import { spawn } from 'node:child_process';
import fs from 'node:fs';
import path from 'node:path';
import { expandHome } from './expand.js';

export function spawnUnit(unit, { logDir } = {}) {
  const cwd = expandHome(unit.cwd || process.cwd());
  const cmd = unit.command?.[0];
  if (!cmd) throw new Error(`unit ${unit.id} has no command`);
  const args = unit.command.slice(1);
  fs.mkdirSync(cwd, { recursive: true });
  let stdout = 'ignore';
  let stderr = 'ignore';
  if (logDir) {
    fs.mkdirSync(logDir, { recursive: true });
    const log = fs.openSync(path.join(logDir, `${unit.id}.log`), 'a');
    stdout = log;
    stderr = log;
  }
  const child = spawn(cmd, args, {
    cwd,
    env: { ...process.env, ...(unit.env || {}) },
    detached: true,
    stdio: ['ignore', stdout, stderr],
  });
  child.unref();
  return { pid: child.pid, child };
}

export function killPid(pid, signal = 'SIGTERM') {
  if (!pid) return false;
  try {
    process.kill(Number(pid), signal);
    return true;
  } catch {
    return false;
  }
}

export function pidAlive(pid) {
  if (!pid) return false;
  try {
    process.kill(Number(pid), 0);
    return true;
  } catch {
    return false;
  }
}