public inherited sharing class CreateOriginPicklistItem {
  public class Request {
    @InvocableVariable(required=true label='Picklist Item Name')
    public String picklistItemName;
  }

  public class Result {
    @InvocableVariable(label='Case Origin')
    public String caseOrigin;

    @InvocableVariable(label='Created')
    public Boolean created;

    @InvocableVariable(label='Metadata Full Name')
    public String metadataFullName;
  }

  @InvocableMethod(
    label='Create Origin Picklist Item'
    description='Adds a value to the Case Origin standard value set when it does not already exist.'
    category='Queue Configuration'
    callout=true
  )
  public static List<Result> createOrigin(List<Request> requests) {
    MetadataXml.require(
      requests != null && requests.size() == 1,
      'Create Origin Picklist Item accepts exactly one request per invocation.'
    );
    String label = requests[0].picklistItemName == null
      ? null
      : requests[0].picklistItemName.trim();
    MetadataXml.require(
      !String.isBlank(label),
      'Picklist Item Name is required.'
    );

    String developerName = MetadataXml.developerName(label);
    Dom.XmlNode valueSet = MetadataApiClient.readMetadata(
      'StandardValueSet',
      'CaseOrigin'
    );
    MetadataXml.require(
      valueSet != null,
      'The CaseOrigin standard value set was not found.'
    );

    for (
      Dom.XmlNode valueNode : MetadataXml.children(valueSet, 'standardValue')
    ) {
      String existingName = MetadataXml.text(valueNode, 'fullName');
      String existingLabel = MetadataXml.text(valueNode, 'label');
      if (
        label.equalsIgnoreCase(existingLabel) ||
        developerName.equalsIgnoreCase(existingName)
      ) {
        if (
          developerName.equalsIgnoreCase(existingName) &&
          !label.equalsIgnoreCase(existingLabel)
        ) {
          throw new IllegalArgumentException(
            'Case Origin developer name ' +
              developerName +
              ' is already used by the label "' +
              existingLabel +
              '".'
          );
        }
        return new List<Result>{ result(existingName, false) };
      }
    }

    String newValueXml =
      '<standardValue><fullName>' +
      MetadataXml.escape(developerName) +
      '</fullName><default>false</default><label>' +
      MetadataXml.escape(label) +
      '</label></standardValue>';
    MetadataApiClient.updateMetadata(
      'StandardValueSet',
      MetadataXml.serializeChildren(valueSet) + newValueXml
    );
    return new List<Result>{ result(developerName, true) };
  }

  private static Result result(String caseOrigin, Boolean created) {
    Result value = new Result();
    value.caseOrigin = caseOrigin;
    value.created = created;
    value.metadataFullName = 'CaseOrigin';
    return value;
  }
}