Description: >
    This template deploys an ECS cluster to the provided VPC and subnets 
    using an Auto Scaling Group

Parameters:

    EnvironmentName:
        Description: An environment name that will be prefixed to resource names
        Type: String

    InstanceType: 
        Description: Which instance type should we use to build the ECS cluster?
        Type: String
        Default: c4.large

    ClusterSize:
        Description: How many ECS hosts do you want to initially deploy?
        Type: Number
        Default: 4

    VPC:
        Description: Choose which VPC this ECS cluster should be deployed to
        Type: AWS::EC2::VPC::Id

    Subnets:
        Description: Choose which subnets this ECS cluster should be deployed to
        Type: List<AWS::EC2::Subnet::Id>

    SecurityGroup:
        Description: Select the Security Group to use for the ECS cluster hosts
        Type: AWS::EC2::SecurityGroup::Id

Mappings:

    # These are the latest ECS optimized AMIs as of [DATE]:
    #
    #   Windows_Server-2016-English-Full-ECS_Optimized-2017.11.24
    #   ECS agent:     
    #   Docker: 17.06.2-ee-5      
    #   ecs-init:     
    #
    # You can find the latest available on this page of our documentation:
    # http://docs.aws.amazon.com/AmazonECS/latest/developerguide/ecs-optimized_AMI.html
    # (note the AMI identifier is region specific) 

    AWSRegionToAMI:
        us-west-2:
            AMI: ami-a68e39de
        us-west-1:
            AMI: ami-e5686b85
        us-east-2:
            AMI: ami-6b9db60e
        us-east-1:
            AMI: ami-ec346f96
        eu-west-2: 
            AMI: ami-29574c4d
        eu-west-1:
            AMI: ami-48eb7931
        eu-central-1:
            AMI: ami-ee30a281
        ca-central-1:
            AMI: ami-1e91147a
        ap-southeast-2: 
            AMI: ami-252fd247
        ap-southeast-1:
            AMI: ami-a6fa89da
        ap-northeast-2:
            AMI: ami-0e63c360
        ap-northeast-1:
            AMI: ami-bf3ca4d9

Resources:

    ECSCluster:
        Type: AWS::ECS::Cluster
        Properties:
            ClusterName: !Ref EnvironmentName

    ECSAutoScalingGroup:
        Type: AWS::AutoScaling::AutoScalingGroup
        Properties: 
            VPCZoneIdentifier: !Ref Subnets
            LaunchConfigurationName: !Ref ECSLaunchConfiguration
            MinSize: !Ref ClusterSize
            MaxSize: !Ref ClusterSize
            DesiredCapacity: !Ref ClusterSize
            Tags: 
                - Key: Name
                  Value: !Sub ${EnvironmentName} ECS host
                  PropagateAtLaunch: 'true'
        CreationPolicy:
            ResourceSignal: 
                Timeout: PT15M
        UpdatePolicy:
            AutoScalingRollingUpdate:
                MinInstancesInService: '1'
                MaxBatchSize: '1'
                PauseTime: PT20M
                WaitOnResourceSignals: 'true'
        
    ECSLaunchConfiguration:
        Type: AWS::AutoScaling::LaunchConfiguration
        Properties:
            ImageId:  !FindInMap [AWSRegionToAMI, !Ref "AWS::Region", AMI]
            InstanceType: !Ref InstanceType
            SecurityGroups: 
                - !Ref SecurityGroup
            IamInstanceProfile: !Ref ECSInstanceProfile
            #Need to someone to check this section.  Was unable to find a good example in YAML for bootstrapping an instance.
            UserData: !Base64 
                Fn::Join:
                    - ''
                    - - '<script>
                        
                        '
                      - 'cfn-init.exe -v -s '
                      - !Ref 'AWS::StackId'
                      - ' -r ECSLaunchConfiguration'
                      - ' --region '
                      - !Ref 'AWS::Region'
                      - '

                        '
                      - 'cfn-signal.exe -e %ERRORLEVEL% --stack '
                      - !Ref 'AWS::StackName'
                      - ' --resource ECSAutoScalingGroup '
                      - ' --region '
                      - !Ref 'AWS::Region'
                      - '
                        
                        '
                      - </script>
        Metadata:
            AWS::CloudFormation::Init:
                config:
                    commands:
                        01_import_powershell_module:
                            command: !Sub powershell.exe -Command Import-Module ECSTools
                        02_add_instance_to_cluster:
                            command: !Sub powershell.exe -Command Initialize-ECSAgent -Cluster ${ECSCluster} -EnableTaskIAMRole
                    files:
                        c:\cfn\cfn-hup.conf:
                            content: !Join ['', ['[main]
                                    ', stack=, !Ref 'AWS::StackId', '
                                    ', region=, !Ref 'AWS::Region', '
                                    ']]
                        c:\cfn\hooks.d\cfn-auto-reloader.conf:
                            content: !Join ['', ['[cfn-auto-reloader-hook]
                                    ', 'triggers=post.update
                                    ', 'path=Resources.ECSLaunchConfiguration.Metadata.AWS::CloudFormation::Init
                                    ', 'action=cfn-init.exe -v -s ', !Ref 'AWS::StackId', ' -r ECSLaunchConfiguration',
                                    ' --region ', !Ref 'AWS::Region', '
                                    ']]
                    services: 
                        windows:
                            cfn-hup: 
                                enabled: 'true'
                                ensureRunning: 'true'
                                files: 
                                    - c:\cfn\cfn-hup.conf
                                    - c:\etc\cfn\hooks.d\cfn-auto-reloader.conf

    # This IAM Role is attached to all of the ECS hosts. It is based on the default role
    # published here:
    # http://docs.aws.amazon.com/AmazonECS/latest/developerguide/instance_IAM_role.html
    #
    # You can add other IAM policy statements here to allow access from your ECS hosts
    # to other AWS services. Please note that this role will be used by ALL containers
    # running on the ECS host.

    ECSRole:
        Type: AWS::IAM::Role
        Properties: 
            Path: /
            RoleName: !Sub ${EnvironmentName}-ECSRole-${AWS::Region}
            AssumeRolePolicyDocument: |
                {
                    "Statement": [{
                        "Action": "sts:AssumeRole",
                        "Effect": "Allow",
                        "Principal": { 
                            "Service": "ec2.amazonaws.com" 
                        }
                    }]
                }
            Policies: 
                - PolicyName: ecs-service
                  PolicyDocument: |
                    {
                        "Statement": [{
                            "Effect": "Allow",
                            "Action": [
                                "ecs:CreateCluster",
                                "ecs:DeregisterContainerInstance",
                                "ecs:DiscoverPollEndpoint",
                                "ecs:Poll",
                                "ecs:RegisterContainerInstance",
                                "ecs:StartTelemetrySession",
                                "ecs:Submit*",
                                "logs:CreateLogStream",
                                "logs:PutLogEvents",
                                "ecr:BatchCheckLayerAvailability",
                                "ecr:BatchGetImage",
                                "ecr:GetDownloadUrlForLayer",
                                "ecr:GetAuthorizationToken"
                            ],
                            "Resource": "*"
                        }]
                    }

    ECSInstanceProfile: 
        Type: AWS::IAM::InstanceProfile
        Properties:
            Path: /
            Roles: 
                - !Ref ECSRole

Outputs:

    Cluster:
        Description: A reference to the ECS cluster
        Value: !Ref ECSCluster