using System;

namespace PKHeX.Core;

public interface IHyperTrain
{
    byte HyperTrainFlags { get; set; }
    bool HT_HP { get; set; }
    bool HT_ATK { get; set; }
    bool HT_DEF { get; set; }
    bool HT_SPA { get; set; }
    bool HT_SPD { get; set; }
    bool HT_SPE { get; set; }
}

public static partial class Extensions
{
    /// <summary>
    /// Toggles the Hyper Training flag for a given stat.
    /// </summary>
    /// <param name="t">Hyper Trainable object</param>
    /// <param name="index">Battle Stat (H/A/B/S/C/D)</param>
    /// <returns>Final Hyper Training Flag value</returns>
    public static bool HyperTrainInvert(this IHyperTrain t, int index) => index switch
    {
        0 => t.HT_HP ^= true,
        1 => t.HT_ATK ^= true,
        2 => t.HT_DEF ^= true,
        3 => t.HT_SPE ^= true,
        4 => t.HT_SPA ^= true,
        5 => t.HT_SPD ^= true,
        _ => false,
    };

    public static bool IsHyperTrainedAll(this IHyperTrain t) => t.HyperTrainFlags == 0x3F;
    public static void HyperTrainClear(this IHyperTrain t) => t.HyperTrainFlags = 0;
    public static bool IsHyperTrained(this IHyperTrain t) => t.HyperTrainFlags != 0;

    /// <summary>
    /// Gets one of the <see cref="IHyperTrain"/> values based on its index within the array.
    /// </summary>
    /// <param name="t">Entity to check.</param>
    /// <param name="index">Index to get</param>
    public static bool IsHyperTrained(this IHyperTrain t, int index) => index switch
    {
        0 => t.HT_HP,
        1 => t.HT_ATK,
        2 => t.HT_DEF,
        3 => t.HT_SPE,
        4 => t.HT_SPA,
        5 => t.HT_SPD,
        _ => throw new ArgumentOutOfRangeException(nameof(index)),
    };

    /// <summary>
    /// Sets <see cref="IHyperTrain.HyperTrainFlags"/> to valid values which may best enhance the <see cref="PKM"/> stats.
    /// </summary>
    /// <param name="pk"></param>
    /// <param name="h">History of evolutions present as</param>
    /// <param name="IVs"><see cref="PKM.IVs"/> to use (if already known). Will fetch the current <see cref="PKM.IVs"/> if not provided.</param>
    public static void SetSuggestedHyperTrainingData(this PKM pk, EvolutionHistory h, ReadOnlySpan<int> IVs)
    {
        if (pk is not IHyperTrain t)
            return;
        if (!pk.IsHyperTrainingAvailable(h))
        {
            t.HyperTrainFlags = 0;
            return;
        }

        t.HT_HP = IVs[0] != 31;
        t.HT_ATK = IVs[1] != 31 && IVs[1] > 2;
        t.HT_DEF = IVs[2] != 31;
        t.HT_SPA = IVs[4] != 31;
        t.HT_SPD = IVs[5] != 31;

        // sometimes unusual speed IVs are desirable for competitive reasons
        // if nothing else was HT'd and the IV isn't too high, it was probably intentional
        t.HT_SPE = IVs[3] != 31 && IVs[3] > 2 &&
                   (IVs[3] > 17 || t.HT_HP || t.HT_ATK || t.HT_DEF || t.HT_SPA || t.HT_SPD);

        if (pk is ICombatPower pb)
            pb.ResetCP();
    }

    /// <inheritdoc cref="SetSuggestedHyperTrainingData(PKM,EvolutionHistory,ReadOnlySpan{int})"/>
    public static void SetSuggestedHyperTrainingData(this PKM pk, ReadOnlySpan<int> IVs) => pk.SetSuggestedHyperTrainingData(EvolutionHistory.Empty, IVs);

    /// <inheritdoc cref="SetSuggestedHyperTrainingData(PKM,EvolutionHistory,ReadOnlySpan{int})"/>
    public static void SetSuggestedHyperTrainingData(this PKM pk)
    {
        Span<int> ivs = stackalloc int[6];
        pk.GetIVs(ivs);
        pk.SetSuggestedHyperTrainingData(ivs);
    }

    /// <summary>
    /// Indicates if Hyper Training is available for toggling.
    /// </summary>
    /// <param name="t">Entity to train</param>
    /// <param name="h">History of evolutions present as</param>
    /// <returns>True if available, otherwise false.</returns>
    public static bool IsHyperTrainingAvailable(this IHyperTrain t, EvolutionHistory h) => t switch
    {
        // Check for game formats where training is unavailable:
        PA8 pa8 => h.Gen7.Length > 0 || pa8.HasVisitedSWSH(h.Gen8) || pa8.HasVisitedBDSP(h.Gen8b),
        _ => true,
    };

    /// <inheritdoc cref="IsHyperTrainingAvailable(IHyperTrain, EvolutionHistory)"/>
    /// <param name="pk">Entity data</param>
    /// <param name="h">History of evolutions present as</param>
    public static bool IsHyperTrainingAvailable(this PKM pk, EvolutionHistory h)
    {
        if (pk is not IHyperTrain t)
            return false;
        if (!t.IsHyperTrainingAvailable(h))
            return false;

        // Gated behind level 100.
        return pk.CurrentLevel == 100;
    }
}