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node_modules/fast-diff/diff.js

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+/**
+ * This library modifies the diff-patch-match library by Neil Fraser
+ * by removing the patch and match functionality and certain advanced
+ * options in the diff function. The original license is as follows:
+ *
+ * ===
+ *
+ * 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.
+ */
+
+
+/**
+ * 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;
+
+
+/**
+ * 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.
+ * @return {Array} Array of diff tuples.
+ */
+function diff_main(text1, text2) {
+  // Check for equality (speedup).
+  if (text1 == text2) {
+    if (text1) {
+      return [[DIFF_EQUAL, text1]];
+    }
+    return [];
+  }
+
+  // Trim off common prefix (speedup).
+  var commonlength = diff_commonPrefix(text1, text2);
+  var commonprefix = text1.substring(0, commonlength);
+  text1 = text1.substring(commonlength);
+  text2 = text2.substring(commonlength);
+
+  // Trim off common suffix (speedup).
+  commonlength = 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 = diff_compute_(text1, text2);
+
+  // Restore the prefix and suffix.
+  if (commonprefix) {
+    diffs.unshift([DIFF_EQUAL, commonprefix]);
+  }
+  if (commonsuffix) {
+    diffs.push([DIFF_EQUAL, commonsuffix]);
+  }
+  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.
+ * @return {Array} Array of diff tuples.
+ */
+function diff_compute_(text1, text2) {
+  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 = 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 = diff_main(text1_a, text2_a);
+    var diffs_b = diff_main(text1_b, text2_b);
+    // Merge the results.
+    return diffs_a.concat([[DIFF_EQUAL, mid_common]], diffs_b);
+  }
+
+  return diff_bisect_(text1, text2);
+};
+
+
+/**
+ * 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.
+ * @return {Array} Array of diff tuples.
+ * @private
+ */
+function diff_bisect_(text1, text2) {
+  // 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++) {
+    // 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 diff_bisectSplit_(text1, text2, x1, y1);
+          }
+        }
+      }
+    }
+
+    // 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 diff_bisectSplit_(text1, text2, x1, y1);
+          }
+        }
+      }
+    }
+  }
+  // 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.
+ * @return {Array} Array of diff tuples.
+ */
+function diff_bisectSplit_(text1, text2, x, y) {
+  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 = diff_main(text1a, text2a);
+  var diffsb = diff_main(text1b, text2b);
+
+  return diffs.concat(diffsb);
+};
+
+
+/**
+ * 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, 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.
+ */
+function diff_commonSuffix(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;
+};
+
+
+/**
+ * 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.
+ */
+function diff_halfMatch_(text1, text2) {
+  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.
+  }
+
+  /**
+   * 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 = diff_commonPrefix(longtext.substring(i),
+                                           shorttext.substring(j));
+      var suffixLength = 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];
+};
+
+
+/**
+ * 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) {
+  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 = 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 = 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) {
+    diff_cleanupMerge(diffs);
+  }
+};
+
+
+var diff = diff_main;
+diff.INSERT = DIFF_INSERT;
+diff.DELETE = DIFF_DELETE;
+diff.EQUAL = DIFF_EQUAL;
+
+
+module.exports = diff;