import WebSocket from 'ws';
import { IncomingMessage } from 'http';
import { v4 as uuidv4 } from 'uuid';
import { verifyToken, extractToken } from '../utils/jwt';
import { safeSend, parseClientMessage, ClientMessage } from '../utils/protocol';
import { setOnline, setOffline, refreshPresence } from '../redis/presenceClient';
import { flushOfflineQueue } from '../redis/messageClient';
import { registry } from '../services/connectionRegistry';
import { buildIceServers } from '../config';
import { logger } from '../utils/logger';
import { handleSignaling } from './signalingHandler';
import { handleMessage } from './messageHandler';
import { handleFileRequest } from './fileHandler';
import { handleFriend } from './friendHandler';

export async function onConnection(
  ws: WebSocket,
  req: IncomingMessage
): Promise<void> {
  // ── 1. Authenticate ──────────────────────────────────────────────────────
  let uid: string;
  try {
    const url = new URL(req.url ?? '/', `http://${req.headers.host}`);
    const token = extractToken(
      req.headers.authorization,
      url.searchParams.get('token') ?? undefined
    );
    const payload = verifyToken(token);
    uid = payload.uid;
  } catch (err) {
    const msg = err instanceof Error ? err.message : 'Auth failed';
    ws.send(JSON.stringify({ type: 'error', payload: { message: msg }, ts: Date.now() }));
    ws.terminate();
    return;
  }

  const socketId = uuidv4();

  // ── 2. Register in process registry + Redis Bucket 1 ────────────────────
  registry.add(socketId, uid, ws);

  // Redis errors must NOT crash the connection handler
  try {
    await setOnline(uid, socketId);
  } catch (err) {
    logger.error('setOnline failed', { uid, error: String(err) });
  }

  logger.info('Client connected', { uid, socketId, total: registry.size() });

  // ── 3. Send welcome + ICE server config ─────────────────────────────────
  safeSend(ws, 'connected', { uid, socketId });
  safeSend(ws, 'ice-servers', { iceServers: buildIceServers() });

  // ── 4. Flush offline message queue (Bucket 2) ────────────────────────────
  try {
    const pending = await flushOfflineQueue(uid);
    if (pending.length > 0) {
      safeSend(ws, 'offline-flush', { messages: pending, count: pending.length });
      logger.info('Flushed offline queue', { uid, count: pending.length });
    }
  } catch (err) {
    logger.error('Offline flush failed', { uid, error: String(err) });
  }

  // ── 5. Message router ────────────────────────────────────────────────────
  ws.on('message', (raw) => {
    const msg = parseClientMessage(raw);
    if (!msg) return; // Malformed — silently drop

    registry.heartbeat(socketId); // Any message counts as a heartbeat

    routeMessage(ws, uid, socketId, msg).catch((err: unknown) => {
      logger.error('Message handler error', { uid, type: msg.type, error: String(err) });
    });
  });

  // ── 6. Cleanup on disconnect ─────────────────────────────────────────────
  ws.on('close', () => {
    registry.remove(socketId);
    setOffline(uid).catch((err: unknown) =>
      logger.error('setOffline failed', { uid, error: String(err) })
    );
    logger.info('Client disconnected', { uid, socketId, total: registry.size() });
  });

  ws.on('error', (err) => {
    logger.error('WebSocket error', { uid, socketId, error: err.message });
    ws.terminate();
  });
}

// ── Message router ────────────────────────────────────────────────────────────

async function routeMessage(
  ws: WebSocket,
  uid: string,
  socketId: string,
  msg: ClientMessage
): Promise<void> {
  switch (msg.type) {
    case 'heartbeat':
      await refreshPresence(uid).catch(() => {}); // Best effort
      break;

    case 'offer':
    case 'answer':
    case 'ice-candidate':
      await handleSignaling(ws, uid, msg);
      break;

    case 'message':
      await handleMessage(ws, uid, msg);
      break;

    case 'get-upload-url':
      await handleFileRequest(ws, uid, msg);
      break;

    case 'relay':
      await handleRelay(ws, uid, msg);
      break;

    case 'friend':
      await handleFriend(ws, uid, msg);
      break;

    default:
      safeSend(ws, 'error', { message: `Unknown message type: ${msg.type}` });
  }
}

// ── WebSocket relay fallback (when WebRTC ICE fails) ─────────────────────────

async function handleRelay(
  _senderWs: WebSocket,
  fromUid: string,
  msg: ClientMessage
): Promise<void> {
  const toUid = msg.payload.toUid as string | undefined;
  if (!toUid || typeof toUid !== 'string') return;

  const target = registry.getByUid(toUid);
  if (!target) return;

  safeSend(target.ws, 'relay', {
    fromUid,
    data: msg.payload.data,
  }, msg.requestId);
}