using System;
using System.Collections.Generic;
using static System.Buffers.Binary.BinaryPrimitives;

namespace PKHeX.Core;

/// <summary>
/// Generation 3 <see cref="SaveFile"/> object for Pokémon Colosseum saves.
/// </summary>
public sealed class SAV3Colosseum : SaveFile, IGCSaveFile, IBoxDetailName, IDaycareStorage, IDaycareExperience
{
    protected internal override string ShortSummary => $"{OT} ({Version}) - {PlayTimeString}";
    public override string Extension => this.GCExtension();
    public override PersonalTable3 Personal => PersonalTable.RS;
    public override ReadOnlySpan<ushort> HeldItems => Legal.HeldItems_RS;
    public SAV3GCMemoryCard? MemoryCard { get; init; }

    private readonly Memory<byte> Raw;
    private new Span<byte> Data => Raw.Span;
    protected override Span<byte> BoxBuffer => Data;
    protected override Span<byte> PartyBuffer => Data;

    // 3 Save files are stored
    // 0x0000-0x6000 contains memory card data
    // 0x6000-0x60000 contains the 3 save slots
    // 0x5A000 / 3 = 0x1E000 per save slot
    // Checksum is SHA1 over 0-0x1DFD7, stored in the last 20 bytes of the save slot.
    // Another SHA1 hash is 0x1DFD8, for 20 bytes. Unknown purpose.
    // Checksum is used as the crypto key.

    private readonly int SaveCount = -1;
    private readonly int SaveIndex = -1;
    private readonly StrategyMemo StrategyMemo;
    public const int MaxShadowID = 0x80; // 128
    private int Memo;
    private int DaycareOffset;

    private readonly bool Japanese;

    public SAV3Colosseum(bool japanese = false)
    {
        Japanese = japanese;

        Raw = new byte[ColoCrypto.SLOT_SIZE];
        StrategyMemo = Initialize();
        ClearBoxes();
    }

    public SAV3Colosseum(byte[] data) : base(data)
    {
        Japanese = data[0] == 0x83; // Japanese game name first character

        // Decrypt most recent save slot
        (SaveIndex, SaveCount) = ColoCrypto.DetectLatest(data);
        Raw = ColoCrypto.GetSlot(data.AsMemory(), SaveIndex);
        StrategyMemo = Initialize();
    }

    private StrategyMemo Initialize()
    {
        // Trainer1 = 0x00078;
        Party = 0x000A8;

        Box = 0x00B90;
        DaycareOffset = 0x08170;
        Memo = 0x082B0;

        // Since PartyCount is not stored in the save file,
        // Count up how many party slots are active.
        for (int i = 0; i < 6; i++)
        {
            var ofs = GetPartyOffset(i);
            var span = Data[ofs..];
            if (ReadUInt16BigEndian(span) != 0) // species is at offset 0x00
                PartyCount++;
        }

        var memo = new StrategyMemo(Data[Memo..], xd: false);
        return memo;
    }

    protected override byte[] GetFinalData()
    {
        var newFile = GetInnerData();

        // Return the gci if Memory Card is not being exported
        if (MemoryCard is null)
            return newFile;

        MemoryCard.WriteSaveGameData(newFile);
        return MemoryCard.Data;
    }

    private byte[] GetInnerData()
    {
        StrategyMemo.Write().CopyTo(Data[Memo..]);
        SetChecksums();

        // Put save slot back in original save data
        byte[] newFile = (byte[])base.Data.Clone();
        ColoCrypto.SetSlot(newFile, SaveIndex, Data);

        return newFile;
    }

    // Configuration
    protected override SAV3Colosseum CloneInternal() => new(GetInnerData()) { MemoryCard = MemoryCard };

    protected override int SIZE_STORED => PokeCrypto.SIZE_3CSTORED;
    protected override int SIZE_PARTY => PokeCrypto.SIZE_3CSTORED; // unused
    public override CK3 BlankPKM => new();
    public override Type PKMType => typeof(CK3);

    public override ushort MaxMoveID => Legal.MaxMoveID_3;
    public override ushort MaxSpeciesID => Legal.MaxSpeciesID_3;
    public override int MaxAbilityID => Legal.MaxAbilityID_3;
    public override int MaxBallID => Legal.MaxBallID_3;
    public override int MaxItemID => Legal.MaxItemID_3_COLO;
    public override GameVersion MaxGameID => Legal.MaxGameID_3;

    public override int MaxEV => EffortValues.Max255;
    public override byte Generation => 3;
    public override EntityContext Context => EntityContext.Gen3;
    public override int MaxStringLengthOT => 10; // as evident by Mattle Ho-Oh
    public override int MaxStringLengthNickname => 10;
    public override int MaxMoney => 9999999;

    public override int BoxCount => 3;
    public override bool IsPKMPresent(ReadOnlySpan<byte> data) => EntityDetection.IsPresentGC(data);

    protected override void SetChecksums() => ColoCrypto.SetChecksums(Data);
    public override bool ChecksumsValid => !ChecksumInfo.Contains("Invalid");

    public override string ChecksumInfo
    {
        get
        {
            (bool isHeaderValid, bool isBodyValid) = ColoCrypto.IsChecksumValid(Data);
            static string valid(bool s) => s ? "Valid" : "Invalid";
            return $"Header Checksum {valid(isHeaderValid)}, Body Checksum {valid(isBodyValid)}.";
        }
    }

    // Trainer Info
    public override GameVersion Version { get => GameVersion.COLO; set { } }

    // Storage
    public override int GetPartyOffset(int slot)
    {
        return Party + (SIZE_STORED * slot);
    }

    public override int GetBoxOffset(int box)
    {
        return Box + (((30 * SIZE_STORED) + 0x14)*box) + 0x14;
    }

    private Span<byte> GetBoxNameSpan(int box) => Data.Slice(Box + (0x24A4 * box), 16);

    public string GetBoxName(int box)
    {
        return GetString(GetBoxNameSpan(box));
    }

    public void SetBoxName(int box, ReadOnlySpan<char> value)
    {
        SetString(GetBoxNameSpan(box), value, 8, StringConverterOption.ClearZero);
    }

    protected override CK3 GetPKM(byte[] data)
    {
        if (data.Length != SIZE_STORED)
            Array.Resize(ref data, SIZE_STORED);
        return new(data);
    }

    protected override byte[] DecryptPKM(byte[] data) => data;

    protected override void SetPKM(PKM pk, bool isParty = false)
    {
        if (pk is not CK3 ck3)
            return;

        ck3.CurrentRegion = (byte)CurrentRegion;
        ck3.OriginalRegion = (byte)OriginalRegion;

        ck3.ForceCorrectFatefulState(Japanese, ck3.FatefulEncounter);
    }

    protected override void SetDex(PKM pk)
    {
        if (pk.Species is 0 or > Legal.MaxSpeciesID_3)
            return;
        if (pk.IsEgg)
            return;

        // Dex Related
        var entry = StrategyMemo.GetEntry(pk.Species);
        if (entry.IsEmpty) // Populate
        {
            entry.Species = pk.Species;
            entry.PID = pk.PID;
            entry.ID32 = pk.ID32;
        }
        if (entry.Matches(pk.Species, pk.PID, pk.ID32))
        {
            entry.Seen = true;
            entry.Owned = true;
        }
        StrategyMemo.SetEntry(entry);
    }

    // Config
    private const int Config = 0x08;

    public GCVersion GCGameIndex { get => (GCVersion)Data[Config + 0x00]; set => Data[Config + 0x00] = (byte)value; }
    public GCRegion CurrentRegion { get => (GCRegion)Data[Config + 0x01]; set => Data[Config + 0x01] = (byte)value; }
    public GCRegion OriginalRegion { get => (GCRegion)Data[Config + 0x02]; set => Data[Config + 0x02] = (byte)value; }
    public LanguageGC GCLanguage { get => (LanguageGC)Data[Config + 0x03]; set => Data[Config + 0x03] = (byte)value; }
    public override int Language { get => (int)GCLanguage.ToLanguageID(); set => GCLanguage = ((LanguageID)value).ToLanguageGC(); }

    private TimeSpan PlayedSpan
    {
        get => TimeSpan.FromSeconds(ReadSingleBigEndian(Data[(Config + 0x20)..]));
        set => WriteSingleBigEndian(Data[(Config + 0x20)..], (float)value.TotalSeconds);
    }

    public override int PlayedHours
    {
        get => (ushort)PlayedSpan.TotalHours;
        set { var time = PlayedSpan; PlayedSpan = time - TimeSpan.FromHours((int)time.TotalHours) + TimeSpan.FromHours(value); }
    }

    public override int PlayedMinutes
    {
        get => (byte)PlayedSpan.Minutes;
        set { var time = PlayedSpan; PlayedSpan = time - TimeSpan.FromMinutes(time.Minutes) + TimeSpan.FromMinutes(value); }
    }

    public override int PlayedSeconds
    {
        get => (byte)PlayedSpan.Seconds;
        set { var time = PlayedSpan; PlayedSpan = time - TimeSpan.FromSeconds(time.Seconds) + TimeSpan.FromSeconds(value); }
    }

    // Trainer Info (offset 0x78, length 0xB18, end @ 0xB90)
    public override string OT { get => GetString(Data.Slice(0x78, 20)); set { SetString(Data.Slice(0x78, 20), value, 10, StringConverterOption.ClearZero); OT2 = value; } }
    public string OT2 { get => GetString(Data.Slice(0x8C, 20)); set => SetString(Data.Slice(0x8C, 20), value, 10, StringConverterOption.ClearZero); }

    public override uint ID32 { get => ReadUInt32BigEndian(Data[0xA4..]); set => WriteUInt32BigEndian(Data[0xA4..], value); }
    public override ushort SID16 { get => ReadUInt16BigEndian(Data[0xA4..]); set => WriteUInt16BigEndian(Data[0xA4..], value); }
    public override ushort TID16 { get => ReadUInt16BigEndian(Data[0xA6..]); set => WriteUInt16BigEndian(Data[0xA6..], value); }

    public override byte Gender { get => Data[0xAF8]; set => Data[0xAF8] = value; }
    public override uint Money { get => ReadUInt32BigEndian(Data[0xAFC..]); set => WriteUInt32BigEndian(Data[0xAFC..], value); }
    public uint Coupons { get => ReadUInt32BigEndian(Data[0xB00..]); set => WriteUInt32BigEndian(Data[0xB00..], value); }
    public string RUI_Name { get => GetString(Data.Slice(0xB3A, 20)); set => SetString(Data.Slice(0xB3A, 20), value, 10, StringConverterOption.ClearZero); }

    public override IReadOnlyList<InventoryPouch> Inventory
    {
        get
        {
            var info = ItemStorage3Colo.Instance;
            InventoryPouch[] pouch =
            [
                new InventoryPouch3GC(InventoryType.Items, info, 99, 0x007F8, 20), // 20 COLO, 30 XD
                new InventoryPouch3GC(InventoryType.KeyItems, info, 1, 0x00848, 43),
                new InventoryPouch3GC(InventoryType.Balls, info, 99, 0x008F4, 16),
                new InventoryPouch3GC(InventoryType.TMHMs, info, 99, 0x00934, 64), // no HMs
                new InventoryPouch3GC(InventoryType.Berries, info, 999, 0x00A34, 46),
                new InventoryPouch3GC(InventoryType.Medicine, info, 99, 0x00AEC, 3), // Cologne
            ];
            return pouch.LoadAll(Data);
        }
        set => value.SaveAll(Data);
    }

    // Daycare Structure:
    // 0x00 -- Occupied
    // 0x01 -- Deposited Level
    // 0x02-0x03 -- unused?
    // 0x04-0x07 -- Initial EXP
    public int DaycareSlotCount => 1;
    public bool IsDaycareOccupied(int slot) => Data[DaycareOffset] != 0;
    public void SetDaycareOccupied(int slot, bool occupied) => Data[DaycareOffset] = (byte)(occupied ? 1 : 0);
    public byte DaycareDepositLevel { get => Data[DaycareOffset + 1]; set => Data[DaycareOffset + 1] = value; }
    public uint GetDaycareEXP(int index) => ReadUInt32BigEndian(Data[(DaycareOffset + 4)..]);
    public void SetDaycareEXP(int index, uint value) => WriteUInt32BigEndian(Data[(DaycareOffset + 4)..], value);
    public Memory<byte> GetDaycareSlot(int slot) => Raw.Slice(DaycareOffset + 8, PokeCrypto.SIZE_3CSTORED);

    public override string GetString(ReadOnlySpan<byte> data) => StringConverter3GC.GetString(data);

    public override int SetString(Span<byte> destBuffer, ReadOnlySpan<char> value, int maxLength, StringConverterOption option)
    {
        return StringConverter3GC.SetString(destBuffer, value, maxLength, option);
    }
}