diff_match_patch.prototype.patch_apply = function()

in kitsune/sumo/static/sumo/js/libs/diff_match_patch_uncompressed.js [1785:1882]

• 89 lines of code
• 18 McCabe index (conditional complexity)

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];
};