AWSTemplateFormatVersion: '2010-09-09'
Description: Creates the dynamoDB table to hold state.  The table name is 'CanaryTable'
  
# This stack uses custom resources.  The following links were useful to me, as I never worked with custom resources before
# http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/walkthrough-custom-resources-lambda-lookup-amiids.html
# https://stackoverflow.com/questions/41452274/how-to-create-a-new-version-of-a-lambda-function-using-cloudformation
# https://stackoverflow.com/questions/42551408/putitem-in-dynamodb-table-by-cloudformation
Parameters:
  DNSName:
    Type: String
  OldLB:
    Type: String
  NewLB:
    Type: String
  HostedZoneID:
    Type: String
  LBZoneID:
    Type: String
  TargetGroup:
    Type: String
  
Resources:
  LambdaRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Principal:
            Service:
            - lambda.amazonaws.com
          Action:
          - sts:AssumeRole
      Path: "/"
      Policies:
        - PolicyName: dynamodbAccessRole
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
            - Effect: Allow
              Action:
              - dynamodb:*
              Resource: "*"
            - Effect: Allow
              Action:
              - logs:*
              Resource: "*"
              
  InitFunction:
    Type: AWS::Lambda::Function
    Properties:
      Code:
        ZipFile: |
          import json
          import cfnresponse
          import boto3
           
          dynamodb = boto3.resource('dynamodb', region_name='us-east-1')
          
          def handler(event, context):
            tableName = event['ResourceProperties']['DynamoTableName']
            newcontainername = event['ResourceProperties']['NewContainerName']
            oldlb = event['ResourceProperties']['OldLB']
            newlb = event['ResourceProperties']['NewLB']
            hostedzone = event['ResourceProperties']['HostedZoneID']
            lbzoneid = event['ResourceProperties']['LBZoneID']
            dnsname = event['ResourceProperties']['DNSName']
            dnsname = dnsname[:-1]
            targetgroup = event['ResourceProperties']['TargetGroup']
            
            table = dynamodb.Table(tableName)
            response = table.put_item(
              Item={
                'NewContainerName': newcontainername,
                'Triggered' : False,
                'RecordName': dnsname,
                'OldLB' : oldlb,
                'NewLB' : newlb,
                'HostedZoneID': hostedzone,
                'LBZoneID': lbzoneid,
                'TargetGroup': targetgroup
                })
            responseData = {}
            responseData['Data'] = response
            cfnresponse.send(event, context, cfnresponse.SUCCESS, responseData)
            return
      Handler: index.handler
      Role:
        Fn::GetAtt: [ LambdaRole , "Arn" ]
      Runtime: python3.6
      Timeout: 5
      
  DynamoDB:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: "CanaryTable"
      AttributeDefinitions: 
        - AttributeName: "NewContainerName"
          AttributeType: "S"
      KeySchema:
        - AttributeName: "NewContainerName"
          KeyType: "HASH"
      ProvisionedThroughput:
        ReadCapacityUnits: 5
        WriteCapacityUnits: 5
      
  InitializeDynamoDB:
    Type: Custom::InitFunction
    DependsOn: DynamoDB
    Properties:
      ServiceToken:
         Fn::GetAtt: [ InitFunction , "Arn" ]
      DynamoTableName: !Ref DynamoDB
      DNSName: !Ref DNSName
      OldLB: !Ref OldLB
      NewLB: !Ref NewLB
      NewContainerName: 'green-app'
      HostedZoneID: !Ref HostedZoneID
      LBZoneID: !Ref LBZoneID
      TargetGroup: !Ref TargetGroup