using Avalonia.Media;
using DynamicData;
using LibHac.Common;
using LibHac.Fs;
using LibHac.Fs.Fsa;
using LibHac.FsSystem;
using LibHac.Ncm;
using LibHac.Tools.Fs;
using LibHac.Tools.FsSystem;
using LibHac.Tools.FsSystem.NcaUtils;
using Ryujinx.Ava.Ui.Models;
using Ryujinx.HLE.FileSystem;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Formats.Png;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Processing;
using System;
using System.Buffers.Binary;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Color = Avalonia.Media.Color;

namespace Ryujinx.Ava.Ui.ViewModels
{
    internal class AvatarProfileViewModel : BaseModel, IDisposable
    {
        private const int MaxImageTasks = 4;
        
        private static readonly Dictionary<string, byte[]> _avatarStore = new();
        private static bool _isPreloading;
        private static Action _loadCompleteAction;

        private ObservableCollection<ProfileImageModel> _images;
        private Color _backgroundColor = Colors.White;

        private int _selectedIndex;
        private int _imagesLoaded;
        private bool _isActive;
        private byte[] _selectedImage;
        private bool _isIndeterminate = true;

        public bool IsActive
        {
            get => _isActive;
            set => _isActive = value;
        }

        public AvatarProfileViewModel()
        {
            _images = new ObservableCollection<ProfileImageModel>();
        }
        
        public AvatarProfileViewModel(Action loadCompleteAction)
        {
            _images = new ObservableCollection<ProfileImageModel>();

            if (_isPreloading)
            {
                _loadCompleteAction = loadCompleteAction;
            }
            else
            {
                ReloadImages();
            }
        }

        public Color BackgroundColor
        {
            get => _backgroundColor;
            set
            {
                _backgroundColor = value;

                IsActive = false;
                
                ReloadImages();
            }
        }

        public ObservableCollection<ProfileImageModel> Images
        {
            get => _images;
            set
            {
                _images = value;
                OnPropertyChanged();
            }
        }

        public bool IsIndeterminate
        {
            get => _isIndeterminate;
            set
            {
                _isIndeterminate = value;
                
                OnPropertyChanged();
            }
        }

        public int ImageCount => _avatarStore.Count;

        public int ImagesLoaded
        {
            get => _imagesLoaded;
            set
            {
                _imagesLoaded = value;
                OnPropertyChanged();
            }
        }

        public int SelectedIndex
        {
            get => _selectedIndex;
            set
            {
                _selectedIndex = value;

                if (_selectedIndex == -1)
                {
                    SelectedImage = null;
                }
                else
                {
                    SelectedImage = _images[_selectedIndex].Data;
                }

                OnPropertyChanged();
            }
        }

        public byte[] SelectedImage
        {
            get => _selectedImage;
            private set => _selectedImage = value;
        }

        public void ReloadImages()
        {
            if (_isPreloading)
            {
                IsIndeterminate = false;
                return;
            }
            Task.Run(() =>
            {
                IsActive = true;

                Images.Clear();
                int selectedIndex = _selectedIndex;
                int index = 0;
                
                ImagesLoaded = 0;
                IsIndeterminate = false;

                var keys = _avatarStore.Keys.ToList();

                var newImages = new List<ProfileImageModel>();
                var tasks = new List<Task>();

                for (int i = 0; i < MaxImageTasks; i++)
                {
                    var start = i;
                    tasks.Add(Task.Run(() => ImageTask(start)));
                }

                Task.WaitAll(tasks.ToArray());
                
                Images.AddRange(newImages);

                void ImageTask(int start)
                {
                    for (int i = start; i < keys.Count; i += MaxImageTasks)
                    {
                        if (!IsActive)
                        {
                            return;
                        }

                        var key = keys[i];
                        var image = _avatarStore[keys[i]];

                        var data = ProcessImage(image);
                        newImages.Add(new ProfileImageModel(key, data));
                        if (index++ == selectedIndex)
                        {
                            SelectedImage = data;
                        }

                        Interlocked.Increment(ref _imagesLoaded);
                        OnPropertyChanged(nameof(ImagesLoaded));
                    }
                }
            });
        }

        private byte[] ProcessImage(byte[] data)
        {
            using (MemoryStream streamJpg = new())
            {
                Image avatarImage = Image.Load(data, new PngDecoder());

                avatarImage.Mutate(x => x.BackgroundColor(new Rgba32(BackgroundColor.R,
                    BackgroundColor.G,
                    BackgroundColor.B,
                    BackgroundColor.A)));
                avatarImage.SaveAsJpeg(streamJpg);

                return streamJpg.ToArray();
            }
        }

        public static void PreloadAvatars(ContentManager contentManager, VirtualFileSystem virtualFileSystem)
        {
            try
            {
                if (_avatarStore.Count > 0)
                {
                    return;
                }

                _isPreloading = true;

                string contentPath =
                    contentManager.GetInstalledContentPath(0x010000000000080A, StorageId.BuiltInSystem,
                        NcaContentType.Data);
                string avatarPath = virtualFileSystem.SwitchPathToSystemPath(contentPath);

                if (!string.IsNullOrWhiteSpace(avatarPath))
                {
                    using (IStorage ncaFileStream = new LocalStorage(avatarPath, FileAccess.Read, FileMode.Open))
                    {
                        Nca nca = new(virtualFileSystem.KeySet, ncaFileStream);
                        IFileSystem romfs = nca.OpenFileSystem(NcaSectionType.Data, IntegrityCheckLevel.ErrorOnInvalid);

                        foreach (DirectoryEntryEx item in romfs.EnumerateEntries())
                        {
                            // TODO: Parse DatabaseInfo.bin and table.bin files for more accuracy.
                            if (item.Type == DirectoryEntryType.File && item.FullPath.Contains("chara") &&
                                item.FullPath.Contains("szs"))
                            {
                                using var file = new UniqueRef<IFile>();

                                romfs.OpenFile(ref file.Ref(), ("/" + item.FullPath).ToU8Span(), OpenMode.Read)
                                    .ThrowIfFailure();

                                using (MemoryStream stream = new())
                                using (MemoryStream streamPng = new())
                                {
                                    file.Get.AsStream().CopyTo(stream);

                                    stream.Position = 0;

                                    Image avatarImage = Image.LoadPixelData<Rgba32>(DecompressYaz0(stream), 256, 256);

                                    avatarImage.SaveAsPng(streamPng);

                                    _avatarStore.Add(item.FullPath, streamPng.ToArray());
                                }
                            }
                        }
                    }
                }
            }
            finally
            {
                _isPreloading = false;
                _loadCompleteAction?.Invoke();
            }
        }

        private static byte[] DecompressYaz0(Stream stream)
        {
            using (BinaryReader reader = new(stream))
            {
                reader.ReadInt32(); // Magic

                uint decodedLength = BinaryPrimitives.ReverseEndianness(reader.ReadUInt32());

                reader.ReadInt64(); // Padding

                byte[] input = new byte[stream.Length - stream.Position];
                stream.Read(input, 0, input.Length);

                uint inputOffset = 0;

                byte[] output = new byte[decodedLength];
                uint outputOffset = 0;

                ushort mask = 0;
                byte header = 0;

                while (outputOffset < decodedLength)
                {
                    if ((mask >>= 1) == 0)
                    {
                        header = input[inputOffset++];
                        mask = 0x80;
                    }

                    if ((header & mask) != 0)
                    {
                        if (outputOffset == output.Length)
                        {
                            break;
                        }

                        output[outputOffset++] = input[inputOffset++];
                    }
                    else
                    {
                        byte byte1 = input[inputOffset++];
                        byte byte2 = input[inputOffset++];

                        uint dist = (uint)((byte1 & 0xF) << 8) | byte2;
                        uint position = outputOffset - (dist + 1);

                        uint length = (uint)byte1 >> 4;
                        if (length == 0)
                        {
                            length = (uint)input[inputOffset++] + 0x12;
                        }
                        else
                        {
                            length += 2;
                        }

                        uint gap = outputOffset - position;
                        uint nonOverlappingLength = length;

                        if (nonOverlappingLength > gap)
                        {
                            nonOverlappingLength = gap;
                        }

                        Buffer.BlockCopy(output, (int)position, output, (int)outputOffset, (int)nonOverlappingLength);
                        outputOffset += nonOverlappingLength;
                        position += nonOverlappingLength;
                        length -= nonOverlappingLength;

                        while (length-- > 0)
                        {
                            output[outputOffset++] = output[position++];
                        }
                    }
                }

                return output;
            }
        }

        public void Dispose()
        {
            _loadCompleteAction = null;
            IsActive = false;
        }
    }
}