import type { AppEnv } from '@/types/hono';
import { Hono } from 'hono';

type EventCallback = (data: string) => void;

class SSEManager {
  private channels: Map<string, Set<EventCallback>> = new Map();

  subscribe(channel: string, callback: EventCallback): () => void {
    if (!this.channels.has(channel)) {
      this.channels.set(channel, new Set());
    }
    this.channels.get(channel)!.add(callback);

    return () => {
      const subs = this.channels.get(channel);
      if (subs) {
        subs.delete(callback);
        if (subs.size === 0) {
          this.channels.delete(channel);
        }
      }
    };
  }

  emit(channel: string, data: string): void {
    const subs = this.channels.get(channel);
    if (subs) {
      for (const callback of subs) {
        callback(data);
      }
    }
  }
}

export const sseManager = new SSEManager();

export function registerEventsRoutes(app: Hono<AppEnv>) {
  app.get('/api/events/:channel', async (c) => {
    const channel = c.req.param('channel');

    const stream = new ReadableStream({
      start(controller) {
        const encoder = new TextEncoder();

        const send = (data: string) => {
          try {
            controller.enqueue(encoder.encode(`data: ${data}\n\n`));
          } catch {
            // Controller closed
          }
        };

        send('connected');

        const unsubscribe = sseManager.subscribe(channel, send);

        const keepAliveInterval = setInterval(() => {
          send('ping');
        }, 30000);

        c.req.raw.signal.addEventListener('abort', () => {
          console.log(`[SSE] Connection closed for channel: ${channel}`);
          clearInterval(keepAliveInterval);
          unsubscribe();
          try {
            controller.close();
          } catch {
            // Already closed
          }
        });
      },
    });

    return new Response(stream, {
      headers: {
        'Content-Type': 'text/event-stream',
        'Cache-Control': 'no-cache',
        Connection: 'keep-alive',
        'X-Accel-Buffering': 'no',
      },
    });
  });
}