AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: S3 bucket to Lambda function

Parameters:
  BucketName:
    Type: String

Resources:
  ## S3 bucket
  MyS3bucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Ref BucketName    

  ## Lambda function
  MyLambdaFunction:
    Type: AWS::Serverless::Function 
    Properties:
      CodeUri: myLambdaFunction/
      Handler: app.handler
      Runtime: nodejs12.x
      MemorySize: 128
      Policies:
        - S3ReadPolicy:
            BucketName: !Ref BucketName
      Events:
        FileUpload:
          Type: S3
          Properties:
            Bucket: !Ref MyS3bucket
            Events: s3:ObjectCreated:*
            Filter: 
              S3Key:
                Rules:
                  - Name: suffix
                    Value: '.jpg'