template.yml

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::Serverless-2016-10-31'
Description: Frontend Deploy Example

Resources:
  TargetBucket:
    Type: AWS::S3::Bucket
    Properties:
      WebsiteConfiguration:
        IndexDocument: index.html

  DeploymentLayer:
    Type: AWS::Serverless::Application
    Properties:
      Location:
        ApplicationId: arn:aws:serverlessrepo:us-east-1:375983427419:applications/deploy-to-s3
        SemanticVersion: 2.4.2
      

  # this function is used only during deployment, 
  # we use the web site assets as the source of the function
  # tricking cloudformation to pack up the web site files
  # using the standard cloudformation package process
  SiteSource:
    Type: AWS::Serverless::Function
    Properties:
      Layers: 
        # the layer contains the deployment code 
        # so the function "source" can just contain the web assets
        - !GetAtt DeploymentLayer.Outputs.Arn

      # point to directory with the assets so cloudformation can
      # package and upload them
      CodeUri: web-site/

      # really important: this will ensure that any change in 
      # the bundled files gets deployed again. we're abusing
      # the custom resource pipeline here, so this will be used
      # to change parameters of the resource and re-trigger it
      AutoPublishAlias: live

      # the following two lines are required to make the layer work
      Runtime: python3.6 
      Handler: deployer.resource_handler

      # set the timeout to something reasonable depending on
      # how long it takes to upload your assets to S3
      Timeout: 600

      # give the function access to the bucket where it
      # will upload the assets
      Policies:
        - S3FullAccessPolicy:
            BucketName: !Ref TargetBucket

  # This is a custom resource that
  # will trigger the function during deployment
  DeploymentResource:
    Type: AWS::CloudFormation::CustomResource
    Properties:

      # the following two lines are required to 
      # ensure that cloudformation will trigger the
      # resource every time you change the bundled files
      ServiceToken: !GetAtt SiteSource.Arn
      Version: !Ref "SiteSource.Version"

      # tell the deployer where to upload the files
      TargetBucket: !Ref TargetBucket

      Substitutions:
        FilePattern: "*.html"
        Values:
          APP_NAME: 'Example Application'
          STACK_ID: !Ref AWS::StackId
      
      # Choose the ACL and caching policies
      # eg, for directly accessible web site
      # use public-read and 10 minutes caching
      Acl: 'public-read'
      CacheControlMaxAge: 600


Outputs:
  DestinationBucket:
    Value: !Ref TargetBucket
  DestinationUrl:
    Value: !GetAtt TargetBucket.WebsiteURL