prototype.js

const sessionStorageKey = 'mp-req-session-id';
let sessionId = wx.getStorageSync(sessionStorageKey);
const loginQueue = [];
let isLoginning = false;

const req = {
  apiUrl: '',
  code2sessionId: null,
  isSessionAvailable: null,
  sessionHeaderKey: 'sessionId',
  init(opt = {}) {
    const {
      apiUrl,
      code2sessionId,
      isSessionAvailable,
      sessionHeaderKey,
    } = opt;
    if (apiUrl) {
      req.apiUrl = apiUrl;
    }
    if (code2sessionId) {
      req.code2sessionId = code2sessionId;
    }
    if (isSessionAvailable) {
      req.isSessionAvailable = isSessionAvailable;
    }
    if (sessionHeaderKey) {
      req.sessionHeaderKey = sessionHeaderKey;
    }
  },
};

/**
 * 判断请求状态是否成功
 * @param {number} status
 */
function isHttpSuccess(status) {
  return (status >= 200 && status < 300) || status === 304;
}

/**
 * promise请求
 * @param {object} options {}
 */
function requestP(options = {}) {
  const {
    success,
    fail,
  } = options;
  // 统一注入约定的header
  const header = Object.assign({
    [req.sessionHeaderKey]: sessionId,
  }, options.header);

  return new Promise((res, rej) => {
    wx.request(Object.assign(
      {},
      options,
      {
        header,
        success(r) {
          const isSuccess = isHttpSuccess(r.statusCode);
          if (isSuccess) { // 成功的请求状态
            if (success) {
              success(r.data);
              return;
            }
            res(r.data);
          } else {
            const err = {
              msg: `服务器好像出了点小问题，请与客服联系~（错误代码：${r.statusCode}）`,
              detail: r,
            };
            if (fail) {
              fail(err);
              return;
            }
            rej(err);
          }
        },
        fail(err) {
          if (fail) {
            fail(err);
            return;
          }
          rej(err);
        },
      },
    ));
  });
}

/**
 * 登录
 */
function login() {
  return new Promise((res, rej) => {
    // 微信登录
    wx.login({
      success(r1) {
        if (r1.code) {
          // 获取sessionId
          if (!req.code2sessionId) {
            rej('code2sessionId未定义');
            return;
          }
          req.code2sessionId(r1.code)
            .then((r2) => {
              const newSessionId = r2;
              sessionId = newSessionId; // 更新sessionId
              // 保存sessionId
              wx.setStorage({
                key: sessionStorageKey,
                data: newSessionId,
              });
              res(r2);
            })
            .catch(rej);
        } else {
          rej(r1);
        }
      },
      fail: rej,
    });
  });
}

/**
 * 获取sessionId
 */
function getSessionId() {
  return new Promise((res, rej) => {
    // 本地sessionId丢失，重新登录
    if (!sessionId) {
      loginQueue.push({ res, rej });

      if (!isLoginning) {
        isLoginning = true;

        login()
          .then((r1) => {
            isLoginning = false;
            while (loginQueue.length) {
              loginQueue.shift().res(r1);
            }
          })
          .catch((err) => {
            isLoginning = false;
            while (loginQueue.length) {
              loginQueue.shift().rej(err);
            }
          });
      }
    } else {
      res(sessionId);
    }
  });
}

/**
 * ajax高级封装
 * @param {object} options {}
 * @param {boolean} keepLogin true
 */
function request(options = {}, keepLogin = true) {
  if (keepLogin) {
    return new Promise((res, rej) => {
      getSessionId()
        .then(() => {
          // 获取sessionId成功之后，发起请求
          requestP(options)
            .then((r2) => {
              if (!req.isSessionAvailable) {
                rej('isSessionAvailable未定义');
                return;
              }
              if (!req.isSessionAvailable(r2)) {
                /**
                 * 登录状态无效，则重新走一遍登录流程
                 * 销毁本地已失效的sessionId
                 */
                sessionId = '';
                getSessionId()
                  .then(() => {
                    requestP(options)
                      .then(res)
                      .catch(rej);
                  })
                  .catch(rej);
              } else {
                res(r2);
              }
            })
            .catch(rej);
        })
        .catch(rej);
    });
  }
  // 不需要sessionId，直接发起请求
  return requestP(options);
}

/**
 * 插件接口
 * @param {object} plugin
 */
function use(plugin) {
  return plugin.install(req, request);
}

req.use = use;

module.exports = req;