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AWSTemplateFormatVersion: "2010-09-09"
Transform: AWS::Serverless-2016-10-31
Description: >
  Send a base64 encoded payload to your LoRaWAN device by publishing to topic cmd/downlink/<AWSIoTCoreforLoRaWAN Device Id>

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Parameters:
  LoRaWANAFPort:
    Type: String
    Default: 1
    Description: FPort to use when sending messages

  LoRaWANTransmitMode:
    Type: Number
    Default: 1
    AllowedValues:
      - 0
      - 1
    Description: 0 for UM (unacknowledge mode), 1 for AM (acknowledge mode)

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Resources:
  SendDataToWirelessDeviceRule:
    Type: "AWS::IoT::TopicRule"
    Properties:
      RuleName: !Sub "${AWS::StackName}_SendDataToWirelessDeviceRule"
      TopicRulePayload:
        AwsIotSqlVersion: "2016-03-23"
        RuleDisabled: false
        Sql: !Sub
          - |
            SELECT aws_lambda("${LambdaARN}",
                              {"TransmitMode": ${TransmitMode}, 
                              "FPort": ${FPort},
                              "WirelessDeviceId": topic(3), 
                               "PayloadData":  encode(*, 'base64')}) as sendresult 
            FROM 'cmd/downlink/#'

          - {
              LambdaARN: !GetAtt SendDataToWirelessDeviceFunction.Arn,
              FPort: !Ref LoRaWANAFPort,
              TransmitMode: !Ref LoRaWANTransmitMode,
            }

        Actions:
          - Republish:
              RoleArn: !GetAtt SendDataToWirelessDeviceRuleRepublishRole.Arn
              Topic: downlink/status/${topic(3)}
              Qos: 0
        ErrorAction:
          Republish:
            RoleArn: !GetAtt SendDataToWirelessDeviceRuleRepublishRole.Arn
            Topic: downlink/error/${topic(3)}
            Qos: 0

  SendDataToWirelessDeviceRuleRepublishRole:
    Type: "AWS::IAM::Role"
    Properties:
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - iot.amazonaws.com
            Action:
              - "sts:AssumeRole"
      Policies:
        - PolicyName: root
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              - Effect: Allow
                Action: iot:Publish
                Resource:
                  !Join [
                    "",
                    [
                      "arn:aws:iot:",
                      !Ref "AWS::Region",
                      ":",
                      !Ref "AWS::AccountId",
                      ":topic/downlink/*",
                    ],
                  ]

  IoTPermissionForSendMessageToDeviceFunction:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !GetAtt SendDataToWirelessDeviceFunction.Arn
      Action: lambda:InvokeFunction
      Principal: iot.amazonaws.com

  SendDataToWirelessDeviceFunction:
    Type: AWS::Serverless::Function
    Name: !Sub "${AWS::StackName}-SendDataToWirelessDeviceFunction"
    Properties:
      CodeUri: src
      Handler: app.lambda_handler
      Runtime: python3.7
      Timeout: 10
      Policies:
        - Statement:
            - Sid: policy1
              Effect: Allow
              Action:
                - iotwireless:SendDataToWirelessDevice
              Resource: "*"

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Outputs:
  SendMessageToDeviceFunctionFunction:
    Description: "Lambda Function ARN"
    Value: !GetAtt SendDataToWirelessDeviceFunction.Arn
  SampleTopic:
    Description: "Use this topic to send a message, replacing <WirelessDeviceId> with the id of your AWS IoT Core for LoRaWAN device"
    Value: cmd/downlink/<WirelessDeviceId>
  SamplePayload:
    Description: "Sample payload (0x00 in base64)"
    Value: "AA=="