'use client';

import { useEffect, useCallback, useRef } from 'react';
import { RealtimeEvent, RealtimeMessage } from '@/lib/realtime/events';

type EventHandler<T = any> = (data: T) => void;

export function useRealtime() {
  const eventSourceRef = useRef<EventSource | null>(null);
  const handlersRef = useRef<Map<RealtimeEvent, Set<EventHandler>>>(new Map());

  useEffect(() => {
    // Connect to SSE endpoint
    const eventSource = new EventSource('/api/v1/realtime/events');
    eventSourceRef.current = eventSource;

    eventSource.onmessage = (event) => {
      try {
        const message: RealtimeMessage = JSON.parse(event.data);

        // Skip connection message
        if ((message as any).type === 'connected') {
          console.log('[Realtime] Connected');
          return;
        }

        // Dispatch to handlers
        const handlers = handlersRef.current.get(message.event);
        if (handlers) {
          handlers.forEach(handler => handler(message.data));
        }
      } catch (error) {
        console.error('[Realtime] Parse error:', error);
      }
    };

    eventSource.onerror = (error) => {
      console.error('[Realtime] Connection error:', error);
      // EventSource will auto-reconnect
    };

    return () => {
      eventSource.close();
      eventSourceRef.current = null;
    };
  }, []);

  const subscribe = useCallback(<T = any>(
    event: RealtimeEvent,
    handler: EventHandler<T>
  ): (() => void) => {
    if (!handlersRef.current.has(event)) {
      handlersRef.current.set(event, new Set());
    }
    handlersRef.current.get(event)!.add(handler);

    // Return unsubscribe function
    return () => {
      handlersRef.current.get(event)?.delete(handler);
    };
  }, []);

  return { subscribe };
}