/**
 * Auto-start helper for the WebSocket relay server.
 *
 * Used by MCP server and CLI to ensure the relay is running
 * before attempting to connect.
 */

import { spawn } from 'child_process';
import { join, dirname } from 'path';
import { fileURLToPath } from 'url';
import WebSocket from 'ws';

const DEFAULT_PORT = 7862;

/**
 * Get the relay URL (configurable via WS_RELAY_PORT env var)
 */
export function getRelayUrl(): string {
  const port = process.env.WS_RELAY_PORT || String(DEFAULT_PORT);
  return `ws://localhost:${port}`;
}

/**
 * Check if the relay server is already running
 */
export async function isRelayRunning(url?: string): Promise<boolean> {
  const relayUrl = url || getRelayUrl();

  return new Promise((resolve) => {
    const ws = new WebSocket(relayUrl);
    const timeout = setTimeout(() => {
      ws.terminate();
      resolve(false);
    }, 1000);

    ws.on('open', () => {
      clearTimeout(timeout);
      ws.close();
      resolve(true);
    });

    ws.on('error', () => {
      clearTimeout(timeout);
      resolve(false);
    });
  });
}

/**
 * Start the relay server as a detached background process.
 * Returns once the relay is accepting connections.
 */
export async function ensureRelayRunning(url?: string): Promise<void> {
  const relayUrl = url || getRelayUrl();

  // Already running?
  if (await isRelayRunning(relayUrl)) {
    return;
  }

  // Find the relay server script (compiled JS)
  const __dirname = dirname(fileURLToPath(import.meta.url));
  const relayScript = join(__dirname, 'server.js');

  console.error(`[Relay] Starting relay server: ${relayScript}`);

  // Spawn as detached process that outlives the parent
  const child = spawn(process.execPath, [relayScript], {
    detached: true,
    stdio: 'ignore',
    env: { ...process.env },
  });
  child.unref();

  // Wait for it to be ready (up to 3 seconds)
  for (let i = 0; i < 30; i++) {
    await new Promise(r => setTimeout(r, 100));
    if (await isRelayRunning(relayUrl)) {
      console.error('[Relay] Server is ready');
      return;
    }
  }

  throw new Error('Relay server failed to start within 3 seconds');
}