using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using System.Text;
using anjianjingling.Vision;

namespace anjianjingling.Capture
{
    /// <summary>
    /// 屏幕录像：GDI 抓帧 → JPEG 编码 → 手写 AVI(MJPG) 封装，无需 ffmpeg。
    /// </summary>
    public sealed class ScreenRecorder : IDisposable
    {
        private readonly ScreenCapture _capture = new();
        private Thread? _thread;
        private volatile bool _running;
        private AviWriter? _writer;

        public bool IsRecording => _running;
        public string? OutputPath { get; private set; }
        public long FrameCount { get; private set; }
        public event Action<string, long>? Finished;

        public int Fps { get; set; } = 15;
        public bool DrawCursor { get; set; } = true;
        public int Quality { get; set; } = 70;

        public void Start(string path, Rectangle region)
        {
            if (_running) return;

            int w = region.Width & ~1;   // 编码器要求偶数宽高更稳
            int h = region.Height & ~1;
            if (w < 16 || h < 16) throw new ArgumentException("录制区域太小");

            Directory.CreateDirectory(Path.GetDirectoryName(Path.GetFullPath(path))!);
            OutputPath = path;
            FrameCount = 0;
            _writer = new AviWriter(path, w, h, Math.Clamp(Fps, 1, 60));
            _running = true;

            var rect = new Rectangle(region.X, region.Y, w, h);
            var codec = GetJpegCodec();
            var ep = new EncoderParameters(1);
            ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)Math.Clamp(Quality, 20, 95));

            _thread = new Thread(() =>
            {
                var sw = System.Diagnostics.Stopwatch.StartNew();
                int frameInterval = Math.Max(1, 1000 / Math.Clamp(Fps, 1, 60));
                long frameIdx = 0;

                while (_running)
                {
                    // 固定帧率：按理论时间点抓帧，抓不动就丢帧，保证 AVI 时长等于真实时长
                    long target = frameIdx * frameInterval;
                    long now = sw.ElapsedMilliseconds;
                    if (now < target)
                    {
                        Thread.Sleep((int)Math.Min(30, target - now));
                        continue;
                    }

                    try
                    {
                        using var bmp = _capture.CaptureRegion(rect.X, rect.Y, rect.Width, rect.Height);
                        if (DrawCursor)
                        {
                            using var g = Graphics.FromImage(bmp);
                            DrawCursorOn(g, rect.X, rect.Y);
                        }
                        using var ms = new MemoryStream();
                        bmp.Save(ms, codec, ep);
                        _writer!.AddFrame(ms.ToArray());
                        FrameCount++;
                    }
                    catch
                    {
                        Thread.Sleep(frameInterval);
                    }

                    frameIdx = Math.Max(frameIdx + 1, now / frameInterval + 1);
                }
            })
            { IsBackground = true, Name = "ScreenRecorder" };
            _thread.Start();
        }

        public void Stop()
        {
            if (!_running) return;
            _running = false;
            _thread?.Join(3000);
            _thread = null;
            _writer?.Complete();
            _writer?.Dispose();
            _writer = null;
            if (OutputPath != null) Finished?.Invoke(OutputPath, FrameCount);
        }

        public void Dispose()
        {
            Stop();
        }

        private static ImageCodecInfo GetJpegCodec()
            => ImageCodecInfo.GetImageEncoders().First(c => c.FormatID == ImageFormat.Jpeg.Guid);

        // ===================== 光标 =====================

        [StructLayout(LayoutKind.Sequential)]
        private struct CURSORINFO
        {
            public int cbSize;
            public int flags;
            public IntPtr hCursor;
            public POINT ptScreenPos;
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct POINT { public int X, Y; }

        [StructLayout(LayoutKind.Sequential)]
        private struct ICONINFO
        {
            public bool fIcon;
            public int xHotspot;
            public int yHotspot;
            public IntPtr hbmMask;
            public IntPtr hbmColor;
        }

        private const int CURSOR_SHOWING = 0x00000001;
        private const int DI_NORMAL = 0x0003;

        [DllImport("user32.dll")]
        private static extern bool GetCursorInfo(ref CURSORINFO pci);

        [DllImport("user32.dll")]
        private static extern bool GetIconInfo(IntPtr hIcon, out ICONINFO piconinfo);

        [DllImport("user32.dll")]
        private static extern bool DrawIconEx(IntPtr hdc, int xLeft, int yTop, IntPtr hIcon,
            int cxWidth, int cyWidth, int istepIfAniCur, IntPtr hbrFlickerFreeDraw, int diFlags);

        [DllImport("gdi32.dll")]
        private static extern bool DeleteObject(IntPtr hObject);

        private static void DrawCursorOn(Graphics g, int offsetX, int offsetY)
        {
            var ci = new CURSORINFO { cbSize = Marshal.SizeOf<CURSORINFO>() };
            if (!GetCursorInfo(ref ci) || (ci.flags & CURSOR_SHOWING) == 0) return;

            int hx = 0, hy = 0;
            if (GetIconInfo(ci.hCursor, out var ii))
            {
                hx = ii.xHotspot;
                hy = ii.yHotspot;
                if (ii.hbmMask != IntPtr.Zero) DeleteObject(ii.hbmMask);
                if (ii.hbmColor != IntPtr.Zero) DeleteObject(ii.hbmColor);
            }

            IntPtr hdc = g.GetHdc();
            try
            {
                DrawIconEx(hdc, ci.ptScreenPos.X - offsetX - hx, ci.ptScreenPos.Y - offsetY - hy,
                    ci.hCursor, 0, 0, 0, IntPtr.Zero, DI_NORMAL);
            }
            finally { g.ReleaseHdc(hdc); }
        }
    }

    /// <summary>
    /// 最小可用 AVI(MJPG) 封装：RIFF/hdrl(avih+strl)/movi/idx1。
    /// </summary>
    internal sealed class AviWriter : IDisposable
    {
        private readonly FileStream _fs;
        private readonly int _w, _h, _fps;
        private readonly List<(long Offset, int Size)> _index = new();
        private long _riffSizePos, _moviSizePos, _moviDataStart;
        private long _avihFramesPos, _strhLengthPos, _avihMaxBytesPos, _avihBufPos, _strhBufPos;
        private int _frames;
        private long _maxBytes;

        public AviWriter(string path, int width, int height, int fps)
        {
            _w = width; _h = height; _fps = fps;
            _fs = new FileStream(path, FileMode.Create, FileAccess.ReadWrite, FileShare.Read);
            WriteHeader();
        }

        private void W(string s) => _fs.Write(Encoding.ASCII.GetBytes(s));
        private void W(int v) => _fs.Write(BitConverter.GetBytes(v));
        private void W(uint v) => _fs.Write(BitConverter.GetBytes(v));
        private void W(short v) => _fs.Write(BitConverter.GetBytes(v));

        private void WriteHeader()
        {
            W("RIFF");
            _riffSizePos = _fs.Position; W(0);
            W("AVI ");

            // ---- LIST hdrl ----（size = 'hdrl' + avih块 + strl整块）
            const int strlContent = 4 + (8 + 56) + (8 + 40);   // 'strl' + strh + strf = 116
            const int strlList = 8 + strlContent;              // 124
            const int hdrlContent = 4 + (8 + 56) + strlList;   // 192
            W("LIST");
            W(hdrlContent);
            W("hdrl");

            // avih
            W("avih"); W(56);
            long avihStart = _fs.Position;
            W(1_000_000 / _fps);                 // dwMicroSecPerFrame
            _avihMaxBytesPos = _fs.Position; W(0);  // dwMaxBytesPerSec
            W(0);                                // dwPaddingGranularity
            W(0x10);                             // dwFlags: AVIF_HASINDEX
            _avihFramesPos = _fs.Position; W(0);    // dwTotalFrames
            W(0);                                // dwInitialFrames
            W(1);                                // dwStreams
            _avihBufPos = _fs.Position; W(0);       // dwSuggestedBufferSize
            W(_w); W(_h);
            W(0); W(0); W(0); W(0);              // reserved

            // ---- LIST strl ----
            W("LIST");
            W(strlContent);
            W("strl");

            W("strh"); W(56);
            W("vids"); W("MJPG");
            W(0);            // dwFlags
            W((short)0);     // wPriority
            W((short)0);     // wLanguage
            W(0);            // dwInitialFrames
            W(1);            // dwScale
            W(_fps);         // dwRate
            W(0);            // dwStart
            _strhLengthPos = _fs.Position; W(0);  // dwLength
            _strhBufPos = _fs.Position; W(0);     // dwSuggestedBufferSize
            W(-1);           // dwQuality
            W(0);            // dwSampleSize
            W((short)0); W((short)0); W((short)_w); W((short)_h);  // rcFrame

            W("strf"); W(40);
            W(40);           // biSize
            W(_w); W(_h);
            W((short)1);     // biPlanes
            W((short)24);    // biBitCount
            W("MJPG");       // biCompression
            W(_w * _h * 3);  // biSizeImage
            W(0); W(0); W(0); W(0);

            // ---- LIST movi ----
            W("LIST");
            _moviSizePos = _fs.Position; W(0);
            W("movi");
            _moviDataStart = _fs.Position;
        }

        public void AddFrame(byte[] jpeg)
        {
            long chunkStart = _fs.Position;
            W("00dc");
            W(jpeg.Length);
            _fs.Write(jpeg);
            if ((jpeg.Length & 1) == 1) _fs.WriteByte(0);

            _index.Add((chunkStart - _moviDataStart, jpeg.Length));
            _frames++;
            if (jpeg.Length > _maxBytes) _maxBytes = jpeg.Length;
        }

        public void Complete()
        {
            long moviEnd = _fs.Position;
            long moviSize = moviEnd - _moviSizePos - 4;   // 不含 'movi' 四字符

            // idx1
            W("idx1");
            W(_index.Count * 16);
            foreach (var (off, size) in _index)
            {
                W("00dc");
                W((uint)0x10);
                W((int)off);
                W(size);
            }

            long fileEnd = _fs.Position;

            // 回填各长度字段
            void Patch(long pos, int val)
            {
                long save = _fs.Position;
                _fs.Position = pos;
                _fs.Write(BitConverter.GetBytes(val));
                _fs.Position = save;
            }

            Patch(_riffSizePos, (int)(fileEnd - 8));
            Patch(_moviSizePos, (int)moviSize);
            Patch(_avihFramesPos, _frames);
            Patch(_strhLengthPos, _frames);
            Patch(_avihMaxBytesPos, (int)(_maxBytes * _fps));
            Patch(_avihBufPos, (int)_maxBytes);
            Patch(_strhBufPos, (int)_maxBytes);

            _fs.Flush();
        }

        public void Dispose() => _fs.Dispose();
    }
}