rework dataset function and class structure

tests/test_DatasetIO.py

@@ -0,0 +1,46 @@
+import unittest
+
+import tempfile, gzip, json
+from pathlib import Path
+
+from server.dataset.DatasetIO import DatasetIO
+
+class TestDatasetIO(unittest.TestCase):
+  def test_resolve_input_files_includes_jsonl_and_gz(self):
+    with tempfile.TemporaryDirectory() as tmp:
+      base = Path(tmp)
+      (base / "a.jsonl").write_text('{"x":1}\n', encoding="utf-8")
+      with gzip.open(base / "b.jsonl.gz", "wt", encoding="utf-8") as handle:
+        handle.write('{"x":2}\n')
+
+      paths = DatasetIO.resolve_input_files([str(base)])
+      names = {path.name for path in paths}
+      self.assertIn("a.jsonl", names)
+      self.assertIn("b.jsonl.gz", names)
+
+  def test_iter_jsonl_rows_reads_gz_file(self):
+    with tempfile.TemporaryDirectory() as tmp:
+      path = Path(tmp) / "rows.jsonl.gz"
+      with gzip.open(path, "wt", encoding="utf-8") as handle:
+        handle.write('{"turn":1}\n')
+        handle.write("\n")
+        handle.write('{"turn":2}\n')
+
+      rows = list(DatasetIO.iter_jsonl_rows(path))
+      self.assertEqual(len(rows), 2)
+      self.assertEqual(rows[0]["turn"], 1)
+      self.assertEqual(rows[1]["turn"], 2)
+
+  def test_append_jsonl_row_supports_gz_output(self):
+    with tempfile.TemporaryDirectory() as tmp:
+      path = Path(tmp) / "append.jsonl.gz"
+      DatasetIO.append_jsonl_row(path, {"move": "up"})
+      DatasetIO.append_jsonl_row(path, {"move": "left"})
+
+      with gzip.open(path, "rt", encoding="utf-8") as handle:
+        lines = handle.read().strip().splitlines()
+      self.assertEqual(len(lines), 2)
+      self.assertEqual(json.loads(lines[0])["move"], "up")
+
+if __name__ == "__main__":
+  unittest.main()