export function buildProcessSessionFixtureSource({
  readyPrefix,
  echoPrefix,
  stoppedMarker,
}) {
  for (const [name, value] of Object.entries({
    readyPrefix,
    echoPrefix,
    stoppedMarker,
  })) {
    if (
      typeof value !== 'string' ||
      value.length === 0 ||
      /[\r\n]/u.test(value)
    ) {
      throw new Error(`invalid process fixture marker: ${name}`);
    }
  }

  return [
    "import { randomBytes } from 'node:crypto';",
    '',
    `const readyPrefix = ${JSON.stringify(readyPrefix)};`,
    `const echoPrefix = ${JSON.stringify(echoPrefix)};`,
    `const stoppedMarker = ${JSON.stringify(stoppedMarker)};`,
    "const challenge = randomBytes(18).toString('hex');",
    'let echoed = false;',
    'let stopping = false;',
    '',
    'function stop() {',
    '  if (stopping) return;',
    '  stopping = true;',
    '  console.log(stoppedMarker);',
    '  process.exit(0);',
    '}',
    "for (const signal of ['SIGINT', 'SIGTERM', 'SIGHUP']) process.on(signal, stop);",
    "console.log(readyPrefix + ' challenge=' + challenge);",
    '',
    "process.stdin.setEncoding('utf8');",
    "let buffered = '';",
    "process.stdin.on('data', (chunk) => {",
    '  buffered += chunk;',
    '  const lines = buffered.split(/\\r?\\n/u);',
    "  buffered = lines.pop() ?? '';",
    '  for (const line of lines) {',
    '    if (!echoed && line === challenge) {',
    '      echoed = true;',
    "      console.log(echoPrefix + ' ' + challenge);",
    "    } else if (line === challenge + ':stop') {",
    '      stop();',
    '    }',
    '  }',
    '});',
    'process.stdin.resume();',
    '',
  ].join('\n');
}