AWSTemplateFormatVersion: "2010-09-09"
Description: "ECR repository cross-region replication"
Parameters:
  TargetRegions:
    Description: Target regions to replicate, comma seperated
    Type: CommaDelimitedList

Resources:
  CodeBuildRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          Effect: Allow
          Principal:
            Service: codebuild.amazonaws.com
          Action: sts:AssumeRole
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/AmazonEC2ContainerRegistryPowerUser
        - arn:aws:iam::aws:policy/AmazonSSMReadOnlyAccess
      Path: "/"
      Policies: 
        - PolicyName: "CodeBuildLogsPolicy"
          PolicyDocument:
            Version: "2012-10-17"
            Statement: 
              - Effect: "Allow"
                Action: 
                  - logs:CreateLogGroup
                  - logs:CreateLogStream
                  - logs:PutLogEvents
                  - ecr:CreateRepository
                Resource: "*"
  CWEventInvokeRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          Effect: Allow
          Principal:
            Service: events.amazonaws.com
          Action: sts:AssumeRole
      Path: "/"
      Policies: 
        - PolicyName: "CWEventInvokeCodeBuild"
          PolicyDocument: 
            Version: "2012-10-17"
            Statement: 
              - Effect: "Allow"
                Action: ["codebuild:StartBuild"]
                Resource: "*"
  CodeBuildECRReplicate:
    Type: AWS::CodeBuild::Project
    Properties:
      Artifacts:
        Type: no_artifacts
      Environment:
        ComputeType: BUILD_GENERAL1_SMALL
        Image: aws/codebuild/standard:4.0
        Type: LINUX_CONTAINER
        PrivilegedMode: true
      ServiceRole: !Ref CodeBuildRole
      Source:
        Type: NO_SOURCE
        BuildSpec: !Sub 
          - |
            version: 0.2
            phases:
              install:
                runtime-versions:
                  docker: 18
              build:
                commands: 
                  - |
                    check_create_repo()
                    {
                      dstRegion=$1
                      repoName=$2
                      #check repository in destation registry
                      if ! repoMsg=$(aws ecr describe-repositories --repository-names $repoName --region $dstRegion 2>&1); then
                        echo -n "$repoName does not exists in ECR@$dstRegion, creating... "
                        aws ecr create-repository --repository-name $repoName --region $dstRegion > /dev/null
                        echo "done."
                      fi
                    }
                    echo "login source registry"
                    $(aws ecr get-login --no-include-email --region $ECR_SRC_REGION)
                    srcImage="$ECR_SRC_REG_ID.dkr.ecr.$ECR_SRC_REGION.${AWS::URLSuffix}/$ECR_REPO_NAME:$ECR_REPO_TAG"
                    echo "pull image"
                    docker pull $srcImage
                    targetRegions=${ECR_TARGET_REGIONS}
                    IFS=","; for reg in $targetRegions; do
                      check_create_repo $reg $ECR_REPO_NAME
                      targetImage="$ECR_SRC_REG_ID.dkr.ecr.$reg.${AWS::URLSuffix}/$ECR_REPO_NAME:$ECR_REPO_TAG"
                      docker tag $srcImage $targetImage
                      echo "login target registry in $reg"
                      aws ecr get-login --no-include-email --region $reg | bash
                      echo "push image to target region $reg"
                      docker push $targetImage
                    done
          - {
              ECR_TARGET_REGIONS: !Join [",", !Ref TargetRegions]
            }
  EventRule:
    Type: AWS::Events::Rule
    Properties: 
      Description: "ECR PUSH event rule to trigger CodeBuild to replicate repository"
      EventPattern: 
        source: [aws.ecr]
        detail:
          action-type: ["PUSH"]
          result: ["SUCCESS"]
      State: ENABLED
      Targets: 
        - Arn: !GetAtt CodeBuildECRReplicate.Arn
          Id: "ECRReplicateCodeBuild"
          RoleArn: !GetAtt CWEventInvokeRole.Arn
          InputTransformer:
            InputPathsMap: 
              awsRegion: $.region
              repoName: $.detail.repository-name
              registryId: $.account
              imageTag: $.detail.image-tag
            InputTemplate: |
              {
                "environmentVariablesOverride": [
                  {
                    "name": "ECR_SRC_REG_ID",
                    "type": "PLAINTEXT",
                    "value": <registryId>
                  },
                  {
                    "name": "ECR_SRC_REGION",
                    "type": "PLAINTEXT",
                    "value": <awsRegion>
                  },
                  {
                    "name": "ECR_REPO_NAME",
                    "type": "PLAINTEXT",
                    "value": <repoName>
                  },
                  {
                    "name": "ECR_REPO_TAG",
                    "type": "PLAINTEXT",
                    "value": <imageTag>
                  }
                 ]
              }