using System;
using System.Collections.Generic;
using System.Linq;

using static PKHeX.Core.Legal;
using static PKHeX.Core.GameVersion;
using static PKHeX.Core.Species;

namespace PKHeX.Core;

/// <summary>
/// Miscellaneous GB Era restriction logic for legality checking
/// </summary>
internal static class GBRestrictions
{
    private static readonly int[] G1Exeggcute_IncompatibleMoves = { 78, 77, 79 };

    private static readonly int[] Stadium_CatchRate =
    {
        167, // Normal Box
        168, // Gorgeous Box
    };

    private static readonly HashSet<int> Stadium_GiftSpecies = new()
    {
        (int)Bulbasaur,
        (int)Charmander,
        (int)Squirtle,
        (int)Psyduck,
        (int)Hitmonlee,
        (int)Hitmonchan,
        (int)Eevee,
        (int)Omanyte,
        (int)Kabuto,
    };

    /// <summary>
    /// Species that have a specific minimum amount of moves based on their evolution state.
    /// </summary>
    private static readonly HashSet<int> SpecialMinMoveSlots = new()
    {
        (int)Pikachu,
        (int)Raichu,
        (int)NidoranF,
        (int)Nidorina,
        (int)Nidoqueen,
        (int)NidoranM,
        (int)Nidorino,
        (int)Nidoking,
        (int)Clefable,
        (int)Ninetales,
        (int)Wigglytuff,
        (int)Arcanine,
        (int)Cloyster,
        (int)Exeggutor,
        (int)Tangela,
        (int)Starmie,
    };

    internal static bool TypeIDExists(int type) => Types_Gen1.Contains(type);

    /// <summary>
    /// Valid type IDs extracted from the Personal Table used for R/G/B/Y games.
    /// </summary>
    private static readonly HashSet<int> Types_Gen1 = new()
    {
        0, 1, 2, 3, 4, 5, 7, 8, 20, 21, 22, 23, 24, 25, 26,
    };

    /// <summary>
    /// Species that have a catch rate value that is different from their pre-evolutions, and cannot be obtained directly.
    /// </summary>
    internal static readonly HashSet<int> Species_NotAvailable_CatchRate = new()
    {
        (int)Butterfree,
        (int)Pidgeot,
        (int)Nidoqueen,
        (int)Nidoking,
        (int)Ninetales,
        (int)Vileplume,
        (int)Persian,
        (int)Arcanine,
        (int)Poliwrath,
        (int)Alakazam,
        (int)Machamp,
        (int)Victreebel,
        (int)Rapidash,
        (int)Cloyster,
        (int)Exeggutor,
        (int)Starmie,
        (int)Dragonite,
    };

    internal static readonly HashSet<int> Trade_Evolution1 = new()
    {
        (int)Kadabra,
        (int)Machoke,
        (int)Graveler,
        (int)Haunter,
    };

    public static bool RateMatchesEncounter(int species, GameVersion version, int rate)
    {
        if (version.Contains(YW))
        {
            if (rate == PersonalTable.Y[species].CatchRate)
                return true;
            if (version == YW) // no RB
                return false;
        }
        return rate == PersonalTable.RB[species].CatchRate;
    }

    private static int[] GetMinLevelLearnMoveG1(int species, List<int> moves)
    {
        var result = new int[moves.Count];
        for (int i = 0; i < result.Length; i++)
            result[i] = MoveLevelUp.GetIsLevelUp1(species, 0, moves[i], 100, 0).Level;
        return result;
    }

    private static int[] GetMaxLevelLearnMoveG1(int species, List<int> moves)
    {
        var result = new int[moves.Count];

        int index = PersonalTable.RB.GetFormIndex(species, 0);
        if (index == 0)
            return result;

        var pi_rb = ((PersonalInfoG1)PersonalTable.RB[index]).Moves;
        var pi_y = ((PersonalInfoG1)PersonalTable.Y[index]).Moves;

        for (int m = 0; m < moves.Count; m++)
        {
            bool start = pi_rb.Contains(moves[m]) && pi_y.Contains(moves[m]);
            result[m] = start ? 1 : Math.Max(GetHighest(LevelUpRB), GetHighest(LevelUpY));
            int GetHighest(IReadOnlyList<Learnset> learn) => learn[index].GetLevelLearnMove(moves[m]);
        }
        return result;
    }

    private static List<int>[] GetExclusiveMovesG1(int species1, int species2, IEnumerable<int> tmhm, IEnumerable<int> moves)
    {
        // Return from two species the exclusive moves that only one could learn and also the current pokemon have it in its current moveset
        var moves1 = MoveLevelUp.GetMovesLevelUp1(species1, 0, 1, 100);
        var moves2 = MoveLevelUp.GetMovesLevelUp1(species2, 0, 1, 100);

        // Remove common moves and remove tmhm, remove not learned moves
        var common = new HashSet<int>(moves1.Intersect(moves2).Concat(tmhm));
        var hashMoves = new HashSet<int>(moves);
        moves1.RemoveAll(x => !hashMoves.Contains(x) || common.Contains(x));
        moves2.RemoveAll(x => !hashMoves.Contains(x) || common.Contains(x));
        return new[] { moves1, moves2 };
    }

    internal static void GetIncompatibleEvolutionMoves(PKM pk, IReadOnlyList<int> moves, IReadOnlyList<int> tmhm, out int previousspecies, out IList<int> incompatible_previous, out IList<int> incompatible_current)
    {
        switch (pk.Species)
        {
            case (int)Nidoking when moves.Contains(31) && moves.Contains(37):
                // Nidoking learns Thrash at level 23
                // Nidorino learns Fury Attack at level 36, Nidoran♂ at level 30
                // Other moves are either learned by Nidoran♂ up to level 23 or by TM
                incompatible_current = new[] { 31 };
                incompatible_previous = new[] { 37 };
                previousspecies = 33;
                return;

            case (int)Exeggutor when moves.Contains(23) && moves.Any(m => G1Exeggcute_IncompatibleMoves.Contains(m)):
                // Exeggutor learns Stomp at level 28
                // Exeggcute learns Stun Spore at 32, PoisonPowder at 37 and Sleep Powder at 48
                incompatible_current = new[] { 23 };
                incompatible_previous = G1Exeggcute_IncompatibleMoves;
                previousspecies = 103;
                return;

            case (int)Vaporeon or (int)Jolteon or (int)Flareon:
                incompatible_previous = new List<int>();
                incompatible_current = new List<int>();
                previousspecies = 133;
                var ExclusiveMoves = GetExclusiveMovesG1((int)Eevee, pk.Species, tmhm, moves);
                var EeveeLevels = GetMinLevelLearnMoveG1((int)Eevee, ExclusiveMoves[0]);
                var EvoLevels = GetMaxLevelLearnMoveG1(pk.Species, ExclusiveMoves[1]);

                for (int i = 0; i < ExclusiveMoves[0].Count; i++)
                {
                    // There is a evolution move with a lower level that current Eevee move
                    var el = EeveeLevels[i];
                    if (EvoLevels.Any(ev => ev < el))
                        incompatible_previous.Add(ExclusiveMoves[0][i]);
                }
                for (int i = 0; i < ExclusiveMoves[1].Count; i++)
                {
                    // There is an Eevee move with a greater level that current evolution move
                    var el = EvoLevels[i];
                    if (EeveeLevels.Any(ev => ev > el))
                        incompatible_current.Add(ExclusiveMoves[1][i]);
                }
                return;
        }
        incompatible_previous = Array.Empty<int>();
        incompatible_current = Array.Empty<int>();
        previousspecies = 0;
    }

    internal static int GetRequiredMoveCount(PK1 pk, IReadOnlyList<int> moves, LegalInfo info, IReadOnlyList<int> initialmoves)
    {
        var enc = info.EncounterMatch;
        var capsuleState = IsTimeCapsuleTransferred(pk, info.Moves, enc);
        if (capsuleState != TimeCapsuleEvaluation.NotTransferred) // No Move Deleter in Gen 1
            return 1; // Move Deleter exits, slots from 2 onwards can always be empty

        if (enc is IMoveset {Moves.Count: 4 })
            return 4;

        int required = GetRequiredMoveCount(pk, moves, info.EncounterMoves.LevelUpMoves, initialmoves, enc.Species);
        if (required >= 4)
            return 4;

        // tm, hm and tutor moves replace a free slots if the pokemon have less than 4 moves
        // Ignore tm, hm and tutor moves already in the learnset table
        var learn = info.EncounterMoves.LevelUpMoves;
        var tmhm = info.EncounterMoves.TMHMMoves;
        var tutor = info.EncounterMoves.TutorMoves;
        var union = initialmoves.Union(learn[1]);
        required += moves.Count(m => m != 0 && union.All(t => t != m) && (tmhm[1].Any(t => t == m) || tutor[1].Any(t => t == m)));

        return Math.Min(4, required);
    }

    private static int GetRequiredMoveCount(PK1 pk, IReadOnlyList<int> moves, IReadOnlyList<int>[] learn, IReadOnlyList<int> initialmoves, int originalSpecies)
    {
        if (SpecialMinMoveSlots.Contains(pk.Species))
            return GetRequiredMoveCountSpecial(pk, moves, learn, originalSpecies);

        // A pokemon is captured with initial moves and can't forget any until have all 4 slots used
        // If it has learn a move before having 4 it will be in one of the free slots
        int required = GetRequiredMoveSlotsRegular(pk, moves, learn, initialmoves, originalSpecies);
        return required != 0 ? required : GetRequiredMoveCountDecrement(pk, moves, learn, initialmoves);
    }

    private static int GetRequiredMoveSlotsRegular(PK1 pk, IReadOnlyList<int> moves, IReadOnlyList<int>[] learn, IReadOnlyList<int> initialmoves, int originalSpecies)
    {
        if (originalSpecies == pk.Species)
            return 0; // Can skip over all learned moves that we can reasonably care about

        return originalSpecies switch
        {
            (int)Caterpie => initialmoves.Union(learn[1]).Distinct().Count(lm => lm != 0 && (lm != (int)Move.Harden   || moves.Contains((int)Move.Harden))),
            (int)Metapod => initialmoves.Union(learn[1]).Distinct().Count(lm => lm != 0 && (lm != (int)Move.Confusion || moves.Contains((int)Move.Confusion))),
            (int)Mankey => initialmoves.Union(learn[1]).Distinct().Count(lm => lm != 0 && (lm != (int)Move.Rage       || moves.Contains((int)Move.Rage))),
            _ => IsMoveCountRequired3(pk.Species, pk.CurrentLevel, moves) ? 3 : 0,
        };
    }

    private static bool IsMoveCountRequired3(int species, int level, IReadOnlyList<int> moves) => species switch
    {
        // Species that evolve and learn the 4th move as evolved species at a greater level than base species
        // The 4th move is included in the level up table set as a pre-evolution move,
        // it should be removed from the used slots count if is not the learn move
        (int)Pidgeotto => level < 21 && !moves.Contains(018), // Whirlwind
        (int)Sandslash => level < 27 && !moves.Contains(040), // Poison Sting
        (int)Parasect  => level < 30 && !moves.Contains(147), // Spore
        (int)Golduck   => level < 39 && !moves.Contains(093), // Confusion
        (int)Dewgong   => level < 44 && !moves.Contains(156), // Rest
        (int)Weezing   => level < 39 && !moves.Contains(108), // Smoke Screen
        (int)Haunter or (int)Gengar => level < 29 && !moves.Contains(095), // Hypnosis
        _ => false,
    };

    private static int GetRequiredMoveCountDecrement(PKM pk, IReadOnlyList<int> moves, IReadOnlyList<int>[] learn, IReadOnlyList<int> initialmoves)
    {
        int usedslots = initialmoves.Union(learn[1]).Where(m => m != 0).Distinct().Count();
        switch (pk.Species)
        {
            case (int)Venonat: // Venonat; ignore Venomoth (by the time Venonat evolves it will always have 4 moves)
                if (pk.CurrentLevel >= 11 && !moves.Contains(48)) // Supersonic
                    usedslots--;
                if (pk.CurrentLevel >= 19 && !moves.Contains(93)) // Confusion
                    usedslots--;
                break;
            case (int)Kadabra or (int)Alakazam: // Abra & Kadabra
                int catch_rate = ((PK1)pk).Catch_Rate;
                if (catch_rate != 100)// Initial Yellow Kadabra Kinesis (move 134)
                    usedslots--;
                if (catch_rate == 200 && pk.CurrentLevel < 20) // Kadabra Disable, not learned until 20 if captured as Abra (move 50)
                    usedslots--;
                break;
            case (int)Cubone or (int)Marowak: // Cubone & Marowak
                if (!moves.Contains((int)Move.TailWhip) && !moves.Contains((int)Move.Headbutt)) // Initial Red
                {
                    usedslots -=2;
                }
                else
                {
                    if (!moves.Contains(39)) // Initial Yellow Tail Whip
                        usedslots--;
                    if (!moves.Contains(125)) // Initial Yellow Bone Club
                        usedslots--;
                }
                if (pk.Species == 105 && pk.CurrentLevel < 33 && !moves.Contains(116)) // Marowak evolved without Focus Energy
                    usedslots--;
                break;
            case (int)Chansey:
                if (!moves.Contains(39)) // Yellow Initial Tail Whip
                    usedslots--;
                if (!moves.Contains(3)) // Yellow Lvl 12 and Initial Red/Blue Double Slap
                    usedslots--;
                break;
            case (int)Mankey when pk.CurrentLevel >= 9 && !moves.Contains(67): // Mankey (Low Kick)
            case (int)Pinsir when pk.CurrentLevel >= 21 && !moves.Contains(20): // Pinsir (Bind)
            case (int)Gyarados when pk.CurrentLevel < 32: // Gyarados
                usedslots--;
                break;
            default: return usedslots;
        }
        return usedslots;
    }

    private static int GetRequiredMoveCountSpecial(PKM pk, IReadOnlyList<int> moves, IReadOnlyList<int>[] learn, int originalSpecies)
    {
        // Species with few mandatory slots, species with stone evolutions that could evolve at lower level and do not learn any more moves
        // and Pikachu and Nidoran family, those only have mandatory the initial moves and a few have one level up moves,
        // every other move could be avoided switching game or evolving
        var mandatory = GetRequiredMoveCountLevel(pk, originalSpecies);
        switch (pk.Species)
        {
            case (int)Exeggutor when pk.CurrentLevel >= 28: // Exeggutor
                // At level 28 learn different move if is a Exeggute or Exeggutor
                if (moves.Contains(73))
                    mandatory.Add(73); // Leech Seed level 28 Exeggute
                if (moves.Contains(23))
                    mandatory.Add(23); // Stomp level 28 Exeggutor
                break;
            case (int)Pikachu when pk.CurrentLevel >= 33:
                mandatory.Add(97); // Pikachu always learns Agility
                break;
            case (int)Tangela:
                mandatory.Add(132); // Tangela always has Constrict as Initial Move
                break;
        }

        // Add to used slots the non-mandatory moves from the learnset table that the pokemon have learned
        return mandatory.Distinct().Count(z => z != 0) + moves.Where(m => m != 0).Count(m => !mandatory.Contains(m) && learn[1].Contains(m));
    }

    private static List<int> GetRequiredMoveCountLevel(PKM pk, int basespecies)
    {
        int species = pk.Species;
        int maxlevel = 1;
        int minlevel = 1;

        if (species == (int)Tangela) // Tangela moves before level 32 are different in RB vs Y
        {
            minlevel = 32;
            maxlevel = pk.CurrentLevel;
        }
        else if (species is >= (int)NidoranF and <= (int)Nidoking && pk.CurrentLevel >= 8)
        {
            maxlevel = 8; // Always learns a third move at level 8
        }

        if (minlevel > pk.CurrentLevel)
            return new List<int>();

        return MoveLevelUp.GetMovesLevelUp1(basespecies, 0, maxlevel, minlevel);
    }

    internal static IEnumerable<GameVersion> GetGen2Versions(IEncounterTemplate enc, bool korean)
    {
        if (ParseSettings.AllowGen2Crystal(korean) && enc.Version is C or GSC)
            yield return C;
        yield return GS;
    }

    internal static IEnumerable<GameVersion> GetGen1Versions(IEncounterTemplate enc)
    {
        if (enc.Species == (int)Eevee && enc.Version == Stadium)
        {
            // Stadium Eevee; check for RB and yellow initial moves
            yield return RB;
            yield return YW;
            yield break;
        }
        if (enc.Version == YW)
        {
            yield return YW;
            yield break;
        }

        // Any encounter marked with version RBY is for pokemon with the same moves and catch rate in RB and Y,
        // it is sufficient to check just RB's case
        yield return RB;
    }

    private static bool GetCatchRateMatchesPreEvolution(PK1 pk, int catch_rate)
    {
        // For species catch rate, discard any species that has no valid encounters and a different catch rate than their pre-evolutions
        var table = EvolutionTree.Evolves1;
        var chain = table.GetValidPreEvolutions(pk, maxLevel: (byte)pk.CurrentLevel);
        foreach (var entry in chain)
        {
            var s = entry.Species;
            if (Species_NotAvailable_CatchRate.Contains(s))
                continue;
            if (catch_rate == PersonalTable.RB[s].CatchRate || catch_rate == PersonalTable.Y[s].CatchRate)
                return true;
        }

        // Krabby encounter trade special catch rate
        int species = pk.Species;
        if (catch_rate == 204 && (species is (int)Krabby or (int)Kingler))
            return true;

        if (Stadium_GiftSpecies.Contains(species) && Stadium_CatchRate.Contains(catch_rate))
            return true;

        return false;
    }

    /// <summary>
    /// Checks if the <see cref="pk"/> can inhabit <see cref="GameVersion.Gen1"></see>
    /// </summary>
    /// <param name="pk">Data to check</param>
    /// <returns>true if can inhabit, false if not.</returns>
    private static bool CanInhabitGen1(this PKM pk)
    {
        // Korean Gen2 games can't trade-back because there are no Gen1 Korean games released
        if (pk.Korean || pk.IsEgg)
            return false;

        // Gen2 format with met data can't receive Gen1 moves, unless Stadium 2 is used (Oak's PC).
        // If you put a Pokemon in the N64 box, the met info is retained, even if you switch over to a Gen I game to teach it TMs
        // You can use rare candies from within the lab, so level-up moves from RBY context can be learned this way as well
        // Stadium 2 is GB Cart Era only (not 3DS Virtual Console).
        if (pk is ICaughtData2 {CaughtData: not 0} && !ParseSettings.AllowGBCartEra)
            return false;

        // Sanity check species, if it could have existed as a pre-evolution.
        int species = pk.Species;
        if (species <= MaxSpeciesID_1)
            return true;
        return EvolutionLegality.FutureEvolutionsGen1.Contains(species);
    }

    /// <summary>
    /// Gets the Tradeback status depending on various values.
    /// </summary>
    /// <param name="pk">Pokémon to guess the tradeback status from.</param>
    internal static PotentialGBOrigin GetTradebackStatusInitial(PKM pk)
    {
        if (pk is PK1 pk1)
            return GetTradebackStatusRBY(pk1);

        if (pk.Format == 2 || pk.VC2) // Check for impossible tradeback scenarios
            return !pk.CanInhabitGen1() ? PotentialGBOrigin.Gen2Only : PotentialGBOrigin.Either;

        // VC2 is released, we can assume it will be TradebackType.Any.
        // Is impossible to differentiate a VC1 pokemon traded to Gen7 after VC2 is available.
        // Met Date cannot be used definitively as the player can change their system clock.
        return PotentialGBOrigin.Either;
    }

    /// <summary>
    /// Gets the Tradeback status depending on the <see cref="PK1.Catch_Rate"/>
    /// </summary>
    /// <param name="pk">Pokémon to guess the tradeback status from.</param>
    private static PotentialGBOrigin GetTradebackStatusRBY(PK1 pk)
    {
        if (!ParseSettings.AllowGen1Tradeback)
            return PotentialGBOrigin.Gen1Only;

        // Detect tradeback status by comparing the catch rate(Gen1)/held item(Gen2) to the species in the pk's evolution chain.
        var catch_rate = pk.Catch_Rate;
        if (catch_rate == 0)
            return PotentialGBOrigin.Either;

        bool matchAny = GetCatchRateMatchesPreEvolution(pk, catch_rate);

        if (!matchAny)
            return PotentialGBOrigin.Either;

        if (HeldItems_GSC.Contains((ushort)catch_rate))
            return PotentialGBOrigin.Either;

        return PotentialGBOrigin.Gen1Only;
    }

    public static TimeCapsuleEvaluation IsTimeCapsuleTransferred(PKM pk, IReadOnlyList<CheckMoveResult> moves, IEncounterTemplate enc)
    {
        foreach (var z in moves)
        {
            if (z.Generation == enc.Generation || z.Generation > 2)
                continue;
            if (pk is PK1 {Catch_Rate: not 0} g1 && !IsTradebackCatchRate(g1.Catch_Rate))
                return TimeCapsuleEvaluation.BadCatchRate;
            return enc.Generation == 2 ? TimeCapsuleEvaluation.Transferred21 : TimeCapsuleEvaluation.Transferred12;
        }

        if (pk is not GBPKM gb)
        {
            return enc.Generation switch
            {
                2 when pk.VC2 => TimeCapsuleEvaluation.Transferred21,
                1 when pk.VC1 => TimeCapsuleEvaluation.Transferred12,
                _ => TimeCapsuleEvaluation.NotTransferred,
            };
        }

        if (gb is ICaughtData2 pk2)
        {
            if (enc.Generation == 1)
                return TimeCapsuleEvaluation.Transferred12;
            if (pk2.CaughtData != 0)
                return TimeCapsuleEvaluation.NotTransferred;
            if (enc.Version == C)
                return TimeCapsuleEvaluation.Transferred21;
            return TimeCapsuleEvaluation.Indeterminate;
        }

        if (gb is PK1 pk1)
        {
            var rate = pk1.Catch_Rate;
            if (rate == 0)
                return TimeCapsuleEvaluation.Transferred12;

            bool isTradebackItem = IsTradebackCatchRate(rate);
            if (IsCatchRateMatchEncounter(enc, pk1))
                return isTradebackItem ? TimeCapsuleEvaluation.Indeterminate : TimeCapsuleEvaluation.NotTransferred;
            return isTradebackItem ? TimeCapsuleEvaluation.Transferred12 : TimeCapsuleEvaluation.BadCatchRate;
        }
        return TimeCapsuleEvaluation.Indeterminate;
    }

    private static bool IsCatchRateMatchEncounter(IEncounterTemplate enc, PK1 pk1) => enc switch
    {
        EncounterStatic1 s when s.GetMatchRating(pk1) != EncounterMatchRating.PartialMatch => true,
        EncounterTrade1 => true,
        _ => RateMatchesEncounter(enc.Species, enc.Version, pk1.Catch_Rate),
    };

    public static bool IsTradebackCatchRate(int rate)
    {
        return HeldItems_GSC.Contains((ushort)rate);
    }
}

public enum PotentialGBOrigin
{
    Either,
    Gen1Only,
    Gen2Only,
}

public enum TimeCapsuleEvaluation
{
    Indeterminate,
    Transferred21,
    Transferred12,
    NotTransferred,
    BadCatchRate,
}

public static class TimeCapsuleEvlautationExtensions
{
    public static bool WasTimeCapsuleTransferred(this TimeCapsuleEvaluation eval) => eval is not (TimeCapsuleEvaluation.Indeterminate or TimeCapsuleEvaluation.NotTransferred or TimeCapsuleEvaluation.BadCatchRate);
}