AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::Serverless-2016-10-31'
Description: A CloudFormation Custom Resource and a Lambda function to create an S3 object. (uksb-1tthgi812) (tag:cfn-custom-resource-s3-create)

# Global values that are applied to all applicable resources in this template
Globals:
  Function:
    CodeUri: ./src
    Runtime: nodejs20.x
    MemorySize: 128
    Timeout: 15

Parameters:
  ExistingS3Bucket:
    Description: Name of an existing S3 bucket, or leave blank to create a new S3 bucket.
    Type: String
    MaxLength: 63
    AllowedPattern: ^[a-z0-9.-]*$

Conditions: 
  CreateS3Bucket: !Equals [!Ref ExistingS3Bucket, ""]

Resources:
  # If an exsiting S3 bucket name was not provided a new S3 bucket will be created
  NewS3Bucket:
    Type: 'AWS::S3::Bucket'
    Condition: CreateS3Bucket
    Properties:
      PublicAccessBlockConfiguration:
        BlockPublicAcls: true
        BlockPublicPolicy: true
        IgnorePublicAcls: true
        RestrictPublicBuckets: true

  # Lambda function to create an S3 object:
  #   This function would normally be deployed in a separate CloudFormation template.
  #   Then the function Arn would be referenced in other CloudFormation templates
  #   as a custom resource whenever an S3 object needs to be created.
  FunctionS3Create:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: app.handler
      Policies:
        - S3CrudPolicy:
            BucketName: !If [CreateS3Bucket, !Ref NewS3Bucket, !Ref ExistingS3Bucket]

  # Example use of a CloudFormation custom resource:
  #   This custom resource can be used in other CloudFormation templates after the function above is deployed.
  #   If the CloudFormation stack is deleted, the S3 object will also be deleted.
  #   More info: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-cfn-customresource.html
  CustomResourceS3Create:
    Type: 'Custom::S3Create'
    Properties:
      # If this custom resource is used in another CloudFormation template: 
      #   Modify the ServiceToken property to retrieve the function Arn from CloudFormation Exports.
      #   For example:  ServiceToken: !ImportValue function-s3-create
      #   However for this example, the function Arn is retrieved from a resource within this template:
      ServiceToken: !GetAtt FunctionS3Create.Arn
      
      # Define the resource properties that the function requires to create the S3 object:
      #   The Body property defines the content of the S3 object.
      #   In this example, an html document named "index.html" is being created.
      #   The html document includes a variable value that equals the S3 bucket name.
      Bucket: !If [CreateS3Bucket, !Ref NewS3Bucket, !Ref ExistingS3Bucket]
      Key: index.html
      ContentType: text/html # application/json, text/css, text/html, text/plain
      Body: !Sub
        - | 
          
          
            Index
          
          
            This object was created by using a CloudFormation custom resource.
            The S3 bucket name is: ${varS3Bucket}
          
          
        - varS3Bucket: !If [CreateS3Bucket, !Ref NewS3Bucket, !Ref ExistingS3Bucket]

Outputs:
  S3BucketName:
    Description: Name of the S3 bucket
    Value: !If [CreateS3Bucket, !Ref NewS3Bucket, !Ref ExistingS3Bucket]
  FunctionS3CreateArn:
    Description: Arn of the Lambda function to create an S3 object
    Value: !GetAtt FunctionS3Create.Arn
    # The name used to reference the function Arn in CloudFormation Exports:
    Export:
      Name: function-s3-create
  ResponseObjectKey:
    Description: ObjectKey from Lambda function response
    Value: !GetAtt CustomResourceS3Create.ObjectKey