Moonchess: vanishing tic-tac-toe, online and practice modes

Online play over WebSockets with any-string game codes, seats and spectators,
and a 1-second heartbeat. Practice mode against Columbina, backed by a full
solver, with an accuracy slider, spoilers, undo and piece freshness.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

practice.py

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+"""Moonchess practice server: play against the computer.
+
+Stateless: the page sends the current position with every request and gets the new
+position back, so there's no session to lose. The page decides whose turn belongs to
+the computer; this server only applies moves and picks them.
+"""
+
+import argparse
+import logging
+
+from aiohttp import web
+
+from game import Game
+from server import STATIC_DIR, no_cache
+from solver import Solver
+
+solver = Solver()  # solves every position up front; takes about a second
+
+
+async def index(request):
+    return web.FileResponse(STATIC_DIR / "practice.html")
+
+
+async def play(request):
+    """Body: {history, turn, cell} to play `cell`, or {history, turn, accuracy} for a
+    computer move, where accuracy (0-1) is the chance it plays a perfect move. A computer
+    move's reply also says how it was chosen, as computerMove: {cell, how}."""
+    try:
+        body = await request.json()
+        game = Game.from_history(body["history"], body["turn"])
+        cell = body.get("cell")
+        accuracy = float(body.get("accuracy", 1))
+    except (ValueError, KeyError, TypeError, AttributeError):
+        return web.json_response({"error": "Invalid request"}, status=400)
+
+    computer_move = None
+    if cell is None and game.winner is None:
+        cell, how = solver.choose(game, accuracy)
+        computer_move = {"cell": cell, "how": how}
+    error = game.play(game.turn, cell)
+    if error:
+        return web.json_response({"error": error}, status=400)
+    return web.json_response({**game.to_dict(), "computerMove": computer_move})
+
+
+def make_app():
+    app = web.Application(middlewares=[no_cache])
+    app.router.add_get("/", index)
+    app.router.add_post("/api/play", play)
+    app.router.add_static("/static", STATIC_DIR)
+    return app
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Moonchess practice server")
+    parser.add_argument("--host", default="127.0.0.1")
+    parser.add_argument("--port", type=int, default=8081)
+    args = parser.parse_args()
+    logging.basicConfig(level=logging.INFO, format="%(asctime)s %(message)s")
+    web.run_app(make_app(), host=args.host, port=args.port)