如何使用我的应用脚本获取用户的gmail？

function getGmail() {
  var clientId = 'YOUR_CLIENT_ID';
  var clientSecret = 'YOUR_CLIENT_SECRET';
  var redirectUri = 'YOUR_REDIRECT_URI';
  var scope = 'https://www.googleapis.com/auth/gmail.readonly';

  var authorizationUrl = 'https://accounts.google.com/o/oauth2/auth';
  authorizationUrl += '?client_id=' + encodeURIComponent(clientId);
  authorizationUrl += '&redirect_uri=' + encodeURIComponent(redirectUri);
  authorizationUrl += '&response_type=code';
  authorizationUrl += '&scope=' + encodeURIComponent(scope);

  var authCode = ScriptApp.getOAuthToken();
  if (!authCode) {
    var authorizationCode = ScriptApp.getAuthorizationInfo(ScriptApp.AuthMode.FULL).authorizationCode;
    if (!authorizationCode) {
      var authorizationPrompt = authorizationUrl + '&access_type=offline&approval_prompt=force';
      Logger.log('Authorization URL: ' + authorizationPrompt);
      return;
    }
    authCode = authorizationCode;
  }

  var tokenUrl = 'https://accounts.google.com/o/oauth2/token';
  var payload = {
    code: authCode,
    client_id: clientId,
    client_secret: clientSecret,
    redirect_uri: redirectUri,
    grant_type: 'authorization_code'
  };
  var options = {
    method: 'post',
    payload: payload
  };
  var response = UrlFetchApp.fetch(tokenUrl, options);
  var token = JSON.parse(response.getContentText());

  var accessToken = token.access_token;
  var refreshToken = token.refresh_token;

  // 使用accessToken和refreshToken进行Gmail API的调用
  // 例如，获取用户的邮件列表
  var gmailUrl = 'https://www.googleapis.com/gmail/v1/users/me/messages';
  var headers = {
    Authorization: 'Bearer ' + accessToken
  };
  options = {
    method: 'get',
    headers: headers
  };
  response = UrlFetchApp.fetch(gmailUrl, options);
  var messages = JSON.parse(response.getContentText());

  Logger.log('User Gmail Messages: ' + JSON.stringify(messages));
}