Description: Create Web servers and ELB

Parameters:
  VPCID:
    Type: "AWS::EC2::VPC::Id"
    Description: Enter a valid VPC Id
  PrivateSubnet1:
    Type: "AWS::EC2::Subnet::Id"
    Description: Enter a valid SubnetId of private subnet in AZ1
  PrivateSubnet2:
    Type: "AWS::EC2::Subnet::Id"
    Description: Enter a valid SubnetId of private subnet in AZ2
  PublicSubnet1:
    Type: "AWS::EC2::Subnet::Id"
    Description: Enter a valid SubnetId of public subnet in AZ1
  PublicSubnet2:
    Type: "AWS::EC2::Subnet::Id"
    Description: Enter a valid SubnetId of public subnet in AZ2
  KeyPair:
    Type: "AWS::EC2::KeyPair::KeyName"
    Description: Enter a valid KeyPair Name
  AMIId:
    Type: "AWS::EC2::Image::Id"
    Description: Enter a valid AMI ID to launch the instance
  WebSG:
    Type: "AWS::EC2::SecurityGroup::Id"
    Description: Enter a valid security group ID for web server
  DBClientSG:
    Type: "AWS::EC2::SecurityGroup::Id"
    Description: Enter a valid security group ID for web server to enable DB access
  ELBSG:
    Type: "AWS::EC2::SecurityGroup::Id"
    Description: Enter a valid security group ID for ELB
  WebIAMProfile:
    Type: String
    Description: Enter ARN of IAM Instance Profile to be attached to web server
  WebInstanceType:
    Type: String
    Description: Enter one of the possible instance type for web server
    AllowedValues:
      - t2.large
      - m4.large
      - m4.xlarge
      - c4.large
  WebMinSize:
    Type: String
    Description: Minimum number of instances in auto scaling group
  WebMaxSize:
    Type: String
    Description: Maximum number of instances in auto scaling group
  Environment:
    Type: String
    Description: Select the appropriate environment
    AllowedValues:
      - dev
      - test
      - uat
      - prod

Resources:
  WebELB:
    Type: "AWS::ElasticLoadBalancing::LoadBalancer"
    Properties:
      LoadBalancerName:
        Fn::Sub: WebELB-${Environment}
      Scheme: internet-facing
      CrossZone: true
      Subnets:
      - Ref: PublicSubnet1
      - Ref: PublicSubnet2
      SecurityGroups:
        - Ref: ELBSG
      Listeners:
        - LoadBalancerPort: '80'
          InstancePort: '80'
          Protocol: HTTP
      HealthCheck:
        Target: HTTP:80/
        HealthyThreshold: '3'
        UnhealthyThreshold: '5'
        Interval: '6'
        Timeout: '5'
      ConnectionDrainingPolicy:
        Enabled: 'true'
        Timeout: '60'
      Tags:
        - Key: Name
          Value:
            Fn::Sub: WebELB-${Environment}

  WebServerLaunchConfig:
    Type: "AWS::AutoScaling::LaunchConfiguration"
    Properties:
      KeyName:
        Ref: KeyPair
      ImageId:
        Ref: AMIId
      UserData: IyEvYmluL2Jhc2gNCnl1bSB1cGRhdGUgLXkNCnl1bSBpbnN0YWxsIC15IGh0dHBkMjQNCnNlcnZpY2UgaHR0cGQgc3RhcnQNCmNoa2NvbmZpZyBodHRwZCBvbg==
      SecurityGroups:
        - Ref: WebSG
        - Ref: DBClientSG
      InstanceType:
        Ref: WebInstanceType
      IamInstanceProfile:
        Ref: WebIAMProfile

  WebServerASG:
    Type: "AWS::AutoScaling::AutoScalingGroup"
    Properties:
      VPCZoneIdentifier:
        - Ref: PrivateSubnet1
        - Ref: PrivateSubnet2
      LaunchConfigurationName:
        Ref: "WebServerLaunchConfig"
      MinSize:
        Ref: WebMinSize
      MaxSize:
        Ref: WebMaxSize
      LoadBalancerNames:
        - Ref: "WebELB"
      Tags:
        - Key: Name
          Value:
            Fn::Sub: WebServer-${Environment}
          PropagateAtLaunch: true

Outputs:
  WebELBURL:
      Description: "URL endpoint of web ELB"
      Value:
        Fn::GetAtt: [ WebELB, DNSName ]