---
AWSTemplateFormatVersion: '2010-09-09'
Parameters:
  SubnetIndex:
    Description: 'Index of the subnet'
    Type: Number
    MinValue: 0
    MaxValue: 5
  SubnetCount:
    Description: 'To slice the IP address ranges you need to specify how many subnets you want to create in the VPC'
    Type: Number
    MinValue: 1
    MaxValue: 6
  Size:
    Type: String
  FirstTierSubnet1CIDR:
    Type: String
Mappings:
  CidrBitsMap:
    "2":
      AZCidrBits: 16
Conditions:
  IsProd: !Equals [!Ref AWS::AccountId, '123456789012']
Resources:
  Subnet:
    Type: 'AWS::EC2::Subnet'
    Properties:
      CidrBlock: !Select [!Ref SubnetIndex, !Cidr [{'Fn::ImportValue': 'vpc-CidrBlock'}, !Ref SubnetCount, 12]]
      VpcId: 'vpc-123456'
  SubnetWihtMap:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: 'vpc-123456'
      CidrBlock: !Select [ 2, !Cidr [ {'Fn::ImportValue': 'vpc-CidrBlock'}, 4, !FindInMap [CidrBitsMap, !Ref Size, AZCidrBits] ]]
  MyVPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
  SubnetWithConditions:
      Type: AWS::EC2::Subnet
      Properties:
        # /28 block #1 (VPC Allocation), inside /26 block #3, inside /24 block #3 (prod) or block #15 (non-prod)
        CidrBlock:
          Fn::Select:
          - 1
          - Fn::Cidr:
            - Fn::Select:
              - 3
              - Fn::Cidr:
                - Fn::If:
                  - IsProd
                  - Fn::Select:
                    - 3
                    - Fn::Cidr:
                      - Fn::GetAtt: MyVPC.CidrBlock
                      - 4
                      - 8
                  - Fn::Select:
                    - 15
                    - Fn::Cidr:
                      - Fn::GetAtt: MyVPC.CidrBlock
                      - 16
                      - 8
                - 4
                - 6
            - 2
            - 4
        VpcId: 'vpc-123456'
  PublicSubnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref MyVPC
      AvailabilityZone: !Select [0, !GetAZs ""]
      CidrBlock: !If
          - IsProd
          - !Ref FirstTierSubnet1CIDR
          - !Select
            - 0
            - !Cidr
              - 10.0.0.0/24
              - !If [IsProd, 16, 8]
              - 4