Pretoken Lambda function to query data from mongo db and insert user info in custom claims

pretokenLambda.js

const MongoClient = require('mongodb').MongoClient;

exports.handler = async (event, context) => {
  const { sub: userId } = event.request.userAttributes;
  const uri = '<your-mongodb-uri>';
  const client = new MongoClient(uri, { useNewUrlParser: true, useUnifiedTopology: true });

  try {
    await client.connect();
    const database = client.db('<your-db-name>');
    const usersCollection = database.collection('<your-users-collection-name>');
    const user = await usersCollection.findOne({ userId });

    if (!user) {
      throw new Error('User not found');
    }

    const email = user.email;
    const claims = event.request.groupConfiguration.groupsToOverride.reduce((acc, group) => {
      acc[group] = true;
      return acc;
    }, {});
    claims.email = email;

    event.response = {
      claimsOverrideDetails: {
        claimsToAddOrOverride: claims,
      },
    };
  } catch (err) {
    console.error(err);
    throw new Error('Failed to add user email to token');
  } finally {
    await client.close();
  }

  return event;
};