serverless.yml

# <DESCRIBE SERVICE>
service: aws-sns-to-slack-publisher

plugins:
  - serverless-python-requirements
  - serverless-iam-roles-per-function
  - serverless-sam


custom:
  stage: "${opt:stage, env:SLS_STAGE, 'dev'}"
  profile: "${opt:aws-profile, env:AWS_PROFILE, env:AWS_DEFAULT_PROFILE, 'default'}"
  log_level: "${env:LOG_LEVEL, 'INFO'}"

  slack_api_token: "${env:SLACK_API_TOKEN, 'INSERT_TOKEN'}"
  # NOTE: passing in a default channel name with the leading '#' triggers an
  # issue with SLS variable interpolation
  slack_default_channel: "${env:SLACK_DEFAULT_CHANNEL, 'notifications'}"

  # If you don't need the SNS response published, then don't publish it.
  sns_publish_response: "${env:SNS_PUBLISH_RESPONSE, 'false'}"

  # Name of export to find SNS topic ARN to subscribe to.
  sns_publisher_topic_export: "${env:SNS_PUBLISHER_TOPIC_EXPORT, ''}"

  pythonRequirements:
    dockerizePip: false


provider:
  name: aws
  profile: ${self:custom.profile}
  stage: ${self:custom.stage}
  runtime: python3.6
  environment:
    LOG_LEVEL: ${self:custom.log_level}
  stackTags:
    x-service: aws-sns-to-slack-publisher
    x-stack: ${self:service}-${self:provider.stage}


functions:
  SlackPublish:
    handler: handlers/aws_sns_to_slack_publisher.handler
    description: "Publish message from SNS to Slack"
    memorySize: 128
    timeout: 60
    iamRoleStatements:
      - Effect: "Allow"
        Action: "SNS:Publish"
        Resource:
          Ref: SlackResponseSnsTopic
    environment:
      SLACK_API_TOKEN:
        Ref: SlackApiToken
      SLACK_DEFAULT_CHANNEL:
        Ref: SlackDefaultChannel
      SNS_PUBLISH_RESPONSE:
        Ref: SnsPublishResponse
      RESPONSE_SNS_TOPIC_ARN:
        Ref: SlackResponseSnsTopic


resources:

  Parameters:
    SlackApiToken:
      Type: String
      Description: "Slack API token"
      Default: "${self:custom.slack_api_token}"

    SlackDefaultChannel:
      Type: String
      Description: "Slack channel to publish to."
      Default: "${self:custom.slack_default_channel}"

    SnsPublishResponse:
      Type: String
      Description: "Whether or not to publish function response to Sns"
      Default: "${self:custom.sns_publish_response}"
      AllowedValues:
        - true
        - false

    SnsPublisherTopicExport:
      Type: String
      Description: "Name of the CloudFormation export wit the Sns topic ARN to subscribe to"
      Default: "${self:custom.sns_publisher_topic_export}"


  Resources:
    EventPublishSnsSubscription:
      Type: "AWS::SNS::Subscription"
      Properties:
        TopicArn:
          Fn::ImportValue:
            Ref: SnsPublisherTopicExport
        Protocol: lambda
        Endpoint:
          Fn::GetAtt:
            - SlackPublishLambdaFunction
            - Arn


    S3BillingItemWriterLambdaPermission:
      Type: 'AWS::Lambda::Permission'
      Properties:
        Action: "lambda:InvokeFunction"
        FunctionName:
          Ref: SlackPublishLambdaFunction
        Principal: 'sns.amazonaws.com'
        SourceArn:
          Fn::ImportValue:
            Ref: SnsPublisherTopicExport


    SlackResponseSnsTopic:
      Type: "AWS::SNS::Topic"


  Outputs:
    SlackResponseSnsTopicArn:
      Description: "AWS SNS Topic ARN"
      Value:
        Ref: SlackResponseSnsTopic
      Export:
        Name: "${self:service}-${self:provider.stage}-SlackResponseSnsTopicArn"