global class Qc_Responses {

    global AccountResponse accountResponse {get;set;}
    global list<ContactResponse> contactResponses {get;set;}
    global ExceptionResponse exceptionResponse {get;set;}

    public class AccountResponse
    {
        public String statusCode;
        public String sfAccountId;
        public String message;

        // account Responses for Success / error
        public AccountResponse(String statusCode, String accId){
            this.statusCode = statusCode;
            SFAccountId = accId;
            this.message = (String.isBlank(accId)) ? 'Account is not Created, Duplicate Account Found' : 'Account Created Successfully' ;
        }

    }

    public class ContactResponse{
        public String statusCode;
        public String message;
        public String sfContactid;
        public String email;
        public String lastName;
        public String phone;
        public ContactResponse(String statusCode,String message, String sfContactid, String email, String lastName, String phone){
            this.statusCode = statusCode;
            this.message = Message;
            this.sfContactid = sfContactid;
            this.email = email;
            this.phone = phone;
            this.lastName = lastName;
        }
    }

    public class ExceptionResponse {
        public String message;
        public String errorCode;
        public ExceptionResponse(String message, String errorcode){
            this.message = message;
            this.errorCode = errorcode;
        }
    }
}

{
    "exceptionResponse": null,
    "contactResponses": [
        {
            "statusCode": "201",
            "sfContactid": "0030k00000RpgLdAAJ",
            "phone": "+610212345678",
            "message": "1Contact(s) Created Successfully",
            "lastName": "Britto",
            "email": "sample1@salesforce.com"
        },
        {
            "statusCode": "201",
            "sfContactid": "0030k00000RpgLeAAJ",
            "phone": "+61-(02)-12346678",
            "message": "2Contact(s) Created Successfully",
            "lastName": "Smith",
            "email": "sample2@salesforce.com"
        }
    ],
    "accountResponse": {
        "statusCode": "201",
        "sfAccountId": "0010k00000PKwIpAAL",
        "message": "Account Created Successfully"
    }
}

@RestResource(urlMapping='/QACAcctServices/')
global with sharing class QAC_AccountServicesProcess
{

    // Instance variables here

    @HttpPost
    global static QAC_Responses dosomeProcess()
    {
        // All Responses from Salesforce after processing
        QAC_Responses qacResp = new QAC_Responses();
        QAC_Responses.AccountResponse myAccResp;
        QAC_Responses.ContactResponse myContResp;
        QAC_Responses.ExceptionResponse myExcepResp;

        // some object responses are returned as lists after processing
        list<QAC_Responses.ContactResponse> myContRespList = new list<QAC_Responses.ContactResponse>();

        // local variables for business logic

        // Getting REST JSON from Request and setting to Response codes
        RestRequest req = RestContext.request;
        RestResponse res = RestContext.response;
        receivedReq = req.requestBody.toString();

        try
        {
            system.debug(' @@ request 1 @@' +receivedReq);
            QAC_AccountServicesAPI acApi = QAC_AccountServicesAPI.parse(receivedReq);

                    QAC_AccountServicesAPI.AccountDetail accRecResp = acApi.agencyRegistration.accountDetail;

                        // insert Account records
                        createdAcc = doAccountCreation(accRecResp);
                        findObject = 'Account';
                        insert createdAcc;

                        if(createdAcc.Id != null)
                        {
                            res.statusCode = 201;
                            myAccResp = new QAC_Responses.AccountResponse('201',
                                                                          accRecResp.referenceId,
                                                                          createdAcc.Id,
                                                                          accRecResp.iataCode,
                                                                          //accRecResp.tidsCode,
                                                                          accRecResp.AgencyABN);

                            qacResp.accountResponse = myAccResp;

                        }

                        // insert Contact (or) ACR Records
                        for(QAC_AccountServicesAPI.ContactDetails contRecResp : accRecResp.contactDetails)
                        {
                            // do some logics here and add ..
                            newContactList.add(doContactCreation(contRecResp,createdAcc));
                        }
                        if(!newContactList.isEmpty())
                        {
                            findObject = 'Contact';
                            insert newContactList;
                            for(Contact eachContact : newContactList){
                                ++i;
                                if(eachContact.Id != null){
                                    res.statusCode = 201;
                                    myContResp = new QAC_Responses.contactResponse('201',i+'Contact(s) Created Successfully',
                                                                                   eachContact.Id,
                                                                                   eachContact.email,
                                                                                   eachContact.LastName,
                                                                                   eachContact.phone);
                                    myContRespList.add(myContResp);
                                }
                            }
                            i=0;
                            qacResp.contactResponses = myContRespList;
                        }
            system.debug('QAC Response**'+qacResp);
            return qacResp;
        }
        catch(Exception ex)
        {
            isException = true;

            res.statusCode = 400;
            String sfErrMessage = ex.getMessage();

            if(ex.getMessage().contains(':')){
                sfErrMessage = ex.getMessage().split(':')[1];
            }

            if(ex.getTypeName().contains('JSON')){
                jsonErrMessage = 'Issue with JSON Format. Please check your Payload';
            }
            else{
                res.statusCode = (findObject == 'Account') ? 500 : 201 ;
                jsonErrMessage = 'Found errors, Registration Process Failed for - '+findObject+'.Please contact Salesforce';
            }

            myExcepResp = new QAC_Responses.ExceptionResponse('400',jsonErrMessage,
                                                              'Exception Found',sfErrMessage);
            qacResp.exceptionResponse = myExcepResp;

            system.debug('QAC Response**'+qacResp);
            return qacResp;
        }
    }
}