wrap unix timestamps in newtype

1 files changed, 44 insertions, 4 deletions

diff --git a/src/clock.rs b/src/clock.rs
index dafd44b..7613930 100644
--- a/src/clock.rs
+++ b/src/clock.rs
@@ -7,6 +7,46 @@
 //! isn't affected.
 
 use std::sync::atomic::{AtomicI64, Ordering};
+use std::time::Duration;
+
+use serde::{Deserialize, Serialize};
+
+/// A point in time as Unix milliseconds, as stored in the document and reported: not a
+/// duration (those are `Duration`, or plain milliseconds named `…_ms`). Comparable
+/// across nodes as far as their clocks agree; for elapsed time within a node use
+/// tokio's `Instant`.
+#[derive(
+    Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize,
+)]
+#[serde(transparent)]
+pub(crate) struct UnixMillis(pub(crate) u64);
+
+impl UnixMillis {
+    pub(crate) fn as_u64(self) -> u64 {
+        self.0
+    }
+
+    /// `ms` milliseconds later (saturating).
+    pub(crate) fn plus_ms(self, ms: u64) -> Self {
+        Self(self.0.saturating_add(ms))
+    }
+
+    /// `duration` later (saturating, to the millisecond).
+    pub(crate) fn plus(self, duration: Duration) -> Self {
+        self.plus_ms(u64::try_from(duration.as_millis()).unwrap_or(u64::MAX))
+    }
+
+    /// Milliseconds from `earlier` to this; 0 if `earlier` is later.
+    pub(crate) fn ms_since(self, earlier: Self) -> u64 {
+        self.0.saturating_sub(earlier.0)
+    }
+}
+
+impl std::fmt::Display for UnixMillis {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0.fmt(f)
+    }
+}
 
 /// The node's wall clock: the system clock plus an offset (zero outside tests).
 #[derive(Debug, Default)]
@@ -15,10 +55,10 @@ pub(crate) struct Clock {
 }
 
 impl Clock {
-    /// Now, in Unix milliseconds.
-    pub(crate) fn now_millis(&self) -> u64 {
+    /// Now.
+    pub(crate) fn now_millis(&self) -> UnixMillis {
         let offset = self.offset_ms.load(Ordering::Relaxed);
-        system_millis().saturating_add_signed(offset)
+        UnixMillis(system_millis().saturating_add_signed(offset))
     }
 
     /// Puts this clock `offset_ms` ahead of the system clock (behind if negative).
@@ -46,7 +86,7 @@ mod tests {
         let before = clock.now_millis();
         clock.set_offset_ms(3_600_000);
         let ahead = clock.now_millis();
-        assert!(ahead >= before + 3_600_000);
+        assert!(ahead >= before.plus_ms(3_600_000));
         clock.set_offset_ms(-3_600_000);
         assert!(clock.now_millis() < before);
     }