Wrapping help text

Wrap a paragraph to the terminal's width with an indent, and to a fixed width in a pipe or a test, so help output never runs off the right edge.

linegauge never reads the terminal's width — the caller passes it. That makes the same code right in a terminal, in a pipe and in a test: ask the terminal when there is one, and pick a width when there is not.

help.mjs

import { wrap } from 'linegauge';

/** The terminal's width when there is one; a fixed width for a pipe, a log or a test. */
const columns = process.stdout.isTTY ? process.stdout.columns : 40;

const text = 'Measures, wraps, truncates and slices styled terminal text without splitting a grapheme cluster or leaking a colour.';
const indent = '  ';
console.log('Usage: gauge [options] <file>\n');
console.log(
  wrap(text, columns - indent.length)
    .split('\n')
    .map((line) => indent + line)
    .join('\n'),
);

node help.mjs

Usage: gauge [options] <file>

  Measures, wraps, truncates and slices
  styled terminal text without splitting
  a grapheme cluster or leaking a
  colour.

Wrap to the width less the indent, then indent each row: indenting first would count the spaces as text and let trim remove them. Because wrap closes every style at the end of a row, putting the indent in front of a row never puts it inside a colour.

A CLI built on burgee gets this for its help already: burgee measures and wraps its help with linegauge.