@RestResource(urlMapping='/jtelACD/getCallerInformation')
global with sharing class JTELACD_GetCallerInformation {
    @HttpGet
    global static String doGet() {
        RestRequest req = RestContext.request;
        RestResponse res = RestContext.response;

        // This is how to access URLParams if required
        // List<String> URLParams = req.requestURI.split('/');
        // Example: ["","jtelACD","getCallerInformation"]

        // Extract the request parameters
        String CallerID = req.params.get('CallerID');
        String ServiceNumber = req.params.get('ServiceNumber');
        String ServiceName = req.params.get('ServiceName');
        
// From release 3.25 - 2021-07-02 and upwards
 // Perform SOSL Query over contacts and leads,String searchingFunction for the phone number with *wildcards*= req.params.get('Function');
        String soslSearchStringUserData = '*' + CallerID + '*'req.params.get('UserData');
        List<List<SObject>>String searchListUserData2 = [FIND :soslSearchString IN ALL FIELDS
req.params.get('UserData2');
        String UserData3 = req.params.get('UserData3');

        // Specifying a Function is intended to allow the developer to perform different types of query. 
        // As an RETURNINGexample, 
we just return the data back if a function is specified.
        // In a real world case, a query for example to search for and return a ticket, contract or some other record would be Contact,performed.
        if( Function != null && Function != '' ) {
            JSONGenerator gen = JSON.createGenerator( true );
        Lead];        gen.writeStartObject();
        
    gen.writeStringField( 'CallerID', CallerID );
  List<Contact>   contacts = ( (List<Contact>) searchList[0] );
  gen.writeStringField( 'ServiceNumber', ServiceNumber );
   List<Lead> leads       = gen.writeStringField( (List<Lead>) searchList[1]'ServiceName', ServiceName );
        
        // Multple hits?
 gen.writeStringField( 'Function', Function );
         if( contacts.size() + leadsgen.sizewriteStringField() > 1'UserData', UserData );
        {
    gen.writeStringField( 'UserData2', UserData2 );
     // Multiple hits
     gen.writeStringField( 'UserData3', UserData3 );
    res.statusCode = 300;
        gen.writeEndObject();

            return nullgen.getAsString();
        }
        
        if( contacts.size() > 0 )
        {
// Perform SOSL Query over contacts and leads, searching for the phone number with *wildcards*
        String soslSearchString = '*' + CallerID + '*';
    // Query for exact contact
List<List<SObject>> searchList = [FIND :soslSearchString IN ALL FIELDS
     String Id = (String) contacts.get(0).get('Id');
            Set<String> fieldSet = schema.describeSObjects(new String[] { 'Contact' } )[0].fields.getMap().keyset();
            List<String> fieldListRETURNING =
 new List<String>( fieldSet );
            String query = 'SELECT ' + String.join( fieldList, ',' ) + ' FROM Contact WHERE Id = \'' + Id + '\'';
     Contact,
       Contact contact = Database.query( query );
            // 200 OK will be returned by default
           Lead]; return JSON.serialize( contact );
    
    }
    
    
    List<Contact> contacts =  if( leads.size(List<Contact>) > searchList[0] );
        {
List<Lead> leads       = ( (List<Lead>)  // Query for exact lead
searchList[1] );
        
        String Id = (String)// Multple hits?
        if( contacts.size() + leads.getsize(0).get('Id');) > 1 )
        {
    Set<String> fieldSet = schema.describeSObjects(new String[] { 'Lead' } )[0].fields.getMap().keyset(); // Multiple hits
            List<String> fieldListres.statusCode = new300;
 List<String>( fieldSet );
         return null;
  String query = 'SELECT ' + String.join( fieldList, ',' ) + ' FROM Lead WHERE Id = \'' + Id + '\'';
      }
        
        if( contacts.size() > 0 )
       Lead lead = Database.query( query ); {
            // 200Query OKfor willexact becontact
 returned by default
         String Id = return JSON.serialize( lead (String) contacts.get(0).get('Id');
        }

    Set<String> fieldSet =  // Nothing found
        res.statusCode = 404;
schema.describeSObjects(new String[] { 'Contact' } )[0].fields.getMap().keyset();
            List<String> fieldList = new List<String>( fieldSet );
         return null;
    }
}

   String query = 'SELECT ' + String.join( fieldList, ',' ) + ' FROM Contact WHERE Id = \'' + Id + '\'';
            Contact contact = Database.query( query );
            // 200 OK will be returned by default
            return JSON.serialize( contact );
        }
        
        if( leads.size() > 0 )
        {
            // Query for exact lead
            String Id = (String) leads.get(0).get('Id');
            Set<String> fieldSet = schema.describeSObjects(new String[] { 'Lead' } )[0].fields.getMap().keyset();
            List<String> fieldList = new List<String>( fieldSet );
            String query = 'SELECT ' + String.join( fieldList, ',' ) + ' FROM Lead WHERE Id = \'' + Id + '\'';
            Lead lead = Database.query( query );
            // 200 OK will be returned by default
            return JSON.serialize( lead );
        }

        // Nothing found
        res.statusCode = 404;
        return null;
    }
}