"""Moonchess practice mode: play against the computer. server.py serves it at /practice.

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 module only applies moves and picks them.
"""

from aiohttp import web

from game import Game
from solver import Solver

solver = Solver()  # solves every position up front; takes about a second


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})