AWS: Lambda with custom resource

const aws = require('aws-sdk');
const s3 = new aws.S3();
const { configure, sendSuccess, sendFailure, sendResponse, LOG_VERBOSE } = require('./cfn-custom-resource.js');

configure({ logLevel: LOG_VERBOSE });

function generatePhysicalId(resourceProperties) {
    return `cfexample-${resourceProperties.BucketName}-${resourceProperties.Countdown}`;
}

async function createObjectResource(bucketName, countdown) {
    let data = '';
    for (let i=0; i < countdown; i++) {
        data = data + i + '\r\n';
    }

    const objectKey = `data-${countdown}.txt`;
    const s3Path =  `s3://${bucketName}/${objectKey}`;
    console.log(`Creating objetct on S3: ${s3Path}.`);

    const params = {
        Bucket : bucketName,
        Key : objectKey,
        Body : data
    };
    const result = await s3.putObject(params).promise();

    return {
        props : {
            DataFile : s3Path,
            Metadata : JSON.stringify(result)
        }
    };
}

async function deleteObjectResource(bucketName, countdown) {
    let objectKey = `data-${countdown}.txt`;
    const s3Path =  `s3://${bucketName}/${objectKey}`;
    console.log(`Deleting objetct on S3: ${s3Path}.`);

    const params = {
        Bucket : bucketName,
        Key : objectKey
    };
    const result = await s3.deleteObject(params).promise();

    return {
        props : {
            DataFile : `s3://${bucketName}/${objectKey}`,
            Metadata : JSON.stringify(result)
        }
    };
}

exports.handler = async (event) => {
    console.log(`Event payload: ${JSON.stringify(event)}.`);
    const physicalResourceId =
      generatePhysicalId(event.ResourceProperties);
    try {
        let result;
        if (event.RequestType === 'Create') {
            console.info(`New Create event received.`);
            result = await createObjectResource(event.ResourceProperties.BucketName, event.ResourceProperties.Countdown);
        } else if (event.RequestType === 'Update') {
            console.info(`New Update event received.`);
            // Only the creation of the new object is required: by changing the physical name of the
            // resource, a Delete event for the old version will be triggered
            result = await createObjectResource(event.ResourceProperties.BucketName, event.ResourceProperties.Countdown);
        } else if (event.RequestType === 'Delete') {
            console.info(`New Delete event received.`);
            result = await deleteObjectResource(event.ResourceProperties.BucketName, event.ResourceProperties.Countdown);
        } else {
            throw `Not supported request type: ${event.RequestType}.`;
        }
        console.log(`Operation completed succesfully. Notifying Cloudformation.`);
        await sendSuccess(physicalResourceId, result, event);
    } catch (err) {
        console.error(`Failed to execute the request. Event <<${JSON.stringify(event)}>> Error <<${JSON.stringify(err)}>>`);
        await sendFailure(physicalResourceId, {Error : err}, event);
    }

};





/*

    - Create the bucket (custom-resource-example) or delete its content if exists
    - Create the lambda
	- Make https://github.com/jgriepentrog/cfn-custom-resource available as file
    - Provide permissions to write to s3
    - Update the cloudformation templates with the ARN of the lambda
    - Update the cloudformation templates with the name of the bucket

*/

/*

cat << EOF > v1.yaml
AWSTemplateFormatVersion: 2010-09-09

Resources:
  CountdownResource:
    Type: 'Custom::CountdownResource'
    Version: '1.0'
    Properties:
      ServiceToken: arn:aws:lambda:eu-west-1:436628946705:function:cf-custom-resource-example
      BucketName : custom-resource-example
      Countdown : 100
EOF

cat << EOF > v2.yaml
AWSTemplateFormatVersion: 2010-09-09

Resources:
  CountdownResource:
    Type: 'Custom::CountdownResource'
    Version: '1.0'
    Properties:
      ServiceToken: arn:aws:lambda:eu-west-1:436628946705:function:cf-custom-resource-example
      BucketName : custom-resource-example
      Countdown : 50
EOF


// Open the lambda logs
aws s3 ls s3://custom-resource-example
aws cloudformation create-stack --stack-name cr-demo --template-body file://v1.yaml
aws s3 ls s3://custom-resource-example
aws cloudformation create-change-set --stack-name cr-demo --change-set-name cr-demo-1-2 --template-body file://v2.yaml
aws cloudformation describe-change-set --stack-name cr-demo --change-set-name cr-demo-1-2
aws cloudformation update-stack --stack-name cr-demo --template-body file://v2.yaml
aws s3 ls s3://custom-resource-example
aws cloudformation delete-stack --stack-name cr-demo
aws s3 ls s3://custom-resource-example

*/