feat(db): find_twins (serial + identical PVS + time window)

sfm/database.py

@@ -603,6 +603,34 @@ class SeismoDb:
             ).fetchall()
         return [dict(r) for r in rows]
 
+    def find_twins(self, event_id: str, *, window_seconds: int = 300) -> list[dict]:
+        """
+        Find this event's histogram/waveform twin(s): rows sharing the same
+        serial and an identical peak_vector_sum, whose timestamp falls
+        within ``window_seconds`` of this event's timestamp.  Excludes the
+        event itself.  Returns [] if the event or any required field
+        (serial / peak_vector_sum / timestamp) is missing.
+        """
+        row = self.get_event(event_id)
+        if not row:
+            return []
+        serial = row.get("serial"); pvs = row.get("peak_vector_sum"); ts = row.get("timestamp")
+        if serial is None or pvs is None or not ts:
+            return []
+        try:
+            t = datetime.datetime.fromisoformat(ts.replace(" ", "T"))
+        except ValueError:
+            return []
+        lo = (t - datetime.timedelta(seconds=window_seconds)).isoformat()
+        hi = (t + datetime.timedelta(seconds=window_seconds)).isoformat()
+        with self._connect() as conn:
+            rows = conn.execute(
+                "SELECT * FROM events WHERE serial=? AND id!=? AND peak_vector_sum=? "
+                "AND timestamp BETWEEN ? AND ?",
+                (serial, event_id, pvs, lo, hi),
+            ).fetchall()
+        return [dict(r) for r in rows]
+
     def set_false_trigger(self, event_id: str, value: bool) -> bool:
         """Set or clear the false_trigger flag on an event. Returns True if found."""
         with self._connect() as conn: