night-shift/src/Features/Items/Domain/HandsInventory.cs

using System;
using Game.Features.Items.Contracts;

namespace Game.Features.Items.Domain;

public sealed class HandsInventory
{
    private ItemInstanceId? _leftHand;
    private ItemInstanceId? _rightHand;

    public bool IsFree(Hand hand) => Get(hand) is null;

    public ItemInstanceId? Get(Hand hand) => hand switch
    {
        Hand.Left => _leftHand,
        Hand.Right => _rightHand,
        _ => throw new ArgumentOutOfRangeException(nameof(hand), hand, null)
    };

    public bool TryHold(ItemInstanceId itemId, HandRequirement requirement, Hand hand)
    {
        if (_leftHand == itemId || _rightHand == itemId)
        {
            return false;
        }

        if (requirement == HandRequirement.Both)
        {
            if (_leftHand is not null || _rightHand is not null)
            {
                return false;
            }

            _leftHand = itemId;
            _rightHand = itemId;
            return true;
        }

        if (!IsFree(hand))
        {
            return false;
        }

        Set(hand, itemId);
        return true;
    }

    public ItemInstanceId? Release(Hand hand)
    {
        ItemInstanceId? itemId = Get(hand);
        if (itemId is null)
        {
            return null;
        }

        if (_leftHand == itemId)
        {
            _leftHand = null;
        }

        if (_rightHand == itemId)
        {
            _rightHand = null;
        }

        return itemId;
    }

    private void Set(Hand hand, ItemInstanceId itemId)
    {
        switch (hand)
        {
            case Hand.Left:
                _leftHand = itemId;
                break;
            case Hand.Right:
                _rightHand = itemId;
                break;
            default:
                throw new ArgumentOutOfRangeException(nameof(hand), hand, null);
        }
    }
}