/* This file is part of MAUS: http://micewww.pp.rl.ac.uk:8080/projects/maus
 *
 * MAUS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * MAUS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with MAUS.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include <algorithm>
#include <cmath>

#include "Geant4/G4Navigator.hh"
#include "Geant4/G4TransportationManager.hh"
#include "Geant4/G4NistManager.hh"

#include "gsl/gsl_odeiv.h"
#include "gsl/gsl_errno.h"

#include "src/common_cpp/DataStructure/ReconEvent.hh"
#include "src/common_cpp/Recon/Global/Particle.hh"
#include "src/common_cpp/Simulation/GeometryNavigator.hh"
#include "src/common_cpp/Utils/Exception.hh"
#include "src/common_cpp/Utils/Globals.hh"

#include "src/legacy/BeamTools/BTField.hh"
#include "src/legacy/Config/MiceModule.hh"

#include "src/common_cpp/Recon/Global/GlobalTools.hh"

namespace MAUS {
namespace GlobalTools {

std::map<DataStructure::Global::DetectorPoint, bool>
    GetReconDetectors(GlobalEvent* global_event) {
  std::map<DataStructure::Global::DetectorPoint, bool> recon_detectors;
  for (int i = 0; i < 27; i++) {
    recon_detectors[static_cast<DataStructure::Global::DetectorPoint>(i)] =
      false;
  }
  DataStructure::Global::TrackPArray* imported_tracks =
      global_event->get_tracks();

  for (auto imported_track_iter = imported_tracks->begin();
       imported_track_iter != imported_tracks->end();
       ++imported_track_iter) {
    std::vector<DataStructure::Global::DetectorPoint> track_detectors =
        (*imported_track_iter)->GetDetectorPoints();
    for (size_t i = 0; i < track_detectors.size(); i++) {
      recon_detectors[track_detectors[i]] = true;
    }
  }

  std::vector<DataStructure::Global::SpacePoint*>*
      imported_spacepoints = global_event->get_space_points();
  for (auto sp_iter = imported_spacepoints->begin();
       sp_iter != imported_spacepoints->end();
       ++sp_iter) {
    recon_detectors[(*sp_iter)->get_detector()] = true;
  }
  return recon_detectors;
}

std::vector<DataStructure::Global::Track*>* GetSpillDetectorTracks(Spill* spill,
    DataStructure::Global::DetectorPoint detector, std::string mapper_name) {
  std::vector<DataStructure::Global::Track*>* detector_tracks = new
      std::vector<DataStructure::Global::Track*>;
  ReconEventPArray* recon_events = spill->GetReconEvents();
  if (recon_events) {
    for (auto recon_event_iter = recon_events->begin();
         recon_event_iter != recon_events->end();
         ++recon_event_iter) {
      GlobalEvent* global_event = (*recon_event_iter)->GetGlobalEvent();
      if (global_event) {
        std::vector<DataStructure::Global::Track*>* global_tracks =
            global_event->get_tracks();
        for (auto track_iter = global_tracks->begin();
             track_iter != global_tracks->end();
             ++track_iter) {
          // The third condition is a bit of a dirty hack here to make sure that
          // if we select for EMR tracks, we only get primaries.
          if (((*track_iter)->HasDetector(detector)) and
              ((*track_iter)->get_mapper_name() == mapper_name) and
              ((*track_iter)->get_emr_range_secondary() < 0.001)) {
            detector_tracks->push_back((*track_iter));
          }
        }
      }
    }
  }
  return detector_tracks;
}

std::vector<DataStructure::Global::Track*>* GetEventDetectorTracks(GlobalEvent* global_event,
    DataStructure::Global::DetectorPoint detector, std::string mapper_name) {
  std::vector<DataStructure::Global::Track*>* detector_tracks = new
      std::vector<DataStructure::Global::Track*>;
  if (global_event) {
    std::vector<DataStructure::Global::Track*>* global_tracks =
        global_event->get_tracks();
    for (auto track_iter = global_tracks->begin();
         track_iter != global_tracks->end();
         ++track_iter) {
      // The third condition is a bit of a dirty hack here to make sure that
      // if we select for EMR tracks, we only get primaries.
      if (((*track_iter)->HasDetector(detector)) and
          ((*track_iter)->get_mapper_name() == mapper_name) and
          ((*track_iter)->get_emr_range_secondary() < 0.001)) {
        detector_tracks->push_back((*track_iter));
      }
    }
  }
  return detector_tracks;
}

std::vector<DataStructure::Global::SpacePoint*>* GetSpillSpacePoints(
    Spill* spill, DataStructure::Global::DetectorPoint detector) {
  std::vector<DataStructure::Global::SpacePoint*>* spill_spacepoints =
      new std::vector<DataStructure::Global::SpacePoint*>;
  ReconEventPArray* recon_events = spill->GetReconEvents();
  if (recon_events) {
    for (auto recon_event_iter = recon_events->begin();
         recon_event_iter != recon_events->end();
         ++recon_event_iter) {
      GlobalEvent* global_event = (*recon_event_iter)->GetGlobalEvent();
      if (global_event) {
        std::vector<DataStructure::Global::SpacePoint*>* spacepoints =
            global_event->get_space_points();
        for (auto sp_iter = spacepoints->begin(); sp_iter != spacepoints->end();
             ++sp_iter) {
          if ((*sp_iter)->get_detector() == detector) {
            spill_spacepoints->push_back(*sp_iter);
          }
        }
      }
    }
  }
  if (spill_spacepoints->size() > 0) {
    return spill_spacepoints;
  } else {
    delete spill_spacepoints;
    return 0;
  }
}

std::vector<DataStructure::Global::SpacePoint*>* GetEventSpacePoints(
    GlobalEvent* global_event, DataStructure::Global::DetectorPoint detector) {
  std::vector<DataStructure::Global::SpacePoint*>* spacepoints =
      new std::vector<DataStructure::Global::SpacePoint*>;
  if (global_event) {
    std::vector<DataStructure::Global::SpacePoint*>* temp_spacepoints =
        global_event->get_space_points();
    for (auto sp_iter = temp_spacepoints->begin(); sp_iter != temp_spacepoints->end();
         ++sp_iter) {
      if ((*sp_iter)->get_detector() == detector) {
        spacepoints->push_back(*sp_iter);
      }
    }
  }
  if (spacepoints->size() > 0) {
    return spacepoints;
  } else {
    delete spacepoints;
    return 0;
  }
}

std::vector<DataStructure::Global::Track*>* GetTracksByMapperName(
    GlobalEvent* global_event, std::string mapper_name) {
  std::vector<DataStructure::Global::Track*>* global_tracks =
      global_event->get_tracks();
  std::vector<DataStructure::Global::Track*>* selected_tracks = new
      std::vector<DataStructure::Global::Track*>;
  for (auto global_track_iter = global_tracks->begin();
       global_track_iter != global_tracks->end();
       ++global_track_iter) {
    if ((*global_track_iter)->get_mapper_name() == mapper_name) {
      selected_tracks->push_back(*global_track_iter);
    }
  }
  return selected_tracks;
}

std::vector<DataStructure::Global::Track*>* GetTracksByMapperName(
    GlobalEvent* global_event, std::string mapper_name,
    DataStructure::Global::PID pid) {
  std::vector<DataStructure::Global::Track*>* global_tracks =
          global_event->get_tracks();
  std::vector<DataStructure::Global::Track*>* selected_tracks = new
      std::vector<DataStructure::Global::Track*>;
  for (auto global_track_iter = global_tracks->begin();
       global_track_iter != global_tracks->end();
       ++global_track_iter) {
    if ((*global_track_iter)->get_mapper_name() == mapper_name) {
      if ((*global_track_iter)->get_pid() == pid) {
        selected_tracks->push_back(*global_track_iter);
      }
    }
  }
  return selected_tracks;
}

std::vector<int> GetTrackerPlane(const DataStructure::Global::TrackPoint*
    track_point, std::vector<double> z_positions) {
  std::vector<int> tracker_plane(3, 0);
  double z = track_point->get_position().Z();
  int plane = 100;
  // First we get a plane number as an integer from 0 to 29 (counting from upstream)
  for (size_t i = 0; i < z_positions.size(); i++) {
    if (approx(z, z_positions[i], 0.25)) {
      plane = i;
      break;
    }
  }
  if (plane < 15) {
    // Tracker 0
    tracker_plane[0] = 0;
    tracker_plane[1] = 5 - plane/3;
    tracker_plane[2] = 2 - plane%3;
  } else if (plane < 30) {
    // Tracker 1
    tracker_plane[0] = 1;
    tracker_plane[1] = plane/3 - 4;
    tracker_plane[2] = plane%3;
  } else {
    // error output
    tracker_plane[0] = 99;
  }
  return tracker_plane;
}

std::vector<double> GetTrackerPlaneZPositions(std::string geo_filename) {
  MiceModule* geo_module = new MiceModule(geo_filename);
  std::vector<const MiceModule*> tracker_planes =
      geo_module->findModulesByPropertyString("SensitiveDetector", "SciFi");
  std::vector<double> z_positions;
  for (size_t i = 0; i < tracker_planes.size(); i++) {
    z_positions.push_back(tracker_planes.at(i)->globalPosition().getZ());
  }
  std::sort(z_positions.begin(), z_positions.end());
  delete geo_module;
  return z_positions;
}

bool approx(double a, double b, double tolerance) {
  if (std::abs(a - b) > std::abs(tolerance)) {
    return false;
  } else {
    return true;
  }
}

DataStructure::Global::TrackPoint* GetNearestZTrackPoint(
    const DataStructure::Global::Track* track, double z_position) {
  std::vector<const DataStructure::Global::TrackPoint*> trackpoints =
      track->GetTrackPoints();
  size_t nearest_index = 0;
  double z_distance = 1.0e20;
  for (size_t i = 0; i < trackpoints.size(); i++) {
    double current_distance = std::abs(z_position -
                                       trackpoints.at(i)->get_position().Z());
    if (current_distance < z_distance) {
      nearest_index = i;
      z_distance = current_distance;
    }
  }
  DataStructure::Global::TrackPoint* nearest_track_point = new
      DataStructure::Global::TrackPoint(*trackpoints.at(nearest_index));
  return nearest_track_point;
}

double dEdx(const G4Material* material, double E, double m) {
  // Equation according to PDG 2014 eq. 32.5
  // Converted constant so we can use electron number density instead of A/Z
  double constant = 0.5*100*0.307075/Avogadro;
  double m_e = 0.510998928;
  double beta = std::sqrt(1 - (m*m)/(E*E));
  double beta2 = beta*beta;
  double gamma = 1/std::sqrt(1 - beta2);
  double bg = beta*gamma;
  double bg2 = bg*bg;
  double mRatio = m_e/m;
  double T_max = 2.0*m_e*bg2/(1.0 + 2.0*gamma*mRatio + mRatio*mRatio);

  double n_e = material->GetElectronDensity();
  double I = material->GetIonisation()->GetMeanExcitationEnergy();

  double logterm = std::log(2.0*m_e*bg2*T_max/(I*I));

  // density correction
  double x = std::log(bg)/std::log(10);
  double delta = material->GetIonisation()->DensityCorrection(x);
  double dEdx = -constant*n_e/beta2*(logterm - 2*beta2 - delta);
  return dEdx;
}

// Need some global variables here
static const BTField* _field;
static int _charge;

void propagate(double* x, double target_z, const BTField* field,
               double step_size, DataStructure::Global::PID pid,
               bool energy_loss) {
  if (std::abs(target_z) > 100000) {
    throw(Exceptions::Exception(Exceptions::recoverable, "Extreme target z",
                    "GlobalTools::propagate"));
  }
  if (std::isnan(x[0]) || std::isnan(x[1]) || std::isnan(x[2]) || std::isnan(x[3]) ||
      std::isnan(x[4]) || std::isnan(x[5]) || std::isnan(x[6]) || std::isnan(x[7])) {
    std::stringstream ios;
    ios << "pos: " << x[0] << " " << x[1] << " " << x[2] << " " << x[3] << std::endl
        << "mom: " << x[4] << " " << x[5] << " " << x[6] << " " << x[7] << std::endl;
    throw(Exceptions::Exception(Exceptions::recoverable, ios.str()+
          "Some components of tracker trackpoint are nan", "GlobalTools::propagate"));
  }
  int prop_dir = 1;
  _field = field;
  _charge = recon::global::Particle::GetInstance().GetCharge(pid);
  double mass = recon::global::Particle::GetInstance().GetMass(pid);
  G4Navigator* g4navigator = G4TransportationManager::GetTransportationManager()
      ->GetNavigatorForTracking();
  G4NistManager* manager = G4NistManager::Instance();
  bool backwards = false;
  // If we propagate backwards, reverse momentum 4-vector
  if (target_z < x[3]) {
    backwards = true;
    _charge *= -1;
    prop_dir = -1;
    for (size_t i = 4; i < 8; i++) {
      x[i] *= -1;
    }
  }
  const gsl_odeiv_step_type * T = gsl_odeiv_step_rk4;
  double absolute_error = (*Globals::GetInstance()->GetConfigurationCards())
                           ["field_tracker_absolute_error"].asDouble();
  double relative_error = (*Globals::GetInstance()->GetConfigurationCards())
                           ["field_tracker_relative_error"].asDouble();
  gsl_odeiv_step    * step    = gsl_odeiv_step_alloc(T, 8);
  gsl_odeiv_control * control = gsl_odeiv_control_y_new(absolute_error,
                                                        relative_error);
  gsl_odeiv_evolve  * evolve  = gsl_odeiv_evolve_alloc(8);
  int (*FuncEqM)(double z, const double y[], double f[], void *params)=NULL;
  FuncEqM = z_equations_of_motion;
  gsl_odeiv_system system  = {FuncEqM, NULL, 8, NULL};
  double h = step_size*prop_dir;
  size_t max_steps = 10000000;
  size_t n_steps = 0;
  double z = x[3];
  // The next 2 lines take ~8ms to execute, perhaps consider moving these outside
  // of this function somehow?
  GeometryNavigator geometry_navigator;
  geometry_navigator.Initialise(g4navigator->GetWorldVolume());
  while (fabs(z - target_z) > 1e-6) {
    n_steps++;
    h = step_size*prop_dir; // revert step size as large step size problematic for dEdx
    int status;
    if (energy_loss) {
      const CLHEP::Hep3Vector posvector(x[1], x[2], x[3]);
      double mommag = std::sqrt(x[5]*x[5] + x[6]*x[6] + x[7]*x[7]);
      const CLHEP::Hep3Vector momvector(x[5]/mommag, x[6]/mommag, x[7]/mommag);
      g4navigator->LocateGlobalPointAndSetup(posvector, &momvector);
      double safety = std::fabs(step_size);
      double boundary_dist = g4navigator->ComputeStep(posvector, momvector, h, safety);
      if (boundary_dist > 1e6) {
        boundary_dist = safety;
      }
      double z_dist = boundary_dist*momvector.z();
      // We need to check if we're in a material with high stopping power, and if yes,
      // decrease the step size as otherwise the underestimated path length due to the
      // curved trajectory will cause problems
      double n_e = manager->FindOrBuildMaterial(geometry_navigator.GetMaterialName()
          )->GetElectronDensity();
      double max_h = 100.0;
      if (n_e > 1e+18) {
        max_h = 1.0*prop_dir;
      }
      // Check if z distance to next material boundary is smaller than step size
      // if yes, we impose a tight limit on the step size to avoid issues
      // arising from the track not being straight
      if (std::abs(z_dist) > 0.00000000001 and
          std::abs(z_dist) < std::abs(h)) {
        if (std::abs(z_dist) > 1.0) {
          h = 0.9*z_dist;
        } else {
          h = z_dist; // will have proper sign from momvector
        }
      }
      if (std::abs(h) > std::abs(max_h)) {
        h = max_h;
      }
      // Making sure we don't get stuck in Zeno's paradox
      if (std::abs(h) < 0.1) {
        h = 0.1*prop_dir;
      }
      double x_prev[] = {x[0], x[1], x[2], x[3], x[4], x[5], x[6], x[7]};
      status = gsl_odeiv_evolve_apply(evolve, control, step, &system, &z,
                                        target_z, &h, x);
      // Calculate energy loss for the step
      geometry_navigator.SetPoint(ThreeVector((x[1] + x_prev[1])/2,
                                  (x[2] + x_prev[2])/2, (x[3] + x_prev[3])/2));
      double step_distance = std::sqrt((x[1]-x_prev[1])*(x[1]-x_prev[1]) +
                                       (x[2]-x_prev[2])*(x[2]-x_prev[2]) +
                                       (x[3]-x_prev[3])*(x[3]-x_prev[3]));
      G4Material* material = manager->FindOrBuildMaterial(geometry_navigator.GetMaterialName());
      double step_energy_loss = dEdx(material, x[4], mass)*step_distance;
      changeEnergy(x, step_energy_loss, mass);
    } else {
      status = gsl_odeiv_evolve_apply(evolve, control, step, &system, &z,
                                        target_z, &h, x);
    }
    if (status != GSL_SUCCESS) {
      throw(Exceptions::Exception(Exceptions::recoverable, "Propagation failed",
                            "GlobalTools::propagate"));
    }

    if (n_steps > max_steps) {
      std::stringstream ios;
      ios << "Stopping at step " << n_steps << " of " << max_steps << "\n"
          << "t: " << x[0] << " pos: " << x[1] << " " << x[2] << " " << x[3] << "\n"
          << "E: " << x[4] << " mom: " << x[5] << " " << x[6] << " " << x[7] << std::endl;
      throw(Exceptions::Exception(Exceptions::recoverable, ios.str()+
            "Exceeded maximum number of steps", "GlobalTools::propagate"));
      break;
    }
    // Terminate if the propagation moves too far from the beamline (should be lost to us anyway)
    // Appears to fix an irregular and so far not fully explained segfault.
    if (std::abs(x[1]) > 700 || std::abs(x[2]) > 700) {
      std::stringstream ios;
      ios << "t: " << x[0] << " pos: " << x[1] << " " << x[2] << " " << x[3] << std::endl;
      throw(Exceptions::Exception(Exceptions::recoverable, ios.str()+
            "Particle terminated: Too far from beam center", "GlobalTools::propagate"));
    }
    // Need to catch the case where the particle is stopped
    if (std::abs(x[4]) < (mass + 0.01)) {
      std::stringstream ios;
      ios << "t: " << x[0] << " pos: " << x[1] << " " << x[2] << " " << x[3] << std::endl;
      throw(Exceptions::Exception(Exceptions::recoverable, ios.str()+
            "Particle terminated with 0 momentum", "GlobalTools::propagate"));
    }
  }
  gsl_odeiv_evolve_free(evolve);
  gsl_odeiv_control_free(control);
  gsl_odeiv_step_free(step);

  // If we propagate backwards, reverse momentum 4-vector back to original sign
  if (backwards) {
    for (size_t i = 4; i < 8; i++) {
      x[i] *= -1;
    }
  }
}

int z_equations_of_motion(double z, const double x[8], double dxdz[8],
                                   void* params) {
  if (fabs(x[7]) < 1e-9) {
  // z-momentum is 0
    return GSL_ERANGE;
  }
  const double c_l = 299.792458; // mm*ns^{-1}
  double field[6] = {0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
  double xfield[4] = {x[1], x[2], x[3], x[0]};
  _field->GetFieldValue(xfield, field);
  double dtdz = x[4]/x[7];
  double dir = fabs(x[7])/x[7]; // direction of motion
  dxdz[0] = dtdz/c_l; // dt/dz
  dxdz[1] = x[5]/x[7]; // dx/dz = px/pz
  dxdz[2] = x[6]/x[7]; // dy/dz = py/pz
  dxdz[3] = 1.0; // dz/dz
  // dE/dz only contains electric field as B conserves energy, not relevant at
  // least in step 4 as all fields are static.
  dxdz[4] = (dxdz[1]*_charge*field[3] + dxdz[2]*_charge*field[4] +
             _charge*field[5])*dir; // dE/dz
  // dpx/dz = q*c*(dy/dz*Bz - dz/dz*By) + q*Ex*dt/dz
  dxdz[5] = _charge*c_l*(dxdz[2]*field[2] - dxdz[3]*field[1])
            + _charge*field[3]*dtdz*dir; // dpx/dz
  dxdz[6] = _charge*c_l*(dxdz[3]*field[0] - dxdz[1]*field[2])
            + _charge*field[4]*dtdz*dir; // dpy/dz
  dxdz[7] = _charge*c_l*(dxdz[1]*field[1] - dxdz[2]*field[0])
            + _charge*field[5]*dtdz*dir; // dpz/dz
  return GSL_SUCCESS;
}

void changeEnergy(double* x, double deltaE, double mass) {
  if (std::isnan(deltaE)) {
    deltaE = -x[4];
  }
  double old_momentum = std::sqrt(x[5]*x[5] + x[6]*x[6] + x[7]*x[7]);
  x[4] += deltaE;
  double new_momentum, momentum_ratio;
  if (std::abs(x[4]) > mass) {
    new_momentum = std::sqrt(x[4]*x[4] - mass*mass);
  } else {
    new_momentum = 0.0;
  }
  momentum_ratio = new_momentum / old_momentum;
  x[5] *= momentum_ratio;
  x[6] *= momentum_ratio;
  x[7] *= momentum_ratio;
}

bool TrackPointSort(const DataStructure::Global::TrackPoint* tp1,
                    const DataStructure::Global::TrackPoint* tp2) {
  return (tp1->get_position().Z() < tp2->get_position().Z());
}

} // ~namespace GlobalTools
} // ~namespace MAUS