AWSTemplateFormatVersion: '2010-09-09'
Description: Redis, and any other resources that the chat app needs.
Parameters:
  EnvironmentName:
    Type: String
    Default: production
    Description: The environment name, used for locating outputs from the
                 prerequisite stacks
Resources:
  # Subnet group to control where the Redis gets placed
  RedisSubnetGroup:
    Type: AWS::ElastiCache::SubnetGroup
    Properties:
      Description: Group of subnets to place Redis into
      SubnetIds:
        - Fn::ImportValue:
            !Join [':', [!Ref 'EnvironmentName', 'PublicSubnetOne']]
        - Fn::ImportValue:
            !Join [':', [!Ref 'EnvironmentName', 'PublicSubnetTwo']]

  # Security group to add the Redis cluster to the VPC,
  # and to allow the Fargate containers to talk to Redis on port 6379
  RedisSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: "Redis Security Group"
      VpcId:
        Fn::ImportValue:
          !Join [':', [!Ref 'EnvironmentName', 'VPCId']]
  RedisIngress:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      Description: Ingress from Fargate containers
      GroupId: !Ref 'RedisSecurityGroup'
      IpProtocol: tcp
      FromPort: 6379
      ToPort: 6379
      SourceSecurityGroupId:
        Fn::ImportValue:
          !Join [':', [!Ref 'EnvironmentName', 'FargateContainerSecurityGroup']]

  # The cluster itself.
  Redis:
    Type: AWS::ElastiCache::CacheCluster
    Properties:
      Engine: redis
      CacheNodeType: cache.m4.large
      NumCacheNodes: 1
      CacheSubnetGroupName: !Ref 'RedisSubnetGroup'
      VpcSecurityGroupIds:
        - !GetAtt 'RedisSecurityGroup.GroupId'

Outputs:
  RedisEndpoint:
    Description: The endpoint of the redis cluster
    Value: !GetAtt 'Redis.RedisEndpoint.Address'
    Export:
      Name: !Join [ ':', [ !Ref 'EnvironmentName', 'RedisEndpoint' ] ]