feat(adapter): implement Balabit CSV parser

ai_mouse/data_adapters/balabit.py

@@ -46,8 +46,35 @@ class Segment:
 
 
 def parse_session_csv(path: Path) -> list[MouseEvent]:
-    """Stub — implemented in Task 3."""
+    """Parse a Balabit session CSV file into MouseEvent objects.
-    raise NotImplementedError
+
+    Malformed rows are logged and skipped (not raised).
+    Client timestamps (seconds, float) are converted to int milliseconds.
+
+    Args:
+        path: Path to a Balabit session CSV file.
+
+    Returns:
+        List of MouseEvent in original order. Empty list if file is empty.
+    """
+    import csv as csv_module
+
+    events: list[MouseEvent] = []
+    with path.open("r", encoding="utf-8", newline="") as f:
+        reader = csv_module.DictReader(f)
+        for row_idx, row in enumerate(reader, 2):  # 1-based, header is line 1
+            try:
+                client_ts = float(row["client timestamp"])
+                t_ms = int(round(client_ts * 1000))
+                button = row["button"].strip()
+                state = row["state"].strip()
+                x = int(row["x"])
+                y = int(row["y"])
+            except (KeyError, ValueError, TypeError) as exc:
+                logger.debug("Skipping malformed row %d in %s: %s", row_idx, path.name, exc)
+                continue
+            events.append(MouseEvent(t_ms=t_ms, button=button, state=state, x=x, y=y))
+    return events
 
 
 def segment_by_clicks(

tests/test_balabit_adapter.py

@@ -34,3 +34,62 @@ def test_segment_dataclass():
     assert s.events == events
     assert s.click_x == 100
     assert s.session_id == "user1_s1"
+
+
+def _write_csv(path: Path, rows: list[str]) -> None:
+    """Helper to write a Balabit-format CSV with header."""
+    header = "record timestamp,client timestamp,button,state,x,y"
+    path.write_text(header + "\n" + "\n".join(rows) + "\n", encoding="utf-8")
+
+
+class TestParseSessionCsv:
+    def test_parses_basic_rows(self, tmp_path):
+        from ai_mouse.data_adapters.balabit import parse_session_csv
+        csv = tmp_path / "session_1"
+        _write_csv(csv, [
+            "1500000000.000,0.000,NoButton,Move,100,200",
+            "1500000000.050,0.050,NoButton,Move,110,210",
+            "1500000000.100,0.100,Left,Pressed,120,220",
+        ])
+        events = parse_session_csv(csv)
+        assert len(events) == 3
+        assert events[0].t_ms == 0
+        assert events[0].state == "Move"
+        assert events[0].x == 100
+        assert events[2].t_ms == 100
+        assert events[2].state == "Pressed"
+        assert events[2].button == "Left"
+
+    def test_handles_float_timestamps(self, tmp_path):
+        """Client timestamps are floats in seconds; we convert to int ms."""
+        from ai_mouse.data_adapters.balabit import parse_session_csv
+        csv = tmp_path / "session_2"
+        _write_csv(csv, [
+            "0,1.234,NoButton,Move,50,60",
+            "0,1.250,NoButton,Move,55,65",
+        ])
+        events = parse_session_csv(csv)
+        assert events[0].t_ms == 1234
+        assert events[1].t_ms == 1250
+
+    def test_skips_malformed_rows(self, tmp_path):
+        """Rows with bad data are logged and skipped, not raised."""
+        from ai_mouse.data_adapters.balabit import parse_session_csv
+        csv = tmp_path / "session_3"
+        _write_csv(csv, [
+            "0,0.000,NoButton,Move,100,200",
+            "BROKEN_ROW",
+            "0,abc,NoButton,Move,100,200",   # bad timestamp
+            "0,0.100,NoButton,Move,150,250",
+        ])
+        events = parse_session_csv(csv)
+        assert len(events) == 2
+        assert events[0].x == 100
+        assert events[1].x == 150
+
+    def test_returns_empty_list_for_empty_file(self, tmp_path):
+        from ai_mouse.data_adapters.balabit import parse_session_csv
+        csv = tmp_path / "session_4"
+        csv.write_text("record timestamp,client timestamp,button,state,x,y\n", encoding="utf-8")
+        events = parse_session_csv(csv)
+        assert events == []