Function chooseInteractive

src/setup/prompt.ts:85–214

Arrow-key driven selector. Redraws the list in place as the highlight moves.

(
  question: string,
  options: Array<{ value: T; label: string; hint?: string }>,
  defaultValue: T,
)

/** Arrow-key driven selector. Redraws the list in place as the highlight moves. */
function chooseInteractive<T extends string>(
  question: string,
  options: Array<{ value: T; label: string; hint?: string }>,
  defaultValue: T,
): Promise<T> {
  return new Promise<T>((resolve) => {
    let idx = initialIndex(options, defaultValue);
    const stdin = process.stdin;
    const stdout = process.stdout;

    // Window the list so it never grows taller than the terminal. Without this, a list longer
    // than the visible rows scrolls the top options off-screen, and the in-place redraw
    // (\x1b[NA) can't reach those rows anymore — so only the bottom few stay visible and the
    // highlight appears stuck. We show a sliding window of `pageSize` rows that follows the
    // cursor, with ▲/▼ markers when there's more above/below.
    const termRows = (stdout.rows && stdout.rows > 0) ? stdout.rows : 24;
    // Reserve rows for: the question line already printed, the hint line, the optional
    // more-above / more-below markers, and a little breathing room.
    const pageSize = Math.max(3, Math.min(options.length, termRows - 5));
    const windowed = options.length > pageSize;
    let top = 0; // index of the first visible option
    // The drawn block = (more-above marker?) + visible rows + (more-below marker?) + hint line.
    let block = 0;
    let drawn = false;

    console.log(question);

    const clampWindow = (): void => {
      if (idx < top) top = idx;
      else if (idx >= top + pageSize) top = idx - pageSize + 1;
      if (top < 0) top = 0;
      if (top > Math.max(0, options.length - pageSize)) top = Math.max(0, options.length - pageSize);
    };

    const render = (): void => {
      clampWindow();
      if (drawn && block > 0) stdout.write(`\x1b[${block}A`); // jump back to the top of the block
      stdout.write('\x1b[0J');                                // clear from cursor down

      // Count PHYSICAL rows (accounting for terminal wrap), not logical lines — a long
      // option that wraps occupies >1 row, and if we undercount the cursor-up leaves the
      // top rows behind and every keypress piles up another stale copy.
      const cols = (stdout.columns && stdout.columns > 0) ? stdout.columns : 80;
      let physical = 0;
      const emit = (s: string): void => { stdout.write(s + '\n'); physical += physicalRows(s, cols); };

      const end = Math.min(options.length, top + pageSize);

      if (windowed && top > 0) emit(dim(`     ↑ ${top} more above`));
      for (let i = top; i < end; i++) {
        const opt = options[i]!;
        const sel = i === idx;
        const marker = sel ? '▸' : ' ';
        const num = String(i + 1).padStart(2);
        const label = sel ? `\x1b[36m\x1b[1m${opt.label}\x1b[0m` : opt.label;
        const hint = opt.hint ? `  ${dim(opt.hint)}` : '';
        emit(`  ${marker} ${num}. ${label}${hint}`);
      }