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

namespace Silky.Interop {
  public class IconManager {
    public const int
     SHIL_LARGE = 0x0,
     SHIL_SMALL = 0x1,
     SHIL_EXTRALARGE = 0x2,
     SHIL_SYSSMALL = 0x3,
     SHIL_JUMBO = 0x4;

    const uint
     SHGFI_USEFILEATTRIBUTES = 0x000000010,
     SHGFI_SYSICONINDEX = 0x4000,
     ILD_TRANSPARENT = 1;

    private struct SHFILEINFO {
      public IntPtr hIcon;
      public int iIcon;
      public uint dwAttributes;
      [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
      public string szDisplayName;
      [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
      public string szTypeName;
    };

    private struct IMAGELISTDRAWPARAMS {
      public int cbmize;
      public IntPtr himl;
      public int i;
      public IntPtr hdcDst;
      public int x;
      public int y;
      public int cx;
      public int cy;
      public int xBitmap;
      public int yBitmap;
      public int rgbBk;
      public int rgbFg;
      public int fStyle;
      public int dwRop;
      public int fState;
      public int Frame;
      public int crEffect;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct IMAGEINFO {
      private readonly IntPtr hbmImage;
      private readonly IntPtr hbmMask;
      private readonly int Unused1;
      private readonly int Unused2;
      private readonly RECT rcImage;
    }

    [ComImport]
    [Guid("46EB5926-582E-4017-9FDF-E8998DAA0950")]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]

    private interface IImageList {
      [PreserveSig]
      int Add(
        IntPtr hbmImage,
        IntPtr hbmMask,
        ref int pi
      );

      [PreserveSig]
      int ReplaceIcon(
        int i,
        IntPtr hicon,
        ref int pi
      );

      [PreserveSig]
      int SetOverlayImage(
        int iImage,
        int iOverlay
      );

      [PreserveSig]
      int Replace(
        int i,
        IntPtr hbmImage,
        IntPtr hbmMask
      );

      [PreserveSig]
      int AddMasked(
        IntPtr hbmImage,
        int crMask,
        ref int pi
      );

      [PreserveSig]
      int Draw(ref IMAGELISTDRAWPARAMS pimldp);

      [PreserveSig]
      int Remove(int i);

      [PreserveSig]
      int GetIcon(
        int i,
        uint flags,
        ref IntPtr picon
      );

      [PreserveSig]
      int GetImageInfo(
        int i,
        ref IMAGEINFO pImageInfo
      );

      [PreserveSig]
      int Copy(
        int iDst,
        IImageList punkSrc,
        int iSrc,
        int uFlags
      );

      [PreserveSig]
      int Merge(
        int i1,
        IImageList punk2,
        int i2,
        int dx,
        int dy,
        ref Guid riid,
        ref IntPtr ppv
      );

      [PreserveSig]
      int Clone(
        ref Guid riid,
        ref IntPtr ppv
      );

      [PreserveSig]
      int GetImageRect(
        int i,
        ref RECT prc
      );

      [PreserveSig]
      int GetIconSize(
        ref int cx,
        ref int cy
      );

      [PreserveSig]
      int SetIconSize(
        int cx,
        int cy
      );

      [PreserveSig]
      int GetImageCount(ref int pi);

      [PreserveSig]
      int SetImageCount(int uNewCount);

      [PreserveSig]
      int SetBkColor(
        int clrBk,
        ref int pclr
      );

      [PreserveSig]
      int GetBkColor(ref int pclr);

      [PreserveSig]
      int BeginDrag(
        int iTrack,
        int dxHotspot,
        int dyHotspot
      );

      [PreserveSig]
      int EndDrag();

      [PreserveSig]
      int DragEnter(
        IntPtr hwndLock,
        int x,
        int y
      );

      [PreserveSig]
      int DragLeave(IntPtr hwndLock);

      [PreserveSig]
      int DragMove(
        int x,
        int y
      );

      [PreserveSig]
      int SetDragCursorImage(
        ref IImageList punk,
        int iDrag,
        int dxHotspot,
        int dyHotspot
      );

      [PreserveSig]
      int DragShowNolock(int fShow);

      [PreserveSig]
      int GetDragImage(
        ref POINT ppt,
        ref POINT pptHotspot,
        ref Guid riid,
        ref IntPtr ppv
      );

      [PreserveSig]
      int GetItemFlags(
        int i,
        ref int dwFlags
      );

      [PreserveSig]
      int GetOverlayImage(
        int iOverlay,
        ref int piIndex
      );
    };

    [DllImport("shell32.dll", EntryPoint = "#727")]
    static extern int SHGetImageList(
      int iImageList,
      ref Guid riid,
      out IImageList ppv
    );

    [DllImport("shell32.dll", CharSet = CharSet.Auto)]
    static extern IntPtr SHGetFileInfo(
      string pszPath,
      uint dwFileAttributes,
      ref SHFILEINFO psfi,
      uint cbFileInfo,
      uint uFlags
    );

    [DllImport("shell32.dll")]
    static extern int SHGetFileInfo(
      string pszPath,
      int dwFileAttributes,
      ref SHFILEINFO psfi,
      int cbFileInfo,
      uint uFlags
    );

    [DllImport("user32.dll")]
    static extern int DestroyIcon(IntPtr hIcon);

    [DllImport("gdi32.dll", SetLastError = true)]
    static extern bool DeleteObject(IntPtr hObject);

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

    public struct ICONINFO {
      public bool fIcon;
      public int xHotspot;
      public int yHotspot;
      public IntPtr hbmMask;
      public IntPtr hbmColor;
    }

    private static Bitmap ArgbBitmapFromHIcon(IntPtr hIcon) {
      ICONINFO ii = new ICONINFO();
      GetIconInfo(hIcon, out ii);
      Bitmap bmp = Bitmap.FromHbitmap(ii.hbmColor);
      DeleteObject(ii.hbmColor);
      DeleteObject(ii.hbmMask);

      if (Bitmap.GetPixelFormatSize(bmp.PixelFormat) < 32) {
        return Bitmap.FromHicon(hIcon);
      }

      BitmapData bmData;
      Rectangle bmBounds = new Rectangle(0, 0, bmp.Width, bmp.Height);

      bmData = bmp.LockBits(bmBounds, ImageLockMode.ReadOnly, bmp.PixelFormat);
      Bitmap dstBitmap = new Bitmap(bmData.Width, bmData.Height, bmData.Stride, PixelFormat.Format32bppArgb, bmData.Scan0);
      bool IsAlphaBitmap = false;

      for (int y = 0; y <= bmData.Height - 1; y++) {
        for (int x = 0; x <= bmData.Width - 1; x++) {
          Color PixelColor = Color.FromArgb(Marshal.ReadInt32(bmData.Scan0, (bmData.Stride * y) + (4 * x)));
          if (PixelColor.A > 0 & PixelColor.A < 255) {
            IsAlphaBitmap = true;
            break;
          }
        }
        if (IsAlphaBitmap) {
          break;
        }
      }

      bmp.UnlockBits(bmData);
      if (IsAlphaBitmap == true) {
        return new Bitmap(dstBitmap);
      } else {
        return Bitmap.FromHicon(hIcon);
      }
    }

    public static Bitmap GetIcon(string FileName, int size) {
      var shfi = new SHFILEINFO();
      var flags = SHGFI_SYSICONINDEX | SHGFI_USEFILEATTRIBUTES;
      var res = SHGetFileInfo(FileName, (int)FileAttributes.Normal, ref shfi, Marshal.SizeOf(shfi), flags);

      if (res == 0) {
        throw (new FileNotFoundException());
      }

      var iidImageList = new Guid("46EB5926-582E-4017-9FDF-E8998DAA0950");

      IImageList iml;
      SHGetImageList(size, ref iidImageList, out iml);
      var hIcon = IntPtr.Zero;
      iml.GetIcon(shfi.iIcon, ILD_TRANSPARENT, ref hIcon);
      var bm = ArgbBitmapFromHIcon(hIcon);
      DestroyIcon(hIcon);
      return bm;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct RECT {
      private readonly int _Left;
      private readonly int _Top;
      private readonly int _Right;
      private readonly int _Bottom;
    }

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

      public POINT(int x, int y) {
        X = x;
        Y = y;
      }

      public static implicit operator Point(POINT p) {
        return new Point(p.X, p.Y);
      }

      public static implicit operator POINT(Point p) {
        return new POINT(p.X, p.Y);
      }
    }
  }
}