#include<iostream>          // For printing messages to the terminal
#include<string>            // For strings
#include<TH1D.h>            // ROOT histograms
#include<TFile.h>           // ROOT files
#include<TCanvas.h>         // ROOT canvas for plotting
#include<TPad.h>            // ROOT pads for advanced plotting
#include<TLegend.h>         // ROOT legends for plots
#include<TLatex.h>          // ROOT latex for flexible text drawing
#include<TLine.h>           // ROOT support for drawing lines
#include<TPad.h>           // ROOT support for drawing lines

void ReadHisto(){
  // Retrieve the histograms from the file
  // Open the file in read-only mode
  TFile* histFileData = new TFile("histodata.root");
  TFile* histFileMC   = new TFile("histoMC.root");
  // Get the data histogram
  TH1D* dataHisto = (TH1D*)histFileData->Get("DATA");
  // Get the MC histogram
  TH1D* mcHisto   = (TH1D*)histFileMC->Get("DATA");
  // Make sure you got the histograms

  if (!dataHisto)
    {
      return;
    }
  if (!mcHisto)
    {
      return;
    }

  // Basic style
  //  Turn off the statistics box
  mcHisto->SetStats(0);
  dataHisto->SetStats(0);
  // Set the line color to red for MC and black for data
  mcHisto->SetLineColor(kRed);
  dataHisto->SetLineColor(kBlack);
  // Set the line width to 2 for MC and data
  mcHisto->SetLineWidth(2);
  dataHisto->SetLineWidth(2);
  // Set axis labels
  mcHisto->GetYaxis()->SetTitle("Number of events");
  dataHisto->GetYaxis()->SetTitle("Number of events");
  mcHisto->GetXaxis()->SetTitle("m_{ll} [MeV]");
  dataHisto->GetXaxis()->SetTitle("m_{ll} [MeV]");
  
  // Prepare the canvas for plotting
  // Make a canvas
  TCanvas *c1 = new TCanvas("c1","c1");
  // Move into the canvas (so anything drawn is part of this canvas)
  c1->Divide(2,1);
  c1->cd(1);gPad->SetLogy();
  mcHisto->DrawCopy();
  c1->cd(2);gPad->SetLogy();
  dataHisto->DrawCopy();
  

  TH1F *hMCscaled = (TH1F*)mcHisto->Clone("hMCscaled");
  hMCscaled->Scale(dataHisto->Integral()/mcHisto->Integral());

  TCanvas *c2 = new TCanvas("c2","c2");
  c2->cd(1);
  hMCscaled->Draw("h");
  dataHisto->Draw("pe,same");

  // Calculate the ratio
  // First clone the current data points
  TH1D* ratio = (TH1D*)dataHisto->Clone("ratio");
  // Divide the data points by the MC histogram
  ratio->Divide(hMCscaled);

  ratio->SetLineColor(kRed);

  //------------------------------------------------------
  
  TCanvas *c3 = new TCanvas("c3","c3",600,800);
  //  c3->cd();

  TPad *pad1 = new TPad("pad1", "pad1", 0, 0.3, 1, 1.0);
  pad1->SetBottomMargin(0); // Upper and lower plot are joined
  pad1->SetGridx();         // Vertical grid
  pad1->SetLogy();         // Vertical grid
  pad1->Draw();             // Draw the upper pad: pad1
  pad1->cd();               // pad1 becomes the current pad
    
  hMCscaled->SetTitle("");                  // Remove the plot title
  hMCscaled->GetXaxis()->SetLabelSize(0);   // Remove x-axis labels for the top pad
  hMCscaled->GetXaxis()->SetTitleSize(0);   // Remove x-axis title for t he top pad
  hMCscaled->GetYaxis()->SetTitleSize(0.04);// Increase y-axis title size (pad is not full page)
  hMCscaled->Draw("h");                     // Draw the MC histo in the current pad
  dataHisto->Draw("pe,same");             // Draw the data points on top of the MC histo
  
  // Add a legend to the top pad
  TLegend *legend = new TLegend(0.48,0.56,0.64,0.71);      // Add a legend near the top right corner
  legend->AddEntry(hMCscaled,"MC");          // Add the MC histogram, labelled as "MC"
  legend->AddEntry(dataHisto,"Data");      // Add the data points, labelled as "Data"
  legend->SetLineWidth(0);                 // Remove the boundary on the legend
  legend->Draw("same");                    // Draw the legend on the plot
    
  // Add other labels with TLatex
  // Note that TLatex is global, not pad-related
  // As such, the percent-based coordinates for TLatex and the above legend are not the same
  TLatex latex;                               // Create the TLatex object
  latex.SetNDC();                             // Set the coordintes to be percent-based
  latex.SetTextSize(0.06);                    // Increase the text size
  latex.DrawText(0.48,0.83,"Exarcise 10");      // Write a label for HASCO
  latex.SetTextSize(0.04);                    // Reduce the text size
  latex.DrawText(0.48,0.77,"Di-muon events");  // Add a label for the selection
  
  // Now draw the ratio
  c3->cd();                                // Go back to the main canvas before defining pad2

  TPad *pad2 = new TPad("pad2", "pad2", 0, 0.05, 1, 0.3);
  pad2->SetTopMargin(0);
  pad2->SetBottomMargin(0.2);
  pad2->SetGridx(); // vertical grid
  pad2->Draw();
  pad2->cd();       // pad2 becomes the current pad
   

  ratio->SetTitle("");                        // Turn off the title to avoid overlap
  ratio->GetXaxis()->SetLabelSize(0.12);      // Larger x-axis labels (pad is not full page)
  ratio->GetXaxis()->SetTitleSize(0.09);      // Larger x-axis title (pad is not full page)
  ratio->GetYaxis()->SetLabelSize(0.1);       // Larger y-axis labels (pad is not full page)
  ratio->GetYaxis()->SetTitleSize(0.15);      // Larger y-axis title (pad is not full page)
  ratio->GetYaxis()->SetTitle("Data/MC");     // Change the y-axis title (this is the ratio)
  ratio->GetYaxis()->SetTitleOffset(0.3);     // Reduce the y-axis title spacing
  ratio->GetYaxis()->SetRangeUser(0.5,1.5);   // Set the y-axis ratio range from 0.5 to 1.5
  ratio->GetYaxis()->SetNdivisions(207);      // Change the y-axis tick-marks to work better
  ratio->Draw("pe");                          // Draw the ratio in the current pad
  
  // Add a line at 1 to the ratio plot
  TLine line(50.e3,1,200.e3,1);       // Draw a line at 1 from 50 GeV to 200 GeV (full plot)
  line.SetLineColor(kBlack);     // Set the line colour to black
  line.SetLineWidth(2);               // Set the line width to 2
  line.Draw("same");                  // Draw the line on the same plot as the ratio
  
  // // Write the ratio plot to the output plot file
  c3->SaveAs("finalPlot.pdf");
  c3->SaveAs("finalPlot.png");
  c3->cd();     
}