AWSTemplateFormatVersion: '2010-09-09'
Description: AWS Fargate cluster running containers in public and private subnets. Supports
             public facing microservices behind load balancer, private microservices, and private service discovery namespaces. Deployed resources are all tagged with defined environment name tag.
Mappings:
  # The VPC and subnet configuration is passed in via the environment spec.
  EnvironmentNameConfig:
    Environment:
      Name: '{{ environment.name}}'
  SubnetConfig:
    VPC:
      CIDR: '{{ environment.inputs.vpc_cidr}}'
    PublicOne:
      CIDR: '{{ environment.inputs.public_subnet_one_cidr}}'
    PublicTwo:
      CIDR: '{{ environment.inputs.public_subnet_two_cidr}}'
    PrivateOne:
      CIDR: '{{ environment.inputs.private_subnet_one_cidr}}'
    PrivateTwo:
      CIDR: '{{ environment.inputs.private_subnet_two_cidr}}'
  ServiceDiscoveryConfig:
    PrivateNamespace:
      Name: '{{ environment.inputs.service_discovery_namespace}}'

Resources:
 # Create the VPC with subnets across 2 Availability Zones, 2 Public subnets, 2 Private subnets,
 # an Internet Gateway, 2 Nat Gateways and the required routetables and routes
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: !FindInMap ['SubnetConfig', 'VPC', 'CIDR']
      EnableDnsHostnames: true
      EnableDnsSupport: true
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  InternetGateway:
    Type: AWS::EC2::InternetGateway
    Properties:
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  InternetGatewayAttachment:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      InternetGatewayId: !Ref InternetGateway
      VpcId: !Ref VPC

  PublicSubnetOne:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone:
        Fn::Select:
        - 0
        - Fn::GetAZs: {Ref: 'AWS::Region'}
      CidrBlock: !FindInMap ['SubnetConfig', 'PublicOne', 'CIDR']
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  PublicSubnetTwo:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone:
        Fn::Select:
        - 1
        - Fn::GetAZs: {Ref: 'AWS::Region'}
      CidrBlock: !FindInMap ['SubnetConfig', 'PublicTwo', 'CIDR']
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  PrivateSubnetOne:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone:
        Fn::Select:
        - 0
        - Fn::GetAZs: {Ref: 'AWS::Region'}
      CidrBlock: !FindInMap ['SubnetConfig', 'PrivateOne', 'CIDR']
      MapPublicIpOnLaunch: false
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  PrivateSubnetTwo:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone:
        Fn::Select:
        - 1
        - Fn::GetAZs: {Ref: 'AWS::Region'}
      CidrBlock: !FindInMap ['SubnetConfig', 'PrivateTwo', 'CIDR']
      MapPublicIpOnLaunch: false
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  NatGatewayOneEIP:
    Type: AWS::EC2::EIP
    DependsOn: InternetGatewayAttachment
    Properties:
      Domain: vpc
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  NatGatewayTwoEIP:
    Type: AWS::EC2::EIP
    DependsOn: InternetGatewayAttachment
    Properties:
      Domain: vpc
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  NatGatewayOne:
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt NatGatewayOneEIP.AllocationId
      SubnetId: !Ref PublicSubnetOne
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  NatGatewayTwo:
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt NatGatewayTwoEIP.AllocationId
      SubnetId: !Ref PublicSubnetTwo
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  PublicRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  DefaultPublicRoute:
    Type: AWS::EC2::Route
    DependsOn: InternetGatewayAttachment
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway

  PublicSubnetOneRouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PublicRouteTable
      SubnetId: !Ref PublicSubnetOne

  PublicSubnetTwoRouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PublicRouteTable
      SubnetId: !Ref PublicSubnetTwo

  PrivateRouteTableOne:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  DefaultPrivateRouteOne:
    Type: AWS::EC2::Route
    Properties:
      RouteTableId: !Ref PrivateRouteTableOne
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId: !Ref NatGatewayOne

  PrivateSubnetOneRouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PrivateRouteTableOne
      SubnetId: !Ref PrivateSubnetOne

  PrivateRouteTableTwo:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  DefaultPrivateRouteTwo:
    Type: AWS::EC2::Route
    Properties:
      RouteTableId: !Ref PrivateRouteTableTwo
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId: !Ref NatGatewayTwo

  PrivateSubnetTwoRouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PrivateRouteTableTwo
      SubnetId: !Ref PrivateSubnetTwo

  # Create a Private namespace for Service Discovery
  PrivateNamespace:
    Type: AWS::ServiceDiscovery::PrivateDnsNamespace
    Properties:
      Name: !FindInMap ['ServiceDiscoveryConfig', 'PrivateNamespace', 'Name']
      Vpc: !Ref 'VPC'

  # Create the ECS Cluster to schedule and orchestrate the Fargate containers
  ECSCluster:
    Type: AWS::ECS::Cluster
    Properties:
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  # A security group for the containers we will run in Fargate.
  # Rules are added to this security group based on what ingress you
  # add for the cluster.
  ContainerSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Access to the Fargate containers
      VpcId: !Ref 'VPC'
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

  # This is a role which is used by the ECS tasks themselves.
  ECSTaskExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Statement:
        - Effect: Allow
          Principal:
            Service: [ecs-tasks.amazonaws.com]
          Action: ['sts:AssumeRole']
      Path: /
      ManagedPolicyArns:
        - 'arn:aws:iam::aws:policy/service-role/AmazonECSTaskExecutionRolePolicy'
      Tags:
        - Key: Name
          Value: !FindInMap ['EnvironmentNameConfig', 'Environment', 'Name']

# These output values will be available to service templates to use.
Outputs:
  ClusterName:
    Description: The name of the ECS cluster
    Value: !Ref 'ECSCluster'
  ECSTaskExecutionRole:
    Description: The ARN of the ECS role
    Value: !GetAtt 'ECSTaskExecutionRole.Arn'
  VpcId:
    Description: The ID of the VPC that this stack is deployed in
    Value: !Ref 'VPC'
  PublicSubnetOne:
    Description: A reference to the public subnet in the 1st Availability Zone
    Value: !Ref 'PublicSubnetOne'
  PublicSubnetTwo:
    Description: A reference to the public subnet in the 2nd Availability Zone
    Value: !Ref 'PublicSubnetTwo'
  PrivateSubnetOne:
    Description: A reference to the private subnet in the 1st Availability Zone
    Value: !Ref 'PrivateSubnetOne'
  PrivateSubnetTwo:
    Description: A reference to the private subnet in the 2nd Availability Zone
    Value: !Ref 'PrivateSubnetTwo'
  ContainerSecurityGroup:
    Description: A security group used to allow Fargate containers to receive traffic
    Value: !Ref 'ContainerSecurityGroup'
  PrivateNamespace:
    Description: The NamespaceId registered for Service Discovery
    Value: !Ref 'PrivateNamespace'