import websocket from '@fastify/websocket';
import type { FastifyInstance } from 'fastify';
import type { WebSocket } from 'ws';
import type { DownloadEventBus, DownloadProgressPayload, DownloadCompletePayload, DownloadFailedPayload } from '../../services/event-bus';

/**
 * WebSocket route plugin.
 *
 * Registers @fastify/websocket and a GET /ws route that broadcasts
 * download events (progress, complete, failed) to all connected clients.
 *
 * The event bus is passed via plugin options. Each connected client
 * gets its own set of event bus listeners, which are cleaned up on disconnect.
 *
 * Auth: The /ws route bypasses API key auth (not under /api/*).
 * This is intentional — WebSocket only broadcasts read-only progress data.
 */
export async function websocketRoutes(
  fastify: FastifyInstance,
  opts: { eventBus: DownloadEventBus }
): Promise<void> {
  const { eventBus } = opts;

  await fastify.register(websocket);

  fastify.get('/ws', { websocket: true }, (socket: WebSocket) => {
    console.log('[websocket] client connected');

    // Create listeners for each event type
    const onProgress = (data: DownloadProgressPayload) => {
      sendJson(socket, { type: 'download:progress', ...data });
    };

    const onComplete = (data: DownloadCompletePayload) => {
      sendJson(socket, { type: 'download:complete', ...data });
    };

    const onFailed = (data: DownloadFailedPayload) => {
      sendJson(socket, { type: 'download:failed', ...data });
    };

    // Subscribe to event bus
    eventBus.onDownload('download:progress', onProgress);
    eventBus.onDownload('download:complete', onComplete);
    eventBus.onDownload('download:failed', onFailed);

    // Cleanup on disconnect
    const cleanup = () => {
      eventBus.offDownload('download:progress', onProgress);
      eventBus.offDownload('download:complete', onComplete);
      eventBus.offDownload('download:failed', onFailed);
      console.log('[websocket] client disconnected');
    };

    socket.on('close', cleanup);
    socket.on('error', (err) => {
      console.log(`[websocket] client error: ${err.message}`);
      cleanup();
    });
  });
}

/**
 * Send a JSON message to a WebSocket client.
 * Silently catches send errors (client may have disconnected).
 */
function sendJson(socket: WebSocket, data: Record<string, unknown>): void {
  try {
    if (socket.readyState === socket.OPEN) {
      socket.send(JSON.stringify(data));
    }
  } catch {
    // Client disconnected — swallow
  }
}