using System;
using System.Collections.Generic;
using System.Linq;
using static PKHeX.Core.Ball;

namespace PKHeX.Core
{
    /// <summary>
    /// Contains logic to apply a new <see cref="Ball"/> value to a <see cref="PKM"/>.
    /// </summary>
    public static class BallRandomizer
    {
        /// <summary>
        /// Gets all balls that are legal for the input <see cref="PKM"/>.
        /// </summary>
        /// <remarks>
        /// Requires checking the <see cref="LegalityAnalysis"/> for every <see cref="Ball"/> that is tried.
        /// </remarks>
        /// <param name="pkm">Pokémon to retrieve a list of valid balls for.</param>
        /// <returns>Enumerable list of <see cref="Ball"/> values that the <see cref="PKM"/> is legal with.</returns>
        public static IEnumerable<Ball> GetLegalBalls(PKM pkm)
        {
            var clone = pkm.Clone();
            foreach (var b in BallList)
            {
                clone.Ball = (int)b;
                if (new LegalityAnalysis(clone).Valid)
                    yield return b;
            }
        }

        /// <summary>
        /// Applies a random legal ball value if any exist.
        /// </summary>
        /// <remarks>
        /// Requires checking the <see cref="LegalityAnalysis"/> for every <see cref="Ball"/> that is tried.
        /// </remarks>
        /// <param name="pkm">Pokémon to modify.</param>
        public static int ApplyBallLegalRandom(PKM pkm)
        {
            var balls = GetBallListFromColor(pkm).ToArray();
            Util.Shuffle(balls);
            return ApplyFirstLegalBall(pkm, balls);
        }

        /// <summary>
        /// Applies a legal ball value if any exist, ordered by color.
        /// </summary>
        /// <remarks>
        /// Requires checking the <see cref="LegalityAnalysis"/> for every <see cref="Ball"/> that is tried.
        /// </remarks>
        /// <param name="pkm">Pokémon to modify.</param>
        public static int ApplyBallLegalByColor(PKM pkm)
        {
            var balls = GetBallListFromColor(pkm);
            return ApplyFirstLegalBall(pkm, balls);
        }

        /// <summary>
        /// Applies a random ball value in a cyclical manner.
        /// </summary>
        /// <param name="pkm">Pokémon to modify.</param>
        public static int ApplyBallNext(PKM pkm)
        {
            var balls = GetBallList(pkm.Ball);
            var next = balls.First();
            return pkm.Ball = (int)next;
        }

        private static int ApplyFirstLegalBall(PKM pkm, IEnumerable<Ball> balls)
        {
            foreach (var b in balls)
            {
                pkm.Ball = (int)b;
                if (new LegalityAnalysis(pkm).Valid)
                    break;
            }
            return pkm.Ball;
        }

        private static IEnumerable<Ball> GetBallList(int ball)
        {
            var balls = BallList;
            var currentBall = (Ball)ball;
            return GetCircularOnce(balls, currentBall);
        }

        private static IEnumerable<Ball> GetBallListFromColor(PKM pkm)
        {
            // Fetch with latest-gen personal info; Gen1/2 don't store color
            var pi = PKX.Personal.GetFormeEntry(pkm.Species, pkm.AltForm);
            var color = (PersonalColor)pi.Color;
            var balls = BallColors[color];
            var currentBall = (Ball)pkm.Ball;
            return GetCircularOnce(balls, currentBall);
        }

        private static IEnumerable<T> GetCircularOnce<T>(T[] items, T current)
        {
            var currentIndex = Array.IndexOf(items, current);
            if (currentIndex < 0)
                currentIndex = items.Length - 2;
            for (int i = currentIndex + 1; i < items.Length; i++)
                yield return items[i];
            for (int i = 0; i <= currentIndex; i++)
                yield return items[i];
        }

        private static readonly Ball[] BallList = (Ball[]) Enum.GetValues(typeof(Ball));

        static BallRandomizer()
        {
            var exclude = new[] {None, Poke};
            var end = new[] {Poke};
            var allBalls = BallList.Except(exclude).ToArray();
            var colors = (PersonalColor[])Enum.GetValues(typeof(PersonalColor));
            foreach (var c in colors)
            {
                var vals = BallColors[c];
                var extra = allBalls.Except(vals).ToArray();
                Util.Shuffle(extra);
                BallColors[c] = vals.Concat(extra).Concat(end).ToArray();
            }
        }

        /// <summary>
        /// Priority Match ball IDs that match the color ID in descending order
        /// </summary>
        private static readonly Dictionary<PersonalColor, Ball[]> BallColors = new Dictionary<PersonalColor, Ball[]>
        {
            [PersonalColor.Red] =    new[] { Cherish, Repeat, Fast, Heal, Great, Dream },
            [PersonalColor.Blue] =   new[] { Dive, Net, Great, Beast },
            [PersonalColor.Yellow] = new[] { Level, Ultra, Repeat, Quick, Moon },
            [PersonalColor.Green] =  new[] { Safari, Friend, Nest, Dusk },
            [PersonalColor.Black] =  new[] { Luxury, Heavy, Ultra, Moon, Net, Beast },

            [PersonalColor.Brown] =  new[] { Level, Heavy },
            [PersonalColor.Purple] = new[] { Master, Love, Dream, Heal },
            [PersonalColor.Gray] =   new[] { Heavy, Premier, Luxury },
            [PersonalColor.White] =  new[] { Premier, Timer, Luxury, Ultra },
            [PersonalColor.Pink] =   new[] { Love, Dream, Heal },
        };

        /// <summary>
        /// Personal Data color IDs
        /// </summary>
        private enum PersonalColor : byte
        {
            Red,
            Blue,
            Yellow,
            Green,
            Black,

            Brown,
            Purple,
            Gray,
            White,
            Pink,
        }
    }
}