From 6413588df62d2fcc835ad5b570a57b0c96e102d7 Mon Sep 17 00:00:00 2001
From: falsycat <me@falsy.cat>
Date: Sun, 6 Aug 2023 16:02:52 +0900
Subject: [PATCH] add subsys::Clock

---
 core/CMakeLists.txt   |  2 ++
 core/clock.hh         | 27 +++++++++++++++++++++++++++
 core/clock_test.cc    | 20 ++++++++++++++++++++
 iface/subsys/clock.hh | 21 +++++++++++++++++++++
 4 files changed, 70 insertions(+)
 create mode 100644 core/clock.hh
 create mode 100644 core/clock_test.cc
 create mode 100644 iface/subsys/clock.hh

diff --git a/core/CMakeLists.txt b/core/CMakeLists.txt
index 210de03..5e7ac83 100644
--- a/core/CMakeLists.txt
+++ b/core/CMakeLists.txt
@@ -16,6 +16,7 @@ target_sources(nf7_core
     luajit/context.hh
     luajit/lambda.hh
     luajit/thread.hh
+    clock.hh
     version.hh
 )
 
@@ -27,6 +28,7 @@ target_sources(nf7_core_test
     luajit/lambda_test.cc
     luajit/thread_test.cc
     luajit/thread_test.hh
+    clock_test.cc
 )
 target_link_libraries(nf7_core_test
   PRIVATE
diff --git a/core/clock.hh b/core/clock.hh
new file mode 100644
index 0000000..ce08898
--- /dev/null
+++ b/core/clock.hh
@@ -0,0 +1,27 @@
+// No copyright
+#pragma once
+
+#include "iface/subsys/clock.hh"
+
+namespace nf7::core {
+
+class Clock : public subsys::Clock {
+ public:
+  static Time GetCurrentTime() noexcept {
+    return std::chrono::time_point_cast<
+        Resolution>(std::chrono::system_clock::now());
+  }
+
+ public:
+  explicit Clock(Time now = GetCurrentTime()) noexcept
+      : subsys::Clock("Clock"), now_(now) { }
+
+  void Tick(Time now = GetCurrentTime()) noexcept { now_ = now; }
+
+  Time now() const noexcept { return now_; }
+
+ private:
+  Time now_;
+};
+
+}  // namespace nf7::core
diff --git a/core/clock_test.cc b/core/clock_test.cc
new file mode 100644
index 0000000..eff015a
--- /dev/null
+++ b/core/clock_test.cc
@@ -0,0 +1,20 @@
+// No copyright
+#include "core/clock.hh"
+
+#include <gtest/gtest.h>
+
+#include <chrono>
+
+
+using namespace std::literals;
+
+TEST(Clock, now) {
+  nf7::core::Clock sut {nf7::core::Clock::Time {0ms}};
+  EXPECT_EQ(sut.now(), nf7::core::Clock::Time {0ms});
+}
+
+TEST(Clock, Tick) {
+  nf7::core::Clock sut {nf7::core::Clock::Time {0ms}};
+  sut.Tick(nf7::core::Clock::Time {1ms});
+  EXPECT_EQ(sut.now(), nf7::core::Clock::Time {1ms});
+}
diff --git a/iface/subsys/clock.hh b/iface/subsys/clock.hh
new file mode 100644
index 0000000..d07927a
--- /dev/null
+++ b/iface/subsys/clock.hh
@@ -0,0 +1,21 @@
+// No copyright
+#pragma once
+
+#include <chrono>
+
+#include "iface/subsys/interface.hh"
+
+
+namespace nf7::subsys {
+
+class Clock : public Interface {
+ public:
+  using Resolution = std::chrono::milliseconds;
+  using Time       = std::chrono::sys_time<Resolution>;
+
+  using Interface::Interface;
+
+  virtual Time now() const noexcept = 0;
+};
+
+}  // namespace nf7::subsys