import { CalendarEvent } from '../types';

type EventCallback = (event: CalendarEvent) => void;

class MCPService {
  private eventSource: EventSource | null = null;
  private listeners: EventCallback[] = [];

  connect(url: string) {
    if (this.eventSource) {
      this.eventSource.close();
    }

    try {
      console.log(`Connecting to MCP Brain at ${url}...`);
      this.eventSource = new EventSource(url);

      this.eventSource.onopen = () => {
        console.log('MCP Brain Connected!');
      };

      this.eventSource.onmessage = (event) => {
        try {
          const data = JSON.parse(event.data);
          // Assuming the backend sends an event structure similar to ours
          // or wraps it in { type: 'new_event', payload: ... }
          if (data.id && data.title) {
            this.notify(data);
          }
        } catch (e) {
          console.error('Failed to parse MCP message', e);
        }
      };

      this.eventSource.onerror = (err) => {
        console.error('MCP Connection Error', err);
        // Optional: Implement retry logic here
      };

    } catch (e) {
      console.error('Invalid URL for MCP', e);
    }
  }

  disconnect() {
    if (this.eventSource) {
      this.eventSource.close();
      this.eventSource = null;
    }
  }

  subscribe(callback: EventCallback) {
    this.listeners.push(callback);
    return () => {
      this.listeners = this.listeners.filter(l => l !== callback);
    };
  }

  private notify(event: CalendarEvent) {
    this.listeners.forEach(cb => cb(event));
  }
}

export const mcpService = new MCPService();