// Copyright © 2017-2025 QL-Win Contributors
//
// This file is part of QuickLook program.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

using LibAPNG;
using QuickLook.Common.ExtensionMethods;
using QuickLook.Common.Plugin;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Media.Imaging;

namespace QuickLook.Plugin.ImageViewer.AnimatedImage.Providers;

internal class APngProvider : AnimationProvider
{
    private readonly Frame _baseFrame;
    private readonly List<FrameInfo> _frames;
    private readonly List<BitmapSource> _renderedFrames;
    private int _lastEffectivePreviousPreviousFrameIndex;
    private NativeProvider _nativeImageProvider;

    public APngProvider(Uri path, MetaProvider meta, ContextObject contextObject) : base(path, meta, contextObject)
    {
        if (!IsAnimatedPng(path.LocalPath))
        {
            _nativeImageProvider = new NativeProvider(path, meta, contextObject);
            Animator = _nativeImageProvider.Animator;
            return;
        }

        var decoder = new APNGBitmap(path.LocalPath);

        _baseFrame = decoder.DefaultImage;
        _frames = new List<FrameInfo>(decoder.Frames.Length);
        _renderedFrames = new List<BitmapSource>(decoder.Frames.Length);
        Enumerable.Repeat(0, decoder.Frames.Length).ForEach(_ => _renderedFrames.Add(null));

        Animator = new Int32AnimationUsingKeyFrames { RepeatBehavior = RepeatBehavior.Forever };

        var wallclock = TimeSpan.Zero;

        for (var i = 0; i < decoder.Frames.Length; i++)
        {
            var frame = decoder.Frames[i];

            _frames.Add(new FrameInfo(decoder.IHDRChunk, frame));

            Animator.KeyFrames.Add(new DiscreteInt32KeyFrame(i, KeyTime.FromTimeSpan(wallclock)));
            wallclock += _frames[i].Delay;
        }
    }

    public override Task<BitmapSource> GetThumbnail(Size renderSize)
    {
        if (_nativeImageProvider != null)
            return _nativeImageProvider.GetThumbnail(renderSize);

        return new Task<BitmapSource>(() =>
        {
            var bs = _baseFrame.GetBitmapSource();

            bs.Freeze();
            return bs;
        });
    }

    public override Task<BitmapSource> GetRenderedFrame(int index)
    {
        if (_nativeImageProvider != null)
            return _nativeImageProvider.GetRenderedFrame(index);

        if (_renderedFrames[index] != null)
            return new Task<BitmapSource>(() => _renderedFrames[index]);

        return new Task<BitmapSource>(() =>
        {
            var rendered = Render(index);
            _renderedFrames[index] = rendered;

            return rendered;
        });
    }

    public override void Dispose()
    {
        if (_nativeImageProvider != null)
        {
            _nativeImageProvider.Dispose();
            _nativeImageProvider = null;
            return;
        }

        _frames.Clear();
        _renderedFrames.Clear();
    }

    private BitmapSource Render(int index)
    {
        var currentFrame = _frames[index];
        FrameInfo previousFrame = null;
        BitmapSource previousRendered = null;
        BitmapSource previousPreviousRendered = null;

        if (index > 0)
        {
            if (_renderedFrames[index - 1] == null)
                _renderedFrames[index - 1] = Render(index - 1);

            previousFrame = _frames[index - 1];
            previousRendered = _renderedFrames[index - 1];
        }

        // when saying APNGDisposeOpPrevious, we need to find the last frame not having APNGDisposeOpPrevious.
        // Only [index-2] is not correct here since that frame may also have APNGDisposeOpPrevious.
        if (index > 1)
            previousPreviousRendered = _renderedFrames[_lastEffectivePreviousPreviousFrameIndex];
        if (_frames[index].DisposeOp != DisposeOps.APNGDisposeOpPrevious)
            _lastEffectivePreviousPreviousFrameIndex = Math.Max(_lastEffectivePreviousPreviousFrameIndex, index);

        var visual = new DrawingVisual();

        using (var context = visual.RenderOpen())
        {
            // protect region
            if (currentFrame.BlendOp == BlendOps.APNGBlendOpSource)
            {
                var freeRegion = new CombinedGeometry(GeometryCombineMode.Xor,
                    new RectangleGeometry(currentFrame.FrameRect),
                    new RectangleGeometry(currentFrame.FrameRect));
                context.PushOpacityMask(
                    new DrawingBrush(new GeometryDrawing(Brushes.Transparent, null, freeRegion)));
            }

            if (previousFrame != null)
                switch (previousFrame.DisposeOp)
                {
                    case DisposeOps.APNGDisposeOpNone:
                        if (previousRendered != null)
                            context.DrawImage(previousRendered, currentFrame.FullRect);
                        break;

                    case DisposeOps.APNGDisposeOpPrevious:
                        if (previousPreviousRendered != null)
                            context.DrawImage(previousPreviousRendered, currentFrame.FullRect);
                        break;

                    case DisposeOps.APNGDisposeOpBackground:
                        // do nothing
                        break;
                }

            // unprotect region and draw current frame
            if (currentFrame.BlendOp == BlendOps.APNGBlendOpSource)
                context.Pop();
            context.DrawImage(currentFrame.Pixels, currentFrame.FrameRect);
        }

        var bitmap = new RenderTargetBitmap(
            (int)currentFrame.FullRect.Width, (int)currentFrame.FullRect.Height,
            Math.Floor(currentFrame.Pixels.DpiX), Math.Floor(currentFrame.Pixels.DpiY),
            PixelFormats.Pbgra32);
        bitmap.Render(visual);

        bitmap.Freeze();
        return bitmap;
    }

    private static bool IsAnimatedPng(string path)
    {
        using (var br = new BinaryReader(new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)))
        {
            if (br.BaseStream.Length < 8 + 4)
                return false;

            uint nextChunk = 8; // skip header

            while (nextChunk > 0 && nextChunk < br.BaseStream.Length)
            {
                br.BaseStream.Position = nextChunk;

                var data_size = ToUInt32BE(br.ReadBytes(4)); // data size in BE

                var window = br.ReadBytes(4); // label

                if (window[0] == 'I' && window[1] == 'D' && window[2] == 'A' && window[3] == 'T')
                    return false;

                if (window[0] == 'a' && window[1] == 'c' && window[2] == 'T' && window[3] == 'L')
                    return true;

                // *[Data Size] + Data Size + Label + CRC
                nextChunk += data_size + 4 + 4 + 4;
            }

            return false;
        }

        uint ToUInt32BE(byte[] data)
        {
            Array.Reverse(data);
            return BitConverter.ToUInt32(data, 0);
        }
    }

    private class FrameInfo
    {
        public readonly BlendOps BlendOp;
        public readonly TimeSpan Delay;
        public readonly DisposeOps DisposeOp;
        public readonly Rect FrameRect;
        public readonly Rect FullRect;
        public readonly BitmapSource Pixels;

        public FrameInfo(IHDRChunk header, Frame frame)
        {
            FullRect = new Rect(0, 0, header.Width, header.Height);
            FrameRect = new Rect(frame.fcTLChunk.XOffset, frame.fcTLChunk.YOffset,
                frame.fcTLChunk.Width, frame.fcTLChunk.Height);

            BlendOp = frame.fcTLChunk.BlendOp;
            DisposeOp = frame.fcTLChunk.DisposeOp;

            Pixels = frame.GetBitmapSource();
            Pixels.Freeze();

            Delay = TimeSpan.FromSeconds((double)frame.fcTLChunk.DelayNum /
                                         (frame.fcTLChunk.DelayDen == 0
                                             ? 100
                                             : frame.fcTLChunk.DelayDen));
        }
    }
}