// Health check service for backend connectivity

export type HealthStatus = 'checking' | 'healthy' | 'unhealthy';

export interface HealthCheckResult {
  status: HealthStatus;
  latencyMs?: number;
  error?: string;
}

/**
 * Check backend health by calling the /api/status endpoint
 */
export async function checkBackendHealth(): Promise<HealthCheckResult> {
  const startTime = performance.now();

  try {
    const response = await fetch('/api/status', {
      method: 'GET',
      headers: {
        'Content-Type': 'application/json',
      },
      // Short timeout for health checks
      signal: AbortSignal.timeout(5000),
    });

    const latencyMs = Math.round(performance.now() - startTime);

    if (!response.ok) {
      return {
        status: 'unhealthy',
        latencyMs,
        error: `HTTP ${response.status}`,
      };
    }

    const data = await response.json();
    if (data.status === 'OK') {
      return {
        status: 'healthy',
        latencyMs,
      };
    }

    return {
      status: 'unhealthy',
      latencyMs,
      error: 'Unexpected response',
    };
  } catch (error) {
    const latencyMs = Math.round(performance.now() - startTime);

    if (error instanceof Error) {
      if (error.name === 'TimeoutError' || error.name === 'AbortError') {
        return {
          status: 'unhealthy',
          latencyMs,
          error: 'Request timeout',
        };
      }
      return {
        status: 'unhealthy',
        latencyMs,
        error: error.message,
      };
    }

    return {
      status: 'unhealthy',
      latencyMs,
      error: 'Connection failed',
    };
  }
}