@RestResource(urlMapping='/Cases/*')

@HttpPut
global static ID upsertCase(String supplierId, String extUserId, String extFormId, String extFormType, String extFormName, String extUrl, String origin) {

    System.debug('upsertCase Call');

         list<RecordType> RecordTypeName = new List<RecordType>([SELECT Id FROM RecordType WHERE SObjectType = 'Case' and Name = 'ThirdPartyApp']);
        system.debug('recordTypeName : ' +RecordTypeName[0].Id);

        list<Account> accountName = new List<Account>([select Id from account where extid__c = :supplierID]);
        system.debug('accountName : ' +accountName[0].Id);

        List<Contact> contactName = new List<Contact>([select Id from contact where extuser_id__c = :extUserId]);
        system.debug('contactName : ' +contactName[0].id);

        system.debug('###1st extFormId : ' +extFormId);
        list<Case> existingCase = new List<Case>([select Id from case where extform_id__c = :extFormId]);
            /*if(existingCase.isempty() ) {
                existingCase[0].Id = null;
                  }    else {
                      existingCase[0].Id = null;
                  }*/
        system.debug('###2nd ExistingCase : ' +existingCase[0].id);

        Case thisCase = new Case(
        RecordTypeId                   = recordTypeName[0].Id,
        AccountId                      = accountName[0].Id,
        ContactId                      = contactName[0].Id,
        extForm_ID__C                  = extFormId,    // Need to use this field to determine existing or new case
        Type                           = extFormType,
        Subject                        = extFormName,
        extURL__C                      = extUrl,
        extUser_ID__c                  = extUserId,
        Status                         = 'New',
        Priority                       = 'Medium',
        Origin                         = origin,
        //Id                           = null);
        Id                             = existingCase[0].id);
    // Match case by Id, if present.
    // Otherwise, create new case.
    upsert thisCase;
    // Return the case ID.
    return thisCase.Id;
}