//
//	Example to loop over events, reading more than one file.
//
//	Input parameters are:
//  - dir:      name of the directory where Level2 files are stored
//  - list:     name of a text file with the list of file names to be processed.
//    If list="" all ROOT files inside the directory are processed (ROOT files that does not
//    match Pamela Level2 structure are automatically discarded)
//  - treelist: string containing the list of trees to be loaded (es: "-ORB-ND" or "-ALL+TRK+CAL+TOF").
//    Possible options are:
//    +ALL +TRK +CAL +TRG +TOF +ND +AC +S4 +ORB
//    -ALL -TRK -CAL -TRG -TOF -ND -AC -S4 -ORB
//	- nmax:     maximum number of events to be processed
//
//  All selected trees in all the files are chained and made friends.
//  The whole "blob" can be accessed as if it was a single tree.
//
//  --- Modified on January 2007 ---
//
//      see the comment at the beginning of example1.C      
//
void example3(TString dir,TString list="", TString treelist="+ALL", Int_t nmax=500000000){

    //   Create a timer object to benchmark this loop
    TStopwatch timer;
    timer.Start();
    TString wd=gSystem->WorkingDirectory();
    //
    PamLevel2*  event  = new PamLevel2();       // << create pamela event
	
    // =========================================================
    // << First a TList of root files is created
    // << (either from a specific list or from the whole input directory)
    TList *l  = event->GetListOfLevel2Files(dir,list);
    // << Hence a TChain is created from the list. 
    // << All the trees required by the user are made friend.
    TChain *T = event->GetPamTree(l,treelist);
    // << In the following the TChain can be used similarly to a TTree.

    //
    TChain *RUNT = event->GetRunTree(dir,list); // << get the run information and store it in RUNT

    //
    // NB! It is still possible to read a single file and get a TTree, by means of the methods:
    // TTree* LoadPamTrees(TFile *f);
    // TTree* LoadPamTrees(TFile *f,TString treelist);
    // =========================================================
	
    Int_t nevent = T->GetEntries();	
		
    Int_t ntrk=0;
    if(nevent < nmax)nmax=nevent;
    cout << endl<<" Start loop over events   "<<endl;
    for (Int_t i=0; i<nmax;i++){
	//
	event->Clear();
	T->GetEntry(i);

	if ( event->UpdateRunInfo(RUNT,i) ) printf(" New RUN at entry = %llu RUN ID is %u NEVENTS is %u \n",i,event->GetRunInfo()->ID,event->GetRunInfo()->NEVENTS);
		
	if(event->GetTrkLevel2()->GetNTracks() > 1)cout << " Ev "<<i << " multiple tracks: "<< event->GetTrkLevel2()->GetNTracks() << endl;
		
	if(event->GetTrkLevel2()->ntrk() >0){
	    ntrk++;
	};
		
	for(Int_t it=0; it<event->GetTrkLevel2()->GetNTracks(); it++){
			
 	    PamTrack *track = event->GetTrack(it);
 	    PamTrack *image = 0;
			
 	    if(track->GetTrkTrack()->HasImage())image = event->GetTrackImage(it);
			
 	};

    };                                       // end loop over the events
    cout << endl << endl << " Done "<< endl<<endl;
    cout << ntrk <<" tracks over "<<nmax<<" events ("<< 100*ntrk/nmax<<"%)"<<endl;

//  Stop timer and print results
    timer.Stop();
    Double_t rtime = timer.RealTime();
    Double_t ctime = timer.CpuTime();
    printf("RealTime=%f seconds, CpuTime=%f seconds\n",rtime,ctime);

    gSystem->ChangeDirectory(wd);
	
};