Email verification for Auth0

/*
 * © 2020, Email Hippo Limited. (http://emailhippo.com)
 *
 * This example requires a valid key to work correctly.
 *
 * License: Apache 2.0 (https://www.apache.org/licenses/LICENSE-2.0)
*/

```javascript--browser

function (user, context, callback) {

  user.app_metadata = user.app_metadata || {};

  // Users with the emailhippo_valid will return an error on login
  // Setting emailhippo_valid to true will allow the user to log back in
  const valid = user.app_metadata.emailhippo_valid;
  if (valid !== undefined) {
    return valid ? callback(null, user, context) : callback('Email address is not valid');
  }

  if(!user.email) {
    return callback(null, user, context);
  }

  const request = require('request');
  
  const key = configuration.HIPPO_API_KEY;
  
  // Sign up at https://www.emailhippo.com/
  const url = 'https://api.hippoapi.com/v3/more/json/'+ key +'/' + user.email;

  request({ url: url }, function (err, resp, body) {
    if (err) {
        return callback(null, user, context);
    }
    if (resp.statusCode !== 200) {
        return callback(null, user, context);
    }

    const hippo_resonse = JSON.parse(body);
    
    const result = hippo_resonse.emailVerification.mailboxVerification.result;
    const reason = hippo_resonse.emailVerification.mailboxVerification.reason;

    user.app_metadata = user.app_metadata || {};

    // Any email address that is either bad or a Disposable email address
    // will be flagged as invalid. You can add your own custom logic if you want.
    let valid = true;
    if (result === 'Bad' || (result === 'Unverifiable' && reason === 'DomainIsWellKnownDea')){
        valid = false;
    } 

    user.app_metadata.emailhippo_result = result;
    user.app_metadata.emailhippo_reason = reason;
    user.app_metadata.emailhippo_valid = valid;

    auth0.users.updateAppMetadata(user.user_id, user.app_metadata)
      .then(function(){
        return valid ? callback(null, user, context) : callback('Email address is not valid');
      })
      .catch(function(err){
        callback(null, user, context);
      });
  });
}
/*
```

*/