---
AWSTemplateFormatVersion: "2010-09-09"
Description: "Create a Lambda function that will take a comma seperated list of key=value pairs and return an array of key value pairs that can then be used in cloudformation tags resource parameter"

Resources:
  LambdaExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      ManagedPolicyArns:
       - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service:
              - lambda.amazonaws.com
            Action:
            - sts:AssumeRole
  LambdaTagParser:
    Type: AWS::Lambda::Function
    Properties:
      Handler: index.main
      Role:
        Fn::GetAtt: 
          - LambdaExecutionRole
          - Arn
      Runtime: nodejs6.10
      Code:
        ZipFile: |
              exports.main = (event, context, callback) => {
                  let keyPairString = event.ResourceProperties.data;
                  let keyPairs = keyPairString.split(',').map( item => ({ Key: item.split('=')[0], Value: item.split('=')[1]}));
                  
                 sendResponse(event,context,"SUCCESS", { result: keyPairs });
              };

              function sendResponse(event, context, status, data, err) {
                 var reason = err ? err.message : '';
                 var responseBody = {
                   StackId: event.StackId,
                   RequestId: event.RequestId,
                   LogicalResourceId: event.LogicalResourceId,
                   PhysicalResourceId: 'tagparser-' + JSON.stringify(event.ResourceProperties.data),
                   Status: status,
                   Data: data
                 };
                 console.log("RESPONSE:\n", JSON.stringify(responseBody));
                 var json = JSON.stringify(responseBody);

                 var https = require("https");
                 var url = require("url");

                 var parsedUrl = url.parse(event.ResponseURL);
                 var options = {
                     hostname: parsedUrl.hostname,
                     port: 443,
                     path: parsedUrl.path,
                     method: "PUT",
                     headers: {
                       "content-type": "",
                       "content-length": json.length
                     }
                   };

                 var request = https.request(options, function(response) {
                     console.log("STATUS: " + response.statusCode);
                     console.log("HEADERS: " + JSON.stringify(response.headers));
                     context.done(null, data);
                   });

                   request.on("error", function(error) {
                     console.log("sendResponse Error:\n", error);
                     context.done(error);
                   });

                   request.on("end", function() {
                     console.log("end");
                   });
                   request.write(json);
                   request.end();
              }

Outputs:
  TemplateId:
    Description: "Template ID"
    Value: "LambdaTagParser"
  StackName:
    Description: "Stack Name"
    Value: !Sub "${AWS::StackName}"
  FunctionArn:
    Description: "Function ARN"
    Value: !Ref LambdaTagParser
    Export:
      Name: !Sub '${AWS::StackName}-FunctionArn'