/**
 * Builds the WebRTC ICE server list from environment variables so a TURN
 * server can be added later without any code changes (see DEPLOYMENT.md).
 * P2P works fine with just STUN for most networks; TURN becomes necessary
 * behind restrictive NATs/firewalls.
 */
export function getIceServers(): RTCIceServer[] {
  const servers: RTCIceServer[] = [
    { urls: process.env.STUN_SERVER || "stun:stun.l.google.com:19302" },
  ];

  const turnServer = process.env.TURN_SERVER;
  if (turnServer) {
    servers.push({
      urls: turnServer,
      username: process.env.TURN_USERNAME || undefined,
      credential: process.env.TURN_PASSWORD || undefined,
    });
  }

  return servers;
}