/**
 * 请求封装模块
 * 封装 uni.request 支持 GET/POST/PUT/DELETE
 * 实现 JWT Token 自动携带
 * 实现 401 状态码拦截和重新认证
 * 支持请求重试机制
 * 支持请求取消机制
 * Requirements: 1.2, 1.4
 */

import { getToken, removeToken, removeUserInfo } from '../utils/storage'
import config from '../config/index'

// 从统一配置获取 API 基础地址
const BASE_URL = config.API_BASE_URL

// 存储进行中的请求任务，用于取消
const pendingRequests = new Map()

/**
 * 生成请求唯一标识
 * @param {Object} options 请求配置
 * @returns {string}
 */
function generateRequestKey(options) {
  const { url, method = 'GET', data = {} } = options
  return `${method}:${url}:${JSON.stringify(data)}`
}

/**
 * 处理401错误 - 清除token
 * Property 2: Auth Redirect on Invalid Token
 */
export function handleUnauthorized() {
  removeToken()
  removeUserInfo()
}

/**
 * 延迟函数
 * @param {number} ms 延迟毫秒数
 */
const delay = (ms) => new Promise(resolve => setTimeout(resolve, ms))

/**
 * 取消指定请求
 * @param {string} requestKey 请求标识
 */
export function cancelRequest(requestKey) {
  if (pendingRequests.has(requestKey)) {
    const task = pendingRequests.get(requestKey)
    if (task && typeof task.abort === 'function') {
      task.abort()
    }
    pendingRequests.delete(requestKey)
  }
}

/**
 * 取消所有进行中的请求
 */
export function cancelAllRequests() {
  pendingRequests.forEach((task) => {
    if (task && typeof task.abort === 'function') {
      task.abort()
    }
  })
  pendingRequests.clear()
}


/**
 * 取消指定URL前缀的所有请求
 * @param {string} urlPrefix URL前缀
 */
export function cancelRequestsByPrefix(urlPrefix) {
  pendingRequests.forEach((task, key) => {
    if (key.includes(urlPrefix)) {
      if (task && typeof task.abort === 'function') {
        task.abort()
      }
      pendingRequests.delete(key)
    }
  })
}

/**
 * 发起请求（带重试和取消机制）
 * @param {Object} options 请求配置
 * @param {number} retryCount 当前重试次数
 * @returns {Promise}
 */
export function request(options, retryCount = 0) {
  const {
    url,
    method = 'GET',
    data = {},
    header = {},
    needAuth = true,
    retry = true,
    cancelable = true,
    cancelPrevious = false
  } = options

  const requestKey = generateRequestKey(options)

  if (cancelPrevious && pendingRequests.has(requestKey)) {
    cancelRequest(requestKey)
  }

  return new Promise((resolve, reject) => {
    const token = getToken()
    
    const requestHeader = {
      'Content-Type': 'application/json',
      ...header
    }
    
    if (needAuth && token) {
      requestHeader['Authorization'] = `Bearer ${token}`
    }

    const requestTask = uni.request({
      url: `${BASE_URL}${url}`,
      method,
      data,
      header: requestHeader,
      timeout: config.REQUEST_TIMEOUT,
      success: (res) => {
        if (cancelable) {
          pendingRequests.delete(requestKey)
        }

        const { statusCode, data: responseData } = res
        
        if (statusCode === 401) {
          handleUnauthorized()
          reject(new Error('未授权，请重新登录'))
          return
        }
        
        if (statusCode >= 400) {
          const errorMsg = responseData?.message || '请求失败'
          reject(new Error(errorMsg))
          return
        }
        
        if (responseData.success === false) {
          reject(new Error(responseData.message || '操作失败'))
          return
        }
        
        resolve(responseData)
      },
      fail: async (err) => {
        if (cancelable) {
          pendingRequests.delete(requestKey)
        }

        if (err.errMsg && err.errMsg.includes('abort')) {
          reject(new Error('请求已取消'))
          return
        }

        console.error('Request failed:', err)
        
        if (retry && retryCount < config.REQUEST_RETRY_COUNT) {
          console.log(`请求失败，${config.REQUEST_RETRY_DELAY}ms 后进行第 ${retryCount + 1} 次重试...`)
          await delay(config.REQUEST_RETRY_DELAY)
          try {
            const result = await request(options, retryCount + 1)
            resolve(result)
          } catch (retryErr) {
            reject(retryErr)
          }
          return
        }
        
        reject(new Error('网络连接失败，请检查网络设置'))
      }
    })

    if (cancelable && requestTask) {
      pendingRequests.set(requestKey, requestTask)
    }
  })
}


/**
 * GET 请求
 */
export function get(url, data = {}, options = {}) {
  return request({ url, method: 'GET', data, ...options })
}

/**
 * POST 请求
 */
export function post(url, data = {}, options = {}) {
  return request({ url, method: 'POST', data, ...options })
}

/**
 * PUT 请求
 */
export function put(url, data = {}, options = {}) {
  return request({ url, method: 'PUT', data, ...options })
}

/**
 * DELETE 请求
 */
export function del(url, data = {}, options = {}) {
  return request({ url, method: 'DELETE', data, ...options })
}

export default {
  request,
  get,
  post,
  put,
  del,
  handleUnauthorized,
  cancelRequest,
  cancelAllRequests,
  cancelRequestsByPrefix
}