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

namespace PKHeX.Core
{
    /// <summary>
    /// Generation 3 <see cref="SaveFile"/> object for Pokémon Ruby Sapphire Box saves.
    /// </summary>
    public sealed class SAV3RSBox : SaveFile, IGCSaveFile
    {
        protected internal override string ShortSummary => $"{Version} #{SaveCount:0000}";
        public override string Extension => this.GCExtension();
        public override PersonalTable Personal => PersonalTable.RS;
        public override IReadOnlyList<ushort> HeldItems => Legal.HeldItems_RS;
        public SAV3GCMemoryCard? MemoryCard { get; init; }
        public readonly bool Japanese = false; // todo?

        public SAV3RSBox(byte[] data, SAV3GCMemoryCard memCard) : this(data) => MemoryCard = memCard;

        public SAV3RSBox() : base(SaveUtil.SIZE_G3BOX)
        {
            Box = 0;
            Blocks = Array.Empty<BlockInfoRSBOX>();
            ClearBoxes();
        }

        public SAV3RSBox(byte[] data) : base(data)
        {
            Blocks = ReadBlocks(data);
            InitializeData();
        }

        private void InitializeData()
        {
            // Detect active save
            int[] SaveCounts = Blocks.Select(block => (int) block.SaveCount).ToArray();
            SaveCount = SaveCounts.Max();
            int ActiveSAV = Array.IndexOf(SaveCounts, SaveCount) / BLOCK_COUNT;
            Blocks = Blocks.Skip(ActiveSAV * BLOCK_COUNT).Take(BLOCK_COUNT).OrderBy(b => b.ID).ToArray();

            // Set up PC data buffer beyond end of save file.
            Box = Data.Length;
            Array.Resize(ref Data, Data.Length + SIZE_RESERVED); // More than enough empty space.

            // Copy block to the allocated location
            const int copySize = BLOCK_SIZE - 0x10;
            foreach (var b in Blocks)
                Array.Copy(Data, b.Offset + 0xC, Data, (int) (Box + (b.ID * copySize)), copySize);
        }

        private static BlockInfoRSBOX[] ReadBlocks(byte[] data)
        {
            var blocks = new BlockInfoRSBOX[2 * BLOCK_COUNT];
            for (int i = 0; i < blocks.Length; i++)
            {
                int offset = BLOCK_SIZE + (i * BLOCK_SIZE);
                blocks[i] = new BlockInfoRSBOX(data, offset);
            }

            return blocks;
        }

        private BlockInfoRSBOX[] Blocks;
        private int SaveCount;
        private const int BLOCK_COUNT = 23;
        private const int BLOCK_SIZE = 0x2000;
        private const int SIZE_RESERVED = BLOCK_COUNT * BLOCK_SIZE; // unpacked box data

        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()
        {
            // Copy Box data back
            const int copySize = BLOCK_SIZE - 0x10;
            foreach (var b in Blocks)
                Array.Copy(Data, (int) (Box + (b.ID * copySize)), Data, b.Offset + 0xC, copySize);

            SetChecksums();

            return GetData(0, Data.Length - SIZE_RESERVED);
        }

        // Configuration
        protected override SaveFile CloneInternal()
        {
            var data = GetInnerData();
            var sav = MemoryCard is not null ? new SAV3RSBox(data, MemoryCard) : new SAV3RSBox(data);
            return sav;
        }

        protected override int SIZE_STORED => PokeCrypto.SIZE_3STORED + 4;
        protected override int SIZE_PARTY => PokeCrypto.SIZE_3PARTY; // unused
        public override PKM BlankPKM => new PK3();
        public override Type PKMType => typeof(PK3);

        public override int MaxMoveID => Legal.MaxMoveID_3;
        public override int MaxSpeciesID => Legal.MaxSpeciesID_3;
        public override int MaxAbilityID => Legal.MaxAbilityID_3;
        public override int MaxItemID => Legal.MaxItemID_3;
        public override int MaxBallID => Legal.MaxBallID_3;
        public override int MaxGameID => Legal.MaxGameID_3;

        public override int MaxEV => 255;
        public override int Generation => 3;
        protected override int GiftCountMax => 1;
        public override int OTLength => 7;
        public override int NickLength => 10;
        public override int MaxMoney => 999999;
        public override bool HasBoxWallpapers => false;

        public override int BoxCount => 50;
        public override bool HasParty => false;
        public override bool IsPKMPresent(ReadOnlySpan<byte> data) => PKX.IsPKMPresentGBA(data);

        // Checksums
        protected override void SetChecksums() => Blocks.SetChecksums(Data);
        public override bool ChecksumsValid => Blocks.GetChecksumsValid(Data);
        public override string ChecksumInfo => Blocks.GetChecksumInfo(Data);

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

        // Storage
        public override int GetPartyOffset(int slot) => -1;
        public override int GetBoxOffset(int box) => Box + 8 + (SIZE_STORED * box * 30);

        public override int CurrentBox
        {
            get => Data[Box + 4] * 2;
            set => Data[Box + 4] = (byte)(value / 2);
        }

        protected override int GetBoxWallpaperOffset(int box)
        {
            // Box Wallpaper is directly after the Box Names
            int offset = Box + 0x1ED19 + (box / 2);
            return offset;
        }

        public override string GetBoxName(int box)
        {
            // Tweaked for the 1-30/31-60 box showing
            int lo = (30 *(box%2)) + 1;
            int hi = 30*((box % 2) + 1);
            string boxName = $"[{lo:00}-{hi:00}] ";
            box /= 2;

            int offset = Box + 0x1EC38 + (9 * box);
            if (Data[offset] is 0 or 0xFF)
                boxName += $"BOX {box + 1}";
            boxName += GetString(offset, 9);

            return boxName;
        }

        public override void SetBoxName(int box, string value)
        {
            int offset = Box + 0x1EC38 + (9 * box);
            var span = Data.AsSpan(offset, 9);
            if (value == $"BOX {box + 1}")
            {
                span.Clear();
                return;
            }
            SetString(span, value.AsSpan(), 8, StringConverterOption.ClearZero);
        }

        protected override PKM GetPKM(byte[] data)
        {
            if (data.Length != PokeCrypto.SIZE_3STORED)
                Array.Resize(ref data, PokeCrypto.SIZE_3STORED);
            return new PK3(data);
        }

        protected override byte[] DecryptPKM(byte[] data)
        {
            if (data.Length != PokeCrypto.SIZE_3STORED)
                Array.Resize(ref data, PokeCrypto.SIZE_3STORED);
            return PokeCrypto.DecryptArray3(data);
        }

        protected override void SetDex(PKM pkm) { /* No Pokedex for this game, do nothing */ }

        public override void WriteBoxSlot(PKM pkm, Span<byte> data, int offset)
        {
            base.WriteBoxSlot(pkm, data, offset);
            WriteUInt16LittleEndian(data[(PokeCrypto.SIZE_3STORED)..], (ushort)pkm.TID);
            WriteUInt16LittleEndian(data[(PokeCrypto.SIZE_3STORED + 2)..], (ushort)pkm.SID);
        }

        public override string GetString(ReadOnlySpan<byte> data) => StringConverter3.GetString(data, Japanese);

        public override int SetString(Span<byte> destBuffer, ReadOnlySpan<char> value, int maxLength, StringConverterOption option)
        {
            return StringConverter3.SetString(destBuffer, value, maxLength, Japanese, option);
        }
    }
}