Function formatDiff

src/components/StructuredDiff/Fallback.tsx:349–422

(lines: string[], startingLineNumber: number, width: number, dim: boolean, overrideTheme?: ThemeName)

  });
}
function formatDiff(lines: string[], startingLineNumber: number, width: number, dim: boolean, overrideTheme?: ThemeName): React.ReactNode[] {
  // Ensure width is at least 1 to prevent rendering issues with very narrow terminals
  const safeWidth = Math.max(1, Math.floor(width));

  // Step 1: Transform lines to line objects with type information
  const lineObjects = transformLinesToObjects(lines);

  // Step 2: Group adjacent add/remove lines for word-level diffing
  const processedLines = processAdjacentLines(lineObjects);

  // Step 3: Number the diff lines
  const ls = numberDiffLines(processedLines, startingLineNumber);

  // Find max line number width for alignment
  const maxLineNumber = Math.max(...ls.map(({
    i
  }) => i), 0);
  const maxWidth = Math.max(maxLineNumber.toString().length + 1, 0);

  // Step 4: Render formatting
  return ls.flatMap((item): React.ReactNode[] => {
    const {
      type,
      code,
      i,
      wordDiff,
      matchedLine
    } = item;

    // Handle word-level diffing for add/remove pairs
    if (wordDiff && matchedLine) {
      const wordDiffElements = generateWordDiffElements(item, safeWidth, maxWidth, dim, overrideTheme);

      // word-diff might refuse (e.g. due to lines being substantially different) in which
      // case we'll fall through to normal renderin gbelow
      if (wordDiffElements !== null) {
        return wordDiffElements;
      }
    }

    // Standard rendering for lines without word diffing or as fallback
    // Calculate available width accounting for line number + space + diff prefix
    const diffPrefixWidth = 2; // "  " for unchanged, "+ " or "- " for changes
    const availableContentWidth = Math.max(1, safeWidth - maxWidth - 1 - diffPrefixWidth); // -1 for space after line number
    const wrappedText = wrapText(code, availableContentWidth, 'wrap');
    const wrappedLines = wrappedText.split('\n');
    return wrappedLines.map((line, lineIndex) => {
      const key = `${type}-${i}-${lineIndex}`;
      const lineNum = lineIndex === 0 ? i : undefined;
      const lineNumStr = (lineNum !== undefined ? lineNum.toString().padStart(maxWidth) : ' '.repeat(maxWidth)) + ' ';
      const sigil = type === 'add' ? '+' : type === 'remove' ? '-' : ' ';
      // Calculate padding to fill the entire terminal width
      const contentWidth = lineNumStr.length + 1 + stringWidth(line); // lineNum + sigil + code
      const padding = Math.max(0, safeWidth - contentWidth);
      const bgColor = type === 'add' ? dim ? 'diffAddedDimmed' : 'diffAdded' : type === 'remove' ? dim ? 'diffRemovedDimmed' : 'diffRemoved' : undefined;

      // Gutter (line number + sigil) is wrapped in <NoSelect> so fullscreen
      // text selection yields clean code. bgColor carries across both boxes