import { DEFAULT_CONFIG_PATH } from './config.ts';

const SERVICE_FILE_PATH = '/etc/systemd/system/uptimerunner.service';

export class UptimeRunnerSystemd {
  private readonly serviceTemplate = `[Unit]
Description=uptime.link Runner Agent
After=network-online.target
Wants=network-online.target

[Service]
ExecStart=/usr/local/bin/uptimerunner run --config ${DEFAULT_CONFIG_PATH}
Restart=always
RestartSec=10
User=root
Group=root
Environment=PATH=/usr/bin:/usr/local/bin
WorkingDirectory=/opt/uptimerunner

[Install]
WantedBy=multi-user.target
`;

  public async install(): Promise<void> {
    this.assertRoot();
    await Deno.writeTextFile(SERVICE_FILE_PATH, this.serviceTemplate);
    await run('systemctl', ['daemon-reload']);
    await run('systemctl', ['enable', 'uptimerunner.service']);
    console.log(`Service installed: ${SERVICE_FILE_PATH}`);
  }

  public async uninstall(): Promise<void> {
    this.assertRoot();
    await run('systemctl', ['disable', '--now', 'uptimerunner.service']).catch(() => null);
    await Deno.remove(SERVICE_FILE_PATH).catch(() => null);
    await run('systemctl', ['daemon-reload']);
    console.log('Service removed.');
  }

  public async start(): Promise<void> {
    await run('systemctl', ['start', 'uptimerunner.service']);
  }

  public async stop(): Promise<void> {
    await run('systemctl', ['stop', 'uptimerunner.service']);
  }

  public async restart(): Promise<void> {
    await run('systemctl', ['restart', 'uptimerunner.service']);
  }

  public async status(): Promise<void> {
    await run('systemctl', ['status', 'uptimerunner.service', '--no-pager']);
  }

  public async logs(): Promise<void> {
    await run('journalctl', ['-u', 'uptimerunner.service', '-n', '120', '--no-pager']);
  }

  private assertRoot(): void {
    if (Deno.uid && Deno.uid() !== 0) {
      throw new Error('This service command must run as root.');
    }
  }
}

async function run(commandArg: string, argsArg: string[]): Promise<void> {
  const command = new Deno.Command(commandArg, {
    args: argsArg,
    stdout: 'inherit',
    stderr: 'inherit',
  });
  const output = await command.output();
  if (!output.success) {
    throw new Error(`${commandArg} ${argsArg.join(' ')} exited with ${output.code}`);
  }
}