const { getBaseUrl } = require('./constants');

function withAuthHeader(needAuth, header) {
  const app = getApp();
  if (!needAuth) return header;
  const token = app && app.globalData ? app.globalData.accessToken : '';
  const refreshToken = app && app.globalData ? app.globalData.refreshToken : '';
  if (typeof token === 'string' && token.length > 0) {
    header = header || {};
    header.Authorization = `Bearer ${token}`;
    header['x-access-token'] = `Bearer ${token}`;
    header['x-refresh-token'] = `Bearer ${refreshToken}`;
  }
  return header;
}

function normalizeError(payload) {
  if (!payload) return new Error('Empty response');
  // RESTfulResult usually has `errors` and/or `message`
  if (typeof payload === 'string') return new Error(payload);
  if (payload.errors) return new Error(payload.errors.toString());
  if (payload.message) return new Error(payload.message);
  return new Error(JSON.stringify(payload));
}

function getHeaderValue(headers, headerName) {
  if (!headers || typeof headers !== 'object') return '';
  const target = String(headerName || '').toLowerCase();
  for (const k in headers) {
    if (Object.prototype.hasOwnProperty.call(headers, k) && String(k).toLowerCase() === target) {
      const v = headers[k];
      return typeof v === 'string' ? v : '';
    }
  }
  return '';
}

function tryUpdateAccessTokenFromResponseHeaders(res) {
  // wx.request 的返回头在 res.header（部分环境也可能是 res.headers）
  const headers = (res && res.header) || (res && res.headers) || null;
  const newAccessToken = getHeaderValue(headers, 'x-access-token');
  if (!newAccessToken) return;

  const app = getApp();
  if (app && typeof app.setAuth === 'function') {
    app.setAuth({ accessToken: newAccessToken });
  } else {
    wx.setStorageSync('accessToken', newAccessToken);
    if (app && app.globalData) app.globalData.accessToken = newAccessToken;
  }
}

function request({
  path,
  method = 'GET',
  data = {},
  needAuth = false,
  contentType = 'application/json',
  // Internal flag: prevent infinite retry when refresh token也失败
  __retry = false
}) {
  const baseUrl = getBaseUrl();
  const url = `${baseUrl}${path}`;

  const header = withAuthHeader(needAuth, {
    'content-type': contentType
  });

  return new Promise((resolve, reject) => {
    wx.request({
      url,
      method: method.toUpperCase(),
      data: method.toUpperCase() === 'GET' ? data : data,
      header: header,
      success(res) {
        // 如果后端在 Response Headers 下发新的 token，就替换本地 token
        tryUpdateAccessTokenFromResponseHeaders(res);

        const payload = res && res.data !== undefined ? res.data : null;

        // Most backend uses RESTfulResult wrapper
        if (payload && typeof payload === 'object' && typeof payload.succeeded === 'boolean') {
          if (payload.succeeded) resolve(payload.data);
          else reject(normalizeError(payload));
          return;
        }

        // Fallback
        resolve(payload);
      },
      fail(err) {
        if (err && err.statusCode === 401 && needAuth && !__retry) {
          // 401: try refresh token, then retry the original request once.
          const originalErr = err;
          try {
            const auth = require('./auth');
            if (auth && typeof auth.refreshAccessToken === 'function') {
              auth
                .refreshAccessToken()
                .then(() => {
                  return request({ path, method, data, needAuth, contentType, __retry: true });
                })
                .then(resolve)
                .catch(() => {
                  reject(originalErr);
                });
              return;
            }
          } catch (e) {
            // ignore and fall through to rejecting original error
          }
        }
        reject(err);
      }
    });
  });
}

module.exports = {
  request
};