Confirm and Link User Accounts

const AWS = require('aws-sdk')
const cognito = new AWS.CognitoIdentityServiceProvider({apiVersion: '2016-04-18' })
// BackendClientIds
// These are needed because JS can't use a app client with a client secret
var backendClientIds = {
  // TO DO: USERPOOLID : BACKENDCLIENTID
  "":""
};

// NOTE: This is not site specific; however, at this time it is only set to work with Facebook
exports.handler = (event, context, callback) => {
  console.log('exports.handler - event:');
  console.log(event);
  if(event.triggerSource.includes('ExternalProvider'))
  {
    // ExternalProvider (ie. Social)
    if (event.request.userAttributes.hasOwnProperty("email")) {
      // Create Native User Always
      var params = {
        ClientId: backendClientIds[event.userPoolId],
        Password: generatePassword(),
        Username: event.request.userAttributes.email
      };
      cognito.signUp(params, function(err, data) {
        if (err) {
          console.log('cognito.signUp:');
          console.log(err, err.stack);
          if(err.code === 'UsernameExistsException')
          {
            // Get and Link Existing User
            getUsersAndLink(event.userPoolId, event.request.userAttributes.email, event);
          }
        }
        else {
          console.log('cognito.signUp:');
          console.log(data);
          if(data.UserConfirmed)
          {
            // Link Newly Created User
            linkUser(data.UserSub, event);
          }
        }
      });
    }
  } else {
    // All Others (ie. Native Accounts)
    // Auto Confirm The User
    event.response.autoConfirmUser = true;
    // Set the email as verified if it is in the request
    if (event.request.userAttributes.hasOwnProperty("email")) {
      event.response.autoVerifyEmail = true;
    }
  }
  // Return to Amazon Cognito
  callback(null, event);
};

function generatePassword() {
    // TO DO: Code returns a string of a random generated password
    // NOTE: We do a 20+ character password random generated by a bulk list of characters
}

function getUsersAndLink(userPoolId, email, event) {
  var params = {
    UserPoolId: userPoolId,
    AttributesToGet: ['sub','email','cognito:user_status'],
    Filter: "email = \"" + email + "\""
  }
  cognito.listUsers(params, (err, data) => {
    if (err) {
      console.log('getUsersAndLink - err - cognito.listUsers:');
      console.log(err, err.stack);
    }
    else {
      console.log('getUsersAndLink - cognito.listUsers:');
      console.log(data);
      linkUsers(data, event);
    }
  });
}

function linkUser(userName, event) {
  var destinationValue = userName;
  var sourceValue = event.userName.split("_")[1];
  console.log('destinationValue: ' + destinationValue);
  console.log('sourceValue: ' + sourceValue);
  // Email Found and CONFIRMED (not EXTERNAL_PROVIDER)
  var params = {
    DestinationUser: {
      ProviderAttributeValue: destinationValue,
      ProviderName: 'Cognito'
    },
    SourceUser: {
      ProviderAttributeName: 'Cognito_Subject',
      ProviderAttributeValue: sourceValue,
      ProviderName: event.userName.split("_")[0]
    },
    UserPoolId: event.userPoolId
  };
  cognito.adminLinkProviderForUser(params, function(err, data) {
    if (err) {
      console.log('linkUser - err - cognito.adminLinkProviderForUser:');
      console.log(err, err.stack);
    }
    else {
      console.log('linkUser - cognito.adminLinkProviderForUser:');
      console.log(data);
    }
  });
}

function linkUsers(usersData, event) {
  if(usersData != null && usersData.Users != null && usersData.Users.length > 0)
  {
    for (var i = 0; i < usersData.Users.length; i++) {
      if(usersData.Users[i] != null)
      {
        var destinationValue = '';
        var sourceValue = '';
        if(usersData.Users[i].UserStatus === 'CONFIRMED') {
          linkUser(usersData.Users[i].Username, event);
        }
      }
    }
  } else {
    console.log("linkUsers: UserData was NULL or Empty")
  }
}