namespace Vanguard.Board3D
{
    /// <summary>
    /// Локальные правила раскладки для UX. Сервер остаётся авторитарным:
    /// эти проверки нужны для подсветки и drag&amp;drop, а не для начисления
    /// результата.
    /// </summary>
    public static class BoardPlacementRules
    {
        public static bool CanRide(BoardZone zone, int slot) =>
            zone == BoardZone.Vanguard && slot == PlaymatLayout.VanguardSlot;

        public static bool CanCall(int slot, bool occupied) =>
            slot >= 0
            && slot < PlaymatLayout.RearGuardCount;
            // Occupied circles are valid call targets: the previous unit is
            // moved to the drop zone.

        public static bool CanGuard(BoardZone zone) =>
            zone == BoardZone.Guardian;

        public static bool CanMove(int fromSlot, int toSlot) =>
            fromSlot >= 0
            && fromSlot < PlaymatLayout.RearGuardCount
            && toSlot >= 0
            && toSlot < PlaymatLayout.RearGuardCount
            && fromSlot != toSlot
            && SameColumn(fromSlot, toSlot);

        public static bool CanAttack(int attackerSlot, int targetSlot) =>
            attackerSlot >= PlaymatLayout.VanguardSlot
            && attackerSlot < PlaymatLayout.RearGuardCount
            && targetSlot >= PlaymatLayout.VanguardSlot
            && targetSlot < PlaymatLayout.RearGuardCount;

        /// <summary>Колонки Classic: левая 0↔3, правая 2↔4; у центра пары нет.</summary>
        public static bool SameColumn(int fromSlot, int toSlot) =>
            (fromSlot, toSlot) is (0, 3) or (3, 0) or (2, 4) or (4, 2);

        /// <summary>Call и Ride входят стоя и открытыми.</summary>
        public static CardState3D EnterFromHand(CircleAttribute circle) => circle switch
        {
            CircleAttribute.Vanguard => CardState3D.FaceUpStand,
            CircleAttribute.RearGuard => CardState3D.FaceUpStand,
            CircleAttribute.Guardian => CardState3D.FaceUpStand,
            _ => CardState3D.FaceUpStand,
        };

        /// <summary>Перемещение RC→RC сохраняет Rest и открытость.</summary>
        public static CardState3D PreserveOnMove(CardState3D state) => state;

        public static BoardZone ZoneOfSlot(int slot) =>
            slot == PlaymatLayout.VanguardSlot
                ? BoardZone.Vanguard
                : BoardZone.RearGuard;
    }
}