1 files changed, 133 insertions, 0 deletions
diff --git a/third_party/rust/sync15/src/server_timestamp.rs b/third_party/rust/sync15/src/server_timestamp.rs
new file mode 100644
index 0000000000..dcd2757453
--- /dev/null
+++ b/third_party/rust/sync15/src/server_timestamp.rs
@@ -0,0 +1,133 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
+
+/// Typesafe way to manage server timestamps without accidentally mixing them up with
+/// local ones.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Default)]
+pub struct ServerTimestamp(pub i64);
+
+impl ServerTimestamp {
+    pub fn from_float_seconds(ts: f64) -> Self {
+        let rf = (ts * 1000.0).round();
+        if !rf.is_finite() || rf < 0.0 || rf >= i64::max_value() as f64 {
+            error_support::report_error!("sync15-illegal-timestamp", "Illegal timestamp: {}", ts);
+            ServerTimestamp(0)
+        } else {
+            ServerTimestamp(rf as i64)
+        }
+    }
+
+    pub fn from_millis(ts: i64) -> Self {
+        // Catch it in tests, but just complain and replace with 0 otherwise.
+        debug_assert!(ts >= 0, "Bad timestamp: {}", ts);
+        if ts >= 0 {
+            Self(ts)
+        } else {
+            error_support::report_error!(
+                "sync15-illegal-timestamp",
+                "Illegal timestamp, substituting 0: {}",
+                ts
+            );
+            Self(0)
+        }
+    }
+}
+
+// This lets us use these in hyper header! blocks.
+impl std::str::FromStr for ServerTimestamp {
+    type Err = std::num::ParseFloatError;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let val = f64::from_str(s)?;
+        Ok(Self::from_float_seconds(val))
+    }
+}
+
+impl std::fmt::Display for ServerTimestamp {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.0 as f64 / 1000.0)
+    }
+}
+
+impl ServerTimestamp {
+    pub const EPOCH: ServerTimestamp = ServerTimestamp(0);
+
+    /// Returns None if `other` is later than `self` (Duration may not represent
+    /// negative timespans in rust).
+    #[inline]
+    pub fn duration_since(self, other: ServerTimestamp) -> Option<Duration> {
+        let delta = self.0 - other.0;
+        if delta < 0 {
+            None
+        } else {
+            Some(Duration::from_millis(delta as u64))
+        }
+    }
+
+    /// Get the milliseconds for the timestamp.
+    #[inline]
+    pub fn as_millis(self) -> i64 {
+        self.0
+    }
+}
+
+impl serde::ser::Serialize for ServerTimestamp {
+    fn serialize<S: serde::ser::Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
+        serializer.serialize_f64(self.0 as f64 / 1000.0)
+    }
+}
+
+impl<'de> serde::de::Deserialize<'de> for ServerTimestamp {
+    fn deserialize<D: serde::de::Deserializer<'de>>(d: D) -> Result<Self, D::Error> {
+        f64::deserialize(d).map(Self::from_float_seconds)
+    }
+}
+
+/// Exposed only for tests that need to create a server timestamp from the system time
+/// Please be cautious when constructing the timestamp directly, as constructing the server
+/// timestamp from system time is almost certainly not what you'd want to do for non-test code
+impl TryFrom<SystemTime> for ServerTimestamp {
+    type Error = std::time::SystemTimeError;
+
+    fn try_from(value: SystemTime) -> Result<Self, Self::Error> {
+        Ok(Self(value.duration_since(UNIX_EPOCH)?.as_millis() as i64))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_server_timestamp() {
+        let t0 = ServerTimestamp(10_300_150);
+        let t1 = ServerTimestamp(10_100_050);
+        assert!(t1.duration_since(t0).is_none());
+        assert!(t0.duration_since(t1).is_some());
+        let dur = t0.duration_since(t1).unwrap();
+        assert_eq!(dur.as_secs(), 200);
+        assert_eq!(dur.subsec_nanos(), 100_000_000);
+    }
+
+    #[test]
+    fn test_serde() {
+        let ts = ServerTimestamp(123_456);
+
+        // test serialize
+        let ser = serde_json::to_string(&ts).unwrap();
+        assert_eq!("123.456".to_string(), ser);
+
+        // test deserialize of float
+        let ts: ServerTimestamp = serde_json::from_str(&ser).unwrap();
+        assert_eq!(ServerTimestamp(123_456), ts);
+
+        // test deserialize of whole number
+        let ts: ServerTimestamp = serde_json::from_str("123").unwrap();
+        assert_eq!(ServerTimestamp(123_000), ts);
+
+        // test deserialize of negative number
+        let ts: ServerTimestamp = serde_json::from_str("-123").unwrap();
+        assert_eq!(ServerTimestamp(0), ts);
+    }
+}