/** \class Herwig7Interface
 *  
 *  Marco A. Harrendorf marco.harrendorf@cern.ch
 *  Dominik Beutel dominik.beutel@cern.ch
 */

#include <cmath>
#include <cstdlib>
#include <fstream>
#include <iostream>
#include <memory>
#include <sstream>

#include <algorithm>

#include <HepMC/GenEvent.h>
#include <HepMC/PdfInfo.h>
#include <HepMC/IO_GenEvent.h>

#include <Herwig/API/HerwigAPI.h>

#include <ThePEG/Utilities/DynamicLoader.h>
#include <ThePEG/Repository/Repository.h>
#include <ThePEG/Handlers/EventHandler.h>
#include <ThePEG/Handlers/XComb.h>
#include <ThePEG/EventRecord/Event.h>
#include <ThePEG/EventRecord/Particle.h>
#include <ThePEG/EventRecord/Collision.h>
#include <ThePEG/EventRecord/TmpTransform.h>
#include <ThePEG/Config/ThePEG.h>
#include <ThePEG/PDF/PartonExtractor.h>
#include <ThePEG/PDF/PDFBase.h>
#include <ThePEG/Utilities/UtilityBase.h>
#include <ThePEG/Vectors/HepMCConverter.h>

#include "FWCore/MessageLogger/interface/MessageLogger.h"

#include "GeneratorInterface/Core/interface/ParameterCollector.h"

#include "GeneratorInterface/Herwig7Interface/interface/Proxy.h"
#include "GeneratorInterface/Herwig7Interface/interface/RandomEngineGlue.h"
#include "GeneratorInterface/Herwig7Interface/interface/Herwig7Interface.h"

#include "CLHEP/Random/RandomEngine.h"

using namespace std;
using namespace gen;

Herwig7Interface::Herwig7Interface(const edm::ParameterSet &pset)
    : randomEngineGlueProxy_(ThePEG::RandomEngineGlue::Proxy::create()),
      dataLocation_(ParameterCollector::resolve(pset.getParameter<string>("dataLocation"))),
      generator_(pset.getParameter<string>("generatorModule")),
      run_(pset.getParameter<string>("run")),
      dumpConfig_(pset.getUntrackedParameter<string>("dumpConfig", "HerwigConfig.in")),
      skipEvents_(pset.getUntrackedParameter<unsigned int>("skipEvents", 0)) {
  // Write events in hepmc ascii format for debugging purposes
  string dumpEvents = pset.getUntrackedParameter<string>("dumpEvents", "");
  if (!dumpEvents.empty()) {
    iobc_ = std::make_unique<HepMC::IO_GenEvent>(dumpEvents, ios::out);
    edm::LogInfo("ThePEGSource") << "Event logging switched on (=> " << dumpEvents << ")";
  }
  // Clear dumpConfig target
  if (!dumpConfig_.empty())
    ofstream cfgDump(dumpConfig_.c_str(), ios_base::trunc);
}

Herwig7Interface::~Herwig7Interface() noexcept {
  if (eg_)
    eg_->finalize();
  edm::LogInfo("Herwig7Interface") << "Event generator finalized";
}

void Herwig7Interface::setPEGRandomEngine(CLHEP::HepRandomEngine *v) {
  randomEngineGlueProxy_->setRandomEngine(v);
  randomEngine = v;
  ThePEG::RandomEngineGlue *rnd = randomEngineGlueProxy_->getInstance();
  if (rnd) {
    rnd->setRandomEngine(v);
  }
}

void Herwig7Interface::initRepository(const edm::ParameterSet &pset) {
  std::string runModeTemp = pset.getUntrackedParameter<string>("runModeList", "read,run");

  // To Lower
  std::transform(runModeTemp.begin(), runModeTemp.end(), runModeTemp.begin(), ::tolower);

  while (!runModeTemp.empty()) {
    // Split first part of List
    std::string choice;
    size_t pos = runModeTemp.find(',');
    if (std::string::npos == pos)
      choice = runModeTemp;
    else
      choice = runModeTemp.substr(0, pos);

    if (pos == std::string::npos)
      runModeTemp.erase();
    else
      runModeTemp.erase(0, pos + 1);

    HwUI_ = std::make_shared<Herwig::HerwigUIProvider>(pset, dumpConfig_, Herwig::RunMode::READ);
    edm::LogInfo("Herwig7Interface") << "HerwigUIProvider object with run mode " << HwUI_->runMode() << " created.\n";

    // Chose run mode
    if (choice == "read") {
      createInputFile(pset);
      HwUI_->setRunMode(Herwig::RunMode::READ, pset, dumpConfig_);
      edm::LogInfo("Herwig7Interface") << "Input file " << dumpConfig_
                                       << " will be passed to Herwig for the read step.\n";
      callHerwigGenerator();
    } else if (choice == "build") {
      createInputFile(pset);
      HwUI_->setRunMode(Herwig::RunMode::BUILD, pset, dumpConfig_);
      edm::LogInfo("Herwig7Interface") << "Input file " << dumpConfig_
                                       << " will be passed to Herwig for the build step.\n";
      callHerwigGenerator();

    } else if (choice == "integrate") {
      std::string runFileName = run_ + ".run";
      edm::LogInfo("Herwig7Interface") << "Run file " << runFileName
                                       << " will be passed to Herwig for the integrate step.\n";
      HwUI_->setRunMode(Herwig::RunMode::INTEGRATE, pset, runFileName);
      callHerwigGenerator();

    } else if (choice == "run") {
      std::string runFileName = run_ + ".run";
      edm::LogInfo("Herwig7Interface") << "Run file " << runFileName << " will be passed to Herwig for the run step.\n";
      HwUI_->setRunMode(Herwig::RunMode::RUN, pset, runFileName);
    } else {
      edm::LogInfo("Herwig7Interface") << "Cannot recognize \"" << choice << "\".\n"
                                       << "Trying to skip step.\n";
      continue;
    }
  }
}

void Herwig7Interface::callHerwigGenerator() {
  try {
    edm::LogInfo("Herwig7Interface") << "callHerwigGenerator function invoked with run mode " << HwUI_->runMode()
                                     << ".\n";

    // Call program switches according to runMode
    switch (HwUI_->runMode()) {
      case Herwig::RunMode::INIT:
        Herwig::API::init(*HwUI_);
        break;
      case Herwig::RunMode::READ:
        Herwig::API::read(*HwUI_);
        break;
      case Herwig::RunMode::BUILD:
        Herwig::API::build(*HwUI_);
        break;
      case Herwig::RunMode::INTEGRATE:
        Herwig::API::integrate(*HwUI_);
        break;
      case Herwig::RunMode::MERGEGRIDS:
        Herwig::API::mergegrids(*HwUI_);
        break;
      case Herwig::RunMode::RUN: {
        HwUI_->setSeed(randomEngine->getSeed());
        eg_ = Herwig::API::prepareRun(*HwUI_);
        break;
      }
      case Herwig::RunMode::ERROR:
        edm::LogError("Herwig7Interface") << "Error during read in of command line parameters.\n"
                                          << "Program execution will stop now.";
        return;
      default:
        HwUI_->quitWithHelp();
    }

    return;

  } catch (ThePEG::Exception &e) {
    edm::LogError("Herwig7Interface") << ": ThePEG::Exception caught.\n"
                                      << e.what() << '\n'
                                      << "See logfile for details.\n";
    return;
  } catch (std::exception &e) {
    edm::LogError("Herwig7Interface") << ": " << e.what() << '\n';
    return;
  } catch (const char *what) {
    edm::LogError("Herwig7Interface") << ": caught exception: " << what << "\n";
    return;
  }
}

bool Herwig7Interface::initGenerator() {
  if (HwUI_->runMode() == Herwig::RunMode::RUN) {
    edm::LogInfo("Herwig7Interface") << "Starting EventGenerator initialization";
    callHerwigGenerator();
    edm::LogInfo("Herwig7Interface") << "EventGenerator initialized";

    // Skip events
    for (unsigned int i = 0; i < skipEvents_; i++) {
      flushRandomNumberGenerator();
      eg_->shoot();
      edm::LogInfo("Herwig7Interface") << "Event discarded";
    }

    return true;

  } else {
    edm::LogInfo("Herwig7Interface") << "Stopped EventGenerator due to missing run mode.";
    return false;
    /*
		throw cms::Exception("Herwig7Interface")
			<< "EventGenerator could not be initialized due to wrong run mode!" << endl;
*/
  }
}

void Herwig7Interface::flushRandomNumberGenerator() {
  /*ThePEG::RandomEngineGlue *rnd = randomEngineGlueProxy_->getInstance();

	if (!rnd)
		edm::LogWarning("ProxyMissing")
			<< "ThePEG not initialised with RandomEngineGlue.";
	else
		rnd->flush();
      */
}

unique_ptr<HepMC::GenEvent> Herwig7Interface::convert(const ThePEG::EventPtr &event) {
  return std::unique_ptr<HepMC::GenEvent>(ThePEG::HepMCConverter<HepMC::GenEvent>::convert(*event));
}

double Herwig7Interface::pthat(const ThePEG::EventPtr &event) {
  using namespace ThePEG;

  if (!event->primaryCollision())
    return -1.0;

  tSubProPtr sub = event->primaryCollision()->primarySubProcess();
  TmpTransform<tSubProPtr> tmp(sub, Utilities::getBoostToCM(sub->incoming()));

  double pthat = (*sub->outgoing().begin())->momentum().perp() / ThePEG::GeV;
  for (PVector::const_iterator it = sub->outgoing().begin(); it != sub->outgoing().end(); ++it)
    pthat = std::min<double>(pthat, (*it)->momentum().perp() / ThePEG::GeV);

  return pthat;
}

void Herwig7Interface::createInputFile(const edm::ParameterSet &pset) {
  /* Initialize the input config for Herwig from
	 * 1. the Herwig7 config files
	 * 2. the CMSSW config blocks
	 * Writes them to an output file which is read by Herwig
	*/

  stringstream logstream;

  // Contains input config passed to Herwig
  stringstream herwiginputconfig;

  // Define output file to which input config is written, too, if dumpConfig parameter is set.
  // Otherwise use default file HerwigConfig.in which is read in by Herwig
  ofstream cfgDump;
  cfgDump.open(dumpConfig_.c_str(), ios_base::app);

  // Read Herwig config files as input
  vector<string> configFiles = pset.getParameter<vector<string> >("configFiles");
  // Loop over the config files
  for (const auto &iter : configFiles) {
    // Open external config file
    ifstream externalConfigFile(iter);
    if (externalConfigFile.is_open()) {
      edm::LogInfo("Herwig7Interface") << "Reading config file (" << iter << ")" << endl;
      stringstream configFileStream;
      configFileStream << externalConfigFile.rdbuf();
      string configFileContent = configFileStream.str();

      // Comment out occurence of saverun in config file since it is set later considering run and generator option
      string searchKeyword("saverun");
      if (configFileContent.find(searchKeyword) != std::string::npos) {
        edm::LogInfo("Herwig7Interface") << "Commented out saverun command in external input config file(" << iter
                                         << ")" << endl;
        configFileContent.insert(configFileContent.find(searchKeyword), "#");
      }
      herwiginputconfig << "# Begin Config file input" << endl
                        << configFileContent << endl
                        << "# End Config file input";
      edm::LogInfo("Herwig7Interface") << "Finished reading config file (" << iter << ")" << endl;
    } else {
      edm::LogWarning("Herwig7Interface") << "Could not read config file (" << iter << ")" << endl;
    }
  }

  edm::LogInfo("Herwig7Interface") << "Start with processing CMSSW config" << endl;
  // Read CMSSW config file parameter sets starting from "parameterSets"
  ParameterCollector collector(pset);
  ParameterCollector::const_iterator iter;
  iter = collector.begin();
  herwiginputconfig << endl << "# Begin Parameter set input\n" << endl;
  for (; iter != collector.end(); ++iter) {
    herwiginputconfig << *iter << endl;
  }

  // Add some additional necessary lines to the Herwig input config
  herwiginputconfig << "saverun " << run_ << " " << generator_ << endl;
  // write the ProxyID for the RandomEngineGlue to fill its pointer in
  ostringstream ss;
  ss << randomEngineGlueProxy_->getID();
  //herwiginputconfig << "set " << generator_ << ":RandomNumberGenerator:ProxyID " << ss.str() << endl;

  // Dump Herwig input config to file, so that it can be read by Herwig
  cfgDump << herwiginputconfig.str() << endl;
  cfgDump.close();
}