using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Runtime.InteropServices;

namespace QuickLook.Plugin.LastResort
{
    [Flags]
    internal enum ThumbnailOptions
    {
        None = 0x00,
        BiggerSizeOk = 0x01,
        InMemoryOnly = 0x02,
        IconOnly = 0x04,
        ThumbnailOnly = 0x08,
        InCacheOnly = 0x10,
        IconBackground = 0x80,
        ScaleUp = 0x100
    }

    internal static class WindowsThumbnailProvider
    {
        private const string IShellItem2Guid = "7E9FB0D3-919F-4307-AB2E-9B1860310C93";

        [DllImport("shell32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        private static extern int SHCreateItemFromParsingName(
            [MarshalAs(UnmanagedType.LPWStr)] string path,
            // The following parameter is not used - binding context.
            IntPtr pbc,
            ref Guid riid,
            [MarshalAs(UnmanagedType.Interface)] out IShellItem shellItem);

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

        public static Bitmap GetThumbnail(string fileName, int width, int height, ThumbnailOptions options)
        {
            var hBitmap = GetHBitmap(Path.GetFullPath(fileName), width, height, options);

            try
            {
                // return a System.Drawing.Bitmap from the hBitmap
                return GetBitmapFromHBitmap(hBitmap);
            }
            finally
            {
                // delete HBitmap to avoid memory leaks
                DeleteObject(hBitmap);
            }
        }

        internal static Bitmap GetBitmapFromHBitmap(IntPtr nativeHBitmap)
        {
            var bmp = Image.FromHbitmap(nativeHBitmap);

            if (Image.GetPixelFormatSize(bmp.PixelFormat) < 32)
                return bmp;

            return CreateAlphaBitmap(bmp, PixelFormat.Format32bppArgb);
        }

        internal static Bitmap CreateAlphaBitmap(Bitmap srcBitmap, PixelFormat targetPixelFormat)
        {
            var result = new Bitmap(srcBitmap.Width, srcBitmap.Height, targetPixelFormat);

            var bmpBounds = new Rectangle(0, 0, srcBitmap.Width, srcBitmap.Height);

            var srcData = srcBitmap.LockBits(bmpBounds, ImageLockMode.ReadOnly, srcBitmap.PixelFormat);

            var isAlplaBitmap = false;

            try
            {
                for (var y = 0; y <= srcData.Height - 1; y++)
                for (var x = 0; x <= srcData.Width - 1; x++)
                {
                    var pixelColor = Color.FromArgb(
                        Marshal.ReadInt32(srcData.Scan0, srcData.Stride * y + 4 * x));

                    if ((pixelColor.A > 0) & (pixelColor.A < 255))
                        isAlplaBitmap = true;

                    result.SetPixel(x, y, pixelColor);
                }
            }
            finally
            {
                srcBitmap.UnlockBits(srcData);
            }

            if (isAlplaBitmap)
                return result;
            return srcBitmap;
        }

        private static IntPtr GetHBitmap(string fileName, int width, int height, ThumbnailOptions options)
        {
            IShellItem nativeShellItem;
            var shellItem2Guid = new Guid(IShellItem2Guid);
            var retCode = SHCreateItemFromParsingName(fileName, IntPtr.Zero, ref shellItem2Guid, out nativeShellItem);

            if (retCode != 0)
                throw Marshal.GetExceptionForHR(retCode);

            var nativeSize = new NativeSize();
            nativeSize.Width = width;
            nativeSize.Height = height;

            IntPtr hBitmap;
            var hr = ((IShellItemImageFactory) nativeShellItem).GetImage(nativeSize, options, out hBitmap);

            Marshal.ReleaseComObject(nativeShellItem);

            if (hr == HResult.Ok) return hBitmap;

            throw Marshal.GetExceptionForHR((int) hr);
        }

        [ComImport]
        [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        [Guid("43826d1e-e718-42ee-bc55-a1e261c37bfe")]
        internal interface IShellItem
        {
            void BindToHandler(IntPtr pbc,
                [MarshalAs(UnmanagedType.LPStruct)] Guid bhid,
                [MarshalAs(UnmanagedType.LPStruct)] Guid riid,
                out IntPtr ppv);

            void GetParent(out IShellItem ppsi);
            void GetDisplayName(SIGDN sigdnName, out IntPtr ppszName);
            void GetAttributes(uint sfgaoMask, out uint psfgaoAttribs);
            void Compare(IShellItem psi, uint hint, out int piOrder);
        }

        internal enum SIGDN : uint
        {
            NORMALDISPLAY = 0,
            PARENTRELATIVEPARSING = 0x80018001,
            PARENTRELATIVEFORADDRESSBAR = 0x8001c001,
            DESKTOPABSOLUTEPARSING = 0x80028000,
            PARENTRELATIVEEDITING = 0x80031001,
            DESKTOPABSOLUTEEDITING = 0x8004c000,
            FILESYSPATH = 0x80058000,
            URL = 0x80068000
        }

        internal enum HResult
        {
            Ok = 0x0000,
            False = 0x0001,
            InvalidArguments = unchecked((int) 0x80070057),
            OutOfMemory = unchecked((int) 0x8007000E),
            NoInterface = unchecked((int) 0x80004002),
            Fail = unchecked((int) 0x80004005),
            ElementNotFound = unchecked((int) 0x80070490),
            TypeElementNotFound = unchecked((int) 0x8002802B),
            NoObject = unchecked((int) 0x800401E5),
            Win32ErrorCanceled = 1223,
            Canceled = unchecked((int) 0x800704C7),
            ResourceInUse = unchecked((int) 0x800700AA),
            AccessDenied = unchecked((int) 0x80030005)
        }

        [ComImport]
        [Guid("bcc18b79-ba16-442f-80c4-8a59c30c463b")]
        [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        internal interface IShellItemImageFactory
        {
            [PreserveSig]
            HResult GetImage(
                [In] [MarshalAs(UnmanagedType.Struct)] NativeSize size,
                [In] ThumbnailOptions flags,
                [Out] out IntPtr phbm);
        }

        [StructLayout(LayoutKind.Sequential)]
        internal struct NativeSize
        {
            private int width;
            private int height;

            public int Width
            {
                set => width = value;
            }
            public int Height
            {
                set => height = value;
            }
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct RGBQUAD
        {
            public byte rgbBlue;
            public byte rgbGreen;
            public byte rgbRed;
            public byte rgbReserved;
        }
    }
}