From 15a1d84c99e73e3e846d5a9c70e5ff4367a16993 Mon Sep 17 00:00:00 2001
From: Giovanni Marchiori <giovanni.marchiori@cern.ch>
Date: Mon, 28 Aug 2023 21:53:19 +0200
Subject: [PATCH] module-theta segmentation with merging per layer

---
 .../DetComponents/src/RedoSegmentation.cpp    | 37 ++++++++++++++++---
 Detector/DetComponents/src/RedoSegmentation.h |  4 ++
 2 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/Detector/DetComponents/src/RedoSegmentation.cpp b/Detector/DetComponents/src/RedoSegmentation.cpp
index a8d1a3d..54bb74d 100644
--- a/Detector/DetComponents/src/RedoSegmentation.cpp
+++ b/Detector/DetComponents/src/RedoSegmentation.cpp
@@ -63,6 +63,17 @@ StatusCode RedoSegmentation::initialize() {
   info() << "Old bitfield:\t" << m_oldDecoder->fieldDescription() << endmsg;
   info() << "New bitfield:\t" << m_segmentation->decoder()->fieldDescription() << endmsg;
   info() << "New segmentation is of type:\t" << m_segmentation->type() << endmsg;
+  if (m_segmentation->type() == "FCCSWGridModuleThetaMerged")
+    m_segmentationType=2;
+  else
+    m_segmentationType=0;
+  m_oldSegmentation = m_geoSvc->lcdd()->readout(m_oldReadoutName).segmentation().segmentation();
+  info() << "Old segmentation is of type:\t" << m_oldSegmentation->type() << endmsg;
+  if (m_oldSegmentation->type() == "FCCSWGridModuleThetaMerged")
+    m_oldSegmentationType=2;
+  else
+    m_oldSegmentationType=0;
+
   m_outHitsCellIDEncoding.put(m_segmentation->decoder()->fieldDescription());
 
   return StatusCode::SUCCESS;
@@ -79,16 +90,32 @@ StatusCode RedoSegmentation::execute() {
     auto newHit = outHits->create();
     newHit.setEnergy(hit.getEnergy());
     // SimCalorimeterHit type (needed for createCaloCells which runs after RedoSegmentation) has no time member
-    //newHit.setTime(hit.getTime());
+    // newHit.setTime(hit.getTime());
     dd4hep::DDSegmentation::CellID cellId = hit.getCellID();
     if (debugIter < m_debugPrint) {
       debug() << "OLD: " << m_oldDecoder->valueString(cellId) << endmsg;
     }
-    // factor 10 to convert mm to cm // TODO: check
-    auto pos = hit.getPosition();
-    dd4hep::DDSegmentation::Vector3D position(pos.x / 10., pos.y / 10., pos.z / 10.);
+    dd4hep::DDSegmentation::Vector3D position;
+    if (m_oldSegmentationType == 2) {
+      position = m_oldSegmentation->position(cellId);
+    }
+    else {
+      auto pos = hit.getPosition();
+      // factor 10 to convert mm to cm
+      position = dd4hep::DDSegmentation::Vector3D (pos.x / 10., pos.y / 10., pos.z / 10.);
+    }
+
     // first calculate proper segmentation fields
-    dd4hep::DDSegmentation::CellID newCellId = m_segmentation->cellID(position, position, 0);
+    // pass volumeID: we need layer / module information
+    // (which is easier/safer to get from cellID than infer from position)
+    dd4hep::DDSegmentation::VolumeID vID = volumeID(cellId);
+    // for module-theta merged segmentation in which we are replacing
+    // initial module number with merged module number, we still want
+    // to pass the initial module number to segmentation->cellID(..)
+    // as part of the volume ID
+    if (m_segmentationType == 2)
+      m_segmentation->decoder()->set(vID, "module", m_oldDecoder->get(cellId, "module"));
+    dd4hep::DDSegmentation::CellID newCellId = m_segmentation->cellID(position, position, vID);
     // now rewrite all other fields (detector ID)
     for (const auto& detectorField : m_detectorIdentifiers) {
       oldid = m_oldDecoder->get(cellId, detectorField);
diff --git a/Detector/DetComponents/src/RedoSegmentation.h b/Detector/DetComponents/src/RedoSegmentation.h
index e22d833..659a808 100644
--- a/Detector/DetComponents/src/RedoSegmentation.h
+++ b/Detector/DetComponents/src/RedoSegmentation.h
@@ -72,9 +72,13 @@ class RedoSegmentation : public GaudiAlgorithm {
       m_outHits,"CellIDEncodingString", Gaudi::DataHandle::Writer};
   /// New segmentation
   dd4hep::DDSegmentation::Segmentation* m_segmentation;
+  int m_segmentationType; // use enum instead? defined in some namespace?
   /// Name of the detector readout used in simulation
   Gaudi::Property<std::string> m_oldReadoutName{this, "oldReadoutName", "",
                                                 "Name of the detector readout used in simulation"};
+  /// Old segmentation
+  dd4hep::DDSegmentation::Segmentation* m_oldSegmentation;
+  int m_oldSegmentationType; // use enum instead? defined in some namespace?
   /// Name of the new detector readout
   Gaudi::Property<std::string> m_newReadoutName{this, "newReadoutName", "", "Name of the new detector readout"};
   /// Old bitfield decoder