Automatically confirm known Amazon Cognito users with a Lambda function using an AWS SDK

Run an interactive scenario at a command prompt.

import (
	"context"
	"errors"
	"log"
	"strings"
	"user_pools_and_lambda_triggers/actions"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/cognitoidentityprovider"
	"github.com/aws/aws-sdk-go-v2/service/cognitoidentityprovider/types"
	"github.com/awsdocs/aws-doc-sdk-examples/gov2/demotools"
)

// AutoConfirm separates the steps of this scenario into individual functions so that
// they are simpler to read and understand.
type AutoConfirm struct {
	helper       IScenarioHelper
	questioner   demotools.IQuestioner
	resources    Resources
	cognitoActor *actions.CognitoActions
}

// NewAutoConfirm constructs a new auto confirm runner.
func NewAutoConfirm(sdkConfig aws.Config, questioner demotools.IQuestioner, helper IScenarioHelper) AutoConfirm {
	scenario := AutoConfirm{
		helper:       helper,
		questioner:   questioner,
		resources:    Resources{},
		cognitoActor: &actions.CognitoActions{CognitoClient: cognitoidentityprovider.NewFromConfig(sdkConfig)},
	}
	scenario.resources.init(scenario.cognitoActor, questioner)
	return scenario
}

// AddPreSignUpTrigger adds a Lambda handler as an invocation target for the PreSignUp trigger.
func (runner *AutoConfirm) AddPreSignUpTrigger(ctx context.Context, userPoolId string, functionArn string) {
	log.Printf("Let's add a Lambda function to handle the PreSignUp trigger from Cognito.\n" +
		"This trigger happens when a user signs up, and lets your function take action before the main Cognito\n" +
		"sign up processing occurs.\n")
	err := runner.cognitoActor.UpdateTriggers(
		ctx, userPoolId,
		actions.TriggerInfo{Trigger: actions.PreSignUp, HandlerArn: aws.String(functionArn)})
	if err != nil {
		panic(err)
	}
	log.Printf("Lambda function %v added to user pool %v to handle the PreSignUp trigger.\n",
		functionArn, userPoolId)
}

// SignUpUser signs up a user from the known user table with a password you specify.
func (runner *AutoConfirm) SignUpUser(ctx context.Context, clientId string, usersTable string) (string, string) {
	log.Println("Let's sign up a user to your Cognito user pool. When the user's email matches an email in the\n" +
		"DynamoDB known users table, it is automatically verified and the user is confirmed.")

	knownUsers, err := runner.helper.GetKnownUsers(ctx, usersTable)
	if err != nil {
		panic(err)
	}
	userChoice := runner.questioner.AskChoice("Which user do you want to use?\n", knownUsers.UserNameList())
	user := knownUsers.Users[userChoice]

	var signedUp bool
	var userConfirmed bool
	password := runner.questioner.AskPassword("Enter a password that has at least eight characters, uppercase, lowercase, numbers and symbols.\n"+
		"(the password will not display as you type):", 8)
	for !signedUp {
		log.Printf("Signing up user '%v' with email '%v' to Cognito.\n", user.UserName, user.UserEmail)
		userConfirmed, err = runner.cognitoActor.SignUp(ctx, clientId, user.UserName, password, user.UserEmail)
		if err != nil {
			var invalidPassword *types.InvalidPasswordException
			if errors.As(err, &invalidPassword) {
				password = runner.questioner.AskPassword("Enter another password:", 8)
			} else {
				panic(err)
			}
		} else {
			signedUp = true
		}
	}
	log.Printf("User %v signed up, confirmed = %v.\n", user.UserName, userConfirmed)

	log.Println(strings.Repeat("-", 88))

	return user.UserName, password
}

// SignInUser signs in a user.
func (runner *AutoConfirm) SignInUser(ctx context.Context, clientId string, userName string, password string) string {
	runner.questioner.Ask("Press Enter when you're ready to continue.")
	log.Printf("Let's sign in as %v...\n", userName)
	authResult, err := runner.cognitoActor.SignIn(ctx, clientId, userName, password)
	if err != nil {
		panic(err)
	}
	log.Printf("Successfully signed in. Your access token starts with: %v...\n", (*authResult.AccessToken)[:10])
	log.Println(strings.Repeat("-", 88))
	return *authResult.AccessToken
}

// Run runs the scenario.
func (runner *AutoConfirm) Run(ctx context.Context, stackName string) {
	defer func() {
		if r := recover(); r != nil {
			log.Println("Something went wrong with the demo.")
			runner.resources.Cleanup(ctx)
		}
	}()

	log.Println(strings.Repeat("-", 88))
	log.Printf("Welcome\n")

	log.Println(strings.Repeat("-", 88))

	stackOutputs, err := runner.helper.GetStackOutputs(ctx, stackName)
	if err != nil {
		panic(err)
	}
	runner.resources.userPoolId = stackOutputs["UserPoolId"]
	runner.helper.PopulateUserTable(ctx, stackOutputs["TableName"])

	runner.AddPreSignUpTrigger(ctx, stackOutputs["UserPoolId"], stackOutputs["AutoConfirmFunctionArn"])
	runner.resources.triggers = append(runner.resources.triggers, actions.PreSignUp)
	userName, password := runner.SignUpUser(ctx, stackOutputs["UserPoolClientId"], stackOutputs["TableName"])
	runner.helper.ListRecentLogEvents(ctx, stackOutputs["AutoConfirmFunction"])
	runner.resources.userAccessTokens = append(runner.resources.userAccessTokens,
		runner.SignInUser(ctx, stackOutputs["UserPoolClientId"], userName, password))

	runner.resources.Cleanup(ctx)

	log.Println(strings.Repeat("-", 88))
	log.Println("Thanks for watching!")
	log.Println(strings.Repeat("-", 88))
}

Handle the PreSignUp trigger with a Lambda function.

import (
	"context"
	"log"
	"os"

	"github.com/aws/aws-lambda-go/events"
	"github.com/aws/aws-lambda-go/lambda"
	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/feature/dynamodb/attributevalue"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb"
	dynamodbtypes "github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
)

const TABLE_NAME = "TABLE_NAME"

// UserInfo defines structured user data that can be marshalled to a DynamoDB format.
type UserInfo struct {
	UserName  string `dynamodbav:"UserName"`
	UserEmail string `dynamodbav:"UserEmail"`
}

// GetKey marshals the user email value to a DynamoDB key format.
func (user UserInfo) GetKey() map[string]dynamodbtypes.AttributeValue {
	userEmail, err := attributevalue.Marshal(user.UserEmail)
	if err != nil {
		panic(err)
	}
	return map[string]dynamodbtypes.AttributeValue{"UserEmail": userEmail}
}

type handler struct {
	dynamoClient *dynamodb.Client
}

// HandleRequest handles the PreSignUp event by looking up a user in an Amazon DynamoDB table and
// specifying whether they should be confirmed and verified.
func (h *handler) HandleRequest(ctx context.Context, event events.CognitoEventUserPoolsPreSignup) (events.CognitoEventUserPoolsPreSignup, error) {
	log.Printf("Received presignup from %v for user '%v'", event.TriggerSource, event.UserName)
	if event.TriggerSource != "PreSignUp_SignUp" {
		// Other trigger sources, such as PreSignUp_AdminInitiateAuth, ignore the response from this handler.
		return event, nil
	}
	tableName := os.Getenv(TABLE_NAME)
	user := UserInfo{
		UserEmail: event.Request.UserAttributes["email"],
	}
	log.Printf("Looking up email %v in table %v.\n", user.UserEmail, tableName)
	output, err := h.dynamoClient.GetItem(ctx, &dynamodb.GetItemInput{
		Key:       user.GetKey(),
		TableName: aws.String(tableName),
	})
	if err != nil {
		log.Printf("Error looking up email %v.\n", user.UserEmail)
		return event, err
	}
	if output.Item == nil {
		log.Printf("Email %v not found. Email verification is required.\n", user.UserEmail)
		return event, err
	}

	err = attributevalue.UnmarshalMap(output.Item, &user)
	if err != nil {
		log.Printf("Couldn't unmarshal DynamoDB item. Here's why: %v\n", err)
		return event, err
	}

	if user.UserName != event.UserName {
		log.Printf("UserEmail %v found, but stored UserName '%v' does not match supplied UserName '%v'. Verification is required.\n",
			user.UserEmail, user.UserName, event.UserName)
	} else {
		log.Printf("UserEmail %v found with matching UserName %v. User is confirmed.\n", user.UserEmail, user.UserName)
		event.Response.AutoConfirmUser = true
		event.Response.AutoVerifyEmail = true
	}

	return event, err
}

func main() {
	ctx := context.Background()
	sdkConfig, err := config.LoadDefaultConfig(ctx)
	if err != nil {
		log.Panicln(err)
	}
	h := handler{
		dynamoClient: dynamodb.NewFromConfig(sdkConfig),
	}
	lambda.Start(h.HandleRequest)
}

Create a struct that performs common tasks.

import (
	"context"
	"log"
	"strings"
	"time"
	"user_pools_and_lambda_triggers/actions"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/cloudformation"
	"github.com/aws/aws-sdk-go-v2/service/cloudwatchlogs"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb"
	"github.com/awsdocs/aws-doc-sdk-examples/gov2/demotools"
)

// IScenarioHelper defines common functions used by the workflows in this example.
type IScenarioHelper interface {
	Pause(secs int)
	GetStackOutputs(ctx context.Context, stackName string) (actions.StackOutputs, error)
	PopulateUserTable(ctx context.Context, tableName string)
	GetKnownUsers(ctx context.Context, tableName string) (actions.UserList, error)
	AddKnownUser(ctx context.Context, tableName string, user actions.User)
	ListRecentLogEvents(ctx context.Context, functionName string)
}

// ScenarioHelper contains AWS wrapper structs used by the workflows in this example.
type ScenarioHelper struct {
	questioner  demotools.IQuestioner
	dynamoActor *actions.DynamoActions
	cfnActor    *actions.CloudFormationActions
	cwlActor    *actions.CloudWatchLogsActions
	isTestRun   bool
}

// NewScenarioHelper constructs a new scenario helper.
func NewScenarioHelper(sdkConfig aws.Config, questioner demotools.IQuestioner) ScenarioHelper {
	scenario := ScenarioHelper{
		questioner:  questioner,
		dynamoActor: &actions.DynamoActions{DynamoClient: dynamodb.NewFromConfig(sdkConfig)},
		cfnActor:    &actions.CloudFormationActions{CfnClient: cloudformation.NewFromConfig(sdkConfig)},
		cwlActor:    &actions.CloudWatchLogsActions{CwlClient: cloudwatchlogs.NewFromConfig(sdkConfig)},
	}
	return scenario
}

// Pause waits for the specified number of seconds.
func (helper ScenarioHelper) Pause(secs int) {
	if !helper.isTestRun {
		time.Sleep(time.Duration(secs) * time.Second)
	}
}

// GetStackOutputs gets the outputs from the specified CloudFormation stack in a structured format.
func (helper ScenarioHelper) GetStackOutputs(ctx context.Context, stackName string) (actions.StackOutputs, error) {
	return helper.cfnActor.GetOutputs(ctx, stackName), nil
}

// PopulateUserTable fills the known user table with example data.
func (helper ScenarioHelper) PopulateUserTable(ctx context.Context, tableName string) {
	log.Printf("First, let's add some users to the DynamoDB %v table we'll use for this example.\n", tableName)
	err := helper.dynamoActor.PopulateTable(ctx, tableName)
	if err != nil {
		panic(err)
	}
}

// GetKnownUsers gets the users from the known users table in a structured format.
func (helper ScenarioHelper) GetKnownUsers(ctx context.Context, tableName string) (actions.UserList, error) {
	knownUsers, err := helper.dynamoActor.Scan(ctx, tableName)
	if err != nil {
		log.Printf("Couldn't get known users from table %v. Here's why: %v\n", tableName, err)
	}
	return knownUsers, err
}

// AddKnownUser adds a user to the known users table.
func (helper ScenarioHelper) AddKnownUser(ctx context.Context, tableName string, user actions.User) {
	log.Printf("Adding user '%v' with email '%v' to the DynamoDB known users table...\n",
		user.UserName, user.UserEmail)
	err := helper.dynamoActor.AddUser(ctx, tableName, user)
	if err != nil {
		panic(err)
	}
}

// ListRecentLogEvents gets the most recent log stream and events for the specified Lambda function and displays them.
func (helper ScenarioHelper) ListRecentLogEvents(ctx context.Context, functionName string) {
	log.Println("Waiting a few seconds to let Lambda write to CloudWatch Logs...")
	helper.Pause(10)
	log.Println("Okay, let's check the logs to find what's happened recently with your Lambda function.")
	logStream, err := helper.cwlActor.GetLatestLogStream(ctx, functionName)
	if err != nil {
		panic(err)
	}
	log.Printf("Getting some recent events from log stream %v\n", *logStream.LogStreamName)
	events, err := helper.cwlActor.GetLogEvents(ctx, functionName, *logStream.LogStreamName, 10)
	if err != nil {
		panic(err)
	}
	for _, event := range events {
		log.Printf("\t%v", *event.Message)
	}
	log.Println(strings.Repeat("-", 88))
}

Create a struct that wraps Amazon Cognito actions.

import (
	"context"
	"errors"
	"log"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/cognitoidentityprovider"
	"github.com/aws/aws-sdk-go-v2/service/cognitoidentityprovider/types"
)

type CognitoActions struct {
	CognitoClient *cognitoidentityprovider.Client
}



// Trigger and TriggerInfo define typed data for updating an Amazon Cognito trigger.
type Trigger int

const (
	PreSignUp Trigger = iota
	UserMigration
	PostAuthentication
)

type TriggerInfo struct {
	Trigger    Trigger
	HandlerArn *string
}

// UpdateTriggers adds or removes Lambda triggers for a user pool. When a trigger is specified with a `nil` value,
// it is removed from the user pool.
func (actor CognitoActions) UpdateTriggers(ctx context.Context, userPoolId string, triggers ...TriggerInfo) error {
	output, err := actor.CognitoClient.DescribeUserPool(ctx, &cognitoidentityprovider.DescribeUserPoolInput{
		UserPoolId: aws.String(userPoolId),
	})
	if err != nil {
		log.Printf("Couldn't get info about user pool %v. Here's why: %v\n", userPoolId, err)
		return err
	}
	lambdaConfig := output.UserPool.LambdaConfig
	for _, trigger := range triggers {
		switch trigger.Trigger {
		case PreSignUp:
			lambdaConfig.PreSignUp = trigger.HandlerArn
		case UserMigration:
			lambdaConfig.UserMigration = trigger.HandlerArn
		case PostAuthentication:
			lambdaConfig.PostAuthentication = trigger.HandlerArn
		}
	}
	_, err = actor.CognitoClient.UpdateUserPool(ctx, &cognitoidentityprovider.UpdateUserPoolInput{
		UserPoolId:   aws.String(userPoolId),
		LambdaConfig: lambdaConfig,
	})
	if err != nil {
		log.Printf("Couldn't update user pool %v. Here's why: %v\n", userPoolId, err)
	}
	return err
}



// SignUp signs up a user with Amazon Cognito.
func (actor CognitoActions) SignUp(ctx context.Context, clientId string, userName string, password string, userEmail string) (bool, error) {
	confirmed := false
	output, err := actor.CognitoClient.SignUp(ctx, &cognitoidentityprovider.SignUpInput{
		ClientId: aws.String(clientId),
		Password: aws.String(password),
		Username: aws.String(userName),
		UserAttributes: []types.AttributeType{
			{Name: aws.String("email"), Value: aws.String(userEmail)},
		},
	})
	if err != nil {
		var invalidPassword *types.InvalidPasswordException
		if errors.As(err, &invalidPassword) {
			log.Println(*invalidPassword.Message)
		} else {
			log.Printf("Couldn't sign up user %v. Here's why: %v\n", userName, err)
		}
	} else {
		confirmed = output.UserConfirmed
	}
	return confirmed, err
}



// SignIn signs in a user to Amazon Cognito using a username and password authentication flow.
func (actor CognitoActions) SignIn(ctx context.Context, clientId string, userName string, password string) (*types.AuthenticationResultType, error) {
	var authResult *types.AuthenticationResultType
	output, err := actor.CognitoClient.InitiateAuth(ctx, &cognitoidentityprovider.InitiateAuthInput{
		AuthFlow:       "USER_PASSWORD_AUTH",
		ClientId:       aws.String(clientId),
		AuthParameters: map[string]string{"USERNAME": userName, "PASSWORD": password},
	})
	if err != nil {
		var resetRequired *types.PasswordResetRequiredException
		if errors.As(err, &resetRequired) {
			log.Println(*resetRequired.Message)
		} else {
			log.Printf("Couldn't sign in user %v. Here's why: %v\n", userName, err)
		}
	} else {
		authResult = output.AuthenticationResult
	}
	return authResult, err
}



// ForgotPassword starts a password recovery flow for a user. This flow typically sends a confirmation code
// to the user's configured notification destination, such as email.
func (actor CognitoActions) ForgotPassword(ctx context.Context, clientId string, userName string) (*types.CodeDeliveryDetailsType, error) {
	output, err := actor.CognitoClient.ForgotPassword(ctx, &cognitoidentityprovider.ForgotPasswordInput{
		ClientId: aws.String(clientId),
		Username: aws.String(userName),
	})
	if err != nil {
		log.Printf("Couldn't start password reset for user '%v'. Here;s why: %v\n", userName, err)
	}
	return output.CodeDeliveryDetails, err
}



// ConfirmForgotPassword confirms a user with a confirmation code and a new password.
func (actor CognitoActions) ConfirmForgotPassword(ctx context.Context, clientId string, code string, userName string, password string) error {
	_, err := actor.CognitoClient.ConfirmForgotPassword(ctx, &cognitoidentityprovider.ConfirmForgotPasswordInput{
		ClientId:         aws.String(clientId),
		ConfirmationCode: aws.String(code),
		Password:         aws.String(password),
		Username:         aws.String(userName),
	})
	if err != nil {
		var invalidPassword *types.InvalidPasswordException
		if errors.As(err, &invalidPassword) {
			log.Println(*invalidPassword.Message)
		} else {
			log.Printf("Couldn't confirm user %v. Here's why: %v", userName, err)
		}
	}
	return err
}



// DeleteUser removes a user from the user pool.
func (actor CognitoActions) DeleteUser(ctx context.Context, userAccessToken string) error {
	_, err := actor.CognitoClient.DeleteUser(ctx, &cognitoidentityprovider.DeleteUserInput{
		AccessToken: aws.String(userAccessToken),
	})
	if err != nil {
		log.Printf("Couldn't delete user. Here's why: %v\n", err)
	}
	return err
}



// AdminCreateUser uses administrator credentials to add a user to a user pool. This method leaves the user
// in a state that requires they enter a new password next time they sign in.
func (actor CognitoActions) AdminCreateUser(ctx context.Context, userPoolId string, userName string, userEmail string) error {
	_, err := actor.CognitoClient.AdminCreateUser(ctx, &cognitoidentityprovider.AdminCreateUserInput{
		UserPoolId:     aws.String(userPoolId),
		Username:       aws.String(userName),
		MessageAction:  types.MessageActionTypeSuppress,
		UserAttributes: []types.AttributeType{{Name: aws.String("email"), Value: aws.String(userEmail)}},
	})
	if err != nil {
		var userExists *types.UsernameExistsException
		if errors.As(err, &userExists) {
			log.Printf("User %v already exists in the user pool.", userName)
			err = nil
		} else {
			log.Printf("Couldn't create user %v. Here's why: %v\n", userName, err)
		}
	}
	return err
}



// AdminSetUserPassword uses administrator credentials to set a password for a user without requiring a
// temporary password.
func (actor CognitoActions) AdminSetUserPassword(ctx context.Context, userPoolId string, userName string, password string) error {
	_, err := actor.CognitoClient.AdminSetUserPassword(ctx, &cognitoidentityprovider.AdminSetUserPasswordInput{
		Password:   aws.String(password),
		UserPoolId: aws.String(userPoolId),
		Username:   aws.String(userName),
		Permanent:  true,
	})
	if err != nil {
		var invalidPassword *types.InvalidPasswordException
		if errors.As(err, &invalidPassword) {
			log.Println(*invalidPassword.Message)
		} else {
			log.Printf("Couldn't set password for user %v. Here's why: %v\n", userName, err)
		}
	}
	return err
}

Create a struct that wraps DynamoDB actions.

import (
	"context"
	"fmt"
	"log"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/feature/dynamodb/attributevalue"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
)

// DynamoActions encapsulates the Amazon Simple Notification Service (Amazon SNS) actions
// used in the examples.
type DynamoActions struct {
	DynamoClient *dynamodb.Client
}

// User defines structured user data.
type User struct {
	UserName  string
	UserEmail string
	LastLogin *LoginInfo `dynamodbav:",omitempty"`
}

// LoginInfo defines structured custom login data.
type LoginInfo struct {
	UserPoolId string
	ClientId   string
	Time       string
}

// UserList defines a list of users.
type UserList struct {
	Users []User
}

// UserNameList returns the usernames contained in a UserList as a list of strings.
func (users *UserList) UserNameList() []string {
	names := make([]string, len(users.Users))
	for i := 0; i < len(users.Users); i++ {
		names[i] = users.Users[i].UserName
	}
	return names
}

// PopulateTable adds a set of test users to the table.
func (actor DynamoActions) PopulateTable(ctx context.Context, tableName string) error {
	var err error
	var item map[string]types.AttributeValue
	var writeReqs []types.WriteRequest
	for i := 1; i < 4; i++ {
		item, err = attributevalue.MarshalMap(User{UserName: fmt.Sprintf("test_user_%v", i), UserEmail: fmt.Sprintf("test_email_%v@example.com", i)})
		if err != nil {
			log.Printf("Couldn't marshall user into DynamoDB format. Here's why: %v\n", err)
			return err
		}
		writeReqs = append(writeReqs, types.WriteRequest{PutRequest: &types.PutRequest{Item: item}})
	}
	_, err = actor.DynamoClient.BatchWriteItem(ctx, &dynamodb.BatchWriteItemInput{
		RequestItems: map[string][]types.WriteRequest{tableName: writeReqs},
	})
	if err != nil {
		log.Printf("Couldn't populate table %v with users. Here's why: %v\n", tableName, err)
	}
	return err
}

// Scan scans the table for all items.
func (actor DynamoActions) Scan(ctx context.Context, tableName string) (UserList, error) {
	var userList UserList
	output, err := actor.DynamoClient.Scan(ctx, &dynamodb.ScanInput{
		TableName: aws.String(tableName),
	})
	if err != nil {
		log.Printf("Couldn't scan table %v for items. Here's why: %v\n", tableName, err)
	} else {
		err = attributevalue.UnmarshalListOfMaps(output.Items, &userList.Users)
		if err != nil {
			log.Printf("Couldn't unmarshal items into users. Here's why: %v\n", err)
		}
	}
	return userList, err
}

// AddUser adds a user item to a table.
func (actor DynamoActions) AddUser(ctx context.Context, tableName string, user User) error {
	userItem, err := attributevalue.MarshalMap(user)
	if err != nil {
		log.Printf("Couldn't marshall user to item. Here's why: %v\n", err)
	}
	_, err = actor.DynamoClient.PutItem(ctx, &dynamodb.PutItemInput{
		Item:      userItem,
		TableName: aws.String(tableName),
	})
	if err != nil {
		log.Printf("Couldn't put item in table %v. Here's why: %v", tableName, err)
	}
	return err
}

Create a struct that wraps CloudWatch Logs actions.

import (
	"context"
	"fmt"
	"log"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/cloudwatchlogs"
	"github.com/aws/aws-sdk-go-v2/service/cloudwatchlogs/types"
)

type CloudWatchLogsActions struct {
	CwlClient *cloudwatchlogs.Client
}

// GetLatestLogStream gets the most recent log stream for a Lambda function.
func (actor CloudWatchLogsActions) GetLatestLogStream(ctx context.Context, functionName string) (types.LogStream, error) {
	var logStream types.LogStream
	logGroupName := fmt.Sprintf("/aws/lambda/%s", functionName)
	output, err := actor.CwlClient.DescribeLogStreams(ctx, &cloudwatchlogs.DescribeLogStreamsInput{
		Descending:   aws.Bool(true),
		Limit:        aws.Int32(1),
		LogGroupName: aws.String(logGroupName),
		OrderBy:      types.OrderByLastEventTime,
	})
	if err != nil {
		log.Printf("Couldn't get log streams for log group %v. Here's why: %v\n", logGroupName, err)
	} else {
		logStream = output.LogStreams[0]
	}
	return logStream, err
}

// GetLogEvents gets the most recent eventCount events from the specified log stream.
func (actor CloudWatchLogsActions) GetLogEvents(ctx context.Context, functionName string, logStreamName string, eventCount int32) (
	[]types.OutputLogEvent, error) {
	var events []types.OutputLogEvent
	logGroupName := fmt.Sprintf("/aws/lambda/%s", functionName)
	output, err := actor.CwlClient.GetLogEvents(ctx, &cloudwatchlogs.GetLogEventsInput{
		LogStreamName: aws.String(logStreamName),
		Limit:         aws.Int32(eventCount),
		LogGroupName:  aws.String(logGroupName),
	})
	if err != nil {
		log.Printf("Couldn't get log event for log stream %v. Here's why: %v\n", logStreamName, err)
	} else {
		events = output.Events
	}
	return events, err
}

Create a struct that wraps AWS CloudFormation actions.

import (
	"context"
	"log"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/cloudformation"
)

// StackOutputs defines a map of outputs from a specific stack.
type StackOutputs map[string]string

type CloudFormationActions struct {
	CfnClient *cloudformation.Client
}

// GetOutputs gets the outputs from a CloudFormation stack and puts them into a structured format.
func (actor CloudFormationActions) GetOutputs(ctx context.Context, stackName string) StackOutputs {
	output, err := actor.CfnClient.DescribeStacks(ctx, &cloudformation.DescribeStacksInput{
		StackName: aws.String(stackName),
	})
	if err != nil || len(output.Stacks) == 0 {
		log.Panicf("Couldn't find a CloudFormation stack named %v. Here's why: %v\n", stackName, err)
	}
	stackOutputs := StackOutputs{}
	for _, out := range output.Stacks[0].Outputs {
		stackOutputs[*out.OutputKey] = *out.OutputValue
	}
	return stackOutputs
}

Clean up resources.

import (
	"context"
	"log"
	"user_pools_and_lambda_triggers/actions"

	"github.com/awsdocs/aws-doc-sdk-examples/gov2/demotools"
)

// Resources keeps track of AWS resources created during an example and handles
// cleanup when the example finishes.
type Resources struct {
	userPoolId       string
	userAccessTokens []string
	triggers         []actions.Trigger

	cognitoActor *actions.CognitoActions
	questioner   demotools.IQuestioner
}

func (resources *Resources) init(cognitoActor *actions.CognitoActions, questioner demotools.IQuestioner) {
	resources.userAccessTokens = []string{}
	resources.triggers = []actions.Trigger{}
	resources.cognitoActor = cognitoActor
	resources.questioner = questioner
}

// Cleanup deletes all AWS resources created during an example.
func (resources *Resources) Cleanup(ctx context.Context) {
	defer func() {
		if r := recover(); r != nil {
			log.Printf("Something went wrong during cleanup.\n%v\n", r)
			log.Println("Use the AWS Management Console to remove any remaining resources \n" +
				"that were created for this scenario.")
		}
	}()

	wantDelete := resources.questioner.AskBool("Do you want to remove all of the AWS resources that were created "+
		"during this demo (y/n)?", "y")
	if wantDelete {
		for _, accessToken := range resources.userAccessTokens {
			err := resources.cognitoActor.DeleteUser(ctx, accessToken)
			if err != nil {
				log.Println("Couldn't delete user during cleanup.")
				panic(err)
			}
			log.Println("Deleted user.")
		}
		triggerList := make([]actions.TriggerInfo, len(resources.triggers))
		for i := 0; i < len(resources.triggers); i++ {
			triggerList[i] = actions.TriggerInfo{Trigger: resources.triggers[i], HandlerArn: nil}
		}
		err := resources.cognitoActor.UpdateTriggers(ctx, resources.userPoolId, triggerList...)
		if err != nil {
			log.Println("Couldn't update Cognito triggers during cleanup.")
			panic(err)
		}
		log.Println("Removed Cognito triggers from user pool.")
	} else {
		log.Println("Be sure to remove resources when you're done with them to avoid unexpected charges!")
	}
}

Configure an interactive "Scenario" run. The JavaScript (v3) examples share a Scenario runner to streamline complex examples. The complete source code is on GitHub.

import { AutoConfirm } from "./scenario-auto-confirm.js";

/**
 * The context is passed to every scenario. Scenario steps
 * will modify the context.
 */
const context = {
  errors: [],
  users: [
    {
      UserName: "test_user_1",
      UserEmail: "test_email_1@example.com",
    },
    {
      UserName: "test_user_2",
      UserEmail: "test_email_2@example.com",
    },
    {
      UserName: "test_user_3",
      UserEmail: "test_email_3@example.com",
    },
  ],
};

/**
 * Three Scenarios are created for the workflow. A Scenario is an orchestration class
 * that simplifies running a series of steps.
 */
export const scenarios = {
  // Demonstrate automatically confirming known users in a database.
  "auto-confirm": AutoConfirm(context),
};

// Call function if run directly
import { fileURLToPath } from "node:url";
import { parseScenarioArgs } from "@aws-doc-sdk-examples/lib/scenario/index.js";

if (process.argv[1] === fileURLToPath(import.meta.url)) {
  parseScenarioArgs(scenarios, {
    name: "Cognito user pools and triggers",
    description:
      "Demonstrate how to use the AWS SDKs to customize Amazon Cognito authentication behavior.",
  });
}

This Scenario demonstrates auto-confirming a known user. It orchestrates the example steps.

import { wait } from "@aws-doc-sdk-examples/lib/utils/util-timers.js";
import {
  Scenario,
  ScenarioAction,
  ScenarioInput,
  ScenarioOutput,
} from "@aws-doc-sdk-examples/lib/scenario/scenario.js";

import {
  getStackOutputs,
  logCleanUpReminder,
  promptForStackName,
  promptForStackRegion,
  skipWhenErrors,
} from "./steps-common.js";
import { populateTable } from "./actions/dynamodb-actions.js";
import {
  addPreSignUpHandler,
  deleteUser,
  getUser,
  signIn,
  signUpUser,
} from "./actions/cognito-actions.js";
import {
  getLatestLogStreamForLambda,
  getLogEvents,
} from "./actions/cloudwatch-logs-actions.js";

/**
 * @typedef {{
 *   errors: Error[],
 *   password: string,
 *   users: { UserName: string, UserEmail: string }[],
 *   selectedUser?: string,
 *   stackName?: string,
 *   stackRegion?: string,
 *   token?: string,
 *   confirmDeleteSignedInUser?: boolean,
 *   TableName?: string,
 *   UserPoolClientId?: string,
 *   UserPoolId?: string,
 *   UserPoolArn?: string,
 *   AutoConfirmHandlerArn?: string,
 *   AutoConfirmHandlerName?: string
 * }} State
 */

const greeting = new ScenarioOutput(
  "greeting",
  (/** @type {State} */ state) => `This demo will populate some users into the \
database created as part of the "${state.stackName}" stack. \
Then the autoConfirmHandler will be linked to the PreSignUp \
trigger from Cognito. Finally, you will choose a user to sign up.`,
  { skipWhen: skipWhenErrors },
);

const logPopulatingUsers = new ScenarioOutput(
  "logPopulatingUsers",
  "Populating the DynamoDB table with some users.",
  { skipWhenErrors: skipWhenErrors },
);

const logPopulatingUsersComplete = new ScenarioOutput(
  "logPopulatingUsersComplete",
  "Done populating users.",
  { skipWhen: skipWhenErrors },
);

const populateUsers = new ScenarioAction(
  "populateUsers",
  async (/** @type {State} */ state) => {
    const [_, err] = await populateTable({
      region: state.stackRegion,
      tableName: state.TableName,
      items: state.users,
    });
    if (err) {
      state.errors.push(err);
    }
  },
  {
    skipWhen: skipWhenErrors,
  },
);

const logSetupSignUpTrigger = new ScenarioOutput(
  "logSetupSignUpTrigger",
  "Setting up the PreSignUp trigger for the Cognito User Pool.",
  { skipWhen: skipWhenErrors },
);

const setupSignUpTrigger = new ScenarioAction(
  "setupSignUpTrigger",
  async (/** @type {State} */ state) => {
    const [_, err] = await addPreSignUpHandler({
      region: state.stackRegion,
      userPoolId: state.UserPoolId,
      handlerArn: state.AutoConfirmHandlerArn,
    });
    if (err) {
      state.errors.push(err);
    }
  },
  {
    skipWhen: skipWhenErrors,
  },
);

const logSetupSignUpTriggerComplete = new ScenarioOutput(
  "logSetupSignUpTriggerComplete",
  (
    /** @type {State} */ state,
  ) => `The lambda function "${state.AutoConfirmHandlerName}" \
has been configured as the PreSignUp trigger handler for the user pool "${state.UserPoolId}".`,
  { skipWhen: skipWhenErrors },
);

const selectUser = new ScenarioInput(
  "selectedUser",
  "Select a user to sign up.",
  {
    type: "select",
    choices: (/** @type {State} */ state) => state.users.map((u) => u.UserName),
    skipWhen: skipWhenErrors,
    default: (/** @type {State} */ state) => state.users[0].UserName,
  },
);

const checkIfUserAlreadyExists = new ScenarioAction(
  "checkIfUserAlreadyExists",
  async (/** @type {State} */ state) => {
    const [user, err] = await getUser({
      region: state.stackRegion,
      userPoolId: state.UserPoolId,
      username: state.selectedUser,
    });

    if (err?.name === "UserNotFoundException") {
      // Do nothing. We're not expecting the user to exist before
      // sign up is complete.
      return;
    }

    if (err) {
      state.errors.push(err);
      return;
    }

    if (user) {
      state.errors.push(
        new Error(
          `The user "${state.selectedUser}" already exists in the user pool "${state.UserPoolId}".`,
        ),
      );
    }
  },
  {
    skipWhen: skipWhenErrors,
  },
);

const createPassword = new ScenarioInput(
  "password",
  "Enter a password that has at least eight characters, uppercase, lowercase, numbers and symbols.",
  { type: "password", skipWhen: skipWhenErrors, default: "Abcd1234!" },
);

const logSignUpExistingUser = new ScenarioOutput(
  "logSignUpExistingUser",
  (/** @type {State} */ state) => `Signing up user "${state.selectedUser}".`,
  { skipWhen: skipWhenErrors },
);

const signUpExistingUser = new ScenarioAction(
  "signUpExistingUser",
  async (/** @type {State} */ state) => {
    const signUp = (password) =>
      signUpUser({
        region: state.stackRegion,
        userPoolClientId: state.UserPoolClientId,
        username: state.selectedUser,
        email: state.users.find((u) => u.UserName === state.selectedUser)
          .UserEmail,
        password,
      });

    let [_, err] = await signUp(state.password);

    while (err?.name === "InvalidPasswordException") {
      console.warn("The password you entered was invalid.");
      await createPassword.handle(state);
      [_, err] = await signUp(state.password);
    }

    if (err) {
      state.errors.push(err);
    }
  },
  { skipWhen: skipWhenErrors },
);

const logSignUpExistingUserComplete = new ScenarioOutput(
  "logSignUpExistingUserComplete",
  (/** @type {State} */ state) =>
    `"${state.selectedUser} was signed up successfully.`,
  { skipWhen: skipWhenErrors },
);

const logLambdaLogs = new ScenarioAction(
  "logLambdaLogs",
  async (/** @type {State} */ state) => {
    console.log(
      "Waiting a few seconds to let Lambda write to CloudWatch Logs...\n",
    );
    await wait(10);

    const [logStream, logStreamErr] = await getLatestLogStreamForLambda({
      functionName: state.AutoConfirmHandlerName,
      region: state.stackRegion,
    });
    if (logStreamErr) {
      state.errors.push(logStreamErr);
      return;
    }

    console.log(
      `Getting some recent events from log stream "${logStream.logStreamName}"`,
    );
    const [logEvents, logEventsErr] = await getLogEvents({
      functionName: state.AutoConfirmHandlerName,
      region: state.stackRegion,
      eventCount: 10,
      logStreamName: logStream.logStreamName,
    });
    if (logEventsErr) {
      state.errors.push(logEventsErr);
      return;
    }

    console.log(logEvents.map((ev) => `\t${ev.message}`).join(""));
  },
  { skipWhen: skipWhenErrors },
);

const logSignInUser = new ScenarioOutput(
  "logSignInUser",
  (/** @type {State} */ state) => `Let's sign in as ${state.selectedUser}`,
  { skipWhen: skipWhenErrors },
);

const signInUser = new ScenarioAction(
  "signInUser",
  async (/** @type {State} */ state) => {
    const [response, err] = await signIn({
      region: state.stackRegion,
      clientId: state.UserPoolClientId,
      username: state.selectedUser,
      password: state.password,
    });

    if (err?.name === "PasswordResetRequiredException") {
      state.errors.push(new Error("Please reset your password."));
      return;
    }

    if (err) {
      state.errors.push(err);
      return;
    }

    state.token = response?.AuthenticationResult?.AccessToken;
  },
  { skipWhen: skipWhenErrors },
);

const logSignInUserComplete = new ScenarioOutput(
  "logSignInUserComplete",
  (/** @type {State} */ state) =>
    `Successfully signed in. Your access token starts with: ${state.token.slice(0, 11)}`,
  { skipWhen: skipWhenErrors },
);

const confirmDeleteSignedInUser = new ScenarioInput(
  "confirmDeleteSignedInUser",
  "Do you want to delete the currently signed in user?",
  { type: "confirm", skipWhen: skipWhenErrors },
);

const deleteSignedInUser = new ScenarioAction(
  "deleteSignedInUser",
  async (/** @type {State} */ state) => {
    const [_, err] = await deleteUser({
      region: state.stackRegion,
      accessToken: state.token,
    });

    if (err) {
      state.errors.push(err);
    }
  },
  {
    skipWhen: (/** @type {State} */ state) =>
      skipWhenErrors(state) || !state.confirmDeleteSignedInUser,
  },
);

const logErrors = new ScenarioOutput(
  "logErrors",
  (/** @type {State}*/ state) => {
    const errorList = state.errors
      .map((err) => ` - ${err.name}: ${err.message}`)
      .join("\n");
    return `Scenario errors found:\n${errorList}`;
  },
  {
    // Don't log errors when there aren't any!
    skipWhen: (/** @type {State} */ state) => state.errors.length === 0,
  },
);

export const AutoConfirm = (context) =>
  new Scenario(
    "AutoConfirm",
    [
      promptForStackName,
      promptForStackRegion,
      getStackOutputs,
      greeting,
      logPopulatingUsers,
      populateUsers,
      logPopulatingUsersComplete,
      logSetupSignUpTrigger,
      setupSignUpTrigger,
      logSetupSignUpTriggerComplete,
      selectUser,
      checkIfUserAlreadyExists,
      createPassword,
      logSignUpExistingUser,
      signUpExistingUser,
      logSignUpExistingUserComplete,
      logLambdaLogs,
      logSignInUser,
      signInUser,
      logSignInUserComplete,
      confirmDeleteSignedInUser,
      deleteSignedInUser,
      logCleanUpReminder,
      logErrors,
    ],
    context,
  );

These are steps that are shared with other Scenarios.

import {
  ScenarioAction,
  ScenarioInput,
  ScenarioOutput,
} from "@aws-doc-sdk-examples/lib/scenario/scenario.js";
import { getCfnOutputs } from "@aws-doc-sdk-examples/lib/sdk/cfn-outputs.js";

export const skipWhenErrors = (state) => state.errors.length > 0;

export const getStackOutputs = new ScenarioAction(
  "getStackOutputs",
  async (state) => {
    if (!state.stackName || !state.stackRegion) {
      state.errors.push(
        new Error(
          "No stack name or region provided. The stack name and \
region are required to fetch CFN outputs relevant to this example.",
        ),
      );
      return;
    }

    const outputs = await getCfnOutputs(state.stackName, state.stackRegion);
    Object.assign(state, outputs);
  },
);

export const promptForStackName = new ScenarioInput(
  "stackName",
  "Enter the name of the stack you deployed earlier.",
  { type: "input", default: "PoolsAndTriggersStack" },
);

export const promptForStackRegion = new ScenarioInput(
  "stackRegion",
  "Enter the region of the stack you deployed earlier.",
  { type: "input", default: "us-east-1" },
);

export const logCleanUpReminder = new ScenarioOutput(
  "logCleanUpReminder",
  "All done. Remember to run 'cdk destroy' to teardown the stack.",
  { skipWhen: skipWhenErrors },
);

A handler for the PreSignUp trigger with a Lambda function.

import type { PreSignUpTriggerEvent, Handler } from "aws-lambda";
import type { UserRepository } from "./user-repository";
import { DynamoDBUserRepository } from "./user-repository";

export class PreSignUpHandler {
  private userRepository: UserRepository;

  constructor(userRepository: UserRepository) {
    this.userRepository = userRepository;
  }

  private isPreSignUpTriggerSource(event: PreSignUpTriggerEvent): boolean {
    return event.triggerSource === "PreSignUp_SignUp";
  }

  private getEventUserEmail(event: PreSignUpTriggerEvent): string {
    return event.request.userAttributes.email;
  }

  async handlePreSignUpTriggerEvent(
    event: PreSignUpTriggerEvent,
  ): Promise<PreSignUpTriggerEvent> {
    console.log(
      `Received presignup from ${event.triggerSource} for user '${event.userName}'`,
    );

    if (!this.isPreSignUpTriggerSource(event)) {
      return event;
    }

    const eventEmail = this.getEventUserEmail(event);
    console.log(`Looking up email ${eventEmail}.`);
    const storedUserInfo =
      await this.userRepository.getUserInfoByEmail(eventEmail);

    if (!storedUserInfo) {
      console.log(
        `Email ${eventEmail} not found. Email verification is required.`,
      );
      return event;
    }

    if (storedUserInfo.UserName !== event.userName) {
      console.log(
        `UserEmail ${eventEmail} found, but stored UserName '${storedUserInfo.UserName}' does not match supplied UserName '${event.userName}'. Verification is required.`,
      );
    } else {
      console.log(
        `UserEmail ${eventEmail} found with matching UserName ${storedUserInfo.UserName}. User is confirmed.`,
      );
      event.response.autoConfirmUser = true;
      event.response.autoVerifyEmail = true;
    }
    return event;
  }
}

const createPreSignUpHandler = (): PreSignUpHandler => {
  const tableName = process.env.TABLE_NAME;
  if (!tableName) {
    throw new Error("TABLE_NAME environment variable is not set");
  }

  const userRepository = new DynamoDBUserRepository(tableName);
  return new PreSignUpHandler(userRepository);
};

export const handler: Handler = async (event: PreSignUpTriggerEvent) => {
  const preSignUpHandler = createPreSignUpHandler();
  return preSignUpHandler.handlePreSignUpTriggerEvent(event);
};

Module of CloudWatch Logs actions.

import {
  CloudWatchLogsClient,
  GetLogEventsCommand,
  OrderBy,
  paginateDescribeLogStreams,
} from "@aws-sdk/client-cloudwatch-logs";

/**
 * Get the latest log stream for a Lambda function.
 * @param {{ functionName: string, region: string }} config
 * @returns {Promise<[import("@aws-sdk/client-cloudwatch-logs").LogStream | null, unknown]>}
 */
export const getLatestLogStreamForLambda = async ({ functionName, region }) => {
  try {
    const logGroupName = `/aws/lambda/${functionName}`;
    const cwlClient = new CloudWatchLogsClient({ region });
    const paginator = paginateDescribeLogStreams(
      { client: cwlClient },
      {
        descending: true,
        limit: 1,
        orderBy: OrderBy.LastEventTime,
        logGroupName,
      },
    );

    for await (const page of paginator) {
      return [page.logStreams[0], null];
    }
  } catch (err) {
    return [null, err];
  }
};

/**
 * Get the log events for a Lambda function's log stream.
 * @param {{
 *   functionName: string,
 *   logStreamName: string,
 *   eventCount: number,
 *   region: string
 * }} config
 * @returns {Promise<[import("@aws-sdk/client-cloudwatch-logs").OutputLogEvent[] | null, unknown]>}
 */
export const getLogEvents = async ({
  functionName,
  logStreamName,
  eventCount,
  region,
}) => {
  try {
    const cwlClient = new CloudWatchLogsClient({ region });
    const logGroupName = `/aws/lambda/${functionName}`;
    const response = await cwlClient.send(
      new GetLogEventsCommand({
        logStreamName: logStreamName,
        limit: eventCount,
        logGroupName: logGroupName,
      }),
    );

    return [response.events, null];
  } catch (err) {
    return [null, err];
  }
};

Module of Amazon Cognito actions.

import {
  AdminGetUserCommand,
  CognitoIdentityProviderClient,
  DeleteUserCommand,
  InitiateAuthCommand,
  SignUpCommand,
  UpdateUserPoolCommand,
} from "@aws-sdk/client-cognito-identity-provider";

/**
 * Connect a Lambda function to the PreSignUp trigger for a Cognito user pool
 * @param {{ region: string, userPoolId: string, handlerArn: string }} config
 * @returns {Promise<[import("@aws-sdk/client-cognito-identity-provider").UpdateUserPoolCommandOutput | null, unknown]>}
 */
export const addPreSignUpHandler = async ({
  region,
  userPoolId,
  handlerArn,
}) => {
  try {
    const cognitoClient = new CognitoIdentityProviderClient({
      region,
    });

    const command = new UpdateUserPoolCommand({
      UserPoolId: userPoolId,
      LambdaConfig: {
        PreSignUp: handlerArn,
      },
    });

    const response = await cognitoClient.send(command);
    return [response, null];
  } catch (err) {
    return [null, err];
  }
};

/**
 * Attempt to register a user to a user pool with a given username and password.
 * @param {{
 *   region: string,
 *   userPoolClientId: string,
 *   username: string,
 *   email: string,
 *   password: string
 * }} config
 * @returns {Promise<[import("@aws-sdk/client-cognito-identity-provider").SignUpCommandOutput | null, unknown]>}
 */
export const signUpUser = async ({
  region,
  userPoolClientId,
  username,
  email,
  password,
}) => {
  try {
    const cognitoClient = new CognitoIdentityProviderClient({
      region,
    });

    const response = await cognitoClient.send(
      new SignUpCommand({
        ClientId: userPoolClientId,
        Username: username,
        Password: password,
        UserAttributes: [{ Name: "email", Value: email }],
      }),
    );
    return [response, null];
  } catch (err) {
    return [null, err];
  }
};

/**
 * Sign in a user to Amazon Cognito using a username and password authentication flow.
 * @param {{ region: string, clientId: string, username: string, password: string }} config
 * @returns {Promise<[import("@aws-sdk/client-cognito-identity-provider").InitiateAuthCommandOutput | null, unknown]>}
 */
export const signIn = async ({ region, clientId, username, password }) => {
  try {
    const cognitoClient = new CognitoIdentityProviderClient({ region });
    const response = await cognitoClient.send(
      new InitiateAuthCommand({
        AuthFlow: "USER_PASSWORD_AUTH",
        ClientId: clientId,
        AuthParameters: { USERNAME: username, PASSWORD: password },
      }),
    );
    return [response, null];
  } catch (err) {
    return [null, err];
  }
};

/**
 * Retrieve an existing user from a user pool.
 * @param {{ region: string, userPoolId: string, username: string }} config
 * @returns {Promise<[import("@aws-sdk/client-cognito-identity-provider").AdminGetUserCommandOutput | null, unknown]>}
 */
export const getUser = async ({ region, userPoolId, username }) => {
  try {
    const cognitoClient = new CognitoIdentityProviderClient({ region });
    const response = await cognitoClient.send(
      new AdminGetUserCommand({
        UserPoolId: userPoolId,
        Username: username,
      }),
    );
    return [response, null];
  } catch (err) {
    return [null, err];
  }
};

/**
 * Delete the signed-in user. Useful for allowing a user to delete their
 * own profile.
 * @param {{ region: string, accessToken: string }} config
 * @returns {Promise<[import("@aws-sdk/client-cognito-identity-provider").DeleteUserCommandOutput | null, unknown]>}
 */
export const deleteUser = async ({ region, accessToken }) => {
  try {
    const client = new CognitoIdentityProviderClient({ region });
    const response = await client.send(
      new DeleteUserCommand({ AccessToken: accessToken }),
    );
    return [response, null];
  } catch (err) {
    return [null, err];
  }
};

Module of DynamoDB actions.

import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import {
  BatchWriteCommand,
  DynamoDBDocumentClient,
} from "@aws-sdk/lib-dynamodb";

/**
 * Populate a DynamoDB table with provide items.
 * @param {{ region: string, tableName: string, items: Record<string, unknown>[] }} config
 * @returns {Promise<[import("@aws-sdk/lib-dynamodb").BatchWriteCommandOutput | null, unknown]>}
 */
export const populateTable = async ({ region, tableName, items }) => {
  try {
    const ddbClient = new DynamoDBClient({ region });
    const docClient = DynamoDBDocumentClient.from(ddbClient);
    const response = await docClient.send(
      new BatchWriteCommand({
        RequestItems: {
          [tableName]: items.map((item) => ({
            PutRequest: {
              Item: item,
            },
          })),
        },
      }),
    );
    return [response, null];
  } catch (err) {
    return [null, err];
  }
};