using System;
using System.Linq;
using static PKHeX.Core.LegalityCheckStrings;
using static PKHeX.Core.MemoryPermissions;
using static PKHeX.Core.EntityContext;

namespace PKHeX.Core;

/// <summary>
/// Verifies the <see cref="IMemoryOT.OT_Memory"/>, <see cref="IMemoryHT.HT_Memory"/>, and associated values.
/// </summary>
public sealed class MemoryVerifier : Verifier
{
    protected override CheckIdentifier Identifier => CheckIdentifier.Memory;

    public override void Verify(LegalityAnalysis data)
    {
        var pk = data.Entity;
        if (ShouldHaveNoMemory(data, pk))
        {
            VerifyOTMemoryIs(data, 0, 0, 0, 0);
            VerifyHTMemoryNone(data, (ITrainerMemories)pk);
            return;
        }
        VerifyOTMemory(data);
        VerifyHTMemory(data);
    }

    private static bool ShouldHaveNoMemory(LegalityAnalysis data, PKM pk)
    {
        if (pk.BDSP || pk.LA)
            return !data.Info.EvoChainsAllGens.HasVisitedSWSH;
        if (pk is PK9)
            return true; // No memories.
        return false;
    }

    private CheckResult VerifyCommonMemory(PKM pk, int handler, EntityContext context, LegalInfo info, MemoryContext mem)
    {
        var memory = MemoryVariableSet.Read((ITrainerMemories)pk, handler);

        // Actionable HM moves
        int hmIndex = MemoryContext6.MoveSpecificMemoryHM.IndexOf(memory.MemoryID);
        if (hmIndex != -1)
        {
            if (context != Gen6) // Gen8 has no HMs, so this memory can never exist.
                return GetInvalid(string.Format(LMemoryArgBadMove, memory.Handler));

            if (pk.Species != (int)Species.Smeargle)
            {
                // All AO hidden machine permissions are super-sets of Gen 3-5 games.
                // Don't need to check the move history -- a learned HM in a prior game can still be learned in Gen6.
                var evos = info.EvoChainsAllGens.Gen6;
                var exists = Array.Exists(evos, z => PersonalTable.AO.GetFormEntry(z.Species, 0).GetIsLearnHM(hmIndex));
                if (!exists)
                    return GetInvalid(string.Format(LMemoryArgBadMove, memory.Handler));
            }
        }

        if (mem.IsInvalidGeneralLocationMemoryValue(memory.MemoryID, memory.Variable, info.EncounterMatch, pk))
            return GetInvalid(string.Format(LMemoryArgBadLocation, memory.Handler));

        if (mem.IsInvalidMiscMemory(memory.MemoryID, memory.Variable))
            return GetInvalid(string.Format(LMemoryArgBadID, memory.Handler));

        switch (memory.MemoryID)
        {
            case 19 when pk.Species is (int)Species.Urshifu   && memory.Variable is not 34: // tall building is the only location for evolving Urshifu
            case 19 when pk.Species is (int)Species.Runerigus && memory.Variable is not 72: // vast field is the only location for evolving Runerigus
                return GetInvalid(string.Format(LMemoryArgBadLocation, memory.Handler));

            // {0} saw {2} carrying {1} on its back. {4} that {3}.
            case 21 when context != Gen6 || !PersonalTable.AO.GetFormEntry(memory.Variable, 0).GetIsLearnHM(2): // Fly
                return GetInvalid(string.Format(LMemoryArgBadMove, memory.Handler));

            // {0} used {2} at {1}’s instruction, but it had no effect. {4} that {3}.
            // The Move Deleter that {0} met through {1} made it forget {2}. {4} that {3}.
            case 16 or 48 when !CanKnowMove(pk, memory, context, info, memory.MemoryID == 16):
                return GetInvalid(string.Format(LMemoryArgBadMove, memory.Handler));

            case 49 when memory.Variable == 0 || !GetCanRelearnMove(pk, memory.Variable, context, info.EvoChainsAllGens, info.EncounterOriginal):
                return GetInvalid(string.Format(LMemoryArgBadMove, memory.Handler));

            // Dynamaxing
            // {0} battled at {1}’s side against {2} that Dynamaxed. {4} that {3}.
            case 71 when !GetCanDynamaxTrainer(memory.Variable, 8, handler == 0 ? (GameVersion)pk.Version : GameVersion.Any):
            // {0} battled {2} and Dynamaxed upon {1}’s instruction. {4} that {3}.
            case 72 when !PersonalTable.SWSH.IsSpeciesInGame(memory.Variable):
                return GetInvalid(string.Format(LMemoryArgBadSpecies, memory.Handler));

            // Move
            // {0} studied about how to use {2} in a Box, thinking about {1}. {4} that {3}.
            // {0} practiced its cool pose for the move {2} in a Box, wishing to be praised by {1}. {4} that {3}.
            case 80 or 81 when !CanKnowMove(pk, memory, context, info):
                return Get(string.Format(LMemoryArgBadMove, memory.Handler), Severity.Invalid);

            // Species
            // With {1}, {0} went fishing, and they caught {2}. {4} that {3}.
            case 7 when !GetCanFishSpecies(memory.Variable, context, handler == 0 ? (GameVersion)pk.Version : GameVersion.Any):
                return GetInvalid(string.Format(LMemoryArgBadSpecies, memory.Handler));

            // {0} saw {1} paying attention to {2}. {4} that {3}.
            // {0} fought hard until it had to use Struggle when it battled at {1}’s side against {2}. {4} that {3}.
            // {0} was taken to a Pokémon Nursery by {1} and left with {2}. {4} that {3}.
            case 9 or 60 or 75 when context == Gen8 && !PersonalTable.SWSH.IsSpeciesInGame(memory.Variable):
                return GetInvalid(string.Format(LMemoryArgBadSpecies, memory.Handler));

            // {0} had a great chat about {1} with the {2} that it was in a Box with. {4} that {3}.
            // {0} became good friends with the {2} in a Box, practiced moves with it, and talked about the day that {0} would be praised by {1}. {4} that {3}.
            // {0} got in a fight with the {2} that it was in a Box with about {1}. {4} that {3}.
            case 82 or 83 or 87 when !PersonalTable.SWSH.IsSpeciesInGame(memory.Variable):
                return GetInvalid(string.Format(LMemoryArgBadSpecies, memory.Handler));

            // {0} had a very hard training session with {1}. {4} that {3}.
            case 53 when context == Gen8 && pk is IHyperTrain t && !t.IsHyperTrained():
                return GetInvalid(string.Format(LMemoryArgBadID, memory.Handler));

            // Item
            // {0} went to a Pokémon Center with {1} to buy {2}. {4} that {3}.
            case 5 when !CanBuyItem(context, memory.Variable, handler == 0 ? (GameVersion)pk.Version : GameVersion.Any):
            // {1} used {2} when {0} was in trouble. {4} that {3}.
            case 15 when !CanUseItem(context, memory.Variable, pk.Species):
            // {0} saw {1} using {2}. {4} that {3}.
            case 26 when !CanUseItemGeneric(context, memory.Variable):
            // {0} planted {2} with {1} and imagined a big harvest. {4} that {3}.
            case 34 when !CanPlantBerry(context, memory.Variable):
            // {1} had {0} hold items like {2} to help it along. {4} that {3}.
            case 40 when !CanHoldItem(context, memory.Variable):
            // {0} was excited when {1} won prizes like {2} through Loto-ID. {4} that {3}.
            case 51 when !CanWinLotoID(context, memory.Variable):
            // {0} was worried if {1} was looking for the {2} that it was holding in a Box. {4} that {3}.
            // When {0} was in a Box, it thought about the reason why {1} had it hold the {2}. {4} that {3}.
            case 84 or 88 when !Legal.HeldItems_SWSH.Contains(memory.Variable) || pk.IsEgg:
                return GetInvalid(string.Format(LMemoryArgBadItem, memory.Handler));
        }

        return VerifyCommonMemoryEtc(memory, mem);
    }

    private CheckResult VerifyCommonMemoryEtc(MemoryVariableSet memory, MemoryContext context)
    {
        if (!context.CanHaveIntensity(memory.MemoryID, memory.Intensity))
        {
            var min = context.GetMinimumIntensity(memory.MemoryID);
            return GetInvalid(string.Format(LMemoryIndexIntensityMin, memory.Handler, min));
        }

        if (!context.CanHaveFeeling(memory.MemoryID, memory.Feeling, memory.Variable))
            return GetInvalid(string.Format(LMemoryFeelInvalid, memory.Handler));

        return GetValid(string.Format(LMemoryF_0_Valid, memory.Handler));
    }

    /// <summary>
    /// Used for enforcing a fixed memory detail.
    /// </summary>
    /// <param name="data">Output storage</param>
    /// <param name="m">Memory ID</param>
    /// <param name="i">Intensity</param>
    /// <param name="t">Text Variable</param>
    /// <param name="f">Feeling</param>
    private void VerifyOTMemoryIs(LegalityAnalysis data, byte m, byte i, ushort t, byte f)
    {
        var pk = (ITrainerMemories)data.Entity;
        if (pk.OT_Memory != m)
            data.AddLine(GetInvalid(string.Format(LMemoryIndexID, L_XOT, m)));
        if (pk.OT_Intensity != i)
            data.AddLine(GetInvalid(string.Format(LMemoryIndexIntensity, L_XOT, i)));
        if (pk.OT_TextVar != t)
            data.AddLine(GetInvalid(string.Format(LMemoryIndexVar, L_XOT, t)));
        if (pk.OT_Feeling != f)
            data.AddLine(GetInvalid(string.Format(LMemoryIndexFeel, L_XOT, f)));
    }

    private void VerifyHTMemoryNone(LegalityAnalysis data, ITrainerMemories pk)
    {
        if (pk.HT_Memory != 0 || pk.HT_TextVar != 0 || pk.HT_Intensity != 0 || pk.HT_Feeling != 0)
            data.AddLine(GetInvalid(string.Format(LMemoryCleared, L_XHT)));
    }

    private void VerifyOTMemory(LegalityAnalysis data)
    {
        var pk = data.Entity;
        var mem = (ITrainerMemories)pk;
        var Info = data.Info;

        // If the encounter has a memory from the OT that could never have it replaced, ensure it was not modified.
        switch (data.EncounterMatch)
        {
            case WC6 {IsEgg: false} g when g.OTGender != 3:
                VerifyOTMemoryIs(data, g.OT_Memory, g.OT_Intensity, g.OT_TextVar, g.OT_Feeling);
                return;
            case WC7 {IsEgg: false} g when g.OTGender != 3:
                VerifyOTMemoryIs(data, g.OT_Memory, g.OT_Intensity, g.OT_TextVar, g.OT_Feeling);
                return;
            case WC8 {IsEgg: false} g when g.OTGender != 3:
                VerifyOTMemoryIs(data, g.OT_Memory, g.OT_Intensity, g.OT_TextVar, g.OT_Feeling);
                return;

            case IMemoryOTReadOnly t and not MysteryGift: // Ignore Mystery Gift cases (covered above)
                VerifyOTMemoryIs(data, t.OT_Memory, t.OT_Intensity, t.OT_TextVar, t.OT_Feeling);
                return;
        }

        var context = Info.EncounterOriginal.Context;
        var memory = mem.OT_Memory;

        if (pk.IsEgg)
        {
            // Traded unhatched eggs in Gen8 have OT link trade memory applied erroneously.
            // They can also have the box-inspect memory!
            if (context != Gen8 || !((pk.Met_Location == Locations.LinkTrade6 && memory == 4) || memory == 85))
            {
                VerifyOTMemoryIs(data, 0, 0, 0, 0); // empty
                return;
            }
        }
        else if (!CanHaveMemoryForOT(pk, context, memory))
        {
            VerifyOTMemoryIs(data, 0, 0, 0, 0); // empty
            return;
        }

        // Bounds checking
        var mc = Memories.GetContext(context);
        if (!mc.CanObtainMemoryOT((GameVersion)pk.Version, memory))
            data.AddLine(GetInvalid(string.Format(LMemoryArgBadID, L_XOT)));

        // Verify memory if specific to OT
        switch (memory)
        {
            // No Memory
            case 0: // SW/SH trades don't set HT memories immediately, which is hilarious.
                data.AddLine(Get(LMemoryMissingOT, context == Gen8 ? Severity.Fishy : Severity.Invalid));
                VerifyOTMemoryIs(data, 0, 0, 0, 0);
                return;

            // {0} hatched from an Egg and saw {1} for the first time at... {2}. {4} that {3}.
            case 2 when !Info.EncounterMatch.EggEncounter:
                data.AddLine(GetInvalid(string.Format(LMemoryArgBadHatch, L_XOT)));
                break;

            // {0} became {1}’s friend when it arrived via Link Trade at... {2}. {4} that {3}.
            case 4 when Info.Generation == 6: // gen8 applies this memory erroneously
                data.AddLine(GetInvalid(string.Format(LMemoryArgBadOTEgg, L_XOT)));
                return;

            // {0} went to the Pokémon Center in {2} with {1} and had its tired body healed there. {4} that {3}.
            case 6 when !mc.HasPokeCenter((GameVersion)pk.Version, mem.OT_TextVar):
                data.AddLine(GetInvalid(string.Format(LMemoryArgBadLocation, L_XOT)));
                return;

            // {0} was with {1} when {1} caught {2}. {4} that {3}.
            case 14:
                var result = GetCanBeCaptured(mem.OT_TextVar, context, (GameVersion)pk.Version) // Any Game in the Handling Trainer's generation
                    ? GetValid(string.Format(LMemoryArgSpecies, L_XOT))
                    : GetInvalid(string.Format(LMemoryArgBadSpecies, L_XOT));
                data.AddLine(result);
                return;
        }

        data.AddLine(VerifyCommonMemory(pk, 0, context, Info, mc));
    }

    private static bool CanHaveMemoryForOT(PKM pk, EntityContext origin, int memory)
    {
        // Eggs cannot have memories
        if (pk.IsEgg)
        {
            if (origin == Gen8) // Gen8 sets for traded eggs.
                return pk.IsTradedEgg;
            return false;
        }

        return origin switch
        {
            Gen1 or Gen2 or Gen7 => memory == 4, // VC transfers can only have Bank memory.
            Gen6 => true,
            Gen8 => !(pk.GO_HOME || pk.Met_Location == Locations.HOME8), // HOME does not set memories.
            _ => false,
        };
    }

    private void VerifyHTMemory(LegalityAnalysis data)
    {
        var pk = data.Entity;
        var mem = (ITrainerMemories)pk;
        var Info = data.Info;

        var memory = mem.HT_Memory;

        if (pk.IsUntraded)
        {
            if (memory == 4 && WasTradedSWSHEgg(pk))
            {
                // Untraded link trade eggs in Gen8 have HT link trade memory applied erroneously.
                // Verify the link trade memory later.
            }
            else
            {
                VerifyHTMemoryNone(data, mem);
                return;
            }
        }

        if (pk.Format == 7)
        {
            VerifyHTMemoryTransferTo7(data, pk, Info);
            return;
        }

        var memoryGen = pk.Format >= 8 ? Gen8 : Gen6;

        // Bounds checking
        var context = Memories.GetContext(memoryGen);
        if (!context.CanObtainMemoryHT((GameVersion)pk.Version, memory))
            data.AddLine(GetInvalid(string.Format(LMemoryArgBadID, L_XHT)));

        // Verify memory if specific to HT
        switch (memory)
        {
            // No Memory
            case 0: // SW/SH memory application has an off-by-one error: [0,99] + 1 <= chance --> don't apply
                var severity = memoryGen switch
                {
                    Gen8 when pk is not PK8 && !pk.SWSH => Severity.Valid,
                    Gen8 => ParseSettings.Gen8MemoryMissingHT,
                    _ => Severity.Invalid,
                };
                if (severity != Severity.Valid)
                    data.AddLine(Get(LMemoryMissingHT, severity));
                VerifyHTMemoryNone(data, mem);
                return;

            // {0} met {1} at... {2}. {1} threw a Poké Ball at it, and they started to travel together. {4} that {3}.
            case 1:
                data.AddLine(GetInvalid(string.Format(LMemoryArgBadCatch, L_XHT)));
                return;

            // {0} hatched from an Egg and saw {1} for the first time at... {2}. {4} that {3}.
            case 2:
                data.AddLine(GetInvalid(string.Format(LMemoryArgBadHatch, L_XHT)));
                return;

            // {0} went to the Pokémon Center in {2} with {1} and had its tired body healed there. {4} that {3}.
            case 6 when !context.HasPokeCenter(GameVersion.Any, mem.HT_TextVar):
                data.AddLine(GetInvalid(string.Format(LMemoryArgBadLocation, L_XHT)));
                return;

            // {0} was with {1} when {1} caught {2}. {4} that {3}.
            case 14:
                var result = GetCanBeCaptured(mem.HT_TextVar, memoryGen, GameVersion.Any) // Any Game in the Handling Trainer's generation
                    ? GetValid(string.Format(LMemoryArgSpecies, L_XHT))
                    : GetInvalid(string.Format(LMemoryArgBadSpecies, L_XHT));
                data.AddLine(result);
                return;
        }

        var commonResult = VerifyCommonMemory(pk, 1, memoryGen, Info, context);
        data.AddLine(commonResult);
    }

    private static bool WasTradedSWSHEgg(PKM pk) => pk.SWSH && (!pk.IsEgg ? pk.Egg_Location : pk.Met_Location) is Locations.LinkTrade6;

    private void VerifyHTMemoryTransferTo7(LegalityAnalysis data, PKM pk, LegalInfo Info)
    {
        var mem = (ITrainerMemories)pk;
        // Bank Transfer adds in the Link Trade Memory.
        // Trading 7<->7 between games (not Bank) clears this data.
        if (mem.HT_Memory == 0)
        {
            VerifyHTMemoryNone(data, mem);
            return;
        }

        // Transfer 6->7 & withdraw to same HT => keeps past gen memory
        // Don't require link trade memory for these past gen cases
        int gen = Info.Generation;
        if (gen is >= 3 and < 7 && pk.CurrentHandler == 1)
            return;

        if (mem.HT_Memory != 4)
            data.AddLine(Severity.Invalid, LMemoryIndexLinkHT, CheckIdentifier.Memory);
        if (mem.HT_TextVar != 0)
            data.AddLine(Severity.Invalid, LMemoryIndexArgHT, CheckIdentifier.Memory);
        if (mem.HT_Intensity != 1)
            data.AddLine(Severity.Invalid, LMemoryIndexIntensityHT1, CheckIdentifier.Memory);
        if (mem.HT_Feeling > 10)
            data.AddLine(Severity.Invalid, LMemoryIndexFeelHT09, CheckIdentifier.Memory);
    }
}