diff static method

TextEdit diff(String oldText, String newText)

Automatically calculates an edit from the differences between two strings. Finds the longest common prefix and suffix; the middle portion is the edit region.

Implementation

static TextEdit diff(String oldText, String newText) {
  if (oldText == newText) return const TextEdit(0, 0, 0);
  if (oldText.isEmpty) return TextEdit(0, 0, newText.length);
  if (newText.isEmpty) return TextEdit(0, oldText.length, 0);

  // Find the common prefix length
  int prefixLen = 0;
  final minLen = math.min(oldText.length, newText.length);
  while (prefixLen < minLen && oldText[prefixLen] == newText[prefixLen]) {
    prefixLen++;
  }

  // Find the common suffix length (without overlapping the prefix)
  int suffixLen = 0;
  final maxSuffix = minLen - prefixLen;
  while (suffixLen < maxSuffix &&
      oldText[oldText.length - 1 - suffixLen] ==
          newText[newText.length - 1 - suffixLen]) {
    suffixLen++;
  }

  return TextEdit(
    prefixLen,
    oldText.length - suffixLen,
    newText.length - suffixLen,
  );
}