fix(da12): {J} decode drops empty/bad timestamps; rename _count_long (review)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

cim_suite/modules/da12/protocol/decoder.py

@@ -22,7 +22,7 @@ def _byte(reader: c.FieldReader) -> int:
         return 0
 
 
-def _byte_long(s: str) -> int:
+def _count_long(s: str) -> int:
     """Parse an unsigned big-endian count field (the {J} record count)."""
     s = s.strip()
     if not s:
@@ -132,7 +132,7 @@ def decode(body: str) -> m.Message | None:
         # tenths (signed). FLAGGED: whether a large reply arrives as one {J} or
         # several frames is hardware-unverified (docs/HARDWARE-VERIFICATION.md);
         # we decode one frame = one batch and accumulate in the domain layer.
-        count = _byte_long(reader.next())
+        count = _count_long(reader.next())
         points: list[m.PlotPoint] = []
         while len(reader):
             ts = reader.next().strip()
@@ -140,9 +140,11 @@ def decode(body: str) -> m.Message | None:
                 break  # lone trailing timestamp with no value -> drop
             val = c.decode_scaled(reader.next(), 1)
             try:
-                timestamp = int(ts, 16) if ts else 0
+                timestamp = int(ts, 16) if ts else None
             except ValueError:
-                continue
+                timestamp = None
+            if timestamp is None:
+                continue  # empty/unparseable timestamp -> drop the point
             points.append(m.PlotPoint(timestamp=timestamp, value=val))
         return m.PlotData(count=count, points=points)
 

tests/test_messages_decoder.py

@@ -114,6 +114,7 @@ def test_decode_plot_data_two_points():
     assert len(msg.points) == 2
     assert msg.points[0].timestamp == 0x60D54E80
     assert abs(msg.points[0].value - 31.0) < 1e-9   # 0x0136 = 310 -> 31.0
+    assert msg.points[1].timestamp == 0x60D54EBC
     assert abs(msg.points[1].value - 31.5) < 1e-9   # 0x013B = 315 -> 31.5
 
 
@@ -137,6 +138,14 @@ def test_decode_plot_data_truncated_pair_ignored():
     assert len(msg.points) == 1
 
 
+def test_decode_plot_data_empty_timestamp_dropped():
+    # An empty timestamp field (still followed by a value) drops that point
+    # rather than emitting a 1970 epoch-0 point.
+    msg = decode("J00000001\t\t0136")
+    assert isinstance(msg, m.PlotData)
+    assert msg.points == []
+
+
 def test_decode_plot_data_long_frame_under_buffer():
     # A long (but <4096) J frame decodes fully (framer cap is 4096).
     pairs = "".join("\t60D54E80\t0136" for _ in range(100))