AWSTemplateFormatVersion: 2010-09-09
Description: Create Macro Template
Resources:
    TransformExecutionRole:
        Type: AWS::IAM::Role
        Properties:
            AssumeRolePolicyDocument:
                Version: 2012-10-17
                Statement:
                    - Effect: Allow
                      Principal:
                        Service: [lambda.amazonaws.com]
                      Action: ['sts:AssumeRole']
            Path: /
            Policies:
                - PolicyName: root
                  PolicyDocument:
                    Version: 2012-10-17
                    Statement:
                        - Effect: Allow
                          Action: ['logs:*']
                          Resource: 'arn:aws:logs:*:*:*'
                        - Effect: Allow
                          Action: ['ec2:*']
                          Resource: '*'
    TransformFunctionPermissions:
        Type: AWS::Lambda::Permission
        Properties:
            Action: 'lambda:InvokeFunction'
            FunctionName: !GetAtt TransformFunction.Arn
            Principal: 'cloudformation.amazonaws.com'
    TransformFunction:
        Type: AWS::Lambda::Function
        Properties:
            Code:
                ZipFile: |
                  import boto3
                  import copy

                  def handler(event, context):

                    # Globals
                    region = event['region']
                    accountId = event['accountId']
                    fragment = event['fragment']
                    transformId = event['transformId']
                    params = event['params']
                    requestId = event['requestId']
                    templateParameterValues = event['templateParameterValues']

                    ec2 = boto3.client('ec2', region_name=region)

                    # Retrieves availability zones for this region
                    response = ec2.describe_availability_zones()
                    AZs = response['AvailabilityZones']

                    #Grab resources that need to be duplicated
                    VPCPubSn1 = fragment['Resources']['VPCPubSn1']
                    VPCPrivSn1 = fragment['Resources']['VPCPrivSn1']
                    PubSnRtAssoc1 = fragment['Resources']['VPCPubSn1RtAssoc']
                    PubSnRtAssoc1 = fragment['Resources']['VPCPrivSn1RtAssoc']

                    #iterate and add new resources
                    for i in range(1,len(AZs)+1): # Create a range from 1 - total number of AZs
                      if not i == 1:   # Only add resources if there is more than 1 AZ

                        # Create new Public Subnet based of VPCPubSN1
                        fragment['Resources']['VPCPubSn' + str(i)] = copy.deepcopy(VPCPubSn1)
                        fragment['Resources']['VPCPubSn' + str(i)]['Properties']['CidrBlock']['Fn::Select'][0] = i - 1
                        fragment['Resources']['VPCPubSn' + str(i)]['Properties']['AvailabilityZone']['Fn::Select'][0] = str(i - 1)

                        # Create new Private Subnet based of VPCPrivSN1
                        fragment['Resources']['VPCPrivSn' + str(i)] = copy.deepcopy(VPCPrivSn1)
                        fragment['Resources']['VPCPrivSn' + str(i)]['Properties']['CidrBlock']['Fn::Select'][0] = len(AZs) + i - 1
                        fragment['Resources']['VPCPrivSn' + str(i)]['Properties']['AvailabilityZone']['Fn::Select'][0] = str(i - 1)

                        # Create Public RT Association
                        fragment['Resources']['VPCPubSn' + str(i) + 'RtAssoc'] = {}
                        fragment['Resources']['VPCPubSn' + str(i) + 'RtAssoc']['Type'] = 'AWS::EC2::SubnetRouteTableAssociation'
                        fragment['Resources']['VPCPubSn' + str(i) + 'RtAssoc']['Properties'] = {}
                        fragment['Resources']['VPCPubSn' + str(i) + 'RtAssoc']['Properties']['RouteTableId'] = {}
                        fragment['Resources']['VPCPubSn' + str(i) + 'RtAssoc']['Properties']['RouteTableId']['Ref'] = 'VPCPubRt1'
                        fragment['Resources']['VPCPubSn' + str(i) + 'RtAssoc']['Properties']['SubnetId'] = {}
                        fragment['Resources']['VPCPubSn' + str(i) + 'RtAssoc']['Properties']['SubnetId']['Ref'] = 'VPCPubSn' + str(i)

                        # Create Private RT Association
                        fragment['Resources']['VPCPrivSn' + str(i) + 'RtAssoc'] = {}
                        fragment['Resources']['VPCPrivSn' + str(i) + 'RtAssoc']['Type'] = 'AWS::EC2::SubnetRouteTableAssociation'
                        fragment['Resources']['VPCPrivSn' + str(i) + 'RtAssoc']['Properties'] = {}
                        fragment['Resources']['VPCPrivSn' + str(i) + 'RtAssoc']['Properties']['RouteTableId'] = {}
                        fragment['Resources']['VPCPrivSn' + str(i) + 'RtAssoc']['Properties']['RouteTableId']['Ref'] = 'VPCPrivRt1'
                        fragment['Resources']['VPCPrivSn' + str(i) + 'RtAssoc']['Properties']['SubnetId'] = {}
                        fragment['Resources']['VPCPrivSn' + str(i) + 'RtAssoc']['Properties']['SubnetId']['Ref'] = 'VPCPrivSn' + str(i)

                    r = {}
                    r['requestId'] = requestId
                    r['status'] = 'SUCCESS'
                    r['fragment'] = fragment

                    return r

            Handler: index.handler
            Runtime: python3.6
            Timeout: '60'
            Role: !GetAtt TransformExecutionRole.Arn
    Transform:
        Type: AWS::CloudFormation::Macro
        Properties:
            Name: CreateSubnetsPerAZ
            Description: Macro to create Subnets for every available AZ
            FunctionName: !GetAtt TransformFunction.Arn