// main31.cc is a part of the PYTHIA event generator.
// Copyright (C) 2023 Torbjorn Sjostrand.
// PYTHIA is licenced under the GNU GPL v2 or later, see COPYING for details.
// Please respect the MCnet Guidelines, see GUIDELINES for details.

// Keywords: matching; merging; powheg

// Example how to perform matching with POWHEG-BOX events,
// based on the code found in include/Pythia8Plugins/PowhegHooks.h.

#include <getopt.h>

#include "Pythia8/Pythia.h"
#include "Pythia8Plugins/PowhegHooks.h"
#include "Pythia8Plugins/Pythia8Rivet.h"
using namespace Pythia8;

//==========================================================================

int main(int argc, char** argv) {

  // Generator
  Pythia pythia;

  // New settings for Rivet interface.
  pythia.settings.addFlag("Main:Rivet", true);
  pythia.settings.addWord("Rivet:output","analysis.yoda");
  pythia.settings.addWVec("Rivet:analyses",vector<string>());

  // Fetch command-line arguments.
  string runcard = "";
  string lhefile = "";
  string outfile = "";
  int    seed    = -1;
  for(;;) {
    switch(getopt(argc, argv, "c:f:o:s:h")) {
    case 'c':
      runcard = string(optarg);
      continue;
    case 'f':
      lhefile = string(optarg);
      continue;
    case 'o':
      outfile = string(optarg);
      continue;
    case 's':
      seed = atoi(optarg);
      continue;
    case '?':
    case 'h':
    default :
      cout << " Usage:" << endl;
      cout << " ./" << argv[0] << " -c <runcard> [optargs]" << endl;
      cout << "\n -c <runcard>" << endl
	   << "\n -f <LHEFile>" << endl
	   << "\n -o <RivetOutput>" << endl;
      break;
    case -1:
      break;
    }
    break;
  }
  // Check if we have a run card.
  if (runcard == "") {
    cerr << " Error: no run card provided\n" << endl;
    return EXIT_FAILURE;
  }

  // Load run card.
  pythia.readFile(runcard);

  // Read in main settings.
  int nEvent      = pythia.settings.mode("Main:numberOfEvents");
  int nError      = pythia.settings.mode("Main:timesAllowErrors");
  // Read in key POWHEG matching settings.
  int vetoMode    = pythia.settings.mode("POWHEG:veto");
  int MPIvetoMode = pythia.settings.mode("POWHEG:MPIveto");
  bool loadHooks  = (vetoMode > 0 || MPIvetoMode > 0);
  // Read in shower settings.
  int showerModel = pythia.settings.mode("PartonShowers:model");
  // Read in LHE file if specified on command line.
  if (lhefile != "") pythia.readString("Beams:LHEF = "+lhefile);
  // Read name of Yoda file if specified on command line.
  if (outfile != "") pythia.readString("Rivet:output = "+outfile);
  // Set seed if specified on command line.
  if (seed >= 0) {
    pythia.readString("Random:setSeed = on");
    pythia.readString("Random:seed    = "+to_string(seed));
  }

  // Add user hooks for shower vetoing.
  shared_ptr<PowhegHooks> powhegHooks;
  if (loadHooks) {
    // Set showers to start at the kinematical limit.
    if (vetoMode > 0) {
      if (showerModel == 1 || showerModel == 3) {
        // Pythia and Dire have separate settings for ISR and FSR.
        pythia.readString("SpaceShower:pTmaxMatch = 2");
        pythia.readString("TimeShower:pTmaxMatch = 2");
      } else if (showerModel == 2) {
        // Vincia only has one common setting for both ISR and FSR.
        pythia.readString("Vincia:pTmaxMatch = 2");
      }
    }

    // Set MPI to start at the kinematical limit.
    if (MPIvetoMode > 0) {
      pythia.readString("MultipartonInteractions:pTmaxMatch = 2");
    }

    powhegHooks = make_shared<PowhegHooks>();
    pythia.setUserHooksPtr((UserHooksPtr)powhegHooks);
  }

  // Rivet interface.
  const bool doRivet = pythia.flag("Main:Rivet");
  Pythia8Rivet rivet(pythia, pythia.word("Rivet:output"));
  vector<string> analyses = pythia.settings.wvec("Rivet:analyses");
  for (const string& analysis : analyses) rivet.addAnalysis(analysis);

  // Initialise PYTHIA.
  if (!pythia.init()) {
    cerr << " Error: PYTHIA initialisation failed" << endl;
    return EXIT_FAILURE;
  }

  // Event loop.
  int iEvent = 0, iError = 0;
  while (true) {
    // Generate the next event
    if (!pythia.next()) {

      // If failure because reached end of file then exit event loop
      if (pythia.info.atEndOfFile()) break;

      // Otherwise count event failure and continue/exit as necessary
      cout << "Warning: event " << iEvent << " failed" << endl;
      if (++iError == nError) {
	cout << "Error: too many event failures... exiting" << endl;
	break;
      }
      continue;
    }

    // Workaround for event weights which are not in "detailed" format.
    double wt = pythia.info.weight();
    for (int iWt(1); iWt<pythia.info.getInitrwgtSize(); ++iWt) {
      pythia.info.weightContainerPtr->weightsLHEF.bookWeight("VAR"+to_string(iWt),
        pythia.info.getWeightsCompressedValue(iWt)/wt);
    }

    // Pass to RIVET.
    if (doRivet) rivet();

    // If nEvent is set, check and exit loop if necessary
    ++iEvent;
    if (nEvent != 0 && iEvent == nEvent) break;
  }

  // Finalise analysis.
  if (doRivet) rivet.done();

  // Statistics.
  pythia.stat();

  // Done.
  return 0;
}