PKHeX/PKHeX.Core/Legality/Restrictions/EvolutionRestrictions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using static PKHeX.Core.Move;
using static PKHeX.Core.Species;

namespace PKHeX.Core
{
    /// <summary>
    /// Restriction logic for evolutions that are a little more complex than <see cref="EvolutionMethod"/> can simply check.
    /// </summary>
    /// <remarks>
    /// Currently only checks "is able to know a move required to level up".
    /// </remarks>
    internal static class EvolutionRestrictions
    {
        /// <summary>
        /// List of species that evolve from a previous species having a move while leveling up
        /// </summary>
        private static readonly Dictionary<int, MoveEvolution> SpeciesEvolutionWithMove = new()
        {
            {(int)Eevee,      new(00, 0)}, // FairyMoves
            {(int)MimeJr,     new(01, (int)Mimic)},
            {(int)Bonsly,     new(02, (int)Mimic)},
            {(int)Aipom,      new(03, (int)Mimic)},
            {(int)Lickitung,  new(04, (int)Rollout)},
            {(int)Tangela,    new(05, (int)AncientPower)},
            {(int)Yanma,      new(06, (int)AncientPower)},
            {(int)Piloswine,  new(07, (int)AncientPower)},
            {(int)Steenee,    new(08, (int)Stomp)},
            {(int)Clobbopus,  new(09, (int)Taunt)},
            {(int)Stantler,   new(10, (int)PsyshieldBash)},
            {(int)Qwilfish,   new(11, (int)BarbBarrage)},
        };

        private readonly record struct MoveEvolution(int ReferenceIndex, int Move);

        private static readonly int[] FairyMoves =
        {
            (int)SweetKiss,
            (int)Charm,
            (int)Moonlight,
            (int)DisarmingVoice,
            (int)DrainingKiss,
            (int)CraftyShield,
            (int)FlowerShield,
            (int)MistyTerrain,
            (int)PlayRough,
            (int)FairyWind,
            (int)Moonblast,
            (int)FairyLock,
            (int)AromaticMist,
            (int)Geomancy,
            (int)DazzlingGleam,
            (int)BabyDollEyes,
            (int)LightofRuin,
            (int)TwinkleTackleP,
            (int)TwinkleTackleS,
            (int)FloralHealing,
            (int)GuardianofAlola,
            (int)FleurCannon,
            (int)NaturesMadness,
            (int)LetsSnuggleForever,
            (int)SparklySwirl,
            (int)MaxStarfall,
            (int)Decorate,
            (int)SpiritBreak,
            (int)StrangeSteam,
            (int)MistyExplosion,
            (int)SpringtideStorm,
        };

        /// <summary>
        /// Minimum current level for a given species to have learned the evolve-move and be successfully evolved.
        /// </summary>
        /// <remarks>Having a value of 0 means the move can't be learned.</remarks>
        private static readonly byte[][] MinLevelEvolutionWithMove =
        {
            new byte[] { 00, 00, 00, 00, 00, 29, 09, 02, 02 }, // Sylveon (Eevee with Fairy Move)
            new byte[] { 00, 00, 00, 00, 18, 15, 15, 02, 32 }, // Mr. Mime (Mime Jr with Mimic)
            new byte[] { 00, 00, 00, 00, 17, 17, 15, 02, 16 }, // Sudowoodo (Bonsly with Mimic)
            new byte[] { 00, 00, 00, 00, 32, 32, 32, 02, 32 }, // Ambipom (Aipom with Double Hit)
            new byte[] { 00, 00, 02, 00, 02, 33, 33, 02, 06 }, // Lickilicky (Lickitung with Rollout)
            new byte[] { 00, 00, 00, 00, 02, 36, 38, 02, 24 }, // Tangrowth (Tangela with Ancient Power)
            new byte[] { 00, 00, 00, 00, 02, 33, 33, 02, 33 }, // Yanmega (Yanma with Ancient Power)
            new byte[] { 00, 00, 00, 00, 02, 02, 02, 02, 02 }, // Mamoswine (Piloswine with Ancient Power)
            new byte[] { 00, 00, 00, 00, 00, 00, 00, 02, 28 }, // Tsareena (Steenee with Stomp)
            new byte[] { 00, 00, 00, 00, 00, 00, 00, 00, 35 }, // Grapploct (Clobbopus with Taunt)
            new byte[] { 00, 00, 00, 00, 00, 00, 00, 00, 00 }, // Wyrdeer (Stantler with AGILE Psyshield Bash)
            new byte[] { 00, 00, 00, 00, 00, 00, 00, 00, 00 }, // Overqwil (Qwilfish with STRONG Barb Barrage)
        };

        private static readonly byte[] MinLevelEvolutionWithMove_8LA =
        {
            00, // Sylveon (Eevee with Fairy Move)
            25, // Mr. Mime (Mime Jr with Mimic)
            29, // Sudowoodo (Bonsly with Mimic)
            25, // Ambipom (Aipom with Double Hit)
            34, // Lickilicky (Lickitung with Rollout)
            34, // Tangrowth (Tangela with Ancient Power)
            34, // Yanmega (Yanma with Ancient Power)
            34, // Mamoswine (Piloswine with Ancient Power)
            99, // Tsareena (Steenee with Stomp)
            99, // Grapploct (Clobbopus with Taunt)
            31, // Wyrdeer (Stantler with AGILE Psyshield Bash) 
            25, // Overqwil (Qwilfish with STRONG Barb Barrage)
        };

        private static readonly bool[][] CanEggHatchWithEvolveMove =
        {
            new [] { false, false,  true,  true,  true,  true,  true,  true,  true }, // Sylveon (Eevee with Fairy Move)
            new [] { false, false, false, false,  true,  true,  true,  true,  true }, // Mr. Mime (Mime Jr with Mimic)
            new [] { false, false, false, false,  true,  true,  true,  true,  true }, // Sudowoodo (Bonsly with Mimic)
            new [] { false, false, false, false,  true,  true,  true,  true,  true }, // Ambipom (Aipom with Double Hit)
            new [] { false, false,  true, false,  true,  true,  true,  true,  true }, // Lickilicky (Lickitung with Rollout)
            new [] { false, false, false, false,  true,  true,  true,  true,  true }, // Tangrowth (Tangela with Ancient Power)
            new [] { false, false, false, false,  true,  true,  true,  true,  true }, // Yanmega (Yanma with Ancient Power)
            new [] { false, false,  true,  true,  true,  true,  true,  true,  true }, // Mamoswine (Piloswine with Ancient Power)
            new [] { false, false, false, false, false, false, false, false, false }, // Tsareena (Steenee with Stomp)
            new [] { false, false, false, false, false, false, false, false,  true }, // Grapploct (Clobbopus with Taunt)
            new [] { false, false, false, false, false, false, false, false, false }, // Wyrdeer (Stantler with AGILE Psyshield Bash)
            new [] { false, false, false, false, false, false, false, false, false }, // Overqwil (Qwilfish with STRONG Barb Barrage)
        };

        /// <summary>
        /// Checks if the <see cref="pkm"/> is correctly evolved, assuming it had a known move requirement evolution in its evolution chain.
        /// </summary>
        /// <returns>True if unnecessary to check or the evolution was valid.</returns>
        public static bool IsValidEvolutionWithMove(PKM pkm, LegalInfo info)
        {
            // Known-move evolutions were introduced in Gen4.
            if (pkm.Format < 4) // doesn't exist yet!
                return true;

            // OK if un-evolved from original encounter
            int species = pkm.Species;
            if (info.EncounterMatch.Species == species)
                return true;

            // Exclude evolution paths that did not require a move w/level-up evolution
            var enc = info.EncounterOriginal;
            if (!SpeciesEvolutionWithMove.TryGetValue(enc.Species, out var entry))
                return true;

            var move = entry.Move;
            if (move == 0)
            {
                // Other evolutions are fine.
                if (pkm.Species != (int)Sylveon)
                    return true;
            }

            // Check if the move was already known when it was originally encountered.
            var gen = info.Generation;
            var index = entry.ReferenceIndex;
            if (enc is EncounterEgg)
            {
                if (CanEggHatchWithEvolveMove[index][gen])
                {
                    var result = move == 0 ? IsMoveInherited(pkm, info, FairyMoves) : IsMoveInherited(pkm, info, move);
                    if (result)
                        return true;
                }
            }
            else if (enc is IMoveset s)
            {
                var result = move == 0 ? s.Moves.Any(FairyMoves.Contains) : s.Moves.Contains(move);
                if (result)
                    return true;
            }

            // Current level must be at least the minimum post-evolution level.
            var lvl = GetMinLevelKnowRequiredMove(pkm, gen, index, info.EvoChainsAllGens);
            return pkm.CurrentLevel >= lvl;
        }

        private static int GetMinLevelKnowRequiredMove(PKM pkm, int gen, int index, EvolutionHistory evos)
        {
            if (gen == 8 && pkm.HasVisitedLA(evos.Gen8a)) // No Level Up required, and different levels than mainline SW/SH.
                return MinLevelEvolutionWithMove_8LA[index];

            var lvl = GetLevelLearnMove(pkm, gen, index);

            // If has original met location the minimum evolution level is one level after met level
            // Gen 3 pokemon in gen 4 games: minimum level is one level after transfer to generation 4
            // VC pokemon: minimum level is one level after transfer to generation 7
            // Sylveon: always one level after met level, for gen 4 and 5 eevees in gen 6 games minimum for evolution is one level after transfer to generation 5
            if (pkm.HasOriginalMetLocation || (pkm.Format == 4 && gen == 3) || pkm.VC || pkm.Species == (int)Sylveon)
                lvl = Math.Max(pkm.Met_Level + 1, lvl);
            return lvl;
        }

        private static int GetLevelLearnMove(PKM pkm, int gen, int index)
        {
            // Get the minimum level in any generation when the pokemon could learn the evolve move
            var levels = MinLevelEvolutionWithMove[index];
            var lvl = 101;
            var end = pkm.Format;
            for (int g = gen; g <= end; g++)
            {
                var l = levels[g];
                if (l == 0)
                    continue;
                if (l == 2)
                    return 2; // true minimum
                if (l < lvl)
                    lvl = l; // best minimum
            }
            return lvl;
        }

        private static bool IsMoveInherited(PKM pkm, LegalInfo info, int move)
        {
            // In 3DS games, the inherited move must be in the relearn moves.
            if (info.Generation >= 6)
                return pkm.RelearnMoves.Contains(move);

            // In Pre-3DS games, the move is inherited if it has the move and it can be hatched with the move.
            if (pkm.HasMove(move))
                return true;

            return DidLearnAndForget(info);
        }

        private static bool IsMoveInherited(PKM pkm, LegalInfo info, int[] moves)
        {
            // In 3DS games, the inherited move must be in the relearn moves.
            if (info.Generation >= 6)
                return pkm.RelearnMoves.Any(moves.Contains);

            // In Pre-3DS games, the move is inherited if it has the move and it can be hatched with the move.
            if (pkm.Moves.Any(moves.Contains))
                return true;

            return DidLearnAndForget(info);
        }

        private static bool DidLearnAndForget(LegalInfo info)
        {
            // If the pokemon does not currently have the move, it could have been an egg move that was forgotten.
            // This requires the pokemon to not have 4 other moves identified as egg moves or inherited level up moves.
            var fromEggCount = info.Moves.Count(m => m.IsEggSource);
            return fromEggCount < 4;
        }
    }
}