refactor!: a lot of stuff

tests/test_usage_unit.py

@@ -0,0 +1,32 @@
+from providers.chatgpt.usage import _parse_window, clamp_percent
+
+
+def test_clamp_percent_bounds():
+    assert clamp_percent(-1) == 0
+    assert clamp_percent(150) == 100
+    assert clamp_percent(49.6) == 50
+
+
+def test_clamp_percent_invalid():
+    assert clamp_percent(None) == 0
+    assert clamp_percent("bad") == 0
+
+
+def test_parse_window_valid():
+    window = {
+        "used_percent": 34.4,
+        "limit_window_seconds": 3600,
+        "reset_after_seconds": 120,
+        "reset_at": 999,
+    }
+    parsed = _parse_window(window)
+    assert parsed == {
+        "used_percent": 34,
+        "limit_window_seconds": 3600,
+        "reset_after_seconds": 120,
+        "reset_at": 999,
+    }
+
+
+def test_parse_window_none():
+    assert _parse_window(None) is None