add rotation

tests/test_syslog_server.py

@@ -0,0 +1,28 @@
+import gzip
+import tempfile
+import unittest
+from pathlib import Path
+
+from fgai.syslog_server import rotate_log_file
+
+
+class SyslogRotationTests(unittest.TestCase):
+    def test_rotation_compresses_and_prunes_archives(self):
+        with tempfile.TemporaryDirectory() as temporary_directory:
+            output = Path(temporary_directory) / "fg_syslog.jsonl"
+            output.write_text("first log line\n", encoding="utf-8")
+
+            archive = rotate_log_file(output, max_archives=1)
+
+            self.assertIsNotNone(archive)
+            self.assertFalse(output.exists())
+            with gzip.open(archive, "rt", encoding="utf-8") as handle:
+                self.assertEqual(handle.read(), "first log line\n")
+
+            output.write_text("second log line\n", encoding="utf-8")
+            rotate_log_file(output, max_archives=1)
+            self.assertEqual(len(list(Path(temporary_directory).glob("fg_syslog.jsonl.*.gz"))), 1)
+
+
+if __name__ == "__main__":
+    unittest.main()