From 8df95b9293bf27cec9fad87bde5123488363978d Mon Sep 17 00:00:00 2001
From: daxpedda <daxpedda@gmail.com>
Date: Sun, 24 Dec 2023 19:13:24 +0100
Subject: [PATCH] Improve performance of `SystemTime` by using `Duration`
 internally

---
 CHANGELOG.md           |  6 ++++++
 src/web/system_time.rs | 29 ++++++++++-------------------
 2 files changed, 16 insertions(+), 19 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9dbf8ce..ef5a78b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Changed
+
+- Improve performance of `SystemTime` by using `Duration` internally.
+
 ## [0.2.3] - 2023-10-23
 
 ### Changed
diff --git a/src/web/system_time.rs b/src/web/system_time.rs
index c66f602..cee0760 100644
--- a/src/web/system_time.rs
+++ b/src/web/system_time.rs
@@ -7,37 +7,30 @@ use std::time::Duration;
 
 /// See [`std::time::SystemTime`].
 #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
-pub struct SystemTime(i64);
+pub struct SystemTime(Duration);
 
 impl SystemTime {
 	/// See [`std::time::SystemTime::UNIX_EPOCH`].
-	pub const UNIX_EPOCH: Self = Self(0);
+	pub const UNIX_EPOCH: Self = Self(Duration::ZERO);
 
 	/// See [`std::time::SystemTime::now()`].
 	#[must_use]
+	#[allow(clippy::missing_panics_doc)]
 	pub fn now() -> Self {
 		#[allow(clippy::as_conversions, clippy::cast_possible_truncation)]
-		Self(js_sys::Date::now() as i64)
+		let ms = js_sys::Date::now() as i64;
+		let ms = ms.try_into().expect("found negative timestamp");
+
+		Self(Duration::from_millis(ms))
 	}
 
 	/// See [`std::time::SystemTime::duration_since()`].
-	#[allow(
-		clippy::missing_errors_doc,
-		clippy::missing_panics_doc,
-		clippy::trivially_copy_pass_by_ref
-	)]
+	#[allow(clippy::missing_errors_doc, clippy::trivially_copy_pass_by_ref)]
 	pub fn duration_since(&self, earlier: Self) -> Result<Duration, SystemTimeError> {
 		if self.0 < earlier.0 {
-			let duration = (earlier.0 - self.0)
-				.try_into()
-				.expect("`self` bigger then `earlier` despite earlier check");
-
-			Err(SystemTimeError(Duration::from_millis(duration)))
+			Err(SystemTimeError(earlier.0 - self.0))
 		} else {
-			let duration = (self.0 - earlier.0)
-				.try_into()
-				.expect("`earlier` bigger then `self` despite earlier check");
-			Ok(Duration::from_millis(duration))
+			Ok(self.0 - earlier.0)
 		}
 	}
 
@@ -50,14 +43,12 @@ impl SystemTime {
 	/// See [`std::time::SystemTime::checked_add()`].
 	#[allow(clippy::trivially_copy_pass_by_ref)]
 	pub fn checked_add(&self, duration: Duration) -> Option<Self> {
-		let duration = duration.as_millis().try_into().ok()?;
 		self.0.checked_add(duration).map(SystemTime)
 	}
 
 	/// See [`std::time::SystemTime::checked_sub()`].
 	#[allow(clippy::trivially_copy_pass_by_ref)]
 	pub fn checked_sub(&self, duration: Duration) -> Option<Self> {
-		let duration = duration.as_millis().try_into().ok()?;
 		self.0.checked_sub(duration).map(SystemTime)
 	}
 }