import axios, { AxiosError, AxiosInstance, InternalAxiosRequestConfig } from 'axios';

// API Response types
export interface ApiResponse<T = unknown> {
  success: boolean;
  data: T;
  statusCode?: number;
  timestamp?: string;
  message?: string;
}

export interface ApiErrorResponse {
  success: false;
  statusCode: number;
  timestamp: string;
  path: string;
  method: string;
  error: string;
  message: string | string[];
  errors?: Array<{ field: string; errors: string[] }>;
}

// Create axios instance
const api: AxiosInstance = axios.create({
  baseURL: process.env.NEXT_PUBLIC_API_URL || 'http://localhost:3001/api/v1',
  timeout: 30000,
  headers: {
    'Content-Type': 'application/json',
  },
});

// Request interceptor
api.interceptors.request.use(
  (config: InternalAxiosRequestConfig) => {
    // Add auth token if available
    if (typeof window !== 'undefined') {
      const token = localStorage.getItem('accessToken');
      if (token && config.headers) {
        config.headers.Authorization = `Bearer ${token}`;
      }
    }
    return config;
  },
  (error: AxiosError) => {
    return Promise.reject(error);
  }
);

// Response interceptor
api.interceptors.response.use(
  (response) => {
    return response;
  },
  async (error: AxiosError<ApiErrorResponse>) => {
    const originalRequest = error.config as InternalAxiosRequestConfig & { _retry?: boolean };

    // Handle 401 Unauthorized - try to refresh token
    if (error.response?.status === 401 && !originalRequest._retry) {
      originalRequest._retry = true;

      try {
        const refreshToken = localStorage.getItem('refreshToken');
        if (refreshToken) {
          const response = await axios.post(
            `${process.env.NEXT_PUBLIC_API_URL || 'http://localhost:3001/api/v1'}/auth/refresh`,
            { refreshToken }
          );

          const { accessToken, refreshToken: newRefreshToken } = response.data.data;
          localStorage.setItem('accessToken', accessToken);
          localStorage.setItem('refreshToken', newRefreshToken);

          // Retry original request with new token
          if (originalRequest.headers) {
            originalRequest.headers.Authorization = `Bearer ${accessToken}`;
          }
          return api(originalRequest);
        }
      } catch (refreshError) {
        // Refresh failed, clear storage and redirect to login
        localStorage.removeItem('accessToken');
        localStorage.removeItem('refreshToken');
        localStorage.removeItem('user');

        if (typeof window !== 'undefined') {
          window.location.href = '/login';
        }
      }
    }

    return Promise.reject(error);
  }
);

// Helper to extract error message
export function getErrorMessage(error: unknown): string {
  if (error instanceof AxiosError) {
    const apiError = error.response?.data as ApiErrorResponse;
    if (apiError?.message) {
      return Array.isArray(apiError.message)
        ? apiError.message.join(', ')
        : apiError.message;
    }
  }
  if (error instanceof Error) {
    return error.message;
  }
  return 'An unexpected error occurred';
}

// Helper to extract field errors
export function getFieldErrors(error: unknown): Array<{ field: string; errors: string[] }> {
  if (error instanceof AxiosError) {
    const apiError = error.response?.data as ApiErrorResponse;
    return apiError?.errors || [];
  }
  return [];
}

export default api;