"""Deterministic AI command selection at three difficulty levels."""

from __future__ import annotations

import random
from typing import TYPE_CHECKING

from python.gems.domain.engine import RuleError, apply_command, score
from python.gems.domain.legal_actions import legal_commands

if TYPE_CHECKING:
    from python.gems.domain.models import ContentPack, GameCommand, GameSettings, GameState


def choose_ai_command(
    state: GameState,
    pack: ContentPack,
    settings: GameSettings,
    seat: int,
    difficulty: str,
) -> GameCommand:
    """Choose from legal commands using only public/current-player information."""
    actions = legal_commands(state, pack, settings, seat)
    if not actions:
        error = "AI has no legal command"
        raise RuntimeError(error)
    rng = random.Random(f"{state.seed}:{state.revision}:{seat}:{difficulty}")  # noqa: S311 - deterministic AI
    if difficulty == "easy":
        return rng.choice(actions)

    ranked = sorted(actions, key=lambda item: _heuristic(item, state, pack), reverse=True)
    if difficulty == "medium":
        return ranked[0]

    # Bounded deterministic rollout: examine at most the twelve strongest actions.
    best = ranked[0]
    best_value = float("-inf")
    for candidate in ranked[:12]:
        try:
            future = apply_command(state, candidate, pack, settings, actor_seat=seat)
        except RuleError:
            continue
        value = score(future.players[seat], pack) * 100 + _heuristic(candidate, state, pack)
        value += rng.random() * 0.001
        if value > best_value:
            best, best_value = candidate, value
    return best


def _heuristic(command: GameCommand, state: GameState, pack: ContentPack) -> float:
    player = state.players[state.current_seat]
    value = 0.0
    if command.type == "purchase":
        card = pack.card(str(command.payload.get("card_id")))
        value += 40 + card.points * 25 + (8 if card.bonus_resource else 0)
        value -= sum(command.payload.get("payment", {}).values())
    elif command.type == "take_distinct":
        value += 10 + len(command.payload.get("resources", []))
    elif command.type == "reserve":
        value += 6
    elif command.type == "take_double":
        value += 4
    elif command.type == "choose":
        value += 20
    elif command.type == "decline":
        value -= 2
    value += score(player, pack) * 0.01
    return value