using System;

namespace PKHeX.Core
{
    /// <summary>
    /// Logic for modifying the <see cref="PKM.Markings"/>.
    /// </summary>
    public static class MarkingApplicator
    {
        /// <summary>
        /// Default <see cref="MarkingMethod"/> when applying markings.
        /// </summary>
        // ReSharper disable once AutoPropertyCanBeMadeGetOnly.Global
        public static Func<PKM, Func<int, int, int>> MarkingMethod { get; set; } = FlagHighLow;

        /// <summary>
        /// Sets the <see cref="PKM.Markings"/> to indicate flawless (or near-flawless) <see cref="PKM.IVs"/>.
        /// </summary>
        /// <param name="pk">Pokémon to modify.</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 SetMarkings(this PKM pk, int[] ivs)
        {
            if (pk.Format <= 3)
                return; // no markings (gen3 only has 4; can't mark stats intelligently

            Span<int> markings = stackalloc int[ivs.Length];
            var method = MarkingMethod(pk);
            for (int i = 0; i < markings.Length; i++)
                markings[i] = method(ivs[i], i);
            PKX.ReorderSpeedLast(markings);
            pk.SetMarkings(markings);
        }

        /// <summary>
        /// Sets the <see cref="PKM.Markings"/> to indicate flawless (or near-flawless) <see cref="PKM.IVs"/>.
        /// </summary>
        /// <param name="pk">Pokémon to modify.</param>
        public static void SetMarkings(this PKM pk)
        {
            if (pk.Format <= 3)
                return; // no markings (gen3 only has 4; can't mark stats intelligently

            Span<int> IVs = stackalloc int[6];
            pk.GetIVs(IVs);
            pk.SetMarkings(IVs);
        }

        /// <summary>
        /// Toggles the marking at a given index.
        /// </summary>
        /// <param name="pk">Pokémon to modify.</param>
        /// <param name="index">Marking index to toggle</param>
        /// <returns>Current marking values</returns>
        public static int[] ToggleMarking(this PKM pk, int index) => pk.ToggleMarking(index, pk.Markings);

        /// <summary>
        /// Toggles the marking at a given index.
        /// </summary>
        /// <param name="pk">Pokémon to modify.</param>
        /// <param name="index">Marking index to toggle</param>
        /// <param name="markings">Current marking values (optional)</param>
        /// <returns>Current marking values</returns>
        public static int[] ToggleMarking(this PKM pk, int index, int[] markings)
        {
            switch (pk.Format)
            {
                case 3 or 4 or 5 or 6: // on/off
                    markings[index] ^= 1; // toggle
                    pk.Markings = markings;
                    break;
                case 7 or 8: // 0 (none) | 1 (blue) | 2 (pink)
                    markings[index] = (markings[index] + 1) % 3; // cycle 0->1->2->0...
                    pk.Markings = markings;
                    break;
            }
            return markings;
        }

        private static Func<int, int, int> FlagHighLow(PKM pk)
        {
            if (pk.Format < 7)
                return GetSimpleMarking;
            return GetComplexMarking;

            static int GetSimpleMarking(int val, int _) => val == 31 ? 1 : 0;
            static int GetComplexMarking(int val, int _) => val switch
            {
                31 or 1 => 1,
                30 or 0 => 2,
                _ => 0,
            };
        }
    }
}