import type { WebSocket } from 'ws';

import { notificationChannelEndpointsDb } from '@/modules/database/index.js';

const DESKTOP_CHANNEL = 'desktop';

const clientsByUserId = new Map<number, Map<string, WebSocket>>();
const clientBySocket = new WeakMap<WebSocket, { userId: number; endpointId: string }>();

function normalizeUserId(userId: unknown): number | null {
  const numeric = Number(userId);
  return Number.isInteger(numeric) && numeric > 0 ? numeric : null;
}

function normalizeEndpointId(endpointId: unknown): string {
  if (typeof endpointId !== 'string') return '';
  return endpointId.trim();
}

function getUserClients(userId: unknown, create = false): Map<string, WebSocket> | null {
  const normalizedUserId = normalizeUserId(userId);
  if (!normalizedUserId) return null;
  let clients = clientsByUserId.get(normalizedUserId);
  if (!clients && create) {
    clients = new Map();
    clientsByUserId.set(normalizedUserId, clients);
  }
  return clients || null;
}

export function registerDesktopNotificationClient({
  userId,
  deviceId,
  label = null,
  platform = null,
  appVersion = null,
  ws,
}: {
  userId: number;
  deviceId: string;
  label?: string | null;
  platform?: string | null;
  appVersion?: string | null;
  ws: WebSocket;
}) {
  const normalizedUserId = normalizeUserId(userId);
  const endpointId = normalizeEndpointId(deviceId);
  if (!normalizedUserId || !endpointId) {
    return false;
  }

  const endpoint = notificationChannelEndpointsDb.upsertEndpoint({
    userId: normalizedUserId,
    channel: DESKTOP_CHANNEL,
    endpointId,
    label,
    metadata: { platform, appVersion },
    enabled: true,
  });

  const clients = getUserClients(normalizedUserId, true)!;
  const previous = clients.get(endpointId);
  if (previous && previous !== ws && previous.readyState === previous.OPEN) {
    previous.close(4000, 'Device reconnected');
  }

  clients.set(endpointId, ws);
  clientBySocket.set(ws, { userId: normalizedUserId, endpointId });
  return endpoint;
}

export function unregisterDesktopNotificationClient(ws: WebSocket): void {
  const registration = clientBySocket.get(ws);
  if (!registration) return;

  const clients = getUserClients(registration.userId);
  if (clients?.get(registration.endpointId) === ws) {
    clients.delete(registration.endpointId);
    if (clients.size === 0) {
      clientsByUserId.delete(registration.userId);
    }
  }
  clientBySocket.delete(ws);
}

export function sendDesktopNotification(userId: unknown, payload: unknown): { attempted: number; sent: number } {
  const normalizedUserId = normalizeUserId(userId);
  if (!normalizedUserId) return { attempted: 0, sent: 0 };

  const clients = getUserClients(normalizedUserId);
  if (!clients?.size) return { attempted: 0, sent: 0 };

  const enabledEndpointIds = new Set(
    notificationChannelEndpointsDb
      .getEnabledEndpoints(normalizedUserId, DESKTOP_CHANNEL)
      .map((endpoint) => endpoint.endpoint_id)
  );

  const message = JSON.stringify({
    type: 'notification',
    id: typeof (payload as any)?.data?.tag === 'string' ? (payload as any).data.tag : `${Date.now()}`,
    payload,
  });

  let attempted = 0;
  let sent = 0;
  for (const [endpointId, ws] of clients.entries()) {
    if (!enabledEndpointIds.has(endpointId)) continue;
    attempted += 1;
    if (ws.readyState !== ws.OPEN) {
      unregisterDesktopNotificationClient(ws);
      continue;
    }
    try {
      ws.send(message);
      notificationChannelEndpointsDb.touchEndpoint(normalizedUserId, DESKTOP_CHANNEL, endpointId);
      sent += 1;
    } catch {
      unregisterDesktopNotificationClient(ws);
    }
  }

  return { attempted, sent };
}