// This module is only meant to be used in Server Components in the app/ directory
// It cannot be imported in Client Components or pages/ directory

import { redirect } from 'next/navigation';
import { CustomerResponse, CustomerStats } from './api-client';

// Dynamically import cookies to prevent build errors
let cookiesModule: any;
try {
  // This will only work in server components
  cookiesModule = require('next/headers');
} catch (error) {
  console.warn('Warning: next/headers only works in Server Components in the app/ directory');
}

/**
 * Constructs a server-side API URL for backend requests
 * Used in Server Components and API routes to directly access the backend API
 * 
 * @param endpoint The API endpoint path
 * @returns A complete URL to the backend API
 */
function getServerApiUrl(endpoint: string): string {
  const apiUrl = process.env.SERVER_API_URL || 'https://internal-api.inboxi.ng/api';
  const cleanEndpoint = endpoint.startsWith('/') ? endpoint.substring(1) : endpoint;
  
  return apiUrl.endsWith('/') 
    ? `${apiUrl}${cleanEndpoint}`
    : `${apiUrl}/${cleanEndpoint}`;
}

/**
 * Server-side fetch wrapper with authentication.
 * Used in Server Components to make authenticated API requests to the backend.
 * This uses the SERVER_API_URL environment variable and is different from client-side fetching.
 * 
 * @throws Error if used outside of a Server Component in the app/ directory
 */
export async function fetchServer<T = unknown>(
  endpoint: string,
  options: RequestInit = {}
): Promise<T> {
  // Check if we're in a server component context
  if (!cookiesModule?.cookies) {
    throw new Error(
      "fetchServer can only be used in Server Components in the app/ directory. " +
      "For client components, use clientFetch or fetchClient instead."
    );
  }
  
  // Get auth token from cookies
  const cookieStore = await cookiesModule.cookies();
  const authToken = cookieStore.get('Authorization')?.value;

  // Redirect to login if not authenticated
  if (!authToken) redirect('/login');
  
  try {
    // Get the complete backend URL using the utility function
    const url = getServerApiUrl(endpoint);
    
    // Make the request with proper auth headers
    const res = await fetch(url, {
      ...options,
      headers: {
        'Content-Type': 'application/json',
        Authorization: `Bearer ${authToken}`,
        ...options.headers,
      },
      cache: 'no-store', // Always fetch fresh data
    });

    // Handle auth failures
    if (res.status === 401) redirect('/login');
    
    // Handle other errors
    if (!res.ok) {
      const errorData = await res.json().catch(() => ({}));
      const errorMessage = errorData.message || errorData.error || `Request failed: ${res.status} ${res.statusText}`;
      throw new Error(errorMessage);
    }

    // Handle 204 No Content responses
    if (res.status === 204) {
      return {} as T;
    }

    return await res.json();
  } catch (error) {
    console.error(`Server request to ${endpoint} failed:`, error);
    throw error;
  }
}

// =========== SERVER API SERVICES ===========

/**
 * Get a paginated list of customers (server-side)
 * @param page Page number (starting from 1)
 * @param limit Number of items per page
 * @returns Promise with customers data and total count
 */
export const getCustomersServer = async (page: number = 1, limit: number = 25): Promise<CustomerResponse> => {
  return fetchServer(`/customers?page=${page}&limit=${limit}`);
};

/**
 * Get detailed stats for a specific customer (server-side)
 * @param userId The customer's user ID
 * @returns Promise with detailed customer stats
 */
export const getCustomerDetailsServer = async (userId: string): Promise<CustomerStats> => {
  return fetchServer(`/customers/${userId}`);
};

// Server-side platform stats function
export async function getPlatformStatsServer(): Promise<any> {
  try {
    return fetchServer('/stats/platform');
  } catch (error) {
    console.error('Error fetching platform stats (server):', error);
    // Return default stats to prevent UI breakage
    return {
      totalProducts: 0,
      totalVendors: 0,
      totalOrders: 0,
      totalCustomers: 0,
      gmv: 0
    };
  }
}