#include "DetectorConstruction.hh"

#include "G4AutoDelete.hh"
#include "G4Box.hh"
#include "G4Colour.hh"
#include "G4GlobalMagFieldMessenger.hh"
#include "G4LogicalVolume.hh"
#include "G4Material.hh"
#include "G4NistManager.hh"
#include "G4PVPlacement.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4VisAttributes.hh"
#include "G4Tubs.hh"
#include "G4Element.hh"
#include "G4SubtractionSolid.hh"


namespace B4
{

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G4ThreadLocal G4GlobalMagFieldMessenger* DetectorConstruction::fMagFieldMessenger = nullptr;

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G4VPhysicalVolume* DetectorConstruction::Construct()
{
  DefineMaterials();
  return DefineVolumes();
}

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void DetectorConstruction::DefineMaterials()
{
  auto nistManager = G4NistManager::Instance();
  
  // Pre-defined materials
  nistManager->FindOrBuildMaterial("G4_AIR");
  nistManager->FindOrBuildMaterial("G4_Al");

  // --- MODIFICATION: Define BC-501A using official datasheet values ---

  // Get the necessary elements
  G4Element* elH = nistManager->FindOrBuildElement("H");
  G4Element* elC = nistManager->FindOrBuildElement("C");
  
  // Define the density of BC-501A from the official datasheet
  G4double density = 0.874 * g/cm3;
  
  // Create the BC-501A material with its density and 2 constituent elements
  G4Material* detectorMaterial = new G4Material("BC501A", density, 2);
  
  // Add the elements by their calculated mass fraction for highest accuracy
  detectorMaterial->AddElement(elH, 0.0921); // Hydrogen mass fraction (9.21%)
  detectorMaterial->AddElement(elC, 0.9079); // Carbon mass fraction (90.79%)
  
  // Print the material table to verify the new material is loaded
  G4cout << *(G4Material::GetMaterialTable()) << G4endl;
}

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G4VPhysicalVolume* DetectorConstruction::DefineVolumes()
{
  // Get materials
  auto airMaterial      = G4Material::GetMaterial("G4_AIR");
  auto housingMaterial  = G4Material::GetMaterial("G4_Al");
  // --- Ensure this line uses the correct material name ---
  auto detectorMaterial = G4Material::GetMaterial("BC501A");

  // World Volume (still required)
  auto worldSize = 15. * m;
  auto worldS = new G4Box("World", worldSize/2, worldSize/2, worldSize/2);
  auto worldLV = new G4LogicalVolume(worldS, airMaterial, "World");
  auto worldPV = new G4PVPlacement(nullptr, G4ThreeVector(), worldLV, "World", nullptr, false, 0, fCheckOverlaps);

  // --- Simplified Geometry: No concrete room ---

  // Detector Geometry Definitions (Unchanged)
  G4double scintRadius = (5. * 2.54 * cm) / 2.0;
  G4double scintHalfLength = (5. * 2.54 * cm) / 2.0;
  
  G4double sleeveThickness = 1.5 * mm;
  G4double backplateThickness = 1.5 * mm;

  // 1. The Cylindrical Sleeve (the walls)
  auto sleeveS = new G4Tubs("Sleeve", scintRadius, scintRadius + sleeveThickness, scintHalfLength, 0., 360.*deg);
  auto sleeveLV = new G4LogicalVolume(sleeveS, housingMaterial, "Sleeve");
  
  // 2. The Backplate (a thin solid disk)
  auto backplateS = new G4Tubs("Backplate", 0., scintRadius + sleeveThickness, backplateThickness/2.0, 0., 360.*deg);
  auto backplateLV = new G4LogicalVolume(backplateS, housingMaterial, "Backplate");

  // 3. The Scintillator Liquid
  auto scintS = new G4Tubs("Scintillator", 0., scintRadius, scintHalfLength, 0., 360.*deg);
  auto scintLV = new G4LogicalVolume(scintS, detectorMaterial, "Scintillator");
  
  // Detector Placement (Position is unchanged)
  G4double distanceFromSource = 1.5 * m;
  G4double detectorCenterZ = distanceFromSource + scintHalfLength;
  G4ThreeVector detectorPosition(0, 0, detectorCenterZ);
  G4ThreeVector backplatePosition = detectorPosition - G4ThreeVector(0, 0, scintHalfLength + backplateThickness/2.0);

  // --- Place the components directly INSIDE the World Volume ---
  new G4PVPlacement(nullptr, detectorPosition, sleeveLV, "Sleeve", worldLV, false, 0, fCheckOverlaps);
  auto scintPV = new G4PVPlacement(nullptr, detectorPosition, scintLV, "Scintillator", worldLV, false, 0, fCheckOverlaps);
  new G4PVPlacement(nullptr, backplatePosition, backplateLV, "Backplate", worldLV, false, 0, fCheckOverlaps);

  // Visualization Attributes
  worldLV->SetVisAttributes(G4VisAttributes::GetInvisible());
  sleeveLV->SetVisAttributes(new G4VisAttributes(G4Colour(0.5, 0.5, 0.5))); // Dark Grey
  backplateLV->SetVisAttributes(new G4VisAttributes(G4Colour(0.5, 0.5, 0.5))); // Dark Grey
  scintLV->SetVisAttributes(new G4VisAttributes(G4Colour(0.0, 1.0, 1.0))); // Cyan

  // Assign Scoring Volume (Unchanged)
  fAbsorberPV = scintPV;
  fGapPV = nullptr;

  return worldPV;
}

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void DetectorConstruction::ConstructSDandField()
{
  G4ThreeVector fieldValue;
  fMagFieldMessenger = new G4GlobalMagFieldMessenger(fieldValue);
  fMagFieldMessenger->SetVerboseLevel(1);
  G4AutoDelete::Register(fMagFieldMessenger);
}

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}  // namespace B4