/**
 * API 统一请求层（规范 §131）
 *
 * 职责：纯 HTTP 客户端，统一处理 Token / 超时 / 错误码 / Session 失效。
 * 不含任何业务域方法（域方法在 services/ 层，规范 §130 页面不直接调用底层 request）。
 */
const { BUSINESS_LIMITS, REQUEST_ERROR } = require('../constants');
const { API_BASE_URL } = require('../env');

class ApiClient {
  constructor() {
    this.baseURL = API_BASE_URL;
    this.token = null;
    this._refreshToken = null;
    /** @type {((reason: any) => void)|null} Session 失效回调，由 AuthStore 注入 */
    this.onSessionExpired = null;
    /** @type {((config: object) => void)|null} 维护态拦截回调，由 AppStore 注入 */
    this.onMaintenance = null;
  }

  /** 读取本地存储的 access token */
  getToken() {
    if (this.token) return this.token;
    try {
      this.token = wx.getStorageSync('accessToken') || null;
      this._refreshToken = wx.getStorageSync('refreshToken') || null;
    } catch (e) {
      // ignore
    }
    return this.token;
  }

  /** 读取本地存储的 refresh token（供 auth service 刷新使用） */
  getRefreshToken() {
    if (this._refreshToken) return this._refreshToken;
    try {
      this._refreshToken = wx.getStorageSync('refreshToken') || null;
    } catch (e) {
      // ignore
    }
    return this._refreshToken;
  }

  /** 持久化 token（登录/刷新成功后调用） */
  saveToken(token, refreshToken) {
    this.token = token;
    this._refreshToken = refreshToken;
    wx.setStorageSync('accessToken', token);
    wx.setStorageSync('refreshToken', refreshToken);
  }

  /** 清除 token（登出/Session 失效后调用） */
  clearToken() {
    this.token = null;
    this._refreshToken = null;
    wx.removeStorageSync('accessToken');
    wx.removeStorageSync('refreshToken');
  }

  /** 生成请求 ID（用于链路追踪） */
  generateRequestId() {
    return Date.now().toString(36) + Math.random().toString(36).substring(2, 8);
  }

  /**
   * 通用请求方法
   * @param {{url: string, method?: string, data?: any, headers?: object, idempotencyKey?: string, timeout?: number}} options
   */
  request(options) {
    const { url, method = 'GET', data, headers = {}, idempotencyKey, timeout } = options;
    const token = this.getToken();
    const requestId = this.generateRequestId();

    return new Promise((resolve, reject) => {
      wx.request({
        url: this.baseURL + url,
        method,
        data,
        timeout: timeout || BUSINESS_LIMITS.REQUEST_TIMEOUT_MS,
        header: {
          'Content-Type': 'application/json',
          'X-Request-Id': requestId,
          ...(idempotencyKey ? { 'Idempotency-Key': idempotencyKey } : {}),
          ...(token ? { Authorization: `Bearer ${token}` } : {}),
          ...headers,
        },
        success: (res) => {
          // 维护态拦截（规范 §77）
          if (res.statusCode === 503) {
            if (typeof this.onMaintenance === 'function') this.onMaintenance(res.data || {});
            reject({
              code: REQUEST_ERROR.MAINTENANCE,
              message: '平台正在维护，请稍后再试',
              requestId,
            });
            return;
          }
          if (res.statusCode === 200) {
            const body = res.data || {};
            if (body.success) {
              resolve(body.data);
            } else {
              reject({
                code: body.code || REQUEST_ERROR.BUSINESS_ERROR,
                message: body.message,
                requestId,
              });
            }
          } else if (res.statusCode === 401) {
            this.clearToken();
            if (typeof this.onSessionExpired === 'function') this.onSessionExpired();
            reject({ code: REQUEST_ERROR.UNAUTHORIZED, message: '请重新登录', requestId });
          } else if (res.statusCode === 403) {
            reject({ code: REQUEST_ERROR.FORBIDDEN, message: '无权限访问', requestId });
          } else if (res.statusCode === 429) {
            reject({ code: REQUEST_ERROR.RATE_LIMITED, message: '请求过于频繁，请稍后重试', requestId });
          } else {
            reject({ code: REQUEST_ERROR.SERVER_ERROR, message: '服务暂时不可用', requestId });
          }
        },
        fail: (err) => {
          reject({
            code: REQUEST_ERROR.NETWORK_ERROR,
            message: '网络连接失败，请检查网络后重试',
            requestId,
            error: err,
          });
        },
      });
    });
  }

  get(url, data, headers) {
    return this.request({ url, method: 'GET', data, headers });
  }

  post(url, data, headers, idempotencyKey) {
    return this.request({ url, method: 'POST', data, headers, idempotencyKey });
  }

  put(url, data, headers, idempotencyKey) {
    return this.request({ url, method: 'PUT', data, headers, idempotencyKey });
  }

  patch(url, data, headers, idempotencyKey) {
    return this.request({ url, method: 'PATCH', data, headers, idempotencyKey });
  }

  delete(url, data, headers, idempotencyKey) {
    return this.request({ url, method: 'DELETE', data, headers, idempotencyKey });
  }
}

const apiClient = new ApiClient();
module.exports = apiClient;