Add conversion between chrono::DateTime<chrono::Utc> and Timestamp

src/typ/timestamp.rs

@@ -52,3 +52,40 @@ impl From<prost_types::Timestamp> for Timestamp {
         Self { seconds, nanos }
     }
 }
+
+#[cfg(feature = "chrono")]
+impl std::convert::TryFrom<Timestamp> for chrono::DateTime<chrono::Utc> {
+    type Error = crate::Error;
+
+    fn try_from(Timestamp { seconds, nanos }: Timestamp) -> Result<Self, Self::Error> {
+        let nanos = u32::try_from(nanos).map_err(|_| {
+            crate::Error::from(crate::error::ErrorCode::Custom(format!(
+                "chrono::DateTime::<chrono::Utc>::try_from(Timestamp) / u32::try_from({})",
+                nanos
+            )))
+        })?;
+        Self::from_timestamp(seconds, nanos).ok_or_else(|| {
+            crate::Error::from(crate::error::ErrorCode::Custom(format!(
+                "chrono::DateTime::<chrono::Utc>::try_from(Timestamp) / chrono::DateTime::<chrono::Utc>::from_timestamp({}, {})",
+                seconds, nanos
+            )))
+        })
+    }
+}
+
+#[cfg(feature = "chrono")]
+impl std::convert::TryFrom<chrono::DateTime<chrono::Utc>> for Timestamp {
+    type Error = crate::Error;
+
+    fn try_from(date_time: chrono::DateTime<chrono::Utc>) -> Result<Self, Self::Error> {
+        let seconds = date_time.timestamp();
+        let nanos = date_time.timestamp_subsec_nanos();
+        let nanos = i32::try_from(nanos).map_err(|_| {
+            crate::Error::from(crate::error::ErrorCode::Custom(format!(
+                "Timestamp::try_from(chrono::DateTime::<chrono::Utc>) / i32::try_from({})",
+                nanos
+            )))
+        })?;
+        Ok(Self { seconds, nanos })
+    }
+}

tests/v0_7_0.rs

@@ -0,0 +1,35 @@
+#[cfg(feature = "chrono")]
+#[test]
+fn test_try_from_timestamp_for_chrono_date_time() -> serde_firestore_value::Result<()> {
+    use serde_firestore_value::Timestamp;
+    let timestamp = Timestamp {
+        seconds: 1_i64,
+        nanos: 2_i32,
+    };
+    let date_time = chrono::DateTime::<chrono::Utc>::try_from(timestamp)?;
+    assert_eq!(
+        date_time.to_rfc3339(),
+        "1970-01-01T00:00:01.000000002+00:00"
+    );
+    Ok(())
+}
+
+#[cfg(feature = "chrono")]
+#[test]
+fn test_try_from_chrono_date_time_for_timestamp() -> anyhow::Result<()> {
+    use serde_firestore_value::Timestamp;
+    let date_time = chrono::DateTime::<chrono::FixedOffset>::parse_from_rfc3339(
+        "1970-01-01T00:00:01.000000002+00:00",
+    )?
+    .naive_utc()
+    .and_utc();
+    let timestamp = Timestamp::try_from(date_time)?;
+    assert_eq!(
+        timestamp,
+        Timestamp {
+            seconds: 1_i64,
+            nanos: 2_i32,
+        }
+    );
+    Ok(())
+}