import { Injectable, signal } from '@angular/core';

/**
 * Service for automatic page reload when server restarts.
 * Connects to WebSocket endpoint and monitors server instance ID.
 * When server restarts with new ID, page automatically reloads.
 */
@Injectable({ providedIn: 'root' })
export class ReloadService {
  private ws: WebSocket | null = null;
  private instanceId = signal<string | null>(null);
  private reconnectAttempts = 0;
  private maxReconnectAttempts = 10;
  private reconnectTimeout: ReturnType<typeof setTimeout> | null = null;

  constructor() {
    this.connect();
  }

  private connect(): void {
    // Clean up any existing connection
    if (this.ws) {
      this.ws.close();
      this.ws = null;
    }

    const protocol = location.protocol === 'https:' ? 'wss:' : 'ws:';
    const wsUrl = `${protocol}//${location.host}/ws/reload`;

    try {
      this.ws = new WebSocket(wsUrl);

      this.ws.onopen = () => {
        console.log('[ReloadService] Connected to server');
        this.reconnectAttempts = 0;
      };

      this.ws.onmessage = (event) => {
        try {
          const data = JSON.parse(event.data);
          if (data.type === 'instance') {
            const currentId = this.instanceId();
            if (currentId !== null && currentId !== data.id) {
              // Server restarted with new ID - reload page
              console.log('[ReloadService] Server restarted, reloading...');
              location.reload();
            } else {
              console.log(`[ReloadService] Instance ID: ${data.id}`);
            }
            this.instanceId.set(data.id);
          }
        } catch (e) {
          console.error('[ReloadService] Failed to parse message:', e);
        }
      };

      this.ws.onclose = () => {
        console.log('[ReloadService] Connection closed');
        this.scheduleReconnect();
      };

      this.ws.onerror = (error) => {
        console.error('[ReloadService] WebSocket error:', error);
        this.ws?.close();
      };
    } catch (e) {
      console.error('[ReloadService] Failed to create WebSocket:', e);
      this.scheduleReconnect();
    }
  }

  private scheduleReconnect(): void {
    if (this.reconnectTimeout) {
      clearTimeout(this.reconnectTimeout);
    }

    if (this.reconnectAttempts < this.maxReconnectAttempts) {
      const delay = Math.min(1000 * Math.pow(2, this.reconnectAttempts), 10000);
      this.reconnectAttempts++;
      console.log(`[ReloadService] Reconnecting in ${delay}ms (attempt ${this.reconnectAttempts}/${this.maxReconnectAttempts})`);
      this.reconnectTimeout = setTimeout(() => this.connect(), delay);
    } else {
      console.log('[ReloadService] Max reconnect attempts reached');
    }
  }
}