Function buildDiffHtml

app/src/modules/renderer.js:104–136

(oldStr, newStr, filePath, startLine)

// ---- Diff Rendering ----
function buildDiffHtml(oldStr, newStr, filePath, startLine) {
  const lineOffset = (startLine || 1) - 1;
  const oldLines = (oldStr || '').split('\n');
  const newLines = (newStr || '').split('\n');
  const m = oldLines.length, n = newLines.length;
  if (m * n > 500000) {
    return buildDiffFallback(oldLines, newLines, filePath, lineOffset);
  }

  const dp = Array.from({ length: m + 1 }, () => new Uint16Array(n + 1));
  for (let i = 1; i <= m; i++)
    for (let j = 1; j <= n; j++)
      dp[i][j] = oldLines[i - 1] === newLines[j - 1]
        ? dp[i - 1][j - 1] + 1
        : Math.max(dp[i - 1][j], dp[i][j - 1]);

  const ops = [];
  let i = m, j = n;
  while (i > 0 || j > 0) {
    if (i > 0 && j > 0 && oldLines[i - 1] === newLines[j - 1]) {
      ops.push({ type: 'ctx', text: oldLines[i - 1], oldLn: i, newLn: j });
      i--; j--;
    } else if (j > 0 && (i === 0 || dp[i][j - 1] >= dp[i - 1][j])) {
      ops.push({ type: 'add', text: newLines[j - 1], newLn: j });
      j--;
    } else {
      ops.push({ type: 'del', text: oldLines[i - 1], oldLn: i });
      i--;
    }
  }
  ops.reverse();
  return renderDiffOps(ops, filePath, lineOffset);
}

function buildDiffFallback(oldLines, newLines, filePath, lineOffset) {
  const ops = [];