From a7411c11549eeab7fbbcf00e6dc267f38d740a64 Mon Sep 17 00:00:00 2001
From: falsycat <me@falsy.cat>
Date: Wed, 16 Aug 2023 11:51:24 +0900
Subject: [PATCH] add uv::Clock

---
 core/CMakeLists.txt |  1 +
 core/uv/clock.hh    | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 core/uv/clock.hh

diff --git a/core/CMakeLists.txt b/core/CMakeLists.txt
index c15e81d..005c90c 100644
--- a/core/CMakeLists.txt
+++ b/core/CMakeLists.txt
@@ -18,6 +18,7 @@ target_sources(nf7_core
     luajit/lambda.hh
     luajit/thread.hh
     uv/context.hh
+    uv/clock.hh
     clock.hh
     logger.hh
     version.hh
diff --git a/core/uv/clock.hh b/core/uv/clock.hh
new file mode 100644
index 0000000..e4d9d9b
--- /dev/null
+++ b/core/uv/clock.hh
@@ -0,0 +1,40 @@
+// No copyright
+#pragma once
+
+#include <chrono>
+#include <memory>
+#include <optional>
+
+#include "iface/subsys/clock.hh"
+#include "iface/env.hh"
+
+#include "core/uv/context.hh"
+#include "core/clock.hh"
+
+namespace nf7::core::uv {
+
+class Clock : public subsys::Clock {
+ public:
+  explicit Clock(Env& env)
+      : subsys::Clock("nf7::core::uv::Clock"),
+        ctx_(env.Get<Context>()) { }
+
+ public:
+  void Reset(Time now = core::Clock::GetCurrentTime()) noexcept {
+    epoch_ = now - std::chrono::milliseconds(ctx_->loop()->now());
+  }
+
+  Time now() const noexcept override {
+    if (std::nullopt == epoch_) {
+      const_cast<Clock&>(*this).Reset();
+    }
+    return *epoch_ + std::chrono::milliseconds(ctx_->loop()->now());
+  }
+
+ private:
+  const std::shared_ptr<Context> ctx_;
+
+  std::optional<Time> epoch_;
+};
+
+}  // namespace nf7::core::uv