#include <iostream>

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

#include "DataFormats/Candidate/interface/CandidateFwd.h"
#include "DataFormats/RecoCandidate/interface/RecoCandidate.h"
#include "DataFormats/RecoCandidate/interface/RecoChargedCandidate.h"
#include "DataFormats/RecoCandidate/interface/RecoChargedCandidateFwd.h"
#include "DataFormats/Candidate/interface/Candidate.h"

#include "DataFormats/TrackReco/interface/TrackFwd.h"
#include "DataFormats/TrackReco/interface/Track.h"

#include "DataFormats/VertexReco/interface/Vertex.h"
#include "DataFormats/VertexReco/interface/VertexFwd.h"
#include "DataFormats/Common/interface/RefToBase.h"
#include "DataFormats/HLTReco/interface/TriggerFilterObjectWithRefs.h"
#include "DataFormats/HLTReco/interface/TriggerRefsCollections.h"

#include "DataFormats/BeamSpot/interface/BeamSpot.h"

#include "DataFormats/Math/interface/Error.h"
#include "DataFormats/Math/interface/Point3D.h"
#include "DataFormats/GeometryVector/interface/GlobalPoint.h"
#include "DataFormats/GeometryCommonDetAlgo/interface/GlobalError.h"

#include "FWCore/ParameterSet/interface/ConfigurationDescriptions.h"

#include "HLTDisplacedmumuFilter.h"
#include "TMath.h"

//
// constructors and destructor
//
HLTDisplacedmumuFilter::HLTDisplacedmumuFilter(const edm::ParameterSet& iConfig)
    : HLTFilter(iConfig),
      fastAccept_(iConfig.getParameter<bool>("FastAccept")),
      minLxySignificance_(iConfig.getParameter<double>("MinLxySignificance")),
      maxLxySignificance_(iConfig.getParameter<double>("MaxLxySignificance")),
      maxNormalisedChi2_(iConfig.getParameter<double>("MaxNormalisedChi2")),
      minVtxProbability_(iConfig.getParameter<double>("MinVtxProbability")),
      minCosinePointingAngle_(iConfig.getParameter<double>("MinCosinePointingAngle")),
      DisplacedVertexTag_(iConfig.getParameter<edm::InputTag>("DisplacedVertexTag")),
      DisplacedVertexToken_(consumes<reco::VertexCollection>(DisplacedVertexTag_)),
      beamSpotTag_(iConfig.getParameter<edm::InputTag>("BeamSpotTag")),
      beamSpotToken_(consumes<reco::BeamSpot>(beamSpotTag_)),
      MuonTag_(iConfig.getParameter<edm::InputTag>("MuonTag")),
      MuonToken_(consumes<reco::RecoChargedCandidateCollection>(MuonTag_)) {}

HLTDisplacedmumuFilter::~HLTDisplacedmumuFilter() = default;

void HLTDisplacedmumuFilter::fillDescriptions(edm::ConfigurationDescriptions& descriptions) {
  edm::ParameterSetDescription desc;
  makeHLTFilterDescription(desc);
  desc.add<bool>("FastAccept", false);
  desc.add<double>("MinLxySignificance", 0.0);
  desc.add<double>("MaxLxySignificance", 0.0);
  desc.add<double>("MaxNormalisedChi2", 10.0);
  desc.add<double>("MinVtxProbability", 0.0);
  desc.add<double>("MinCosinePointingAngle", -2.0);
  desc.add<edm::InputTag>("DisplacedVertexTag", edm::InputTag("hltDisplacedmumuVtx"));
  desc.add<edm::InputTag>("BeamSpotTag", edm::InputTag("hltOnlineBeamSpot"));
  desc.add<edm::InputTag>("MuonTag", edm::InputTag("hltL3MuonCandidates"));
  descriptions.add("hltDisplacedmumuFilter", desc);
}

// ------------ method called once each job just before starting event loop  ------------
void HLTDisplacedmumuFilter::beginJob() {}

// ------------ method called once each job just after ending the event loop  ------------
void HLTDisplacedmumuFilter::endJob() {}

// ------------ method called on each new Event  ------------
bool HLTDisplacedmumuFilter::hltFilter(edm::Event& iEvent,
                                       const edm::EventSetup& iSetup,
                                       trigger::TriggerFilterObjectWithRefs& filterproduct) const {
  // get beam spot
  reco::BeamSpot vertexBeamSpot;
  edm::Handle<reco::BeamSpot> recoBeamSpotHandle;
  iEvent.getByToken(beamSpotToken_, recoBeamSpotHandle);
  vertexBeamSpot = *recoBeamSpotHandle;

  // get displaced vertices
  reco::VertexCollection displacedVertexColl;
  edm::Handle<reco::VertexCollection> displacedVertexCollHandle;
  bool foundVertexColl = iEvent.getByToken(DisplacedVertexToken_, displacedVertexCollHandle);
  if (foundVertexColl)
    displacedVertexColl = *displacedVertexCollHandle;

  // get muon collection
  edm::Handle<reco::RecoChargedCandidateCollection> mucands;
  iEvent.getByToken(MuonToken_, mucands);

  // All HLT filters must create and fill an HLT filter object,
  // recording any reconstructed physics objects satisfying (or not)
  // this HLT filter, and place it in the Event.

  // Ref to Candidate object to be recorded in filter object
  reco::RecoChargedCandidateRef ref1;
  reco::RecoChargedCandidateRef ref2;

  if (saveTags())
    filterproduct.addCollectionTag(MuonTag_);

  bool triggered = false;

  // loop over vertex collection
  for (const auto& displacedVertex : displacedVertexColl) {
    // check if the vertex actually consists of exactly two muon tracks, throw exception if not
    if (displacedVertex.tracksSize() != 2)
      throw cms::Exception("BadLogic") << "HLTDisplacedmumuFilter: ERROR: the Jpsi vertex must have exactly two muons "
                                          "by definition. It now has n muons = "
                                       << displacedVertex.tracksSize() << std::endl;

    float normChi2 = displacedVertex.normalizedChi2();
    if (normChi2 > maxNormalisedChi2_)
      continue;

    double vtxProb = 0.0;
    if ((displacedVertex.chi2() >= 0.0) && (displacedVertex.ndof() > 0))
      vtxProb = TMath::Prob(displacedVertex.chi2(), displacedVertex.ndof());
    if (vtxProb < minVtxProbability_)
      continue;

    // get the two muons from the vertex
    auto trackIt = displacedVertex.tracks_begin();
    reco::TrackRef vertextkRef1 = (*trackIt).castTo<reco::TrackRef>();
    // the second one
    trackIt++;
    reco::TrackRef vertextkRef2 = (*trackIt).castTo<reco::TrackRef>();

    // first find these two tracks in the muon collection
    reco::RecoChargedCandidateCollection::const_iterator cand1;
    reco::RecoChargedCandidateCollection::const_iterator cand2;

    int iFoundRefs = 0;
    for (auto cand = mucands->begin(); cand != mucands->end(); cand++) {
      reco::TrackRef tkRef = cand->get<reco::TrackRef>();
      if (tkRef == vertextkRef1) {
        cand1 = cand;
        iFoundRefs++;
      }
      if (tkRef == vertextkRef2) {
        cand2 = cand;
        iFoundRefs++;
      }
    }
    if (iFoundRefs < 2)
      throw cms::Exception("BadLogic") << "HLTDisplacedmumuFilter: ERROR: the muons matched with the Jpsi vertex "
                                          "tracks should be at least two by definition."
                                       << std::endl;

    // calculate two-track transverse momentum
    math::XYZVector pperp(cand1->px() + cand2->px(), cand1->py() + cand2->py(), 0.);

    const reco::Vertex::Point& vpoint = displacedVertex.position();
    //translate to global point, should be improved
    GlobalPoint secondaryVertex(vpoint.x(), vpoint.y(), vpoint.z());

    reco::Vertex::Error verr = displacedVertex.error();
    // translate to global error, should be improved
    GlobalError err(verr.At(0, 0), verr.At(1, 0), verr.At(1, 1), verr.At(2, 0), verr.At(2, 1), verr.At(2, 2));

    GlobalPoint displacementFromBeamspot(-1 * ((vertexBeamSpot.x0() - secondaryVertex.x()) +
                                               (secondaryVertex.z() - vertexBeamSpot.z0()) * vertexBeamSpot.dxdz()),
                                         -1 * ((vertexBeamSpot.y0() - secondaryVertex.y()) +
                                               (secondaryVertex.z() - vertexBeamSpot.z0()) * vertexBeamSpot.dydz()),
                                         0);

    float lxy = displacementFromBeamspot.perp();
    float lxyerr = sqrt(err.rerr(displacementFromBeamspot));

    //calculate the angle between the decay length and the mumu momentum
    reco::Vertex::Point vperp(displacementFromBeamspot.x(), displacementFromBeamspot.y(), 0.);

    float cosAlpha = vperp.Dot(pperp) / (vperp.R() * pperp.R());

    // check thresholds
    if (cosAlpha < minCosinePointingAngle_)
      continue;
    if (minLxySignificance_ > 0. && lxy / lxyerr < minLxySignificance_)
      continue;
    if (maxLxySignificance_ > 0. && lxy / lxyerr > maxLxySignificance_)
      continue;
    triggered = true;

    // now add the muons that passed to the filter object

    ref1 = reco::RecoChargedCandidateRef(
        edm::Ref<reco::RecoChargedCandidateCollection>(mucands, distance(mucands->begin(), cand1)));
    filterproduct.addObject(trigger::TriggerMuon, ref1);

    ref2 = reco::RecoChargedCandidateRef(
        edm::Ref<reco::RecoChargedCandidateCollection>(mucands, distance(mucands->begin(), cand2)));
    filterproduct.addObject(trigger::TriggerMuon, ref2);
  }

  LogDebug("HLTDisplacedMumuFilter") << " >>>>> Result of HLTDisplacedMumuFilter is " << triggered << std::endl;

  return triggered;
}