ]
-  }
-
-  // Check to see if the problem can be split in two.
-  var hm = this.diff_halfMatch_(text1, text2)
-  if (hm) {
-    // A half-match was found, sort out the return data.
-    var text1_a = hm[0]
-    var text1_b = hm[1]
-    var text2_a = hm[2]
-    var text2_b = hm[3]
-    var mid_common = hm[4]
-    // Send both pairs off for separate processing.
-    var diffs_a = this.diff_main(text1_a, text2_a, checklines, deadline)
-    var diffs_b = this.diff_main(text1_b, text2_b, checklines, deadline)
-    // Merge the results.
-    return diffs_a.concat([[DIFF_EQUAL, mid_common]], diffs_b)
-  }
-
-  if (checklines && text1.length > 100 && text2.length > 100) {
-    return this.diff_lineMode_(text1, text2, deadline)
-  }
-
-  return this.diff_bisect_(text1, text2, deadline)
-}
-
-/**
- * Do a quick line-level diff on both strings, then rediff the parts for
- * greater accuracy.
- * This speedup can produce non-minimal diffs.
- * @param {string} text1 Old string to be diffed.
- * @param {string} text2 New string to be diffed.
- * @param {number} deadline Time when the diff should be complete by.
- * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
- * @private
- */
-diff_match_patch.prototype.diff_lineMode_ = function (text1, text2, deadline) {
-  // Scan the text on a line-by-line basis first.
-  var a = this.diff_linesToChars_(text1, text2)
-  text1 = a.chars1
-  text2 = a.chars2
-  var linearray = a.lineArray
-
-  var diffs = this.diff_main(text1, text2, false, deadline)
-
-  // Convert the diff back to original text.
-  this.diff_charsToLines_(diffs, linearray)
-  // Eliminate freak matches (e.g. blank lines)
-  this.diff_cleanupSemantic(diffs)
-
-  // Rediff any replacement blocks, this time character-by-character.
-  // Add a dummy entry at the end.
-  diffs.push([DIFF_EQUAL, ''])
-  var pointer = 0
-  var count_delete = 0
-  var count_insert = 0
-  var text_delete = ''
-  var text_insert = ''
-  while (pointer < diffs.length) {
-    switch (diffs[pointer][0]) {
-      case DIFF_INSERT:
-        count_insert++
-        text_insert += diffs[pointer][1]
-        break
-      case DIFF_DELETE:
-        count_delete++
-        text_delete += diffs[pointer][1]
-        break
-      case DIFF_EQUAL:
-        // Upon reaching an equality, check for prior redundancies.
-        if (count_delete >= 1 && count_insert >= 1) {
-          // Delete the offending records and add the merged ones.
-          diffs.splice(
-            pointer - count_delete - count_insert,
-            count_delete + count_insert
-          )
-          pointer = pointer - count_delete - count_insert
-          var a = this.diff_main(text_delete, text_insert, false, deadline)
-          for (var j = a.length - 1; j >= 0; j--) {
-            diffs.splice(pointer, 0, a[j])
-          }
-          pointer = pointer + a.length
-        }
-        count_insert = 0
-        count_delete = 0
-        text_delete = ''
-        text_insert = ''
-        break
-    }
-    pointer++
-  }
-  diffs.pop() // Remove the dummy entry at the end.
-
-  return diffs
-}
-
-/**
- * Find the 'middle snake' of a diff, split the problem in two
- * and return the recursively constructed diff.
- * See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
- * @param {string} text1 Old string to be diffed.
- * @param {string} text2 New string to be diffed.
- * @param {number} deadline Time at which to bail if not yet complete.
- * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
- * @private
- */
-diff_match_patch.prototype.diff_bisect_ = function (text1, text2, deadline) {
-  // Cache the text lengths to prevent multiple calls.
-  var text1_length = text1.length
-  var text2_length = text2.length
-  var max_d = Math.ceil((text1_length + text2_length) / 2)
-  var v_offset = max_d
-  var v_length = 2 * max_d
-  var v1 = new Array(v_length)
-  var v2 = new Array(v_length)
-  // Setting all elements to -1 is faster in Chrome & Firefox than mixing
-  // integers and undefined.
-  for (var x = 0; x < v_length; x++) {
-    v1[x] = -1
-    v2[x] = -1
-  }
-  v1[v_offset + 1] = 0
-  v2[v_offset + 1] = 0
-  var delta = text1_length - text2_length
-  // If the total number of characters is odd, then the front path will collide
-  // with the reverse path.
-  var front = delta % 2 != 0
-  // Offsets for start and end of k loop.
-  // Prevents mapping of space beyond the grid.
-  var k1start = 0
-  var k1end = 0
-  var k2start = 0
-  var k2end = 0
-  for (var d = 0; d < max_d; d++) {
-    // Bail out if deadline is reached.
-    if (new Date().getTime() > deadline) {
-      break
-    }
-
-    // Walk the front path one step.
-    for (var k1 = -d + k1start; k1 <= d - k1end; k1 += 2) {
-      var k1_offset = v_offset + k1
-      var x1
-      if (k1 == -d || (k1 != d && v1[k1_offset - 1] < v1[k1_offset + 1])) {
-        x1 = v1[k1_offset + 1]
-      } else {
-        x1 = v1[k1_offset - 1] + 1
-      }
-      var y1 = x1 - k1
-      while (
-        x1 < text1_length &&
-        y1 < text2_length &&
-        text1.charAt(x1) == text2.charAt(y1)
-      ) {
-        x1++
-        y1++
-      }
-      v1[k1_offset] = x1
-      if (x1 > text1_length) {
-        // Ran off the right of the graph.
-        k1end += 2
-      } else if (y1 > text2_length) {
-        // Ran off the bottom of the graph.
-        k1start += 2
-      } else if (front) {
-        var k2_offset = v_offset + delta - k1
-        if (k2_offset >= 0 && k2_offset < v_length && v2[k2_offset] != -1) {
-          // Mirror x2 onto top-left coordinate system.
-          var x2 = text1_length - v2[k2_offset]
-          if (x1 >= x2) {
-            // Overlap detected.
-            return this.diff_bisectSplit_(text1, text2, x1, y1, deadline)
-          }
-        }
-      }
-    }
-
-    // Walk the reverse path one step.
-    for (var k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
-      var k2_offset = v_offset + k2
-      var x2
-      if (k2 == -d || (k2 != d && v2[k2_offset - 1] < v2[k2_offset + 1])) {
-        x2 = v2[k2_offset + 1]
-      } else {
-        x2 = v2[k2_offset - 1] + 1
-      }
-      var y2 = x2 - k2
-      while (
-        x2 < text1_length &&
-        y2 < text2_length &&
-        text1.charAt(text1_length - x2 - 1) ==
-          text2.charAt(text2_length - y2 - 1)
-      ) {
-        x2++
-        y2++
-      }
-      v2[k2_offset] = x2
-      if (x2 > text1_length) {
-        // Ran off the left of the graph.
-        k2end += 2
-      } else if (y2 > text2_length) {
-        // Ran off the top of the graph.
-        k2start += 2
-      } else if (!front) {
-        var k1_offset = v_offset + delta - k2
-        if (k1_offset >= 0 && k1_offset < v_length && v1[k1_offset] != -1) {
-          var x1 = v1[k1_offset]
-          var y1 = v_offset + x1 - k1_offset
-          // Mirror x2 onto top-left coordinate system.
-          x2 = text1_length - x2
-          if (x1 >= x2) {
-            // Overlap detected.
-            return this.diff_bisectSplit_(text1, text2, x1, y1, deadline)
-          }
-        }
-      }
-    }
-  }
-  // Diff took too long and hit the deadline or
-  // number of diffs equals number of characters, no commonality at all.
-  return [
-    [DIFF_DELETE, text1],
-    [DIFF_INSERT, text2]
-  ]
-}
-
-/**
- * Given the location of the 'middle snake', split the diff in two parts
- * and recurse.
- * @param {string} text1 Old string to be diffed.
- * @param {string} text2 New string to be diffed.
- * @param {number} x Index of split point in text1.
- * @param {number} y Index of split point in text2.
- * @param {number} deadline Time at which to bail if not yet complete.
- * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
- * @private
- */
-diff_match_patch.prototype.diff_bisectSplit_ = function (
-  text1,
-  text2,
-  x,
-  y,
-  deadline
-) {
-  var text1a = text1.substring(0, x)
-  var text2a = text2.substring(0, y)
-  var text1b = text1.substring(x)
-  var text2b = text2.substring(y)
-
-  // Compute both diffs serially.
-  var diffs = this.diff_main(text1a, text2a, false, deadline)
-  var diffsb = this.diff_main(text1b, text2b, false, deadline)
-
-  return diffs.concat(diffsb)
-}
-
-/**
- * Split two texts into an array of strings.  Reduce the texts to a string of
- * hashes where each Unicode character represents one line.
- * @param {string} text1 First string.
- * @param {string} text2 Second string.
- * @return {{chars1: string, chars2: string, lineArray: !Array.<string>}}
- *     An object containing the encoded text1, the encoded text2 and
- *     the array of unique strings.
- *     The zeroth element of the array of unique strings is intentionally blank.
- * @private
- */
-diff_match_patch.prototype.diff_linesToChars_ = function (text1, text2) {
-  var lineArray = [] // e.g. lineArray[4] == 'Hello\n'
-  var lineHash = {} // e.g. lineHash['Hello\n'] == 4
-
-  // '\x00' is a valid character, but various debuggers don't like it.
-  // So we'll insert a junk entry to avoid generating a null character.
-  lineArray[0] = ''
-
-  /**
-   * Split a text into an array of strings.  Reduce the texts to a string of
-   * hashes where each Unicode character represents one line.
-   * Modifies linearray and linehash through being a closure.
-   * @param {string} text String to encode.
-   * @return {string} Encoded string.
-   * @private
-   */
-  function diff_linesToCharsMunge_(text) {
-    var chars = ''
-    // Walk the text, pulling out a substring for each line.
-    // text.split('\n') would would temporarily double our memory footprint.
-    // Modifying text would create many large strings to garbage collect.
-    var lineStart = 0
-    var lineEnd = -1
-    // Keeping our own length variable is faster than looking it up.
-    var lineArrayLength = lineArray.length
-    while (lineEnd < text.length - 1) {
-      lineEnd = text.indexOf('\n', lineStart)
-      if (lineEnd == -1) {
-        lineEnd = text.length - 1
-      }
-      var line = text.substring(lineStart, lineEnd + 1)
-      lineStart = lineEnd + 1
-
-      if (
-        lineHash.hasOwnProperty
-          ? lineHash.hasOwnProperty(line)
-          : lineHash[line] !== undefined
-      ) {
-        chars += String.fromCharCode(lineHash[line])
-      } else {
-        chars += String.fromCharCode(lineArrayLength)
-        lineHash[line] = lineArrayLength
-        lineArray[lineArrayLength++] = line
-      }
-    }
-    return chars
-  }
-
-  var chars1 = diff_linesToCharsMunge_(text1)
-  var chars2 = diff_linesToCharsMunge_(text2)
-  return { chars1: chars1, chars2: chars2, lineArray: lineArray }
-}
-
-/**
- * Rehydrate the text in a diff from a string of line hashes to real lines of
- * text.
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- * @param {!Array.<string>} lineArray Array of unique strings.
- * @private
- */
-diff_match_patch.prototype.diff_charsToLines_ = function (diffs, lineArray) {
-  for (var x = 0; x < diffs.length; x++) {
-    var chars = diffs[x][1]
-    var text = []
-    for (var y = 0; y < chars.length; y++) {
-      text[y] = lineArray[chars.charCodeAt(y)]
-    }
-    diffs[x][1] = text.join('')
-  }
-}
-
-/**
- * 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.
- */
-diff_match_patch.prototype.diff_commonPrefix = function (text1, text2) {
-  // Quick check for common null cases.
-  if (!text1 || !text2 || text1.charAt(0) != text2.charAt(0)) {
-    return 0
-  }
-  // Binary search.
-  // Performance analysis: http://neil.fraser.name/news/2007/10/09/
-  var pointermin = 0
-  var pointermax = Math.min(text1.length, text2.length)
-  var pointermid = pointermax
-  var 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.
- */
-diff_match_patch.prototype.diff_commonSuffix = function (text1, text2) {
-  // 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: http://neil.fraser.name/news/2007/10/09/
-  var pointermin = 0
-  var pointermax = Math.min(text1.length, text2.length)
-  var pointermid = pointermax
-  var 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
- */
-diff_match_patch.prototype.diff_commonOverlap_ = function (text1, text2) {
-  // Cache the text lengths to prevent multiple calls.
-  var text1_length = text1.length
-  var 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)
-  }
-  var 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: http://neil.fraser.name/news/2010/11/04/
-  var best = 0
-  var length = 1
-  while (true) {
-    var pattern = text1.substring(text_length - length)
-    var 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++
-    }
-  }
-}
-
-/**
- * Do the two texts share a substring which is at least half the length of the
- * longer text?
- * This speedup can produce non-minimal diffs.
- * @param {string} text1 First string.
- * @param {string} text2 Second string.
- * @return {Array.<string>} Five element Array, containing the prefix of
- *     text1, the suffix of text1, the prefix of text2, the suffix of
- *     text2 and the common middle.  Or null if there was no match.
- * @private
- */
-diff_match_patch.prototype.diff_halfMatch_ = function (text1, text2) {
-  if (this.Diff_Timeout <= 0) {
-    // Don't risk returning a non-optimal diff if we have unlimited time.
-    return null
-  }
-  var longtext = text1.length > text2.length ? text1 : text2
-  var shorttext = text1.length > text2.length ? text2 : text1
-  if (longtext.length < 4 || shorttext.length * 2 < longtext.length) {
-    return null // Pointless.
-  }
-  var dmp = this // 'this' becomes 'window' in a closure.
-
-  /**
-   * Does a substring of shorttext exist within longtext such that the substring
-   * is at least half the length of longtext?
-   * Closure, but does not reference any external variables.
-   * @param {string} longtext Longer string.
-   * @param {string} shorttext Shorter string.
-   * @param {number} i Start index of quarter length substring within longtext.
-   * @return {Array.<string>} Five element Array, containing the prefix of
-   *     longtext, the suffix of longtext, the prefix of shorttext, the suffix
-   *     of shorttext and the common middle.  Or null if there was no match.
-   * @private
-   */
-  function diff_halfMatchI_(longtext, shorttext, i) {
-    // Start with a 1/4 length substring at position i as a seed.
-    var seed = longtext.substring(i, i + Math.floor(longtext.length / 4))
-    var j = -1
-    var best_common = ''
-    var best_longtext_a, best_longtext_b, best_shorttext_a, best_shorttext_b
-    while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
-      var prefixLength = dmp.diff_commonPrefix(
-        longtext.substring(i),
-        shorttext.substring(j)
-      )
-      var suffixLength = dmp.diff_commonSuffix(
-        longtext.substring(0, i),
-        shorttext.substring(0, j)
-      )
-      if (best_common.length < suffixLength + prefixLength) {
-        best_common =
-          shorttext.substring(j - suffixLength, j) +
-          shorttext.substring(j, j + prefixLength)
-        best_longtext_a = longtext.substring(0, i - suffixLength)
-        best_longtext_b = longtext.substring(i + prefixLength)
-        best_shorttext_a = shorttext.substring(0, j - suffixLength)
-        best_shorttext_b = shorttext.substring(j + prefixLength)
-      }
-    }
-    if (best_common.length * 2 >= longtext.length) {
-      return [
-        best_longtext_a,
-        best_longtext_b,
-        best_shorttext_a,
-        best_shorttext_b,
-        best_common
-      ]
-    } else {
-      return null
-    }
-  }
-
-  // First check if the second quarter is the seed for a half-match.
-  var hm1 = diff_halfMatchI_(
-    longtext,
-    shorttext,
-    Math.ceil(longtext.length / 4)
-  )
-  // Check again based on the third quarter.
-  var hm2 = diff_halfMatchI_(
-    longtext,
-    shorttext,
-    Math.ceil(longtext.length / 2)
-  )
-  var hm
-  if (!hm1 && !hm2) {
-    return null
-  } else if (!hm2) {
-    hm = hm1
-  } else if (!hm1) {
-    hm = hm2
-  } else {
-    // Both matched.  Select the longest.
-    hm = hm1[4].length > hm2[4].length ? hm1 : hm2
-  }
-
-  // A half-match was found, sort out the return data.
-  var text1_a, text1_b, text2_a, text2_b
-  if (text1.length > text2.length) {
-    text1_a = hm[0]
-    text1_b = hm[1]
-    text2_a = hm[2]
-    text2_b = hm[3]
-  } else {
-    text2_a = hm[0]
-    text2_b = hm[1]
-    text1_a = hm[2]
-    text1_b = hm[3]
-  }
-  var mid_common = hm[4]
-  return [text1_a, text1_b, text2_a, text2_b, mid_common]
-}
-
-/**
- * Reduce the number of edits by eliminating semantically trivial equalities.
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- */
-diff_match_patch.prototype.diff_cleanupSemantic = function (diffs) {
-  var changes = false
-  var equalities = [] // Stack of indices where equalities are found.
-  var equalitiesLength = 0 // Keeping our own length var is faster in JS.
-  /** @type {?string} */
-  var lastequality = null
-  // Always equal to diffs[equalities[equalitiesLength - 1]][1]
-  var pointer = 0 // Index of current position.
-  // Number of characters that changed prior to the equality.
-  var length_insertions1 = 0
-  var length_deletions1 = 0
-  // Number of characters that changed after the equality.
-  var length_insertions2 = 0
-  var 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, [
-          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) {
-    this.diff_cleanupMerge(diffs)
-  }
-  this.diff_cleanupSemanticLossless(diffs)
-
-  // Find any overlaps between deletions and insertions.
-  // e.g: <del>abcxxx</del><ins>xxxdef</ins>
-  //   -> <del>abc</del>xxx<ins>def</ins>
-  // e.g: <del>xxxabc</del><ins>defxxx</ins>
-  //   -> <ins>def</ins>xxx<del>abc</del>
-  // 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
-    ) {
-      var deletion = diffs[pointer - 1][1]
-      var insertion = diffs[pointer][1]
-      var overlap_length1 = this.diff_commonOverlap_(deletion, insertion)
-      var overlap_length2 = this.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, [
-            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, [
-            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++
-  }
-}
-
-/**
- * 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 c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- */
-diff_match_patch.prototype.diff_cleanupSemanticLossless = function (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, two) {
-    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.
-    var char1 = one.charAt(one.length - 1)
-    var char2 = two.charAt(0)
-    var nonAlphaNumeric1 = char1.match(diff_match_patch.nonAlphaNumericRegex_)
-    var nonAlphaNumeric2 = char2.match(diff_match_patch.nonAlphaNumericRegex_)
-    var whitespace1 =
-      nonAlphaNumeric1 && char1.match(diff_match_patch.whitespaceRegex_)
-    var whitespace2 =
-      nonAlphaNumeric2 && char2.match(diff_match_patch.whitespaceRegex_)
-    var lineBreak1 =
-      whitespace1 && char1.match(diff_match_patch.linebreakRegex_)
-    var lineBreak2 =
-      whitespace2 && char2.match(diff_match_patch.linebreakRegex_)
-    var blankLine1 =
-      lineBreak1 && one.match(diff_match_patch.blanklineEndRegex_)
-    var blankLine2 =
-      lineBreak2 && two.match(diff_match_patch.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
-  }
-
-  var 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.
-      var equality1 = diffs[pointer - 1][1]
-      var edit = diffs[pointer][1]
-      var equality2 = diffs[pointer + 1][1]
-
-      // First, shift the edit as far left as possible.
-      var commonOffset = this.diff_commonSuffix(equality1, edit)
-      if (commonOffset) {
-        var 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.
-      var bestEquality1 = equality1
-      var bestEdit = edit
-      var bestEquality2 = equality2
-      var 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)
-        var 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++
-  }
-}
-
-// Define some regex patterns for matching boundaries.
-diff_match_patch.nonAlphaNumericRegex_ = /[^a-zA-Z0-9]/
-diff_match_patch.whitespaceRegex_ = /\s/
-diff_match_patch.linebreakRegex_ = /[\r\n]/
-diff_match_patch.blanklineEndRegex_ = /\n\r?\n$/
-diff_match_patch.blanklineStartRegex_ = /^\r?\n\r?\n/
-
-/**
- * Reduce the number of edits by eliminating operationally trivial equalities.
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- */
-diff_match_patch.prototype.diff_cleanupEfficiency = function (diffs) {
-  var changes = false
-  var equalities = [] // Stack of indices where equalities are found.
-  var equalitiesLength = 0 // Keeping our own length var is faster in JS.
-  /** @type {?string} */
-  var lastequality = null
-  // Always equal to diffs[equalities[equalitiesLength - 1]][1]
-  var pointer = 0 // Index of current position.
-  // Is there an insertion operation before the last equality.
-  var pre_ins = false
-  // Is there a deletion operation before the last equality.
-  var pre_del = false
-  // Is there an insertion operation after the last equality.
-  var post_ins = false
-  // Is there a deletion operation after the last equality.
-  var post_del = false
-  while (pointer < diffs.length) {
-    if (diffs[pointer][0] == DIFF_EQUAL) {
-      // Equality found.
-      if (
-        diffs[pointer][1].length < this.Diff_EditCost &&
-        (post_ins || post_del)
-      ) {
-        // Candidate found.
-        equalities[equalitiesLength++] = pointer
-        pre_ins = post_ins
-        pre_del = post_del
-        lastequality = diffs[pointer][1]
-      } else {
-        // Not a candidate, and can never become one.
-        equalitiesLength = 0
-        lastequality = null
-      }
-      post_ins = post_del = false
-    } else {
-      // An insertion or deletion.
-      if (diffs[pointer][0] == DIFF_DELETE) {
-        post_del = true
-      } else {
-        post_ins = true
-      }
-      /*
-       * Five types to be split:
-       * <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
-       * <ins>A</ins>X<ins>C</ins><del>D</del>
-       * <ins>A</ins><del>B</del>X<ins>C</ins>
-       * <ins>A</del>X<ins>C</ins><del>D</del>
-       * <ins>A</ins><del>B</del>X<del>C</del>
-       */
-      if (
-        lastequality &&
-        ((pre_ins && pre_del && post_ins && post_del) ||
-          (lastequality.length < this.Diff_EditCost / 2 &&
-            pre_ins + pre_del + post_ins + post_del == 3))
-      ) {
-        // Duplicate record.
-        diffs.splice(equalities[equalitiesLength - 1], 0, [
-          DIFF_DELETE,
-          lastequality
-        ])
-        // Change second copy to insert.
-        diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT
-        equalitiesLength-- // Throw away the equality we just deleted;
-        lastequality = null
-        if (pre_ins && pre_del) {
-          // No changes made which could affect previous entry, keep going.
-          post_ins = post_del = true
-          equalitiesLength = 0
-        } else {
-          equalitiesLength-- // Throw away the previous equality.
-          pointer = equalitiesLength > 0 ? equalities[equalitiesLength - 1] : -1
-          post_ins = post_del = false
-        }
-        changes = true
-      }
-    }
-    pointer++
-  }
-
-  if (changes) {
-    this.diff_cleanupMerge(diffs)
-  }
-}
-
-/**
- * Reorder and merge like edit sections.  Merge equalities.
- * Any edit section can move as long as it doesn't cross an equality.
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- */
-diff_match_patch.prototype.diff_cleanupMerge = function (diffs) {
-  diffs.push([DIFF_EQUAL, '']) // Add a dummy entry at the end.
-  var pointer = 0
-  var count_delete = 0
-  var count_insert = 0
-  var text_delete = ''
-  var text_insert = ''
-  var 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 prefixies.
-            commonlength = this.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, [
-                  DIFF_EQUAL,
-                  text_insert.substring(0, commonlength)
-                ])
-                pointer++
-              }
-              text_insert = text_insert.substring(commonlength)
-              text_delete = text_delete.substring(commonlength)
-            }
-            // Factor out any common suffixies.
-            commonlength = this.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.
-          if (count_delete === 0) {
-            diffs.splice(pointer - count_insert, count_delete + count_insert, [
-              DIFF_INSERT,
-              text_insert
-            ])
-          } else if (count_insert === 0) {
-            diffs.splice(pointer - count_delete, count_delete + count_insert, [
-              DIFF_DELETE,
-              text_delete
-            ])
-          } else {
-            diffs.splice(
-              pointer - count_delete - count_insert,
-              count_delete + count_insert,
-              [DIFF_DELETE, text_delete],
-              [DIFF_INSERT, text_insert]
-            )
-          }
-          pointer =
-            pointer -
-            count_delete -
-            count_insert +
-            (count_delete ? 1 : 0) +
-            (count_insert ? 1 : 0) +
-            1
-        } 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[diffs.length - 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: A<ins>BA</ins>C -> <ins>AB</ins>AC
-  var 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) {
-    this.diff_cleanupMerge(diffs)
-  }
-}
-
-/**
- * loc is a location in text1, compute and return the equivalent location in
- * text2.
- * e.g. 'The cat' vs 'The big cat', 1->1, 5->8
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- * @param {number} loc Location within text1.
- * @return {number} Location within text2.
- */
-diff_match_patch.prototype.diff_xIndex = function (diffs, loc) {
-  var chars1 = 0
-  var chars2 = 0
-  var last_chars1 = 0
-  var last_chars2 = 0
-  var x
-  for (x = 0; x < diffs.length; x++) {
-    if (diffs[x][0] !== DIFF_INSERT) {
-      // Equality or deletion.
-      chars1 += diffs[x][1].length
-    }
-    if (diffs[x][0] !== DIFF_DELETE) {
-      // Equality or insertion.
-      chars2 += diffs[x][1].length
-    }
-    if (chars1 > loc) {
-      // Overshot the location.
-      break
-    }
-    last_chars1 = chars1
-    last_chars2 = chars2
-  }
-  // Was the location was deleted?
-  if (diffs.length != x && diffs[x][0] === DIFF_DELETE) {
-    return last_chars2
-  }
-  // Add the remaining character length.
-  return last_chars2 + (loc - last_chars1)
-}
-
-/**
- * Convert a diff array into a pretty HTML report.
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- * @return {string} HTML representation.
- */
-diff_match_patch.prototype.diff_prettyHtml = function (diffs) {
-  var html = []
-  var pattern_amp = /&/g
-  var pattern_lt = /</g
-  var pattern_gt = />/g
-  var pattern_para = /\n/g
-  for (var x = 0; x < diffs.length; x++) {
-    var op = diffs[x][0] // Operation (insert, delete, equal)
-    var data = diffs[x][1] // Text of change.
-    var text = data
-      .replace(pattern_amp, '&amp;')
-      .replace(pattern_lt, '&lt;')
-      .replace(pattern_gt, '&gt;')
-      .replace(pattern_para, '&para;<br>')
-    switch (op) {
-      case DIFF_INSERT:
-        html[x] = '<ins style="background:#e6ffe6;">' + text + '</ins>'
-        break
-      case DIFF_DELETE:
-        html[x] = '<del style="background:#ffe6e6;">' + text + '</del>'
-        break
-      case DIFF_EQUAL:
-        html[x] = '<span>' + text + '</span>'
-        break
-    }
-  }
-  return html.join('')
-}
-
-/**
- * Compute and return the source text (all equalities and deletions).
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- * @return {string} Source text.
- */
-diff_match_patch.prototype.diff_text1 = function (diffs) {
-  var text = []
-  for (var x = 0; x < diffs.length; x++) {
-    if (diffs[x][0] !== DIFF_INSERT) {
-      text[x] = diffs[x][1]
-    }
-  }
-  return text.join('')
-}
-
-/**
- * Compute and return the destination text (all equalities and insertions).
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- * @return {string} Destination text.
- */
-diff_match_patch.prototype.diff_text2 = function (diffs) {
-  var text = []
-  for (var x = 0; x < diffs.length; x++) {
-    if (diffs[x][0] !== DIFF_DELETE) {
-      text[x] = diffs[x][1]
-    }
-  }
-  return text.join('')
-}
-
-/**
- * Compute the Levenshtein distance; the number of inserted, deleted or
- * substituted characters.
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- * @return {number} Number of changes.
- */
-diff_match_patch.prototype.diff_levenshtein = function (diffs) {
-  var levenshtein = 0
-  var insertions = 0
-  var deletions = 0
-  for (var x = 0; x < diffs.length; x++) {
-    var op = diffs[x][0]
-    var data = diffs[x][1]
-    switch (op) {
-      case DIFF_INSERT:
-        insertions += data.length
-        break
-      case DIFF_DELETE:
-        deletions += data.length
-        break
-      case DIFF_EQUAL:
-        // A deletion and an insertion is one substitution.
-        levenshtein += Math.max(insertions, deletions)
-        insertions = 0
-        deletions = 0
-        break
-    }
-  }
-  levenshtein += Math.max(insertions, deletions)
-  return levenshtein
-}
-
-/**
- * Crush the diff into an encoded string which describes the operations
- * required to transform text1 into text2.
- * E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.
- * Operations are tab-separated.  Inserted text is escaped using %xx notation.
- * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
- * @return {string} Delta text.
- */
-diff_match_patch.prototype.diff_toDelta = function (diffs) {
-  var text = []
-  for (var x = 0; x < diffs.length; x++) {
-    switch (diffs[x][0]) {
-      case DIFF_INSERT:
-        text[x] = '+' + encodeURI(diffs[x][1])
-        break
-      case DIFF_DELETE:
-        text[x] = '-' + diffs[x][1].length
-        break
-      case DIFF_EQUAL:
-        text[x] = '=' + diffs[x][1].length
-        break
-    }
-  }
-  return text.join('\t').replace(/%20/g, ' ')
-}
-
-/**
- * Given the original text1, and an encoded string which describes the
- * operations required to transform text1 into text2, compute the full diff.
- * @param {string} text1 Source string for the diff.
- * @param {string} delta Delta text.
- * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
- * @throws {!Error} If invalid input.
- */
-diff_match_patch.prototype.diff_fromDelta = function (text1, delta) {
-  var diffs = []
-  var diffsLength = 0 // Keeping our own length var is faster in JS.
-  var pointer = 0 // Cursor in text1
-  var tokens = delta.split(/\t/g)
-  for (var x = 0; x < tokens.length; x++) {
-    // Each token begins with a one character parameter which specifies the
-    // operation of this token (delete, insert, equality).
-    var param = tokens[x].substring(1)
-    switch (tokens[x].charAt(0)) {
-      case '+':
-        try {
-          diffs[diffsLength++] = [DIFF_INSERT, decodeURI(param)]
-        } catch (ex) {
-          // Malformed URI sequence.
-          throw new Error('Illegal escape in diff_fromDelta: ' + param)
-        }
-        break
-      case '-':
-      // Fall through.
-      case '=':
-        var n = parseInt(param, 10)
-        if (isNaN(n) || n < 0) {
-          throw new Error('Invalid number in diff_fromDelta: ' + param)
-        }
-        var text = text1.substring(pointer, (pointer += n))
-        if (tokens[x].charAt(0) == '=') {
-          diffs[diffsLength++] = [DIFF_EQUAL, text]
-        } else {
-          diffs[diffsLength++] = [DIFF_DELETE, text]
-        }
-        break
-      default:
-        // Blank tokens are ok (from a trailing \t).
-        // Anything else is an error.
-        if (tokens[x]) {
-          throw new Error(
-            'Invalid diff operation in diff_fromDelta: ' + tokens[x]
-          )
-        }
-    }
-  }
-  if (pointer != text1.length) {
-    throw new Error(
-      'Delta length (' +
-        pointer +
-        ') does not equal source text length (' +
-        text1.length +
-        ').'
-    )
-  }
-  return diffs
-}
-
-//  MATCH FUNCTIONS
-
-/**
- * Locate the best instance of 'pattern' in 'text' near 'loc'.
- * @param {string} text The text to search.
- * @param {string} pattern The pattern to search for.
- * @param {number} loc The location to search around.
- * @return {number} Best match index or -1.
- */
-diff_match_patch.prototype.match_main = function (text, pattern, loc) {
-  // Check for null inputs.
-  if (text == null || pattern == null || loc == null) {
-    throw new Error('Null input. (match_main)')
-  }
-
-  loc = Math.max(0, Math.min(loc, text.length))
-  if (text == pattern) {
-    // Shortcut (potentially not guaranteed by the algorithm)
-    return 0
-  } else if (!text.length) {
-    // Nothing to match.
-    return -1
-  } else if (text.substring(loc, loc + pattern.length) == pattern) {
-    // Perfect match at the perfect spot!  (Includes case of null pattern)
-    return loc
-  } else {
-    // Do a fuzzy compare.
-    return this.match_bitap_(text, pattern, loc)
-  }
-}
-
-/**
- * Locate the best instance of 'pattern' in 'text' near 'loc' using the
- * Bitap algorithm.
- * @param {string} text The text to search.
- * @param {string} pattern The pattern to search for.
- * @param {number} loc The location to search around.
- * @return {number} Best match index or -1.
- * @private
- */
-diff_match_patch.prototype.match_bitap_ = function (text, pattern, loc) {
-  if (pattern.length > this.Match_MaxBits) {
-    throw new Error('Pattern too long for this browser.')
-  }
-
-  // Initialise the alphabet.
-  var s = this.match_alphabet_(pattern)
-
-  var dmp = this // 'this' becomes 'window' in a closure.
-
-  /**
-   * Compute and return the score for a match with e errors and x location.
-   * Accesses loc and pattern through being a closure.
-   * @param {number} e Number of errors in match.
-   * @param {number} x Location of match.
-   * @return {number} Overall score for match (0.0 = good, 1.0 = bad).
-   * @private
-   */
-  function match_bitapScore_(e, x) {
-    var accuracy = e / pattern.length
-    var proximity = Math.abs(loc - x)
-    if (!dmp.Match_Distance) {
-      // Dodge divide by zero error.
-      return proximity ? 1.0 : accuracy
-    }
-    return accuracy + proximity / dmp.Match_Distance
-  }
-
-  // Highest score beyond which we give up.
-  var score_threshold = this.Match_Threshold
-  // Is there a nearby exact match? (speedup)
-  var best_loc = text.indexOf(pattern, loc)
-  if (best_loc != -1) {
-    score_threshold = Math.min(match_bitapScore_(0, best_loc), score_threshold)
-    // What about in the other direction? (speedup)
-    best_loc = text.lastIndexOf(pattern, loc + pattern.length)
-    if (best_loc != -1) {
-      score_threshold = Math.min(
-        match_bitapScore_(0, best_loc),
-        score_threshold
-      )
-    }
-  }
-
-  // Initialise the bit arrays.
-  var matchmask = 1 << (pattern.length - 1)
-  best_loc = -1
-
-  var bin_min, bin_mid
-  var bin_max = pattern.length + text.length
-  var last_rd
-  for (var d = 0; d < pattern.length; d++) {
-    // Scan for the best match; each iteration allows for one more error.
-    // Run a binary search to determine how far from 'loc' we can stray at this
-    // error level.
-    bin_min = 0
-    bin_mid = bin_max
-    while (bin_min < bin_mid) {
-      if (match_bitapScore_(d, loc + bin_mid) <= score_threshold) {
-        bin_min = bin_mid
-      } else {
-        bin_max = bin_mid
-      }
-      bin_mid = Math.floor((bin_max - bin_min) / 2 + bin_min)
-    }
-    // Use the result from this iteration as the maximum for the next.
-    bin_max = bin_mid
-    var start = Math.max(1, loc - bin_mid + 1)
-    var finish = Math.min(loc + bin_mid, text.length) + pattern.length
-
-    var rd = Array(finish + 2)
-    rd[finish + 1] = (1 << d) - 1
-    for (var j = finish; j >= start; j--) {
-      // The alphabet (s) is a sparse hash, so the following line generates
-      // warnings.
-      var charMatch = s[text.charAt(j - 1)]
-      if (d === 0) {
-        // First pass: exact match.
-        rd[j] = ((rd[j + 1] << 1) | 1) & charMatch
-      } else {
-        // Subsequent passes: fuzzy match.
-        rd[j] =
-          (((rd[j + 1] << 1) | 1) & charMatch) |
-          (((last_rd[j + 1] | last_rd[j]) << 1) | 1) |
-          last_rd[j + 1]
-      }
-      if (rd[j] & matchmask) {
-        var score = match_bitapScore_(d, j - 1)
-        // This match will almost certainly be better than any existing match.
-        // But check anyway.
-        if (score <= score_threshold) {
-          // Told you so.
-          score_threshold = score
-          best_loc = j - 1
-          if (best_loc > loc) {
-            // When passing loc, don't exceed our current distance from loc.
-            start = Math.max(1, 2 * loc - best_loc)
-          } else {
-            // Already passed loc, downhill from here on in.
-            break
-          }
-        }
-      }
-    }
-    // No hope for a (better) match at greater error levels.
-    if (match_bitapScore_(d + 1, loc) > score_threshold) {
-      break
-    }
-    last_rd = rd
-  }
-  return best_loc
-}
-
-/**
- * Initialise the alphabet for the Bitap algorithm.
- * @param {string} pattern The text to encode.
- * @return {!Object} Hash of character locations.
- * @private
- */
-diff_match_patch.prototype.match_alphabet_ = function (pattern) {
-  var s = {}
-  for (var i = 0; i < pattern.length; i++) {
-    s[pattern.charAt(i)] = 0
-  }
-  for (var i = 0; i < pattern.length; i++) {
-    s[pattern.charAt(i)] |= 1 << (pattern.length - i - 1)
-  }
-  return s
-}
-
-//  PATCH FUNCTIONS
-
-/**
- * Increase the context until it is unique,
- * but don't let the pattern expand beyond Match_MaxBits.
- * @param {!diff_match_patch.patch_obj} patch The patch to grow.
- * @param {string} text Source text.
- * @private
- */
-diff_match_patch.prototype.patch_addContext_ = function (patch, text) {
-  if (text.length == 0) {
-    return
-  }
-  var pattern = text.substring(patch.start2, patch.start2 + patch.length1)
-  var padding = 0
-
-  // Look for the first and last matches of pattern in text.  If two different
-  // matches are found, increase the pattern length.
-  while (
-    text.indexOf(pattern) != text.lastIndexOf(pattern) &&
-    pattern.length < this.Match_MaxBits - this.Patch_Margin - this.Patch_Margin
-  ) {
-    padding += this.Patch_Margin
-    pattern = text.substring(
-      patch.start2 - padding,
-      patch.start2 + patch.length1 + padding
-    )
-  }
-  // Add one chunk for good luck.
-  padding += this.Patch_Margin
-
-  // Add the prefix.
-  var prefix = text.substring(patch.start2 - padding, patch.start2)
-  if (prefix) {
-    patch.diffs.unshift([DIFF_EQUAL, prefix])
-  }
-  // Add the suffix.
-  var suffix = text.substring(
-    patch.start2 + patch.length1,
-    patch.start2 + patch.length1 + padding
-  )
-  if (suffix) {
-    patch.diffs.push([DIFF_EQUAL, suffix])
-  }
-
-  // Roll back the start points.
-  patch.start1 -= prefix.length
-  patch.start2 -= prefix.length
-  // Extend the lengths.
-  patch.length1 += prefix.length + suffix.length
-  patch.length2 += prefix.length + suffix.length
-}
-
-/**
- * Compute a list of patches to turn text1 into text2.
- * Use diffs if provided, otherwise compute it ourselves.
- * There are four ways to call this function, depending on what data is
- * available to the caller:
- * Method 1:
- * a = text1, b = text2
- * Method 2:
- * a = diffs
- * Method 3 (optimal):
- * a = text1, b = diffs
- * Method 4 (deprecated, use method 3):
- * a = text1, b = text2, c = diffs
- *
- * @param {string|!Array.<!diff_match_patch.Diff>} a text1 (methods 1,3,4) or
- * Array of diff tuples for text1 to text2 (method 2).
- * @param {string|!Array.<!diff_match_patch.Diff>} opt_b text2 (methods 1,4) or
- * Array of diff tuples for text1 to text2 (method 3) or undefined (method 2).
- * @param {string|!Array.<!diff_match_patch.Diff>} opt_c Array of diff tuples
- * for text1 to text2 (method 4) or undefined (methods 1,2,3).
- * @return {!Array.<!diff_match_patch.patch_obj>} Array of Patch objects.
- */
-diff_match_patch.prototype.patch_make = function (a, opt_b, opt_c) {
-  var text1, diffs
-  if (
-    typeof a == 'string' &&
-    typeof opt_b == 'string' &&
-    typeof opt_c == 'undefined'
-  ) {
-    // Method 1: text1, text2
-    // Compute diffs from text1 and text2.
-    text1 = /** @type {string} */ (a)
-    diffs = this.diff_main(text1, /** @type {string} */ (opt_b), true)
-    if (diffs.length > 2) {
-      this.diff_cleanupSemantic(diffs)
-      this.diff_cleanupEfficiency(diffs)
-    }
-  } else if (
-    a &&
-    typeof a == 'object' &&
-    typeof opt_b == 'undefined' &&
-    typeof opt_c == 'undefined'
-  ) {
-    // Method 2: diffs
-    // Compute text1 from diffs.
-    diffs = /** @type {!Array.<!diff_match_patch.Diff>} */ (a)
-    text1 = this.diff_text1(diffs)
-  } else if (
-    typeof a == 'string' &&
-    opt_b &&
-    typeof opt_b == 'object' &&
-    typeof opt_c == 'undefined'
-  ) {
-    // Method 3: text1, diffs
-    text1 = /** @type {string} */ (a)
-    diffs = /** @type {!Array.<!diff_match_patch.Diff>} */ (opt_b)
-  } else if (
-    typeof a == 'string' &&
-    typeof opt_b == 'string' &&
-    opt_c &&
-    typeof opt_c == 'object'
-  ) {
-    // Method 4: text1, text2, diffs
-    // text2 is not used.
-    text1 = /** @type {string} */ (a)
-    diffs = /** @type {!Array.<!diff_match_patch.Diff>} */ (opt_c)
-  } else {
-    throw new Error('Unknown call format to patch_make.')
-  }
-
-  if (diffs.length === 0) {
-    return [] // Get rid of the null case.
-  }
-  var patches = []
-  var patch = new diff_match_patch.patch_obj()
-  var patchDiffLength = 0 // Keeping our own length var is faster in JS.
-  var char_count1 = 0 // Number of characters into the text1 string.
-  var char_count2 = 0 // Number of characters into the text2 string.
-  // Start with text1 (prepatch_text) and apply the diffs until we arrive at
-  // text2 (postpatch_text).  We recreate the patches one by one to determine
-  // context info.
-  var prepatch_text = text1
-  var postpatch_text = text1
-  for (var x = 0; x < diffs.length; x++) {
-    var diff_type = diffs[x][0]
-    var diff_text = diffs[x][1]
-
-    if (!patchDiffLength && diff_type !== DIFF_EQUAL) {
-      // A new patch starts here.
-      patch.start1 = char_count1
-      patch.start2 = char_count2
-    }
-
-    switch (diff_type) {
-      case DIFF_INSERT:
-        patch.diffs[patchDiffLength++] = diffs[x]
-        patch.length2 += diff_text.length
-        postpatch_text =
-          postpatch_text.substring(0, char_count2) +
-          diff_text +
-          postpatch_text.substring(char_count2)
-        break
-      case DIFF_DELETE:
-        patch.length1 += diff_text.length
-        patch.diffs[patchDiffLength++] = diffs[x]
-        postpatch_text =
-          postpatch_text.substring(0, char_count2) +
-          postpatch_text.substring(char_count2 + diff_text.length)
-        break
-      case DIFF_EQUAL:
-        if (
-          diff_text.length <= 2 * this.Patch_Margin &&
-          patchDiffLength &&
-          diffs.length != x + 1
-        ) {
-          // Small equality inside a patch.
-          patch.diffs[patchDiffLength++] = diffs[x]
-          patch.length1 += diff_text.length
-          patch.length2 += diff_text.length
-        } else if (diff_text.length >= 2 * this.Patch_Margin) {
-          // Time for a new patch.
-          if (patchDiffLength) {
-            this.patch_addContext_(patch, prepatch_text)
-            patches.push(patch)
-            patch = new diff_match_patch.patch_obj()
-            patchDiffLength = 0
-            // Unlike Unidiff, our patch lists have a rolling context.
-            // http://code.google.com/p/google-diff-match-patch/wiki/Unidiff
-            // Update prepatch text & pos to reflect the application of the
-            // just completed patch.
-            prepatch_text = postpatch_text
-            char_count1 = char_count2
-          }
-        }
-        break
-    }
-
-    // Update the current character count.
-    if (diff_type !== DIFF_INSERT) {
-      char_count1 += diff_text.length
-    }
-    if (diff_type !== DIFF_DELETE) {
-      char_count2 += diff_text.length
-    }
-  }
-  // Pick up the leftover patch if not empty.
-  if (patchDiffLength) {
-    this.patch_addContext_(patch, prepatch_text)
-    patches.push(patch)
-  }
-
-  return patches
-}
-
-/**
- * Given an array of patches, return another array that is identical.
- * @param {!Array.<!diff_match_patch.patch_obj>} patches Array of Patch objects.
- * @return {!Array.<!diff_match_patch.patch_obj>} Array of Patch objects.
- */
-diff_match_patch.prototype.patch_deepCopy = function (patches) {
-  // Making deep copies is hard in JavaScript.
-  var patchesCopy = []
-  for (var x = 0; x < patches.length; x++) {
-    var patch = patches[x]
-    var patchCopy = new diff_match_patch.patch_obj()
-    patchCopy.diffs = []
-    for (var y = 0; y < patch.diffs.length; y++) {
-      patchCopy.diffs[y] = patch.diffs[y].slice()
-    }
-    patchCopy.start1 = patch.start1
-    patchCopy.start2 = patch.start2
-    patchCopy.length1 = patch.length1
-    patchCopy.length2 = patch.length2
-    patchesCopy[x] = patchCopy
-  }
-  return patchesCopy
-}
-
-/**
- * Merge a set of patches onto the text.  Return a patched text, as well
- * as a list of true/false values indicating which patches were applied.
- * @param {!Array.<!diff_match_patch.patch_obj>} patches Array of Patch objects.
- * @param {string} text Old text.
- * @return {!Array.<string|!Array.<boolean>>} Two element Array, containing the
- *      new text and an array of boolean values.
- */
-diff_match_patch.prototype.patch_apply = function (patches, text) {
-  if (patches.length == 0) {
-    return [text, []]
-  }
-
-  // Deep copy the patches so that no changes are made to originals.
-  patches = this.patch_deepCopy(patches)
-
-  var nullPadding = this.patch_addPadding(patches)
-  text = nullPadding + text + nullPadding
-
-  this.patch_splitMax(patches)
-  // delta keeps track of the offset between the expected and actual location
-  // of the previous patch.  If there are patches expected at positions 10 and
-  // 20, but the first patch was found at 12, delta is 2 and the second patch
-  // has an effective expected position of 22.
-  var delta = 0
-  var results = []
-  for (var x = 0; x < patches.length; x++) {
-    var expected_loc = patches[x].start2 + delta
-    var text1 = this.diff_text1(patches[x].diffs)
-    var start_loc
-    var end_loc = -1
-    if (text1.length > this.Match_MaxBits) {
-      // patch_splitMax will only provide an oversized pattern in the case of
-      // a monster delete.
-      start_loc = this.match_main(
-        text,
-        text1.substring(0, this.Match_MaxBits),
-        expected_loc
-      )
-      if (start_loc != -1) {
-        end_loc = this.match_main(
-          text,
-          text1.substring(text1.length - this.Match_MaxBits),
-          expected_loc + text1.length - this.Match_MaxBits
-        )
-        if (end_loc == -1 || start_loc >= end_loc) {
-          // Can't find valid trailing context.  Drop this patch.
-          start_loc = -1
-        }
-      }
-    } else {
-      start_loc = this.match_main(text, text1, expected_loc)
-    }
-    if (start_loc == -1) {
-      // No match found.  :(
-      results[x] = false
-      // Subtract the delta for this failed patch from subsequent patches.
-      delta -= patches[x].length2 - patches[x].length1
-    } else {
-      // Found a match.  :)
-      results[x] = true
-      delta = start_loc - expected_loc
-      var text2
-      if (end_loc == -1) {
-        text2 = text.substring(start_loc, start_loc + text1.length)
-      } else {
-        text2 = text.substring(start_loc, end_loc + this.Match_MaxBits)
-      }
-      if (text1 == text2) {
-        // Perfect match, just shove the replacement text in.
-        text =
-          text.substring(0, start_loc) +
-          this.diff_text2(patches[x].diffs) +
-          text.substring(start_loc + text1.length)
-      } else {
-        // Imperfect match.  Run a diff to get a framework of equivalent
-        // indices.
-        var diffs = this.diff_main(text1, text2, false)
-        if (
-          text1.length > this.Match_MaxBits &&
-          this.diff_levenshtein(diffs) / text1.length >
-            this.Patch_DeleteThreshold
-        ) {
-          // The end points match, but the content is unacceptably bad.
-          results[x] = false
-        } else {
-          this.diff_cleanupSemanticLossless(diffs)
-          var index1 = 0
-          var index2
-          for (var y = 0; y < patches[x].diffs.length; y++) {
-            var mod = patches[x].diffs[y]
-            if (mod[0] !== DIFF_EQUAL) {
-              index2 = this.diff_xIndex(diffs, index1)
-            }
-            if (mod[0] === DIFF_INSERT) {
-              // Insertion
-              text =
-                text.substring(0, start_loc + index2) +
-                mod[1] +
-                text.substring(start_loc + index2)
-            } else if (mod[0] === DIFF_DELETE) {
-              // Deletion
-              text =
-                text.substring(0, start_loc + index2) +
-                text.substring(
-                  start_loc + this.diff_xIndex(diffs, index1 + mod[1].length)
-                )
-            }
-            if (mod[0] !== DIFF_DELETE) {
-              index1 += mod[1].length
-            }
-          }
-        }
-      }
-    }
-  }
-  // Strip the padding off.
-  text = text.substring(nullPadding.length, text.length - nullPadding.length)
-  return [text, results]
-}
-
-/**
- * Add some padding on text start and end so that edges can match something.
- * Intended to be called only from within patch_apply.
- * @param {!Array.<!diff_match_patch.patch_obj>} patches Array of Patch objects.
- * @return {string} The padding string added to each side.
- */
-diff_match_patch.prototype.patch_addPadding = function (patches) {
-  var paddingLength = this.Patch_Margin
-  var nullPadding = ''
-  for (var x = 1; x <= paddingLength; x++) {
-    nullPadding += String.fromCharCode(x)
-  }
-
-  // Bump all the patches forward.
-  for (var x = 0; x < patches.length; x++) {
-    patches[x].start1 += paddingLength
-    patches[x].start2 += paddingLength
-  }
-
-  // Add some padding on start of first diff.
-  var patch = patches[0]
-  var diffs = patch.diffs
-  if (diffs.length == 0 || diffs[0][0] != DIFF_EQUAL) {
-    // Add nullPadding equality.
-    diffs.unshift([DIFF_EQUAL, nullPadding])
-    patch.start1 -= paddingLength // Should be 0.
-    patch.start2 -= paddingLength // Should be 0.
-    patch.length1 += paddingLength
-    patch.length2 += paddingLength
-  } else if (paddingLength > diffs[0][1].length) {
-    // Grow first equality.
-    var extraLength = paddingLength - diffs[0][1].length
-    diffs[0][1] = nullPadding.substring(diffs[0][1].length) + diffs[0][1]
-    patch.start1 -= extraLength
-    patch.start2 -= extraLength
-    patch.length1 += extraLength
-    patch.length2 += extraLength
-  }
-
-  // Add some padding on end of last diff.
-  patch = patches[patches.length - 1]
-  diffs = patch.diffs
-  if (diffs.length == 0 || diffs[diffs.length - 1][0] != DIFF_EQUAL) {
-    // Add nullPadding equality.
-    diffs.push([DIFF_EQUAL, nullPadding])
-    patch.length1 += paddingLength
-    patch.length2 += paddingLength
-  } else if (paddingLength > diffs[diffs.length - 1][1].length) {
-    // Grow last equality.
-    var extraLength = paddingLength - diffs[diffs.length - 1][1].length
-    diffs[diffs.length - 1][1] += nullPadding.substring(0, extraLength)
-    patch.length1 += extraLength
-    patch.length2 += extraLength
-  }
-
-  return nullPadding
-}
-
-/**
- * Look through the patches and break up any which are longer than the maximum
- * limit of the match algorithm.
- * Intended to be called only from within patch_apply.
- * @param {!Array.<!diff_match_patch.patch_obj>} patches Array of Patch objects.
- */
-diff_match_patch.prototype.patch_splitMax = function (patches) {
-  var patch_size = this.Match_MaxBits
-  for (var x = 0; x < patches.length; x++) {
-    if (patches[x].length1 <= patch_size) {
-      continue
-    }
-    var bigpatch = patches[x]
-    // Remove the big old patch.
-    patches.splice(x--, 1)
-    var start1 = bigpatch.start1
-    var start2 = bigpatch.start2
-    var precontext = ''
-    while (bigpatch.diffs.length !== 0) {
-      // Create one of several smaller patches.
-      var patch = new diff_match_patch.patch_obj()
-      var empty = true
-      patch.start1 = start1 - precontext.length
-      patch.start2 = start2 - precontext.length
-      if (precontext !== '') {
-        patch.length1 = patch.length2 = precontext.length
-        patch.diffs.push([DIFF_EQUAL, precontext])
-      }
-      while (
-        bigpatch.diffs.length !== 0 &&
-        patch.length1 < patch_size - this.Patch_Margin
-      ) {
-        var diff_type = bigpatch.diffs[0][0]
-        var diff_text = bigpatch.diffs[0][1]
-        if (diff_type === DIFF_INSERT) {
-          // Insertions are harmless.
-          patch.length2 += diff_text.length
-          start2 += diff_text.length
-          patch.diffs.push(bigpatch.diffs.shift())
-          empty = false
-        } else if (
-          diff_type === DIFF_DELETE &&
-          patch.diffs.length == 1 &&
-          patch.diffs[0][0] == DIFF_EQUAL &&
-          diff_text.length > 2 * patch_size
-        ) {
-          // This is a large deletion.  Let it pass in one chunk.
-          patch.length1 += diff_text.length
-          start1 += diff_text.length
-          empty = false
-          patch.diffs.push([diff_type, diff_text])
-          bigpatch.diffs.shift()
-        } else {
-          // Deletion or equality.  Only take as much as we can stomach.
-          diff_text = diff_text.substring(
-            0,
-            patch_size - patch.length1 - this.Patch_Margin
-          )
-          patch.length1 += diff_text.length
-          start1 += diff_text.length
-          if (diff_type === DIFF_EQUAL) {
-            patch.length2 += diff_text.length
-            start2 += diff_text.length
-          } else {
-            empty = false
-          }
-          patch.diffs.push([diff_type, diff_text])
-          if (diff_text == bigpatch.diffs[0][1]) {
-            bigpatch.diffs.shift()
-          } else {
-            bigpatch.diffs[0][1] = bigpatch.diffs[0][1].substring(
-              diff_text.length
-            )
-          }
-        }
-      }
-      // Compute the head context for the next patch.
-      precontext = this.diff_text2(patch.diffs)
-      precontext = precontext.substring(precontext.length - this.Patch_Margin)
-      // Append the end context for this patch.
-      var postcontext = this.diff_text1(bigpatch.diffs).substring(
-        0,
-        this.Patch_Margin
-      )
-      if (postcontext !== '') {
-        patch.length1 += postcontext.length
-        patch.length2 += postcontext.length
-        if (
-          patch.diffs.length !== 0 &&
-          patch.diffs[patch.diffs.length - 1][0] === DIFF_EQUAL
-        ) {
-          patch.diffs[patch.diffs.length - 1][1] += postcontext
-        } else {
-          patch.diffs.push([DIFF_EQUAL, postcontext])
-        }
-      }
-      if (!empty) {
-        patches.splice(++x, 0, patch)
-      }
-    }
-  }
-}
-
-/**
- * Take a list of patches and return a textual representation.
- * @param {!Array.<!diff_match_patch.patch_obj>} patches Array of Patch objects.
- * @return {string} Text representation of patches.
- */
-diff_match_patch.prototype.patch_toText = function (patches) {
-  var text = []
-  for (var x = 0; x < patches.length; x++) {
-    text[x] = patches[x]
-  }
-  return text.join('')
-}
-
-/**
- * Parse a textual representation of patches and return a list of Patch objects.
- * @param {string} textline Text representation of patches.
- * @return {!Array.<!diff_match_patch.patch_obj>} Array of Patch objects.
- * @throws {!Error} If invalid input.
- */
-diff_match_patch.prototype.patch_fromText = function (textline) {
-  var patches = []
-  if (!textline) {
-    return patches
-  }
-  var text = textline.split('\n')
-  var textPointer = 0
-  var patchHeader = /^@@ -(\d+),?(\d*) \+(\d+),?(\d*) @@$/
-  while (textPointer < text.length) {
-    var m = text[textPointer].match(patchHeader)
-    if (!m) {
-      throw new Error('Invalid patch string: ' + text[textPointer])
-    }
-    var patch = new diff_match_patch.patch_obj()
-    patches.push(patch)
-    patch.start1 = parseInt(m[1], 10)
-    if (m[2] === '') {
-      patch.start1--
-      patch.length1 = 1
-    } else if (m[2] == '0') {
-      patch.length1 = 0
-    } else {
-      patch.start1--
-      patch.length1 = parseInt(m[2], 10)
-    }
-
-    patch.start2 = parseInt(m[3], 10)
-    if (m[4] === '') {
-      patch.start2--
-      patch.length2 = 1
-    } else if (m[4] == '0') {
-      patch.length2 = 0
-    } else {
-      patch.start2--
-      patch.length2 = parseInt(m[4], 10)
-    }
-    textPointer++
-
-    while (textPointer < text.length) {
-      var sign = text[textPointer].charAt(0)
-      try {
-        var line = decodeURI(text[textPointer].substring(1))
-      } catch (ex) {
-        // Malformed URI sequence.
-        throw new Error('Illegal escape in patch_fromText: ' + line)
-      }
-      if (sign == '-') {
-        // Deletion.
-        patch.diffs.push([DIFF_DELETE, line])
-      } else if (sign == '+') {
-        // Insertion.
-        patch.diffs.push([DIFF_INSERT, line])
-      } else if (sign == ' ') {
-        // Minor equality.
-        patch.diffs.push([DIFF_EQUAL, line])
-      } else if (sign == '@') {
-        // Start of next patch.
-        break
-      } else if (sign === '') {
-        // Blank line?  Whatever.
-      } else {
-        // WTF?
-        throw new Error('Invalid patch mode "' + sign + '" in: ' + line)
-      }
-      textPointer++
-    }
-  }
-  return patches
-}
-
-/**
- * Class representing one patch operation.
- * @constructor
- */
-diff_match_patch.patch_obj = function () {
-  /** @type {!Array.<!diff_match_patch.Diff>} */
-  this.diffs = []
-  /** @type {?number} */
-  this.start1 = null
-  /** @type {?number} */
-  this.start2 = null
-  /** @type {number} */
-  this.length1 = 0
-  /** @type {number} */
-  this.length2 = 0
-}
-
-/**
- * Emmulate GNU diff's format.
- * Header: @@ -382,8 +481,9 @@
- * Indicies are printed as 1-based, not 0-based.
- * @return {string} The GNU diff string.
- */
-diff_match_patch.patch_obj.prototype.toString = function () {
-  var coords1, coords2
-  if (this.length1 === 0) {
-    coords1 = this.start1 + ',0'
-  } else if (this.length1 == 1) {
-    coords1 = this.start1 + 1
-  } else {
-    coords1 = this.start1 + 1 + ',' + this.length1
-  }
-  if (this.length2 === 0) {
-    coords2 = this.start2 + ',0'
-  } else if (this.length2 == 1) {
-    coords2 = this.start2 + 1
-  } else {
-    coords2 = this.start2 + 1 + ',' + this.length2
-  }
-  var text = ['@@ -' + coords1 + ' +' + coords2 + ' @@\n']
-  var op
-  // Escape the body of the patch with %xx notation.
-  for (var x = 0; x < this.diffs.length; x++) {
-    switch (this.diffs[x][0]) {
-      case DIFF_INSERT:
-        op = '+'
-        break
-      case DIFF_DELETE:
-        op = '-'
-        break
-      case DIFF_EQUAL:
-        op = ' '
-        break
-    }
-    text[x + 1] = op + encodeURI(this.diffs[x][1]) + '\n'
-  }
-  return text.join('').replace(/%20/g, ' ')
-}
-
-// Export these global variables so that they survive Google's JS compiler.
-// In a browser, 'this' will be 'window'.
-// Users of node.js should 'require' the uncompressed version since Google's
-// JS compiler may break the following exports for non-browser environments.
-this['diff_match_patch'] = diff_match_patch
-this['DIFF_DELETE'] = DIFF_DELETE
-this['DIFF_INSERT'] = DIFF_INSERT
-this['DIFF_EQUAL'] = DIFF_EQUAL

services/document-updater/package-lock.json

@@ -1475,7 +1475,7 @@
     "d64": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/d64/-/d64-1.0.0.tgz",
-      "integrity": "sha1-QAKofoUMv8n52XBrYPymE6MzbpA="
+      "integrity": "sha512-5eNy3WZziVYnrogqgXhcdEmqcDB2IHurTqLcrgssJsfkMVCUoUaZpK6cJjxxvLV2dUm5SuJMNcYfVGoin9UIRw=="
     },
     "damerau-levenshtein": {
       "version": "1.0.6",
@@ -1583,6 +1583,10 @@
       "integrity": "sha1-gAwN0eCov7yVg1wgKtIg/jF+WhI=",
       "dev": true
     },
+    "diff-match-patch": {
+      "version": "https://github.com/overleaf/diff-match-patch/archive/89805f9c671a77a263fc53461acd62aa7498f688.tar.gz",
+      "integrity": "sha512-rX+9ry8tosctHzJfYG9Vjpof6wTYYA/oFHnzpv6O1vkUd+5dTc9LpZCTUv+FK8i4grpITxY8BYSk8A3u4anwJQ=="
+    },
     "dlv": {
       "version": "1.1.3",
       "resolved": "https://registry.npmjs.org/dlv/-/dlv-1.1.3.tgz",
@@ -3463,12 +3467,12 @@
     "lodash.at": {
       "version": "4.6.0",
       "resolved": "https://registry.npmjs.org/lodash.at/-/lodash.at-4.6.0.tgz",
-      "integrity": "sha1-k83OZk8KGZTqM9181A4jr9EbD/g="
+      "integrity": "sha512-GOTh0SEp+Yosnlpjic+8cl2WM9MykorogkGA9xyIFkkObQ3H3kNZqZ+ohuq4K3FrSVo7hMcZBMataJemrxC3BA=="
     },
     "lodash.camelcase": {
       "version": "4.3.0",
       "resolved": "https://registry.npmjs.org/lodash.camelcase/-/lodash.camelcase-4.3.0.tgz",
-      "integrity": "sha1-soqmKIorn8ZRA1x3EfZathkDMaY="
+      "integrity": "sha512-TwuEnCnxbc3rAvhf/LbG7tJUDzhqXyFnv3dtzLOPgCG/hODL7WFnsbwktkD7yUV0RrreP/l1PALq/YSg6VvjlA=="
     },
     "lodash.defaults": {
       "version": "4.2.0",
@@ -3489,7 +3493,7 @@
     "lodash.has": {
       "version": "4.5.2",
       "resolved": "https://registry.npmjs.org/lodash.has/-/lodash.has-4.5.2.tgz",
-      "integrity": "sha1-0Z9NwQlQWMzL4rDN9O4P5Ko3yGI="
+      "integrity": "sha512-rnYUdIo6xRCJnQmbVFEwcxF144erlD+M3YcJUVesflU9paQaE8p+fJDcIQrlMYbxoANFL+AB9hZrzSBBk5PL+g=="
     },
     "lodash.memoize": {
       "version": "4.1.2",
@@ -5262,7 +5266,7 @@
     "redis-commands": {
       "version": "1.5.0",
       "resolved": "https://registry.npmjs.org/redis-commands/-/redis-commands-1.5.0.tgz",
-      "integrity": "sha512-6KxamqpZ468MeQC3bkWmCB1fp56XL64D4Kf0zJSwDZbVLLm7KFkoIcHrgRvQ+sk8dnhySs7+yBg94yIkAK7aJg=="
+      "integrity": "sha1-gNLiBpj+aI8icSf/nlFkp90X54U="
     },
     "redis-errors": {
       "version": "1.2.0",
@@ -5479,7 +5483,7 @@
     "safe-json-stringify": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/safe-json-stringify/-/safe-json-stringify-1.2.0.tgz",
-      "integrity": "sha512-gH8eh2nZudPQO6TytOvbxnuhYBOvDBBLW52tz5q6X58lJcd/tkmqFR+5Z9adS8aJtURSXWThWy/xJtJwixErvg==",
+      "integrity": "sha1-NW5EvJjx+TzkXfFLzXwBzahuCv0=",
       "optional": true
     },
     "safer-buffer": {
@@ -5773,7 +5777,7 @@
     "standard-as-callback": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/standard-as-callback/-/standard-as-callback-2.0.1.tgz",
-      "integrity": "sha512-NQOxSeB8gOI5WjSaxjBgog2QFw55FV8TkS6Y07BiB3VJ8xNTvUYm0wl0s8ObgQ5NhdpnNfigMIKjgPESzgr4tg=="
+      "integrity": "sha1-7YuyVkjhWDF1m2Ajvbh+a2CzgSY="
     },
     "statuses": {
       "version": "1.5.0",
@@ -5892,7 +5896,7 @@
     "stubs": {
       "version": "3.0.0",
       "resolved": "https://registry.npmjs.org/stubs/-/stubs-3.0.0.tgz",
-      "integrity": "sha1-6NK6H6nJBXAwPAMLaQD31fiavls="
+      "integrity": "sha512-PdHt7hHUJKxvTCgbKX9C1V/ftOcjJQgz8BZwNfV5c4B6dcGqlpelTbJ999jBGZ2jYiPAwcX5dP6oBwVlBlUbxw=="
     },
     "supports-color": {
       "version": "5.4.0",
@@ -6024,12 +6028,12 @@
     "to-no-case": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/to-no-case/-/to-no-case-1.0.2.tgz",
-      "integrity": "sha1-xyKQcWTvaxeBMsjmmTAhLRtKoWo="
+      "integrity": "sha512-Z3g735FxuZY8rodxV4gH7LxClE4H0hTIyHNIHdk+vpQxjLm0cwnKXq/OFVZ76SOQmto7txVcwSCwkU5kqp+FKg=="
     },
     "to-snake-case": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/to-snake-case/-/to-snake-case-1.0.0.tgz",
-      "integrity": "sha1-znRpE4l5RgGah+Yu366upMYIq4w=",
+      "integrity": "sha512-joRpzBAk1Bhi2eGEYBjukEWHOe/IvclOkiJl3DtA91jV6NwQ3MwXA4FHYeqk8BNp/D8bmi9tcNbRu/SozP0jbQ==",
       "requires": {
         "to-space-case": "^1.0.0"
       }
@@ -6037,7 +6041,7 @@
     "to-space-case": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/to-space-case/-/to-space-case-1.0.0.tgz",
-      "integrity": "sha1-sFLar7Gysp3HcM6gFj5ewOvJ/Bc=",
+      "integrity": "sha512-rLdvwXZ39VOn1IxGL3V6ZstoTbwLRckQmn/U8ZDLuWwIXNpuZDhQ3AiRUlhTbOXFVE9C+dR51wM0CBDhk31VcA==",
       "requires": {
         "to-no-case": "^1.0.0"
       }

services/document-updater/package.json

@@ -24,6 +24,7 @@
     "async": "^2.5.0",
     "body-parser": "^1.19.0",
     "bunyan": "~0.22.1",
+    "diff-match-patch": "https://github.com/overleaf/diff-match-patch/archive/89805f9c671a77a263fc53461acd62aa7498f688.tar.gz",
     "express": "4.17.1",
     "lodash": "^4.17.19",
     "logger-sharelatex": "^1.9.1",