From 1e46059a75705f616e5a7a1da91b268fc2d4b36e Mon Sep 17 00:00:00 2001
From: Bohdan Dudar <bohdan.dudar@desy.de>
Date: Wed, 31 Aug 2022 14:11:56 +0200
Subject: [PATCH] Add a utility function to return a leading track of the
 ReconstructedParticle

---
 src/cpp/CMakeLists.txt                            |  1 +
 src/cpp/include/UTIL/ReconstructedParticleTools.h | 15 +++++++++++++++
 src/cpp/src/UTIL/ReconstructedParticleTools.cc    | 15 +++++++++++++++
 3 files changed, 31 insertions(+)
 create mode 100644 src/cpp/include/UTIL/ReconstructedParticleTools.h
 create mode 100644 src/cpp/src/UTIL/ReconstructedParticleTools.cc

diff --git a/src/cpp/CMakeLists.txt b/src/cpp/CMakeLists.txt
index 38e1d7cda..8bcd22a21 100644
--- a/src/cpp/CMakeLists.txt
+++ b/src/cpp/CMakeLists.txt
@@ -122,6 +122,7 @@ SET( LCIO_UTIL_SRCS
   ./src/UTIL/ProcessFlag.cc
   ./src/UTIL/TrackTools.cc
   ./src/UTIL/LCCollectionTools.cc
+  ./src/UTIL/ReconstructedParticleTools.cc
 )
 
 SET( LCIO_MT_SRCS
diff --git a/src/cpp/include/UTIL/ReconstructedParticleTools.h b/src/cpp/include/UTIL/ReconstructedParticleTools.h
new file mode 100644
index 000000000..acb133ac1
--- /dev/null
+++ b/src/cpp/include/UTIL/ReconstructedParticleTools.h
@@ -0,0 +1,15 @@
+#ifndef UTIL_ReconstructedParticleTools_H
+#define UTIL_ReconstructedParticleTools_H 1
+
+#include "EVENT/ReconstructedParticle.h"
+#include "EVENT/Track.h"
+
+namespace UTIL{
+    /** Extract the leading track in case of multiple tracks attached to a single ReconstructedParticle.
+    * @author Bohdan Dudar
+    * @version August 2022
+    */
+    EVENT::Track* getLeadingTrack(const EVENT::ReconstructedParticle* particle, double bz);
+}
+
+#endif
diff --git a/src/cpp/src/UTIL/ReconstructedParticleTools.cc b/src/cpp/src/UTIL/ReconstructedParticleTools.cc
new file mode 100644
index 000000000..792965311
--- /dev/null
+++ b/src/cpp/src/UTIL/ReconstructedParticleTools.cc
@@ -0,0 +1,15 @@
+#include "UTIL/ReconstructedParticleTools.h"
+#include <algorithm>
+#include "UTIL/TrackTools.h"
+// #include <vector>
+
+namespace UTIL{
+    EVENT::Track* getLeadingTrack(const EVENT::ReconstructedParticle* particle, double bz){
+        const EVENT::TrackVec& tracks = particle->getTracks();
+        if ( tracks.empty() ) return nullptr;
+        auto sortByMomentum = [bz](const EVENT::Track* a, const EVENT::Track* b) { return getTrackMomentum(a, bz) < getTrackMomentum(b, bz); };
+        auto* leadingTrack = *(std::max_element(tracks.begin(), tracks.end(), sortByMomentum));
+
+        return leadingTrack;
+    }
+}