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

namespace PKHeX.Core;

/// <summary>
/// Generation 4 <see cref="SaveFile"/> object for My Pokémon Ranch saves.
/// </summary>
public sealed class SAV4Ranch : BulkStorage, ISaveFileRevision
{
    protected override int SIZE_STORED => 0x88 + 0x1C;
    protected override int SIZE_PARTY => SIZE_STORED;

    public int SaveRevision => Version == GameVersion.DP ? 0 : 1;
    public string SaveRevisionString => Version == GameVersion.DP ? "-DP" : "-Pt";

    public override int BoxCount { get; }
    public override int SlotCount { get; }

    public override IPersonalTable Personal => PersonalTable.Pt;
    public override IReadOnlyList<ushort> HeldItems => Legal.HeldItems_Pt;
    protected override SaveFile CloneInternal() => new SAV4Ranch((byte[])Data.Clone());
    public override string PlayTimeString => $"{Checksums.CRC16Invert(Data):X4}";
    protected internal override string ShortSummary => $"{OT} {PlayTimeString}";
    public override string Extension => ".bin";

    protected override PKM GetPKM(byte[] data) => new PK4(data);
    protected override byte[] DecryptPKM(byte[] data) => PokeCrypto.DecryptArray45(data);
    public override StorageSlotSource GetSlotFlags(int index) => index >= SlotCount ? StorageSlotSource.Locked : StorageSlotSource.None;
    protected override bool IsSlotSwapProtected(int box, int slot) => IsSlotOverwriteProtected(box, slot);

    public SAV4Ranch(byte[] data) : base(data, typeof(PK4), 0)
    {
        Version = Data.Length == SaveUtil.SIZE_G4RANCH_PLAT ? GameVersion.Pt : GameVersion.DP;

        OT = GetString(0x770, 0x12);

        // 0x18 starts the header table
        // Block 00, Offset = ???
        // Block 01, Offset = Mii Data
        // Block 02, Offset = Mii Link Data
        // Block 03, Offset = Pokemon Data
        // Block 04, Offset = ??

        // Unpack the binary a little:
        // size, count, Mii data[count]
        // size, count, Mii Link data[count]
        // size, count, Pokemon (PK4 + metadata)[count]
        // size, count, ???

        /* ====Metadata====
         * uint8_t poke_type;// 01 trainer, 04 hayley, 05 traded
         * uint8_t tradeable;// 02 is tradeable, normal 00
         * uint16_t tid;
         * uint16_t sid;
         * uint32_t name1;
         * uint32_t name2;
         * uint32_t name3;
         * uint32_t name4;
         */

        var pkCountOffset = ReadInt32BigEndian(Data.AsSpan(0x34)) + 4;
        SlotCount = ReadInt32BigEndian(Data.AsSpan(pkCountOffset));
        BoxCount = (int)Math.Ceiling((decimal)SlotCount / SlotsPerBox);

        Box = pkCountOffset + 4;

        FinalCountOffset = ReadInt32BigEndian(Data.AsSpan(0x3C));
        FinalCount = ReadInt32BigEndian(Data.AsSpan(FinalCountOffset));
    }

    private readonly int FinalCount;
    private readonly int FinalCountOffset;

    protected override void SetChecksums()
    {
        // ensure the final data is written if the user screws stuff up
        WriteInt32BigEndian(Data.AsSpan(FinalCountOffset), FinalCount);
        var goodlen = (FinalCountOffset + 4);
        Array.Clear(Data, goodlen, Data.Length - goodlen);

        // 20 byte SHA checksum at the top of the file, which covers all data that follows.
        using var hash = SHA1.Create();
        var result = hash.ComputeHash(Data, 20, Data.Length - 20);
        SetData(result, 0);
    }

    public override string GetString(ReadOnlySpan<byte> data) => StringConverter4GC.GetStringUnicode(data);

    public override int SetString(Span<byte> destBuffer, ReadOnlySpan<char> value, int maxLength, StringConverterOption option)
    {
        return StringConverter4GC.SetStringUnicode(value, destBuffer, maxLength, option);
    }
}