feat: japan node ranking and leftover route detection

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

py_modules/mudfish_decky/nodes.py

@@ -0,0 +1,40 @@
+"""Japan node filtering and ping ranking."""
+from dataclasses import dataclass
+from typing import Optional
+
+JAPAN_PREFIX = "JP "
+
+
+@dataclass(frozen=True)
+class Node:
+    sid: int
+    label: str
+    rtt: Optional[float]
+
+
+def rtts_from_response(resp: dict) -> dict:
+    """Map sid -> average RTT (ms) from /do/rtt/staticnodes, skipping failed probes.
+
+    While Mudfish is mid-round the endpoint answers {"status": 300} without "rtts".
+    """
+    return {r["sid"]: float(r["rttavg"]) for r in resp.get("rtts", []) if r.get("success", 0) > 0}
+
+
+def _label(location: str) -> str:
+    start, end = location.find("("), location.rfind(")")
+    if start == -1 or end <= start:
+        return location
+    return location[start + 1:end]
+
+
+def japan_nodes(static_nodes: list, rtts: dict) -> list:
+    """Japan nodes sorted by ping; unmeasured nodes go last, by label."""
+    nodes = [Node(n["sid"], _label(n["location"]), rtts.get(n["sid"]))
+             for n in static_nodes if n["location"].startswith(JAPAN_PREFIX)]
+    measured = sorted((n for n in nodes if n.rtt is not None), key=lambda n: n.rtt)
+    unmeasured = sorted((n for n in nodes if n.rtt is None), key=lambda n: n.label)
+    return measured + unmeasured
+
+
+def pick_auto(nodes: list) -> Optional[Node]:
+    return next((n for n in nodes if n.rtt is not None), None)