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 // SPDX-License-Identifier: LGPL-3.0-or-later
 // Copyright (C) 2022 - 2025 Chao Peng, Wouter Deconinck, Sylvester Joosten, Barak Schmookler, David Lawrence, Akio Ogawa
 
 // A general digitization for CalorimeterHit from simulation
 // 1. Smear energy deposit with a/sqrt(E/GeV) + b + c/E or a/sqrt(E/GeV) (relative value)
 // 2. Digitize the energy with dynamic ADC range and add pedestal (mean +- sigma)
 // 3. Time conversion with smearing resolution (absolute value)
 // 4. Signal is summed if the SumFields are provided
 //
 // Author: Chao Peng
 // Date: 06/02/2021
 
 #include "CalorimeterHitDigi.h"
 
 #include <DD4hep/Detector.h>
 #include <DD4hep/IDDescriptor.h>
 #include <DD4hep/Readout.h>
 #include <DDSegmentation/BitFieldCoder.h>
 #include <Evaluator/DD4hepUnits.h>
 #include <algorithms/service.h>
 #include <edm4eic/MCRecoCalorimeterHitAssociationCollection.h>
 #include <edm4hep/CaloHitContributionCollection.h>
 #include <fmt/format.h>
 #include <podio/RelationRange.h>
 #include <podio/detail/Link.h>
 #include <podio/detail/LinkCollectionImpl.h>
 #include <algorithm>
 #include <cmath>
 #include <cstddef>
 #include <gsl/pointers>
 #include <limits>
 #include <map>
 #include <memory>
 #include <random>
 #include <stdexcept>
 #include <string>
 #include <tuple>
 #include <unordered_map>
 #include <utility>
 #include <vector>
 
 #include "algorithms/calorimetry/CalorimeterHitDigiConfig.h"
 #include "services/evaluator/EvaluatorSvc.h"
 
 using namespace dd4hep;
 
 namespace eicrecon {
 
 //
 // TODO:
 // - Array type configuration parameters are not yet supported in JANA (needs to be added)
 // - Random number service needs to bew resolved (on global scale)
 // - It is possible standard running of this with Gaudi relied on a number of parameters
 //   being set in the config. If that is the case, they should be moved into the default
 //   values here. This needs to be confirmed.
 
 void CalorimeterHitDigi::init() {
 
   // Gaudi implements a random number generator service. It is not clear to me how this
   // can work. There are multiple race conditions that occur in parallel event processing:
   // 1. The exact same events processed by a given thread in one invocation will not
   //    necessarily be the combination of events any thread sees in a subsequent
   //    invocation. Thus, you can't rely on thread_local storage.
   // 2. Its possible for the factory execution order to be modified by the presence of
   //    a processor (e.g. monitoring plugin). This is not as serious since changing the
   //    command line should cause one not to expect reproducibility. Still, one may
   //    expect the inclusion of an "observer" plugin not to have such side affects.
   //
   // More information will be needed. In the meantime, we implement a local random number
   // generator. Ideally, this would be seeded with the run number+event number, but for
   // now, just use default values defined in header file.
 
   // set energy resolution numbers
   if (m_cfg.eRes.empty()) {
     m_cfg.eRes.resize(3);
   } else if (m_cfg.eRes.size() != 3) {
     error("Invalid m_cfg.eRes.size()");
     throw std::runtime_error("Invalid m_cfg.eRes.size()");
   }
 
   // using juggler internal units (GeV, mm, radian, ns)
   tRes    = m_cfg.tRes / dd4hep::ns;
   stepTDC = dd4hep::ns / m_cfg.resolutionTDC;
 
   // sanity checks
   if (m_cfg.readout.empty()) {
     error("readoutClass is not provided, it is needed to know the fields in readout ids");
     throw std::runtime_error("readoutClass is not provided");
   }
 
   // get decoders
   try {
     id_spec = m_geo.detector()->readout(m_cfg.readout).idSpec();
   } catch (...) {
     // Can not be more verbose. In JANA2, this will be attempted at each event, which
     // pollutes output for geometries that are less than complete.
     // We could save an exception and throw it from process.
     debug("Failed to load ID decoder for {}", m_cfg.readout);
     throw std::runtime_error(fmt::format("Failed to load ID decoder for {}", m_cfg.readout));
   }
 
   decltype(id_mask) id_inverse_mask = 0;
   // all these are for signal sum at digitization level
   if (!m_cfg.fields.empty()) {
     for (auto& field : m_cfg.fields) {
       id_inverse_mask |= id_spec.field(field)->mask();
     }
     debug("ID mask in {:s}: {:#064b}", m_cfg.readout, id_mask);
   }
   id_mask = ~id_inverse_mask;
 
   std::function hit_to_map = [this](const edm4hep::SimCalorimeterHit& h) {
     std::unordered_map<std::string, double> params;
     for (const auto& p : id_spec.fields()) {
       const std::string& name                  = p.first;
       const dd4hep::IDDescriptor::Field* field = p.second;
       params.emplace(name, field->value(h.getCellID()));
       trace("{} = {}", name, field->value(h.getCellID()));
     }
     return params;
   };
 
   auto& serviceSvc = algorithms::ServiceSvc::instance();
   corrMeanScale =
       serviceSvc.service<EvaluatorSvc>("EvaluatorSvc")->compile(m_cfg.corrMeanScale, hit_to_map);
 
   std::map<std::string, readout_enum> readoutTypes{{"simple", kSimpleReadout},
                                                    {"poisson_photon", kPoissonPhotonReadout},
                                                    {"sipm", kSipmReadout}};
   if (not readoutTypes.count(m_cfg.readoutType)) {
     error("Invalid readoutType \"{}\"", m_cfg.readoutType);
     throw std::runtime_error(fmt::format("Invalid readoutType \"{}\"", m_cfg.readoutType));
   }
   readoutType = readoutTypes.at(m_cfg.readoutType);
 }
 
 void CalorimeterHitDigi::process(const CalorimeterHitDigi::Input& input,
                                  const CalorimeterHitDigi::Output& output) const {
 
   const auto [headers, simhits]    = input;
   auto [rawhits, links, rawassocs] = output;
 
   // local random generator
   auto seed = m_uid.getUniqueID(*headers, name());
   std::default_random_engine generator(seed);
   std::normal_distribution<double> gaussian;
 
   // find the hits that belong to the same group (for merging)
   std::unordered_map<uint64_t, std::vector<std::size_t>> merge_map;
   std::size_t ix = 0;
   for (const auto& ahit : *simhits) {
     uint64_t hid = ahit.getCellID() & id_mask;
 
     trace("org cell ID in {:s}: {:#064b}", m_cfg.readout, ahit.getCellID());
     trace("new cell ID in {:s}: {:#064b}", m_cfg.readout, hid);
 
     merge_map[hid].push_back(ix);
 
     ix++;
   }
 
   // signal sum
   // NOTE: we take the cellID of the most energetic hit in this group so it is a real cellID from an MC hit
   for (const auto& [id, ixs] : merge_map) {
 
     // create hit and association in advance
     edm4hep::MutableRawCalorimeterHit rawhit;
     std::vector<edm4eic::MutableMCRecoCalorimeterHitLink> links_staging;
     std::vector<edm4eic::MutableMCRecoCalorimeterHitAssociation> rawassocs_staging;
 
     double edep      = 0;
     double time      = std::numeric_limits<double>::max();
     double max_edep  = 0;
     auto leading_hit = (*simhits)[ixs[0]];
     // sum energy, take time from the most energetic hit
     for (unsigned long i : ixs) {
       auto hit = (*simhits)[i];
 
       double timeC = std::numeric_limits<double>::max();
       for (const auto& c : hit.getContributions()) {
         timeC = std::min<double>(c.getTime(), timeC);
       }
       if (timeC > m_cfg.capTime) {
         debug("retaining hit, even though time %f ns > %f ns", timeC / dd4hep::ns,
               m_cfg.capTime / dd4hep::ns);
       }
       edep += hit.getEnergy();
       trace("adding {} \t total: {}", hit.getEnergy(), edep);
 
       // change maximum hit energy & time if necessary
       if (hit.getEnergy() > max_edep) {
         max_edep    = hit.getEnergy();
         leading_hit = hit;
         time        = std::min(timeC, time);
       }
 
       edm4eic::MutableMCRecoCalorimeterHitAssociation assoc;
       assoc.setRawHit(rawhit);
       assoc.setSimHit(hit);
       assoc.setWeight(hit.getEnergy());
       rawassocs_staging.push_back(assoc);
       edm4eic::MutableMCRecoCalorimeterHitLink link;
       link.setFrom(rawhit);
       link.setTo(hit);
       link.setWeight(hit.getEnergy());
       links_staging.push_back(link);
     }
     if (time > m_cfg.capTime) {
       debug("retaining hit, even though time %f ns > %f ns", time / dd4hep::ns,
             m_cfg.capTime / dd4hep::ns);
     }
 
     // safety check
     const double eResRel =
         (edep > m_cfg.threshold)
             ? gaussian(generator) *
                   std::sqrt(std::pow(m_cfg.eRes[0] / std::sqrt(edep), 2) +
                             std::pow(m_cfg.eRes[1], 2) + std::pow(m_cfg.eRes[2] / (edep), 2))
             : 0;
 
     double corrMeanScale_value = corrMeanScale(leading_hit);
 
     double ped = m_cfg.pedMeanADC + gaussian(generator) * m_cfg.pedSigmaADC;
 
     // Note: both adc and tdc values must be positive numbers to avoid integer wraparound
     unsigned long long adc = 0;
     unsigned long long tdc = std::llround((time + gaussian(generator) * tRes) * stepTDC);
 
     //smear edep by resolution function before photon and SiPM simulation
     edep *= std::max(0.0, 1.0 + eResRel);
 
     if (readoutType == kSimpleReadout) {
       adc = std::max(
           std::llround(ped + edep * corrMeanScale_value / m_cfg.dyRangeADC * m_cfg.capADC), 0LL);
     } else if (readoutType == kPoissonPhotonReadout) {
       const long long int n_photons_mean =
           edep * m_cfg.lightYield * m_cfg.photonDetectionEfficiency;
       std::poisson_distribution<> n_photons_detected_dist(n_photons_mean);
       const long long int n_photons_detected = n_photons_detected_dist(generator);
       const long long int n_max_photons =
           m_cfg.dyRangeADC * m_cfg.lightYield * m_cfg.photonDetectionEfficiency;
       trace("n_photons_detected {}", n_photons_detected);
       adc = std::max(std::llround(ped + n_photons_detected * corrMeanScale_value / n_max_photons *
                                             m_cfg.capADC),
                      0LL);
     } else if (readoutType == kSipmReadout) {
       const long long int n_photons = edep * m_cfg.lightYield;
       std::binomial_distribution<> n_photons_detected_dist(n_photons,
                                                            m_cfg.photonDetectionEfficiency);
       const long long int n_photons_detected = n_photons_detected_dist(generator);
       const long long int n_pixels_fired =
           m_cfg.numEffectiveSipmPixels *
           (1 - exp(-n_photons_detected / (double)m_cfg.numEffectiveSipmPixels));
       const long long int n_max_photons =
           m_cfg.dyRangeADC * m_cfg.lightYield * m_cfg.photonDetectionEfficiency;
       trace("n_photons_detected {}, n_pixels_fired {}, n_max_photons {}", n_photons_detected,
             n_pixels_fired, n_max_photons);
       adc = std::max(
           std::llround(ped + n_pixels_fired * corrMeanScale_value / n_max_photons * m_cfg.capADC),
           0LL);
     }
 
     if (edep > 1.e-3) {
       trace("E sim {} \t adc: {} \t time: {}\t maxtime: {} \t tdc: {} \t corrMeanScale: {}", edep,
             adc, time, m_cfg.capTime, tdc, corrMeanScale_value);
     }
 
     rawhit.setCellID(leading_hit.getCellID());
     rawhit.setAmplitude(adc > m_cfg.capADC ? m_cfg.capADC : adc);
     rawhit.setTimeStamp(tdc);
     rawhits->push_back(rawhit);
 
     for (auto& link : links_staging) {
       link.setWeight(link.getWeight() / edep);
       links->push_back(link);
     }
     for (auto& assoc : rawassocs_staging) {
       assoc.setWeight(assoc.getWeight() / edep);
       rawassocs->push_back(assoc);
     }
   }
 }
 
 } // namespace eicrecon

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