using System;
using System.Runtime.InteropServices;
using Avalonia;
using Avalonia.Media.Imaging;
using Avalonia.Platform;

namespace Notify.Interop;

/// <summary>
/// 从 exe 提取图标并转成 Avalonia 位图
///
/// ExtractIconEx 拿 HICON，再用 GDI 读出 BGRA 像素构造 Bitmap；不依赖
/// System.Drawing（其 AOT 不友好）
/// </summary>
internal static partial class AppIcon
{
    public static Bitmap? Extract(string exePath)
    {
        if (string.IsNullOrEmpty(exePath))
        {
            return null;
        }

        var hIcon = IntPtr.Zero;
        try
        {
            if (ExtractIconExW(exePath, 0, out hIcon, out _, 1) == 0 || hIcon == IntPtr.Zero)
            {
                return null;
            }

            return IconToBitmap(hIcon);
        }
        catch
        {
            return null;
        }
        finally
        {
            if (hIcon != IntPtr.Zero)
            {
                DestroyIcon(hIcon);
            }
        }
    }

    private static Bitmap? IconToBitmap(IntPtr hIcon)
    {
        if (!GetIconInfo(hIcon, out var ii))
        {
            return null;
        }

        try
        {
            var bm = default(BITMAP);
            if (GetObjectW(ii.hbmColor, Marshal.SizeOf<BITMAP>(), ref bm) == 0 || bm.bmWidth <= 0 || bm.bmHeight <= 0)
            {
                return null;
            }

            var w = bm.bmWidth;
            var h = bm.bmHeight;
            var buffer = new byte[w * h * 4];

            var bmi = new BITMAPINFOHEADER
            {
                biSize = (uint)Marshal.SizeOf<BITMAPINFOHEADER>(),
                biWidth = w,
                biHeight = -h, // 负数 = 自上而下，行序正常
                biPlanes = 1,
                biBitCount = 32,
                biCompression = 0,
            };

            var hdc = GetDC(IntPtr.Zero);
            try
            {
                if (GetDIBits(hdc, ii.hbmColor, 0, (uint)h, buffer, ref bmi, 0) == 0)
                {
                    return null;
                }
            }
            finally
            {
                ReleaseDC(IntPtr.Zero, hdc);
            }

            // 某些老图标无 alpha 通道（全 0），那样会整块透明，补成不透明
            var anyAlpha = false;
            for (var i = 3; i < buffer.Length; i += 4)
            {
                if (buffer[i] != 0)
                {
                    anyAlpha = true;
                    break;
                }
            }

            if (!anyAlpha)
            {
                for (var i = 3; i < buffer.Length; i += 4)
                {
                    buffer[i] = 255;
                }
            }

            var handle = GCHandle.Alloc(buffer, GCHandleType.Pinned);
            try
            {
                return new Bitmap(
                    PixelFormat.Bgra8888,
                    AlphaFormat.Unpremul,
                    handle.AddrOfPinnedObject(),
                    new PixelSize(w, h),
                    new Vector(96, 96),
                    w * 4);
            }
            finally
            {
                handle.Free();
            }
        }
        finally
        {
            if (ii.hbmColor != IntPtr.Zero)
            {
                DeleteObject(ii.hbmColor);
            }

            if (ii.hbmMask != IntPtr.Zero)
            {
                DeleteObject(ii.hbmMask);
            }
        }
    }

    [LibraryImport("shell32.dll", EntryPoint = "ExtractIconExW", StringMarshalling = StringMarshalling.Utf16)]
    private static partial uint ExtractIconExW(string lpszFile, int nIconIndex, out IntPtr phiconLarge, out IntPtr phiconSmall, uint nIcons);

    [LibraryImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool GetIconInfo(IntPtr hIcon, out ICONINFO piconinfo);

    [LibraryImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool DestroyIcon(IntPtr hIcon);

    [LibraryImport("gdi32.dll", EntryPoint = "GetObjectW")]
    private static partial int GetObjectW(IntPtr hgdiobj, int cbBuffer, ref BITMAP lpvObject);

    [LibraryImport("gdi32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool DeleteObject(IntPtr hObject);

    [LibraryImport("gdi32.dll")]
    private static partial int GetDIBits(IntPtr hdc, IntPtr hbmp, uint uStartScan, uint cScanLines, [Out] byte[] lpvBits, ref BITMAPINFOHEADER lpbi, uint uUsage);

    [LibraryImport("user32.dll")]
    private static partial IntPtr GetDC(IntPtr hWnd);

    [LibraryImport("user32.dll")]
    private static partial int ReleaseDC(IntPtr hWnd, IntPtr hDC);
}

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

[StructLayout(LayoutKind.Sequential)]
internal struct BITMAP
{
    public int bmType;
    public int bmWidth;
    public int bmHeight;
    public int bmWidthBytes;
    public ushort bmPlanes;
    public ushort bmBitsPixel;
    public IntPtr bmBits;
}

[StructLayout(LayoutKind.Sequential)]
internal struct BITMAPINFOHEADER
{
    public uint biSize;
    public int biWidth;
    public int biHeight;
    public ushort biPlanes;
    public ushort biBitCount;
    public uint biCompression;
    public uint biSizeImage;
    public int biXPelsPerMeter;
    public int biYPelsPerMeter;
    public uint biClrUsed;
    public uint biClrImportant;
}