Function annotateDiffWithLineRanges

src/codeScan/git/diffAnnotator.ts:23–106

(patch: string)

 * Annotate a unified diff patch with absolute line numbers and extract valid line ranges.
 */
export function annotateDiffWithLineRanges(patch: string): AnnotationResult {
  if (!patch || patch.trim() === '') {
    return { annotatedDiff: patch, lineRanges: [] };
  }

  const lines = patch.split('\n');
  const result: string[] = [];
  const lineRanges: LineRange[] = [];
  let currentNewLine = 0;
  let inHunk = false;
  let hunkStartLine = 0;

  for (let i = 0; i < lines.length; i++) {
    const line = lines[i];
    const isLastLine = i === lines.length - 1;
    // Check if this is a hunk header: @@ -start,count +start,count @@
    const hunkHeader = parseHunkHeader(line);

    if (hunkHeader) {
      // Save the previous hunk's range if we have one
      if (hunkStartLine > 0 && currentNewLine > hunkStartLine) {
        lineRanges.push({
          start: hunkStartLine,
          end: currentNewLine - 1,
        });
      }

      // Extract the starting line number for the new file (right side)
      currentNewLine = hunkHeader.newStart;
      inHunk = true;

      // Start tracking new hunk (unless it's a pure deletion with 0 new lines)
      hunkStartLine = hunkHeader.newCount === 0 ? 0 : hunkHeader.newStart;

      // Hunk headers are not annotated
      result.push(line);
      continue;
    }

    // If we haven't encountered a hunk yet, preserve the line as-is
    // (file headers like "diff --git", "---", "+++" etc.)
    if (!inHunk) {
      result.push(line);
      continue;
    }

    // Process lines within a hunk
    if (line.startsWith('-')) {
      // Removed line - doesn't exist in new file, no line number
      result.push(line);
    } else if (line.startsWith('+')) {
      // Added line - exists in new file at currentNewLine
      result.push(`L${currentNewLine}: ${line}`);
      currentNewLine++;
    } else if (line.startsWith(' ')) {
      // Context line - exists in new file at currentNewLine
      result.push(`L${currentNewLine}: ${line}`);
      currentNewLine++;