mergeSocialUsers.js

/** 
If User logged in using social login

i). create cognate user using email and a random password 
ii). then create social user and link it to Cognito user

**/
const { CognitoIdentityServiceProvider } = require("aws-sdk");

const handler = async (event) => {
	const userPoolId = event.userPoolId;
	const trigger = event.triggerSource;
	const email = event.request.userAttributes.email;
	const givenName = event.request.userAttributes.given_name;
	const familyName = event.request.userAttributes.family_name;
	const emailVerified = event.request.userAttributes.email_verified;
	const identity = event.userName;
	const client = new CognitoIdentityServiceProvider();

	console.log("emailVerified", emailVerified);

	if (trigger === "PreSignUp_ExternalProvider") {
		await client
			.listUsers({
				UserPoolId: userPoolId,
				AttributesToGet: ["email", "family_name", "given_name"],
				Filter: `email = "${email}"`,
			})
			.promise()
			.then(({ Users }) =>
				Users.sort((a, b) =>
					a.UserCreateDate > b.UserCreateDate ? 1 : -1
				)
			)
			.then((users) => (users.length > 0 ? users[0] : null))
			.then(async (user) => {
				// user with username password already exists, do nothing
				if (user) {
					return user;
				}

				// user with username password does not exists, create one
				const newUser = await client
					.adminCreateUser({
						UserPoolId: userPoolId,
						Username: email,
						MessageAction: "SUPPRESS", // dont send email to user
						UserAttributes: [
							{
								Name: "given_name",
								Value: givenName,
							},
							{
								Name: "family_name",
								Value: familyName,
							},
							{
								Name: "email",
								Value: email,
							},
							{
								Name: "email_verified",
								Value: emailVerified,
							},
						],
					})
					.promise();

				console.log("newUser", JSON.stringify(newUser));

				try {
					// gotta set the password, else user wont be able to reset it
					const randomPassword = Math.random()
						.toString(36)
						.substring(2);

					await client
						.adminSetUserPassword({
							UserPoolId: userPoolId,
							Username: newUser.User.Username,
							Password: randomPassword,
							Permanent: true,
						})
						.promise();
				} catch (e) {
					console.log("password error: ", e);
				}

				return newUser.User.Username;
			})
			.then((username) => {
				// link external user to cognito user
				const split = identity.split("_");
				const providerValue = split.length > 1 ? split[1] : null;
				const provider = ["Google", "Facebook"].find(
					(val) => split[0].toUpperCase() === val.toUpperCase()
				);

				if (!provider || !providerValue) {
					return Promise.reject(new Error("Invalid external user"));
				}

				return client
					.adminLinkProviderForUser({
						UserPoolId: userPoolId,
						DestinationUser: {
							ProviderName: "Cognito",
							ProviderAttributeValue: username,
						},
						SourceUser: {
							ProviderName: provider,
							ProviderAttributeName: "Cognito_Subject",
							ProviderAttributeValue: providerValue,
						},
					})
					.promise();
			});
	}

	return event;
};

module.exports = {
	handler,
};