Add oldest and newest timestamp to ring buffer

Signed-off-by: cwasicki <[email protected]>

Author: cwasicki

src/frequenz/sdk/timeseries/_ringbuffer/buffer.py

@@ -190,10 +190,39 @@ def time_bound_newest(self) -> datetime:
         Return the time bounds of the ring buffer.
 
         Returns:
-            The timestamp of the newest sample of the ring buffer.
+            The timestamp of the newest sample of the ring buffer
+            or None if the buffer is empty.
         """
         return self._datetime_newest
 
+    @property
+    def oldest_timestamp(self) -> datetime | None:
+        """Return the oldest timestamp in the buffer.
+
+        Returns:
+            The oldest timestamp in the buffer
+            or None if the buffer is empty.
+        """
+        if len(self) == 0:
+            return None
+
+        if self.is_missing(self.time_bound_oldest):
+            return min(g.end for g in self.gaps)
+
+        return self.time_bound_oldest
+
+    @property
+    def newest_timestamp(self) -> datetime | None:
+        """Return the newest timestamp in the buffer.
+
+        Returns:
+            The newest timestamp in the buffer.
+        """
+        if len(self) == 0:
+            return None
+
+        return self.time_bound_newest
+
     def datetime_to_index(
         self, timestamp: datetime, allow_outside_range: bool = False
     ) -> int:

tests/timeseries/test_ringbuffer.py

@@ -204,51 +204,73 @@ def dt(i: int) -> datetime:  # pylint: disable=invalid-name
     return datetime.fromtimestamp(i, tz=timezone.utc)
 
 
-def test_gaps() -> None:
+def test_gaps() -> None:  # pylint: disable=too-many-statements
     """Test gap treatment in ordered ring buffer."""
     buffer = OrderedRingBuffer([0.0] * 5, ONE_SECOND)
+    assert buffer.oldest_timestamp is None
+    assert buffer.newest_timestamp is None
     assert len(buffer) == 0
     assert len(buffer.gaps) == 0
 
     buffer.update(Sample(dt(0), Quantity(0)))
+    assert buffer.oldest_timestamp == dt(0)
+    assert buffer.newest_timestamp == dt(0)
     assert len(buffer) == 1
     assert len(buffer.gaps) == 1
 
     buffer.update(Sample(dt(6), Quantity(0)))
+    assert buffer.oldest_timestamp == dt(6)
+    assert buffer.newest_timestamp == dt(6)
     assert len(buffer) == 1
     assert len(buffer.gaps) == 1
 
     buffer.update(Sample(dt(2), Quantity(2)))
     buffer.update(Sample(dt(3), Quantity(3)))
     buffer.update(Sample(dt(4), Quantity(4)))
+    assert buffer.oldest_timestamp == dt(2)
+    assert buffer.newest_timestamp == dt(6)
     assert len(buffer) == 4
     assert len(buffer.gaps) == 1
 
     buffer.update(Sample(dt(3), None))
+    assert buffer.oldest_timestamp == dt(2)
+    assert buffer.newest_timestamp == dt(6)
     assert len(buffer) == 3
     assert len(buffer.gaps) == 2
 
     buffer.update(Sample(dt(3), Quantity(np.nan)))
+    assert buffer.oldest_timestamp == dt(2)
+    assert buffer.newest_timestamp == dt(6)
     assert len(buffer) == 3
     assert len(buffer.gaps) == 2
 
     buffer.update(Sample(dt(2), Quantity(np.nan)))
+    assert buffer.oldest_timestamp == dt(4)
+    assert buffer.newest_timestamp == dt(6)
     assert len(buffer) == 2
     assert len(buffer.gaps) == 2
 
     buffer.update(Sample(dt(3), Quantity(3)))
+    assert buffer.oldest_timestamp == dt(3)
+    assert buffer.newest_timestamp == dt(6)
     assert len(buffer) == 3
     assert len(buffer.gaps) == 2
 
     buffer.update(Sample(dt(2), Quantity(2)))
+    assert buffer.oldest_timestamp == dt(2)
+    assert buffer.newest_timestamp == dt(6)
     assert len(buffer) == 4
     assert len(buffer.gaps) == 1
 
     buffer.update(Sample(dt(5), Quantity(5)))
+    assert buffer.oldest_timestamp == dt(2)
+    assert buffer.newest_timestamp == dt(6)
     assert len(buffer) == 5
     assert len(buffer.gaps) == 0
 
     buffer.update(Sample(dt(99), None))
+    assert buffer.oldest_timestamp == dt(95)  # bug: should be None
+    assert buffer.newest_timestamp == dt(99)  # bug: should be None
     assert len(buffer) == 4  # bug: should be 0 (whole range gap)
     assert len(buffer.gaps) == 1