sam.yml

AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: 'Publish messages received from SNS to Slack'
Resources:
  EventPublishSnsSubscription:
    Type: 'AWS::SNS::Subscription'
    Properties:
      TopicArn:
        'Fn::ImportValue':
          Ref: SnsPublisherTopicExport
      Protocol: lambda
      Endpoint:
        'Fn::GetAtt':
          - SlackPublish
          - Arn
  SlackResponseSnsTopic:
    Type: 'AWS::SNS::Topic'
  SlackPublish:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: handlers/aws_sns_to_slack_publisher.handler
      Runtime: python3.6
      Description: Publish message from SNS to Slack
      MemorySize: 128
      Timeout: 60
      Environment:
        Variables:
          LOG_LEVEL: INFO
          SLACK_API_TOKEN:
            Ref: SlackApiToken
          SLACK_DEFAULT_CHANNEL:
            Ref: SlackDefaultChannel
          SNS_PUBLISH_RESPONSE:
            Ref: SnsPublishResponse
          RESPONSE_SNS_TOPIC_ARN:
            Ref: SlackResponseSnsTopic
      Events:
        SnsMessage:
          Type: SNS
          Properties:
            Topic:
              Fn::ImportValue:
                Ref: SnsPublisherTopicExport
      Policies:
        - SNSPublishMessagePolicy:
            TopicName:
              Ref: SlackResponseSnsTopic
Outputs:
  SlackResponseSnsTopicArn:
    Description: AWS SNS Topic ARN
    Value:
      Ref: SlackResponseSnsTopic
    Export:
      Name:
        Fn::Sub: ${AWS::StackName}-SlackResponseSnsTopicArn
Parameters:
  SlackApiToken:
    Type: String
    Description: Slack API token
  SlackDefaultChannel:
    Type: String
    Description: Slack channel to publish to.
    Default: notifications
  SnsPublishResponse:
    Type: String
    Description: Whether or not to publish function response to Sns
    Default: 'false'
    AllowedValues:
      - true
      - false
  SnsPublisherTopicExport:
    Type: String
    Description: Name of the CloudFormation export wit the Sns topic ARN to subscribe to