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/// \file B1/src/DetectorConstruction.cc
/// \brief Implementation of the B1::DetectorConstruction class

#include "DetectorConstruction.hh"

#include "G4Box.hh"
#include "G4Orb.hh"
#include "G4LogicalVolume.hh"
#include "G4NistManager.hh"
#include "G4PVPlacement.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

namespace B1
{

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

G4VPhysicalVolume* DetectorConstruction::Construct()
{
  // Get nist material manager
  G4NistManager* nist = G4NistManager::Instance();

  // Envelope parameters
  G4double env_sizeXY = 3*cm, env_sizeZ = 30*cm;
  G4Material* env_mat = nist->FindOrBuildMaterial("G4_AIR");

  // Option to switch on/off the overlap check
  G4bool checkOverlaps = false;

  // World
  G4double world_sizeXY = 1.2 * env_sizeXY;
  G4double world_sizeZ  = 1.2 * env_sizeZ;
  G4Material* world_mat = nist->FindOrBuildMaterial("G4_AIR");

  auto solidWorld = new G4Box("World", 0.5*world_sizeXY, 0.5*world_sizeXY, 0.5*world_sizeZ);
  auto logicWorld = new G4LogicalVolume(solidWorld, world_mat, "World");
  auto physWorld  = new G4PVPlacement(nullptr, G4ThreeVector(), logicWorld, "World", nullptr,
                                     false, 0, checkOverlaps);

  // Envelope
  auto solidEnv = new G4Box("Envelope", 0.5*env_sizeXY, 0.5*env_sizeXY, 0.5*env_sizeZ);
  auto logicEnv = new G4LogicalVolume(solidEnv, env_mat, "Envelope");
  new G4PVPlacement(nullptr, G4ThreeVector(), logicEnv, "Envelope", logicWorld,
                    false, 0, checkOverlaps);

  // Construct detector
  constexpr G4int NP = 30000;     // required number of spheres
  constexpr G4int NSLICE = 200;   // number of slices
  constexpr G4double r = 0.5*mm;  // radius of a sphere
  constexpr G4double DMIN = 2*r;  // min distance between two spheres

  // Construct logical volume for Box
  G4double dx = 1*cm, dy = 1*cm, dz = 10*cm; // box dimentions
  G4Material* box_material = nist->FindOrBuildMaterial("G4_AIR");

  auto box = new G4Box("Box", dx, dy, dz);
  auto box_logical = new G4LogicalVolume(box, box_material, "Box");
  new G4PVPlacement(0, G4ThreeVector(), box_logical, "Box", logicEnv,
                    false, 0, checkOverlaps);

  // Generate positions inside Box
  G4ThreeVector bmin, bmax;
  box->BoundingLimits(bmin, bmax); // get bounding box
  std::vector<G4ThreeVector> positions[NSLICE];
  G4int nspheres = 0;
  G4double delz = 2*dz/NSLICE; // width of a slice
  while (nspheres < NP) {
    G4double x = bmin.x() + (bmax.x() - bmin.x())*G4UniformRand();
    G4double y = bmin.y() + (bmax.y() - bmin.y())*G4UniformRand();
    G4double z = bmin.z() + (bmax.z() - bmin.z())*G4UniformRand();
    G4ThreeVector p(x, y, z);
    // check position
    G4bool accept = true;
    if (box->Inside(p) != kInside) continue;
    if (box->DistanceToOut(p) < 0.5*DMIN) continue;
    G4int icurr = (z - bmin.z())/delz;                       // current slice
    G4int iprev = (icurr ==   0) ? icurr : icurr - 1;        // previous slice
    G4int inext = (icurr == NSLICE - 1) ? icurr : icurr + 1; // next slice
    for (auto islice = iprev; islice <= inext; ++islice)
    {
      std::vector<G4ThreeVector>& pos = positions[islice];
      G4int size = pos.size();
      for (auto k = 0; k < size; ++k) {
        if ((pos[k] - p).mag() < DMIN) { accept = false; break; }
      }
      if (accept == false) break;
    }
    if (accept == true)
    {
      nspheres++;
      if (nspheres%1000 == 0) G4cout << "nspheres = " << nspheres << G4endl;
      positions[icurr].push_back(p); // add position to the list
    }
  }

  // create a logical volume for Spheres
  G4Material* sph_material = nist->FindOrBuildMaterial("G4_WATER");
  auto sphere = new G4Orb("Sphere", r);
  auto sph_logical = new G4LogicalVolume(sphere, sph_material, "Sphere");

  // create physical volumes for spheres
  for (auto islice = 0; islice < NSLICE; ++islice)
  {
    std::vector<G4ThreeVector>& pos = positions[islice];
    G4int size = pos.size();
    for (auto k = 0; k < size; ++k) {
      new G4PVPlacement(0, pos[k], sph_logical, "Sphere", box_logical,
                      false, 0, checkOverlaps);
    }
  }

  // create physical volume for Box
  fScoringVolume = box_logical;

  //
  // always return the physical World
  //
  return physWorld;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

}  // namespace B1