{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "Buiding a Dynamic DNS for Route 53 using Cloudwatch Events and Lambda based on https://github.com/awslabs/aws-lambda-ddns-function",
    "Parameters": {
        "LambdaBucketName": {
            "Description": "Name of S3 Bucket for where Lambda function zip files are uploaded to",
            "Type": "String",
            "MinLength": "3"
        }
    },
    "Resources": {
        "snsTopic" : {
            "Type" : "AWS::SNS::Topic",
            "Properties" : {
                "Subscription" : [{
                        "Endpoint" : "willrubel@gmail.com",
                        "Protocol" : "email"
                    }
                ],
                "TopicName" : "DDNSAlerts"
            }
        },
        "ddnslambdarole": {
            "Type": "AWS::IAM::Role",
            "Properties": {
                "AssumeRolePolicyDocument": {
                    "Version": "2012-10-17",
                    "Statement": [
                        {
                            "Sid": "",
                            "Effect": "Allow",
                            "Principal": {
                                "Service": "lambda.amazonaws.com"
                            },
                            "Action": "sts:AssumeRole"
                        }
                    ]
                },
                "RoleName": "ddns-lambda-role",
                "Policies": [
                    {
                        "PolicyName": "ddns-lambda-role",
                        "PolicyDocument": {
                            "Version": "2012-10-17",
                            "Statement": [
                                {
                                    "Effect": "Allow",
                                    "Action": "ec2:Describe*",
                                    "Resource": "*"
                                },
                                {
                                    "Effect": "Allow",
                                    "Action": [
                                        "dynamodb:*"
                                    ],
                                    "Resource": "*"
                                },
                                {
                                    "Effect": "Allow",
                                    "Action": [
                                        "logs:CreateLogGroup",
                                        "logs:CreateLogStream",
                                        "logs:PutLogEvents"
                                    ],
                                    "Resource": "*"
                                },
                                {
                                    "Effect": "Allow",
                                    "Action": [
                                        "route53:*"
                                    ],
                                    "Resource": [
                                        "*"
                                    ]
                                },
                                {
                                    "Effect": "Allow",
                                    "Action": [
                                        "SNS:Publish"
                                    ],
                                    "Resource": [

                                        { "Fn::Join": ["", [ "arn:aws:sns:",{"Ref":"AWS::Region"}, ":",{"Ref":"AWS::AccountId"},":DDNSAlerts"]]}
                                    ]

                                }
                            ]
                        }
                    }
                ]
            }
        },
        "ddnslambda": {
            "Type": "AWS::Lambda::Function",
            "Properties": {
                "Handler": "union.lambda_handler",
                "FunctionName": "ddns_lambda",
                "Description": "Create A and PTR records for Private Hosted Zone for EC2 instance launches",
                "Role": {
                    "Fn::GetAtt": [
                        "ddnslambdarole",
                        "Arn"
                    ]
                },
                "Code": {
                    "S3Bucket": {
                        "Ref": "LambdaBucketName"
                    },
                    "S3Key": "union.py.zip"
                },
                "Runtime": "python3.6",
                "Timeout": "90"
            }
        },
        "DdnsRule": {
            "Type": "AWS::Events::Rule",
            "Properties": {
                "Description": "trigger whenever CloudWatch detects a change to the state of an EC2 instance",
                "Name": "ec2_lambda_ddns_rule",
                "EventPattern": {
                    "source": [
                        "aws.ec2"
                    ],
                    "detail-type": [
                        "EC2 Instance State-change Notification"
                    ],
                    "detail": {
                        "state": [
                            "running",
                            "shutting-down",
                            "stopped"
                        ]
                    }
                },
                "State": "ENABLED",
                "Targets": [
                    {
                        "Arn": {
                            "Fn::GetAtt": [
                                "ddnslambda",
                                "Arn"
                            ]
                        },
                        "Id": "TargetFunctionV1"
                    }
                ]
            }
        },
        "PermissionForEventsToInvokeLambda": {
            "Type": "AWS::Lambda::Permission",
            "Properties": {
                "FunctionName": {
                    "Ref": "ddnslambda"
                },
                "Action": "lambda:InvokeFunction",
                "Principal": "events.amazonaws.com",
                "SourceArn": {
                    "Fn::GetAtt": [
                        "DdnsRule",
                        "Arn"
                    ]
                }
            }
        }
    },
    "Outputs": {}
}