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="pkm"></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 pkm, int[]? IVs = null)
        {
            if (pkm is not IHyperTrain t)
                return;
            if (!pkm.IsHyperTrainingAvailable())
            {
                t.HyperTrainFlags = 0;
                return;
            }
            IVs ??= pkm.IVs;

            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 (pkm is PB7 pb)
                pb.ResetCP();
        }

        /// <summary>
        /// Indicates if Hyper Training is available for toggling.
        /// </summary>
        /// <param name="t">Entity to train</param>
        /// <returns>True if available, otherwise false.</returns>
        public static bool IsHyperTrainingAvailable(this IHyperTrain t) => t switch
        {
            // Check for game formats where training is unavailable:
            PA8 => false,
            _ => true,
        };

        /// <inheritdoc cref="IsHyperTrainingAvailable(IHyperTrain)"/>
        /// <param name="pk">Entity data</param>
        public static bool IsHyperTrainingAvailable(this PKM pk)
        {
            if (pk is not IHyperTrain t)
                return false;
            if (!t.IsHyperTrainingAvailable())
                return false;

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