void GetMinMax(TH1* h, Double_t& ymin, Double_t& ymax)
{
  ymax = -1e30;
  ymin =  1e30;
  for (Int_t i = 1; i <= h->GetNbinsX(); i++) {
    Double_t y = h->GetBinContent(i);
    ymax = TMath::Max(ymax,y);
    if (y > 0)
      ymin = TMath::Min(ymin,y);
  }
}

Bool_t LogScale(TH1* h) {
  Double_t ymin, ymax;
  GetMinMax(h, ymin, ymax);
  if (ymin > ymax) return false;
  return (ymax > ymin * 1000);
}
   
  
  
void CompareTrees(TTree* mine, TTree* dev, TDirectory* ret, TCanvas* canvas)
{

  TDirectory* sub = ret->mkdir(mine->GetName());

  auto mineL = mine->GetListOfBranches();
  Int_t ncol = mineL->GetEntriesFast() > 10 ? 3 : 2;
  Int_t nrow = (mineL->GetEntriesFast() + ncol-1) / ncol;
  canvas->Clear();
  canvas->Divide(ncol, nrow);
  canvas->Draw();
  
  TVirtualPad* pad = 0;
  Int_t ipad = 1;

  Int_t mineN = mine->GetEntries();
  Int_t devN  = dev ->GetEntries();
  if (mineN != devN) {
    Warning(mine->GetName(),
            "Inconsistent selected %d (mine) vs %d (dev)",
            mineN, devN);
  }
  
  sub->cd();
  for (auto ob : *mineL) {
    TBranch* mineB = static_cast<TBranch*>(ob);

    TObject* db = dev->GetListOfBranches()->FindObject(mineB->GetName());
    if (not db) {
      Warning(mineB->GetName(),"Branch not in dev %s",
              dev->GetName());
      continue;
    }

    TBranch* devB = static_cast<TBranch*>(db);

    
    Info(""," %s/%s", mine->GetName(), mineB->GetName());
      
    mine->Draw(Form("%s>>hmine",mineB->GetName()),"","goff");
    dev ->Draw(Form("%s>>hdev", devB ->GetName()),"","goff");

    mineN           = mine->GetSelectedRows();
    devN            = dev ->GetSelectedRows();
    Double_t* mineX = mine->GetV1();
    Double_t* devX  = dev ->GetV1();
    Int_t     nDiff = 0;
    Int_t     diff1 = -1;
    for (size_t i = 0; i < TMath::Min(mineN,devN); i++) {
      if (TMath::Abs((mineX[i] - devX[i]) / devX[i]) > 0.001) {
        nDiff++;
        // Info(mineB->GetName(), "    %8d: %g  vs  %g",
        //      i, mineX[i], devX[i]);
        if (diff1 >= 0) continue;
        diff1 = i;
      }
    }
    if (nDiff > 0)
      Warning(mineB->GetName(), "%d values differ, starting at %d",
              nDiff, diff1);
    
      
    
    TH1* mineH = static_cast<TH1*>(sub->Get("hmine"));
    TH1* devH  = static_cast<TH1*>(sub->Get("hdev"));

    if ((mineH and not devH) or (not mineH and devH)) {
      Warning(mineB->GetName(),"One histogram is missing %p %p",
              mineH, devH);
      continue;
    }
    if (not mineH and not devH) {
      // Warning(mineB->GetName(),"No histograms"); 
      continue;
    }

    mineH->SetName(mineB->GetName());
    mineH->SetTitle("Mine");
    mineH->SetLineColor(kRed+1);
    mineH->SetFillColor(kRed+1);
    mineH->SetMarkerColor(kRed+1);
    mineH->SetMarkerStyle(20);
    devH ->SetName(devB->GetName());
    devH ->SetTitle("Dev");
    devH ->SetLineColor  (kBlue+1);
    devH ->SetFillColor  (kBlue+1);
    devH ->SetMarkerColor(kBlue+1);
    devH ->SetMarkerStyle(25);
    devH ->SetMarkerSize(1.2);

    THStack* stack = new THStack(mineB->GetName(), mineB->GetName());
    stack->Add(mineH);
    stack->Add(devH);
    stack->Write();

    pad = canvas->cd(ipad);
    stack->Draw("no stack ep");
    TH1* h = stack->GetHistogram();
    if (LogScale(mineH) or LogScale(devH))
      pad->SetLogy();
    
    pad->BuildLegend();
    ipad++;
  }
}


void CompareAO2D()
{
  TFile* mineFile = TFile::Open("mine/AO2D.root","READ");
  TFile* devFile  = TFile::Open("dev/AO2D.root", "READ");
  TFile* output   = TFile::Open("compare.root","RECREATE");
  
  TDirectory* mineDF = mineFile->GetDirectory("DF_1");
  TDirectory* devDF  = devFile->GetDirectory("DF_1");
  Printf("%p %p", mineDF, devDF);

  TCanvas* canvas = new TCanvas("compare","Compare AODs",600,800);
  canvas->Print(Form("%s.pdf[",canvas->GetName()));

  
  for (auto key : *mineDF->GetListOfKeys()) {
    Info("","%s",key->GetName());
    TObject* mineO = static_cast<TKey*>(key)->ReadObj();
    if (not mineO) {
      Warning(key->GetName(),"Gave up on this");
      continue;
    }

    if (not mineO->InheritsFrom(TTree::Class())) {
      Warning(mineO->GetName(),"Not a TTree");
      continue;
    }

    TObject* devO = devDF->Get(mineO->GetName());
    if (not devO) {
      if (not TString(mineO->GetName()).BeginsWith("O2hepmc"))
        Warning(mineO->GetName(), "Object not found in dev output");
      continue;
    }

    if (not devO->InheritsFrom(TTree::Class())) {
      Warning(devO->GetName(),"Is not a TTree");
      continue;
    }
    
    TTree* mineT = static_cast<TTree*>(mineO);
    TTree* devT  = static_cast<TTree*>(devO);

    CompareTrees(mineT,devT,output, canvas);

    canvas->Print(Form("%s.pdf",canvas->GetName()),
                  Form("Title: %s", mineT->GetName()));
    
  }
  canvas->Print(Form("%s.pdf]",canvas->GetName()));
  output->Write();
  
}