diff_match_patch.prototype.patch_make = function()

in pontoon/base/static/js/lib/diff.js [1636:1746]

• 106 lines of code
• 34 McCabe index (conditional complexity)

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;
};