import axios, {
  AxiosError,
  AxiosResponse,
  CancelTokenSource,
  InternalAxiosRequestConfig,
} from 'axios';
import { toast } from 'sonner';
import { apiConfig, getApiBaseUrl } from './config';
import {
  ApiErrorBase,
  ForbiddenError,
  NetworkError,
  NotFoundError,
  ServerError,
  TimeoutError,
  UnauthorizedError,
  ValidationError,
} from './errors';
import { ApiError, ApiResponse } from './types';

/**
 * API 客户端实例
 * 统一处理请求配置、响应解析和错误处理
 */
const apiClient = axios.create({
  baseURL: apiConfig.baseURL,
  timeout: apiConfig.timeout,
  withCredentials: apiConfig.withCredentials,
  // Fail fast on slash redirect loops between Next dev proxy and Gin legacy routes.
  maxRedirects: 5,
  // Gin QueryArray("hosts") expects hosts=a&hosts=b, not hosts[]=a.
  paramsSerializer: {
    indexes: null,
  },
  headers: {
    'Content-Type': 'application/json',
  },
});

/** Normalize legacy /api/* paths: strip trailing slash to avoid 308/301 loops in dev proxy. */
function normalizeApiPath(url?: string): string | undefined {
  if (!url || !url.startsWith('/api/')) {
    return url;
  }
  if (url.length > 5 && url.endsWith('/')) {
    return url.replace(/\/+$/, '');
  }
  return url;
}

/**
 * 请求取消令牌存储
 */
const cancelTokens = new Map<string, CancelTokenSource>();

/**
 * 请求缓存存储
 * 存储正在进行的请求 Promise，避免重复请求
 */
const pendingRequests = new Map<string, Promise<AxiosResponse<ApiResponse>>>();

/**
 * 生成请求的唯一键
 * 包含方法、URL 和请求数据的哈希，确保不同参数的请求不会被误取消
 */
function getRequestKey(config: {
  method?: string;
  url?: string;
  data?: unknown;
}): string {
  const baseKey = `${config.method?.toUpperCase()}_${config.url}`;

  /* 序列化加入键中 */
  if (config.data) {
    try {
      const dataHash = JSON.stringify(config.data);
      return `${baseKey}_${dataHash}`;
    } catch {
      // 失败使用基础键
      return baseKey;
    }
  }

  return baseKey;
}

/**
 * 请求拦截器
 * 添加取消令牌和其他配置
 */
apiClient.interceptors.request.use(
  (config: InternalAxiosRequestConfig) => {
    // Browser must use same-origin relative URLs so Session Cookie hits Next rewrite (3010→3000).
    if (typeof window !== 'undefined') {
      config.baseURL = getApiBaseUrl();
    }
    config.url = normalizeApiPath(config.url);

    const requestKey = getRequestKey(config);
    const source = axios.CancelToken.source();
    config.cancelToken = source.token;
    cancelTokens.set(requestKey, source);

    return config;
  },
  (error: unknown) => Promise.reject(error),
);

/**
 * 直接启动登录流程
 * @param currentPath - 当前路径，用于登录成功后重定向回来
 */
function initiateLogin(currentPath: string): Promise<never> {
  if (currentPath.startsWith('/login') || currentPath.startsWith('/callback')) {
    return Promise.reject(new UnauthorizedError());
  }

  if (typeof window !== 'undefined') {
    sessionStorage.setItem('redirect_after_login', currentPath);
    const loginUrl = new URL('/login', window.location.origin);
    loginUrl.searchParams.set('callbackUrl', currentPath);
    window.location.href = loginUrl.toString();
  }

  return new Promise<never>(() => {});
}

/**
 * 响应拦截器
 * 处理 API 响应和统一错误处理
 */
apiClient.interceptors.response.use(
  (response: AxiosResponse<ApiResponse>) => {
    const requestKey = getRequestKey(response.config);
    cancelTokens.delete(requestKey);
    pendingRequests.delete(requestKey);

    const resData = response.data as ApiError & ApiResponse;
    if (resData && resData.error_msg) {
      return Promise.reject(new ApiErrorBase(resData.error_msg));
    }

    return response;
  },
  (error: AxiosError<ApiError>) => {
    if (error.config) {
      const requestKey = getRequestKey(error.config);
      cancelTokens.delete(requestKey);
      pendingRequests.delete(requestKey);
    }

    /* 请求被取消时静默处理 */
    if (axios.isCancel(error)) {
      const cancelError = new Error(
        error.message || '请求已被取消',
      ) as Error & { __CANCEL__?: boolean };
      cancelError.__CANCEL__ = true;
      return Promise.reject(cancelError);
    }

    /* 401 未授权错误 */
    if (error.response?.status === 401) {
      return initiateLogin(window.location.pathname + window.location.search);
    }

    /* 403 权限不足错误 */
    if (error.response?.status === 403) {
      return Promise.reject(
        new ForbiddenError(
          error.response.data?.error_msg || '权限不足，请过盾后重试',
          error.response.data?.error_code,
          error.response.data?.details,
        ),
      );
    }

    /* 404 资源未找到错误 */
    if (error.response?.status === 404) {
      return Promise.reject(
        new NotFoundError(error.response.data?.error_msg || '请求的资源不存在'),
      );
    }

    /* 400 验证错误 */
    if (error.response?.status === 400) {
      return Promise.reject(
        new ValidationError(
          error.response.data?.error_msg || '请求参数验证失败',
          error.response.data?.details,
        ),
      );
    }

    /* 429 速率限制错误 */
    if (error.response?.status === 429) {
      const retryAfter = error.response.headers?.['retry-after'];
      const message =
        error.response.data?.error_msg ||
        `请求过于频繁，请 ${retryAfter || '稍后'} 秒后重试`;

      toast.error('请求频率限制', {
        description: message,
        id: 'rate-limit-error',
      });

      return Promise.reject(new ApiErrorBase(message, 'RATE_LIMITED', 429));
    }

    /* 5xx 服务器错误 */
    if (error.response && error.response.status >= 500) {
      return Promise.reject(
        new ServerError(
          error.response.data?.error_msg || '服务器内部错误，请稍后重试',
          error.response.status,
        ),
      );
    }

    /* 网络超时错误 */
    if (error.code === 'ECONNABORTED' || error.code === 'ETIMEDOUT') {
      return Promise.reject(new TimeoutError());
    }

    /* 网络连接错误（ECONNREFUSED, ERR_NETWORK 等） */
    if (
      !error.response ||
      error.code === 'ECONNREFUSED' ||
      error.code === 'ERR_NETWORK' ||
      error.message?.includes('Network Error') ||
      error.message?.includes('Failed to fetch')
    ) {
      return Promise.reject(
        new NetworkError('无法连接到服务器，请确认后端服务已启动'),
      );
    }

    /* 其他后端返回的错误 */
    if (error.response?.data?.error_msg) {
      return Promise.reject(
        new ApiErrorBase(
          error.response.data.error_msg,
          error.response.data.error_code,
          error.response.status,
          error.response.data.details,
        ),
      );
    }

    /* 兜底错误 */
    return Promise.reject(new ApiErrorBase(error.message || '网络请求失败'));
  },
);

/**
 * 取消指定请求
 * @param method - 请求方法
 * @param url - 请求 URL
 */
export function cancelRequest(method: string, url: string): void {
  const requestKey = `${method.toUpperCase()}_${url}`;
  const source = cancelTokens.get(requestKey);
  if (source) {
    source.cancel('请求已被手动取消');
    cancelTokens.delete(requestKey);
  }
}

/**
 * 取消所有请求
 */
export function cancelAllRequests(): void {
  cancelTokens.forEach((source) => {
    source.cancel('所有请求已被取消');
  });
  cancelTokens.clear();
}

/**
 * 创建带有请求去重功能的请求方法
 * @param method HTTP 方法名
 * @param hasBody 是否包含请求体
 */
function createRequestMethod(
  method: 'get' | 'post' | 'put' | 'patch' | 'delete',
  hasBody: boolean,
) {
  if (hasBody) {
    return <T = ApiResponse>(
      url: string,
      data?: unknown,
      config?: InternalAxiosRequestConfig,
    ) => {
      const requestKey = getRequestKey({
        method: method.toUpperCase(),
        url,
        data,
      });

      if (pendingRequests.has(requestKey)) {
        return pendingRequests.get(requestKey) as Promise<AxiosResponse<T>>;
      }

      const promise = apiClient[method]<T>(url, data, config);
      pendingRequests.set(
        requestKey,
        promise as Promise<AxiosResponse<ApiResponse>>,
      );

      promise.then(
        () => pendingRequests.delete(requestKey),
        () => pendingRequests.delete(requestKey),
      );

      return promise;
    };
  }

  return <T = ApiResponse>(
    url: string,
    config?: InternalAxiosRequestConfig,
  ) => {
    const requestKey = getRequestKey({
      method: method.toUpperCase(),
      url,
      data: config?.params,
    });

    if (pendingRequests.has(requestKey)) {
      return pendingRequests.get(requestKey) as Promise<AxiosResponse<T>>;
    }

    const promise = apiClient[method]<T>(url, config);
    pendingRequests.set(
      requestKey,
      promise as Promise<AxiosResponse<ApiResponse>>,
    );

    promise.then(
      () => pendingRequests.delete(requestKey),
      () => pendingRequests.delete(requestKey),
    );

    return promise;
  };
}

/**
 * 包装的 API 客户端
 * 在原有 axios 实例基础上添加请求缓存功能
 */
const wrappedApiClient = {
  get: createRequestMethod('get', false) as <T = ApiResponse>(
    url: string,
    config?: InternalAxiosRequestConfig,
  ) => Promise<AxiosResponse<T>>,
  post: createRequestMethod('post', true) as <T = ApiResponse>(
    url: string,
    data?: unknown,
    config?: InternalAxiosRequestConfig,
  ) => Promise<AxiosResponse<T>>,
  put: createRequestMethod('put', true) as <T = ApiResponse>(
    url: string,
    data?: unknown,
    config?: InternalAxiosRequestConfig,
  ) => Promise<AxiosResponse<T>>,
  patch: createRequestMethod('patch', true) as <T = ApiResponse>(
    url: string,
    data?: unknown,
    config?: InternalAxiosRequestConfig,
  ) => Promise<AxiosResponse<T>>,
  delete: createRequestMethod('delete', false) as <T = ApiResponse>(
    url: string,
    config?: InternalAxiosRequestConfig,
  ) => Promise<AxiosResponse<T>>,
};

export default wrappedApiClient;