import axios, { type AxiosError, type AxiosInstance, type AxiosRequestConfig, type AxiosResponse } from 'axios'
import { clearTokens, getAccessToken, getRefreshToken, setTokens } from '@/utils/token'

/** 后端统一响应包裹：{ code, message, data }，code=0 成功。 */
interface ApiEnvelope<T = unknown> {
  code: number
  message: string
  data: T
}

/** 业务错误（code 为 HTTP 状态码 * 100，如 40100/40300/50000）。 */
export class ApiError extends Error {
  constructor(
    public code: number,
    message: string,
  ) {
    super(message)
    this.name = 'ApiError'
  }
}

/** 会话过期回调（token 刷新失败时触发），由应用启动时注册。 */
let onAuthExpired: (() => void) | null = null

export function setAuthExpiredHandler(handler: () => void): void {
  onAuthExpired = handler
}

interface HttpClientOptions {
  baseURL?: string
  timeout?: number
}

/**
 * 面向对象的 Axios 封装：
 * - 请求拦截器：注入 Authorization 头
 * - 响应拦截器：拆 { code, message, data }，code=0 返回 data；401 自动刷新重放；其余抛 ApiError
 */
export class HttpClient {
  private instance: AxiosInstance
  /** 无拦截器的裸实例，供刷新令牌等内部请求使用（避免递归拦截）。 */
  private rawInstance: AxiosInstance
  private refreshing: Promise<string> | null = null

  constructor(options: HttpClientOptions = {}) {
    const baseURL = options.baseURL ?? import.meta.env.VITE_API_BASE_URL ?? 'http://localhost:3000/api/v1'
    const timeout = options.timeout ?? 10000

    this.instance = axios.create({ baseURL, timeout })
    this.rawInstance = axios.create({ baseURL, timeout })
    this.setupInterceptors()
  }

  private setupInterceptors(): void {
    this.instance.interceptors.request.use((config) => {
      const token = getAccessToken()
      if (token) config.headers.Authorization = `Bearer ${token}`
      return config
    })

    this.instance.interceptors.response.use(
      (response) => {
        const body = response.data as ApiEnvelope
        if (body.code === 0) return body.data as AxiosResponse
        return Promise.reject(new ApiError(body.code, body.message))
      },
      async (error: AxiosError) => {
        const config = error.config as (AxiosRequestConfig & { _retry?: boolean }) | undefined
        const url = config?.url ?? ''
        const isAuthEndpoint = url.includes('/auth/login') || url.includes('/auth/refresh')
        // 401 自动刷新并重放一次（登录/刷新接口自身 401 不重放，_retry 防死循环）
        if (error.response?.status === 401 && config && !config._retry && !isAuthEndpoint) {
          config._retry = true
          try {
            const token = await this.refresh()
            config.headers = config.headers ?? {}
            config.headers.Authorization = `Bearer ${token}`
            return this.instance.request(config)
          } catch {
            clearTokens()
            onAuthExpired?.()
          }
        }
        const body = error.response?.data as ApiEnvelope | undefined
        return Promise.reject(new ApiError(body?.code ?? -1, body?.message ?? error.message))
      },
    )
  }

  /** 刷新令牌（并发去重），返回新 accessToken。 */
  private refresh(): Promise<string> {
    if (!this.refreshing) {
      this.refreshing = this.doRefresh().finally(() => {
        this.refreshing = null
      })
    }
    return this.refreshing
  }

  private async doRefresh(): Promise<string> {
    const refreshToken = getRefreshToken()
    if (!refreshToken) throw new ApiError(40100, '未登录')
    const { data } = await this.rawInstance.post<ApiEnvelope<{ accessToken: string; refreshToken: string }>>(
      '/auth/refresh',
      { refreshToken },
    )
    if (data.code !== 0) throw new ApiError(data.code, data.message)
    setTokens(data.data.accessToken, data.data.refreshToken)
    return data.data.accessToken
  }

  request<T>(config: AxiosRequestConfig): Promise<T> {
    return this.instance.request(config) as Promise<T>
  }

  get<T>(url: string, config?: AxiosRequestConfig): Promise<T> {
    return this.request<T>({ ...config, method: 'GET', url })
  }

  post<T>(url: string, data?: unknown, config?: AxiosRequestConfig): Promise<T> {
    return this.request<T>({ ...config, method: 'POST', url, data })
  }

  put<T>(url: string, data?: unknown, config?: AxiosRequestConfig): Promise<T> {
    return this.request<T>({ ...config, method: 'PUT', url, data })
  }

  patch<T>(url: string, data?: unknown, config?: AxiosRequestConfig): Promise<T> {
    return this.request<T>({ ...config, method: 'PATCH', url, data })
  }

  delete<T>(url: string, config?: AxiosRequestConfig): Promise<T> {
    return this.request<T>({ ...config, method: 'DELETE', url })
  }
}

/** 全局单例，业务直接使用 http.get/post/... */
export const http = new HttpClient()