From 1030e5ba8cae096239bee9dd214cb344ab720525 Mon Sep 17 00:00:00 2001
From: Thomas Madlener <thomas.madlener@desy.de>
Date: Fri, 20 Dec 2024 15:16:22 +0100
Subject: [PATCH] Add a variadic overload for multiple metadata objects

---
 test/utils/test_PIDHandler.cpp                | 22 +++++++++++++++++++
 utils/include/edm4hep/utils/ParticleIDUtils.h |  8 +++++++
 2 files changed, 30 insertions(+)

diff --git a/test/utils/test_PIDHandler.cpp b/test/utils/test_PIDHandler.cpp
index 9e60195d5..a9f138153 100644
--- a/test/utils/test_PIDHandler.cpp
+++ b/test/utils/test_PIDHandler.cpp
@@ -161,6 +161,28 @@ TEST_CASE("PIDHandler w/ addMetaInfo", "[pid_utils]") {
   REQUIRE(handler.getParamIndex(42, "p2").value_or(-1) == 1);
 }
 
+TEST_CASE("PIDHandler add multiple meta info objects", "[pid_utils]") {
+  using namespace edm4hep::utils;
+  auto handler = PIDHandler();
+
+  const auto pidInfo1 = ParticleIDMeta{"fancyAlgo", {"param1", "param2"}};
+  const auto pidInfo2 = ParticleIDMeta{"fancyAlgo2", {"p1", "p2"}};
+  const auto pidInfo3 = ParticleIDMeta{"fancyAlgo3", {"p1", "p2"}};
+
+  // Can add all of them at once or do it in steps
+  handler.addMetaInfos(pidInfo1);
+  handler.addMetaInfos(pidInfo2, pidInfo3);
+
+  REQUIRE(handler.getParamIndex(pidInfo1.algoType(), "param2").value() == 1);
+  REQUIRE(handler.getParamIndex(pidInfo2.algoType(), "p1").value() == 0);
+  REQUIRE(handler.getParamIndex(pidInfo3.algoType(), "p2").value() == 1);
+  REQUIRE(handler.getAlgoType("fancyAlgo").value() == pidInfo1.algoType());
+  REQUIRE(handler.getAlgoType("fancyAlgo3").value() == pidInfo3.algoType());
+
+  const auto duplicate = ParticleIDMeta{"fancyAlgo", {}};
+  REQUIRE_THROWS_AS(handler.addMetaInfos(duplicate), std::runtime_error);
+}
+
 TEST_CASE("PIDHandler from Frame w/ metadata", "[pid_utils]") {
   using namespace edm4hep;
   const auto& [event, metadata] = createEventAndMetadata();
diff --git a/utils/include/edm4hep/utils/ParticleIDUtils.h b/utils/include/edm4hep/utils/ParticleIDUtils.h
index d9c2791f6..ae3b54d36 100644
--- a/utils/include/edm4hep/utils/ParticleIDUtils.h
+++ b/utils/include/edm4hep/utils/ParticleIDUtils.h
@@ -85,6 +85,14 @@ class PIDHandler {
   /// Add meta information for a collection
   void addMetaInfo(const edm4hep::utils::ParticleIDMeta& pidInfo);
 
+  /// Add several meta informations simultaneously
+  template <typename... PIDMetas>
+  void addMetaInfos(const PIDMetas&... pidMetas) {
+    static_assert((std::is_same_v<PIDMetas, edm4hep::utils::ParticleIDMeta> && ...),
+                  "Only ParticleIDMeta can be used to add metadata to a PIDHandler");
+    (addMetaInfo(pidMetas), ...);
+  }
+
   /// Retrieve all ParticleIDs that are related to the passed
   /// ReconstructedParticle
   std::vector<edm4hep::ParticleID> getPIDs(const edm4hep::ReconstructedParticle& reco) const;