// **************************************************************************** 
//
// Author: Mihaly Novak 
// Date  : 12 May 2022 
// -------------------
// 
// Description: 
// ------------
//
// The main of our application at the state where we stopped at the end of day3
// I added comments that explain some of the details. This is the state where 
// we start developing further our application at the beginning of day4:
//  - first we will add User Interaction possibilities
//  - then we will extend our application with (optinal) user actions  
//    that will make possible to collect some infomation during teh simualtion 
//          
// **************************************************************************** 


// for some Geant4 types and io
#include "globals.hh"


// to obtain a run manager, the top level manager
// - where we need to register our detector, physics
//   and action objects after their construction
// - that controls the complete flow of initialisation
//   and simulation 
#include "G4RunManagerFactory.hh"


// for our detector implementation (mandatory)
#include "YourDetectorConstruction.hh"

// for our action implementation (mandatory) 
// this includes our primary generator action
#include "YourActionInitialization.hh"

// for the physics list (mandatory)
// (we use a reference physics list to keep is simple)
#include "G4PhysListFactory.hh"


// to able to use units e.g. CLHEP::cm
#include "G4SystemOfUnits.hh"

// only to set the tracking verbose to see that simulation happens 
// (see more on day4)
#include "G4UImanager.hh"


int main() {

  // ==============================================================================
  // Create the run manager then construct all mandatory user initializations and 
  // register them in the run manager  
  // ==============================================================================

  // Construct the run manager
  auto* runMgr = G4RunManagerFactory::CreateRunManager();

  // Construct our detector description object and register in the run manager
  YourDetectorConstruction* det = new YourDetectorConstruction();
  runMgr->SetUserInitialization( det );  

  // Construct a (reference: "FTFP_BERT") physics list and register in the run manager 
  const G4String plName = "FTFP_BERT"; 
  G4PhysListFactory plFactory;
  G4VModularPhysicsList* pl= plFactory.GetReferencePhysList(plName); 
  runMgr->SetUserInitialization( pl );
   
  // Construct our action initialization and register in the run manager 
  // ------------------------------------------------------------------------------
  // NOTE: it's action INITIALIZATION since it encapsulates the construction and 
  //       registration of ALL user ACTIONS (at least the primary generator action)
  YourActionInitialization* action = new YourActionInitialization(det);
  runMgr->SetUserInitialization( action );


  // ==============================================================================
  // The bare minimum setup is ready at this point, the simulation can be 
  // initialized and executed now
  // ==============================================================================


  // Ask the run manager to initialize the simulation
  // ------------------------------------------------------------------------------
  // NOTE: a chain of action will be done/triggered at this point by the run 
  //       manager calling some interace methods. First the Constrcut() interface
  //       method of our registerred detetctor construction as part of the 
  //       geometry initialization. Then the physics initialization is triggered
  //       by the run manager invoking the physics list ConstrcutParticles() and 
  //       ConstructProcesses() interafec methods (many more happens inside all).
  //
  // NOTE:
  //    - the interface methods that we have implemented are not necessarily 
  //      invoked at the construction of the given object but later at this 
  //      initialisation of only during the run
  //    - the complete initialization chain is invoked by the run maneger 
  //      before the very first run of an execution which is not necessarily 
  //      the case for subsequent runs
  //    - what is exactly re-constructed/re-initialised and how, might be 
  //      controlled by G4RunManager:
  //      + PhysicsHasBeenModified()  --> re-initialize physics 
  //      + GeometryHasBeenModified() --> re-compute some geometry optimisations
  //                                      (! the geometry is not re-constrcuted !)
  //      + ReinitializeGeometry()    --> re-initialize geometry by re-calling 
  //                                      the Construct() interface method of the 
  //                                      detector construction     
  // ------------------------------------------------------------------------------
  runMgr->Initialize();


  // NOTE: this is just to see that simulation actually indeed happens since we 
  //       could not see anything otherwise as long as we don't implement further,
  //       optional user actions. Those will make possible to interact with the 
  //       simulation during the process at each level and collect information 
  //       (see form day4).
  G4UImanager::GetUIpointer()->ApplyCommand("/tracking/verbose 1");

  // After the initialisation is done, we can ask the run manager to simulate
  // a given number of event (1 event this case)
  runMgr->BeamOn(1);


  
  // When the very first run is completed, we might change the target thickness
  // ------------------------------------------------------------------------------
  // We can investigate:
  //  - if our `soft` solution, implemented in the detector construction to handle
  //    the possible change of the target thickness/material works fine (yes)
  //  - we can see that we need to update by hand the gun-position! We do this
  //    now (temporarily) inside our `YourPrimaryGenerator::GeneratePrimaries()`
  //    interafec method. Please see the related comments there.
  //
  //  - we might deactivate the `soft` solution related code in our detector 
  //    constrcution and try to see what happens (target is not resized then)
  //  - try to call again runMgr->Initialize() and see if it helps (NO, it  
  //    doesn't see above at runMgr->Initialize() why!)  
  //  - we can try runMgr->GeometryHasBeenModified() and see if it helps (NO, 
  //    doesn't and see above at runMgr->Initialize() why!)
  //  - we can try then runMgr->ReinitializeGeometry() that will work well! 
  //    (also possible with UI command e.g. "/run/reinitializeGeometry"
  // ------------------------------------------------------------------------------
  // 
  // Chnage the target thickness (from the default 1 cm) to 10 cm now
  det->SetTargetThickness(10*CLHEP::cm); 

  // Simulate 1 event again and inspect the output (thanks to tracking verbose 1)
  runMgr->BeamOn(1);



  // Delete the run manager at the end of the run
  delete runMgr;
  
  return 0;
}