AWSTemplateFormatVersion: '2010-09-09'
Description: Deploys a Lambda Function to rewrite CloudFront url to include index.html of subdirectories

Resources:
  LambdaRewrite:
    Type: AWS::Lambda::Function
    Properties: 
      Runtime: nodejs12.x
      Role: !GetAtt LambdaExecutionRole.Arn
      Handler: index.handler
      Code: 
        ZipFile: |
          'use strict';
          exports.handler = (event, context, callback) => {
              
              // Extract the request from the CloudFront event that is sent to Lambda@Edge 
              var request = event.Records[0].cf.request;

              // Extract the URI from the request
              var olduri = request.uri;

              // Match any '/' that occurs at the end of a URI. Replace it with a default index
              var newuri = olduri.replace(/\/$/, '\/index.html');
              
              // Log the URI as received by CloudFront and the new URI to be used to fetch from origin
              console.log("Old URI: " + olduri);
              console.log("New URI: " + newuri);
              
              // Replace the received URI with the URI that includes the index page
              request.uri = newuri;
              
              // Return to CloudFront
              return callback(null, request);

          }; 
      Description: Created by CloudFormation - Handler to rewrite url ending in / to /index.html

  LambdaExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Principal:
            Service:
            - lambda.amazonaws.com
            - edgelambda.amazonaws.com
          Action:
          - sts:AssumeRole
      Path: "/"
      Policies:
      - PolicyName: root
        PolicyDocument:
          Version: '2012-10-17'
          Statement:
          - Effect: Allow
            Action:
            - logs:*
            Resource: arn:aws:logs:*:*:*  

  LambdaVersion:
    Type: AWS::Lambda::Version
    Properties: 
      FunctionName: !Ref LambdaRewrite
      Description: v1