module.exports = (resource, logicalId) => {
  // different resource types
  const lambdaResourceGroup = 'Lambda';
  const stepFunctionResourceGroup = 'StepFunctions';
  const apiResourceGroup = 'API';
  const logsResourceGroup = 'Logs';
  const iamResourceGroup = 'IAM';

  // first figure out which type it is so we can determine which
  // nested stack it should go into
  let resourceGroup = '';
  if (
    resource.Type.startsWith('AWS::Lambda::') ||
    resource.Type === 'Custom::S3' ||
    resource.Type === 'AWS::Events::Rule'
  ) {
    resourceGroup = lambdaResourceGroup;
  } else if (resource.Type.startsWith('AWS::StepFunctions::')) {
    resourceGroup = stepFunctionResourceGroup;
  } else if (resource.Type.startsWith('AWS::ApiGateway::')) {
    resourceGroup = apiResourceGroup;
  } else if (resource.Type.startsWith('AWS::Logs::')) {
    resourceGroup = logsResourceGroup;
  } else if (resource.Type.startsWith('AWS::IAM::')) {
    resourceGroup = iamResourceGroup;
  }
  // nothing matching goes to root stack
  else {
    return false;
  }

  // some overrides for sending things to the main stack
  // so the nested stacks have limited dependencies between each other

  // api gateway deployment
  if (resource.Type === 'AWS::ApiGateway::Deployment') {
    return false;
  }
  // common request validator
  else if (resource.Type === 'AWS::ApiGateway::RequestValidator') {
    return false;
  }
  // custom resources lambda created by serverless...
  else if (
    logicalId === 'CustomDashresourceDashexistingDashs3LambdaFunction' ||
    logicalId === 'IamRoleCustomResourcesLambdaExecution'
  ) {
    return false;
  }

  // We need some special handling for different resources
  // because their naming conventions are different and we need a way
  // to group them alphabetically
  let identifier = logicalId.toLowerCase();
  if (resource.Type === 'AWS::ApiGateway::Method') {
    identifier = identifier.replace(/^apigatewaymethod/, '');
  } else if (resource.Type === 'AWS::ApiGateway::Resource') {
    identifier = identifier.replace(/^apigatewayresource/, '');
  } else if (resource.Type === 'AWS::StepFunctions::StateMachine') {
    identifier = resource.Properties.StateMachineName.split('-').pop();
  } else if (resource.Type === 'AWS::IAM::Role') {
    if (identifier.startsWith('app')) {
      identifier = identifier.split('dash').pop();
    }
  } else if (resource.Type === 'Custom::S3') {
    identifier = resource.Properties.FunctionName.split('-').pop();
  }

  // we will split stacks for the resources that we need to split
  if ([apiResourceGroup, lambdaResourceGroup, logsResourceGroup].includes(resourceGroup)) {
    const index = getStackIndex(identifier);
    return { destination: `${resourceGroup}${index}` };
  }
  // otherwise we just have 1 stack for the group
  else {
    return { destination: resourceGroup };
  }
};

// Function to determine stack index by first letter
function getStackIndex(identifier) {
  const firstLetter = identifier.charAt(0);
  if (!firstLetter.match(/[a-z]/)) return 1; // Non-alphabetical defaults to 1.. unlikely anything falls into this case

  const letterGroups = ['abcd', 'efgh', 'ijkl', 'mnop', 'qrs', 'tuvwxyz'];
  for (let i = 0; i < letterGroups.length; i++) {
    if (letterGroups[i].includes(firstLetter)) {
      return i + 1;
    }
  }
}