From e4130ea27cc3a13780e95bd0654675336fa564ec Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Sat, 13 Jul 2024 15:29:54 +0200
Subject: domain/participant: add three way comparison operator

---
 domain/include/turns/domain/participant.hpp |  6 ++++++
 domain/src/participant.cpp                  | 10 ++++++++++
 domain/tests/participant.cpp                | 30 +++++++++++++++++++++++++++++
 3 files changed, 46 insertions(+)

diff --git a/domain/include/turns/domain/participant.hpp b/domain/include/turns/domain/participant.hpp
index 760ba31..f6ceff7 100644
--- a/domain/include/turns/domain/participant.hpp
+++ b/domain/include/turns/domain/participant.hpp
@@ -1,6 +1,8 @@
 #ifndef TURNS_DOMAIN_PARTICIPANT_HPP
 #define TURNS_DOMAIN_PARTICIPANT_HPP
 
+#include <compare>
+
 #include <glibmm/object.h>
 #include <glibmm/refptr.h>
 #include <glibmm/ustring.h>
@@ -12,6 +14,8 @@ namespace turns::domain
   {
     auto static create(Glib::ustring name, float order_value) -> Glib::RefPtr<participant>;
 
+    auto operator<=>(participant const & other) const noexcept -> std::partial_ordering;
+
     auto name() const noexcept -> Glib::ustring const &;
     auto name(Glib::ustring value) -> participant &;
 
@@ -25,6 +29,8 @@ namespace turns::domain
     float m_order_value;
   };
 
+  auto operator<=>(Glib::RefPtr<participant> const & lhs, Glib::RefPtr<participant> const & rhs) -> std::partial_ordering;
+
 }  // namespace turns::domain
 
 #endif
\ No newline at end of file
diff --git a/domain/src/participant.cpp b/domain/src/participant.cpp
index 8302024..d7e6b30 100644
--- a/domain/src/participant.cpp
+++ b/domain/src/participant.cpp
@@ -16,6 +16,11 @@ namespace turns::domain
   {
   }
 
+  auto participant::operator<=>(participant const & other) const noexcept -> std::partial_ordering
+  {
+    return order() <=> other.order();
+  }
+
   auto participant::name() const noexcept -> Glib::ustring const &
   {
     return m_name;
@@ -38,4 +43,9 @@ namespace turns::domain
     return *this;
   }
 
+  auto operator<=>(Glib::RefPtr<participant> const & lhs, Glib::RefPtr<participant> const & rhs) -> std::partial_ordering
+  {
+    return *lhs <=> *rhs;
+  }
+
 }  // namespace turns::domain
\ No newline at end of file
diff --git a/domain/tests/participant.cpp b/domain/tests/participant.cpp
index b7429aa..ee8af74 100644
--- a/domain/tests/participant.cpp
+++ b/domain/tests/participant.cpp
@@ -1,8 +1,11 @@
 #include "turns/domain/participant.hpp"
 
 #include <catch2/catch_test_macros.hpp>
+
 #include <glibmm/init.h>
 
+#include <compare>
+
 namespace turns::domain::tests
 {
 
@@ -38,6 +41,33 @@ namespace turns::domain::tests
       instance->order(8);
       REQUIRE(instance->order() == 8);
     }
+
+    SECTION("can be compared with another participant")
+    {
+      auto equivalent_instance = participant::create("Equivalent", constructed_order);
+      auto lesser_instance = participant::create("Lesser", constructed_order - 1);
+      auto greater_instance = participant::create("Greater", constructed_order + 1);
+
+      SECTION("yielding std::partial_ordering::equivalent for itself")
+      {
+        REQUIRE((instance <=> equivalent_instance) == std::partial_ordering::equivalent);
+      }
+
+      SECTION("yielding std::partial_ordering::equivalent for an equivalent participant")
+      {
+        REQUIRE((instance <=> equivalent_instance) == std::partial_ordering::equivalent);
+      }
+
+      SECTION("yielding std::partial_ordering::greater for a lesser participant")
+      {
+        REQUIRE((instance <=> lesser_instance) == std::partial_ordering::greater);
+      }
+
+      SECTION("yielding std::partial_ordering::less for a greater participant")
+      {
+        REQUIRE((instance <=> greater_instance) == std::partial_ordering::less);
+      }
+    }
   }
 
 }  // namespace turns::domain::tests
\ No newline at end of file
-- 
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