PKHeX/PKHeX.Core/Legality/Restrictions/ItemRestrictions.cs

using System;
using System.Collections.Generic;

using static PKHeX.Core.Legal;

namespace PKHeX.Core;

/// <summary>
/// Information about Held Item Restrictions
/// </summary>
public static class ItemRestrictions
{
    /// <summary>
    /// Checks if a <see cref="PKM.HeldItem"/> is available to be held in the current <see cref="PKM.Format"/>.
    /// </summary>
    /// <param name="pk">Entity data</param>
    /// <returns>True if able to be held, false if not</returns>
    public static bool IsHeldItemAllowed(PKM pk)
    {
        if (pk is PB7 pb7) // no held items in game
            return pb7.HeldItem == 0;
        return IsHeldItemAllowed(pk.HeldItem, pk.Format, pk);
    }

    /// <summary>
    /// Checks if an <see cref="item"/> is available to be held in <see cref="generation"/>.
    /// </summary>
    /// <param name="item">Held Item ID</param>
    /// <param name="generation">Generation Number</param>
    /// <param name="pk">Entity context to check</param>
    /// <returns>True if able to be held, false if not</returns>
    public static bool IsHeldItemAllowed(int item, int generation, PKM pk)
    {
        if (item == 0)
            return true;
        var items = GetReleasedHeldItems(generation, pk);
        return (uint)item < items.Count && items[item];
    }

    private static IReadOnlyList<bool> GetReleasedHeldItems(int generation, PKM pk) => generation switch
    {
        2 => ReleasedHeldItems_2,
        3 => ReleasedHeldItems_3,
        4 => ReleasedHeldItems_4,
        5 => ReleasedHeldItems_5,
        6 => ReleasedHeldItems_6,
        7 => ReleasedHeldItems_7,
        8 when pk is PA8 => Array.Empty<bool>(),
        8 when pk is PB8 => ReleasedHeldItems_8b,
        8 => ReleasedHeldItems_8,
        _ => Array.Empty<bool>(),
    };
}