import { createServer } from 'node:http';
import { pathToFileURL } from 'node:url';
import { WebSocketServer } from 'ws';

function isFocusEvent(value) {
  return (
    typeof value === 'object' &&
    value !== null &&
    value.type === 'FOCUS_NAME' &&
    typeof value.cloudId === 'string' &&
    typeof value.name === 'string' &&
    typeof value.messageId === 'string' &&
    typeof value.sentAt === 'number' &&
    (value.targetIndex === undefined ||
      (typeof value.targetIndex === 'number' &&
        Number.isInteger(value.targetIndex) &&
        value.targetIndex >= 0))
  );
}

export function createRealtimeServer(port = Number(process.env.REALTIME_PORT || 8787)) {
  const server = createServer((request, response) => {
    if (request.url === '/healthz') {
      response.writeHead(200, { 'content-type': 'application/json' });
      response.end(JSON.stringify({ status: 'ok' }));
      return;
    }

    response.writeHead(404, { 'content-type': 'text/plain' });
    response.end('Not found');
  });
  const realtime = new WebSocketServer({
    server,
    maxPayload: 16 * 1024,
  });
  const heartbeat = setInterval(() => {
    for (const socket of realtime.clients) {
      if (socket.isAlive === false) {
        socket.terminate();
        continue;
      }

      socket.isAlive = false;
      socket.ping();
    }
  }, 30_000);

  heartbeat.unref();

  realtime.on('connection', (socket) => {
    socket.isAlive = true;
    socket.on('pong', () => {
      socket.isAlive = true;
    });

    socket.on('message', (data) => {
      let value;

      try {
        value = JSON.parse(data.toString());
      } catch {
        return;
      }

      if (!isFocusEvent(value)) {
        return;
      }

      const message = JSON.stringify(value);

      for (const client of realtime.clients) {
        if (client !== socket && client.readyState === client.OPEN) {
          client.send(message);
        }
      }
    });
  });

  realtime.on('close', () => {
    clearInterval(heartbeat);
  });

  return server;
}

if (import.meta.url === pathToFileURL(process.argv[1] || '').href) {
  const port = Number(process.env.REALTIME_PORT || 8787);
  createRealtimeServer(port).listen(port, () => {
    console.log(`Realtime WebSocket server listening on port ${port}`);
  });
}