Description: >
  This template deploys a VPC, with a pair of public and private subnets spread 
  across two Availabilty Zones. It deploys an Internet Gateway, with a default 
  route on the public subnets. It deploys a pair of NAT Gateways (one in each AZ), 
  and default routes for them in the private subnets.

Parameters:

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

  VpcCIDR: 
    Description: Please enter the IP range (CIDR notation) for this VPC
    Type: String
    Default: 10.0.0.0/16

  PublicSubnet1CIDR:
    Description: Please enter the IP range (CIDR notation) for the public subnet in the first Availability Zone
    Type: String
    Default: 10.0.0.0/19

  PublicSubnet2CIDR:
    Description: Please enter the IP range (CIDR notation) for the public subnet in the second Availability Zone
    Type: String
    Default: 10.0.32.0/19

  PrivateSubnet1CIDR:
    Description: Please enter the IP range (CIDR notation) for the private subnet in the first Availability Zone
    Type: String
    Default: 10.0.64.0/19

  PrivateSubnet2CIDR:
    Description: Please enter the IP range (CIDR notation) for the private subnet in the second Availability Zone
    Type: String
    Default: 10.0.96.0/19

Resources:

  VPC: 
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: !Ref VpcCIDR
      EnableDnsHostnames: true
      Tags: 
        - Key: Name 
          Value: !Ref EnvironmentName
      
  InternetGateway:
    Type: AWS::EC2::InternetGateway
    Properties:
      Tags:
        - Key: Name
          Value: !Ref EnvironmentName
      
  InternetGatewayAttachment:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      InternetGatewayId: !Ref InternetGateway
      VpcId: !Ref VPC

  PublicSubnet1: 
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone: !Select [ 0, !GetAZs '' ]
      CidrBlock: !Ref PublicSubnet1CIDR
      MapPublicIpOnLaunch: true
      Tags: 
        - Key: Name 
          Value: !Sub ${EnvironmentName} Public Subnet (AZ1)

  PublicSubnet2: 
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone: !Select [ 1, !GetAZs '' ]
      CidrBlock: !Ref PublicSubnet2CIDR
      MapPublicIpOnLaunch: true
      Tags: 
        - Key: Name 
          Value: !Sub ${EnvironmentName} Public Subnet (AZ2)

  PrivateSubnet1: 
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone: !Select [ 0, !GetAZs '' ]
      CidrBlock: !Ref PrivateSubnet1CIDR
      MapPublicIpOnLaunch: false
      Tags: 
        - Key: Name 
          Value: !Sub ${EnvironmentName} Private Subnet (AZ1)
        - Key: "kubernetes.io/role/internal-elb"
          Value: "1"

  PrivateSubnet2: 
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone: !Select [ 1, !GetAZs '' ]
      CidrBlock: !Ref PrivateSubnet2CIDR
      MapPublicIpOnLaunch: false
      Tags: 
        - Key: Name 
          Value: !Sub ${EnvironmentName} Private Subnet (AZ2)
        - Key: "kubernetes.io/role/internal-elb"
          Value: "1"

  NatGateway1EIP:
    Type: AWS::EC2::EIP
    DependsOn: InternetGatewayAttachment
    Properties: 
      Domain: vpc

  NatGateway2EIP:
    Type: AWS::EC2::EIP
    DependsOn: InternetGatewayAttachment
    Properties:
      Domain: vpc

  NatGateway1: 
    Type: AWS::EC2::NatGateway
    Properties: 
      AllocationId: !GetAtt NatGateway1EIP.AllocationId
      SubnetId: !Ref PublicSubnet1

  NatGateway2: 
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt NatGateway2EIP.AllocationId
      SubnetId: !Ref PublicSubnet2

  PublicRouteTable:
    Type: AWS::EC2::RouteTable
    Properties: 
      VpcId: !Ref VPC
      Tags: 
        - Key: Name 
          Value: !Sub ${EnvironmentName} Public Routes

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

  PublicSubnet1RouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PublicRouteTable
      SubnetId: !Ref PublicSubnet1

  PublicSubnet2RouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PublicRouteTable
      SubnetId: !Ref PublicSubnet2
  

  PrivateRouteTable1:
    Type: AWS::EC2::RouteTable
    Properties: 
      VpcId: !Ref VPC
      Tags: 
        - Key: Name 
          Value: !Sub ${EnvironmentName} Private Routes (AZ1)

  DefaultPrivateRoute1:
    Type: AWS::EC2::Route
    Properties:
      RouteTableId: !Ref PrivateRouteTable1
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId: !Ref NatGateway1

  PrivateSubnet1RouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PrivateRouteTable1
      SubnetId: !Ref PrivateSubnet1

  PrivateRouteTable2:
    Type: AWS::EC2::RouteTable
    Properties: 
      VpcId: !Ref VPC
      Tags: 
        - Key: Name 
          Value: !Sub ${EnvironmentName} Private Routes (AZ2)

  DefaultPrivateRoute2:
    Type: AWS::EC2::Route
    Properties:
      RouteTableId: !Ref PrivateRouteTable2
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId: !Ref NatGateway2

  PrivateSubnet2RouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PrivateRouteTable2
      SubnetId: !Ref PrivateSubnet2

Outputs: 

  VPC: 
    Description: A reference to the created VPC
    Value: !Ref VPC
    Export: 
      Name: !Sub "${EnvironmentName}:VPC"

  PublicSubnet1:
    Description: A reference to the public subnet in the 1st Availability Zone
    Value: !Ref PublicSubnet1
    Export: 
      Name: !Sub "${EnvironmentName}:PublicSubnet1"

  PublicSubnet2: 
    Description: A reference to the public subnet in the 2nd Availability Zone
    Value: !Ref PublicSubnet2
    Export: 
      Name: !Sub "${EnvironmentName}:PublicSubnet2"

  PrivateSubnet1:
    Description: A reference to the private subnet in the 1st Availability Zone
    Value: !Ref PrivateSubnet1
    Export: 
      Name: !Sub "${EnvironmentName}:PrivateSubnet1"

  PrivateSubnet2: 
    Description: A reference to the private subnet in the 2nd Availability Zone
    Value: !Ref PrivateSubnet2
    Export: 
      Name: !Sub "${EnvironmentName}:PrivateSubnet2"

  VpcCIDR:
    Description: VPC CIDR
    Value: !Ref VpcCIDR
    Export:
      Name: !Sub "${EnvironmentName}:VpcCIDR"