class BackendRegistry {
  constructor() {
    this.backends = new Map();
    this.log = require('./event-bus').log;
  }

  register(serviceId, ws) {
    this.backends.set(serviceId, {
      ws,
      connectedAt: new Date().toISOString(),
      lastPing: null,
    });
    this.log('info', `[registry] registered backend: ${serviceId}`);
  }

  unregister(serviceId) {
    if (this.backends.has(serviceId)) {
      this.backends.delete(serviceId);
      this.log('info', `[registry] unregistered backend: ${serviceId}`);
    }
  }

  get(serviceId) {
    const entry = this.backends.get(serviceId);
    return entry ? entry.ws : null;
  }

  list() {
    return Array.from(this.backends.entries()).map(([serviceId, entry]) => ({
      serviceId,
      connectedAt: entry.connectedAt,
      lastPing: entry.lastPing,
    }));
  }

  updatePing(serviceId) {
    const entry = this.backends.get(serviceId);
    if (entry) {
      entry.lastPing = new Date().toISOString();
    }
  }

  count() {
    return this.backends.size;
  }
}

module.exports = new BackendRegistry();