using NTwain.Interop;
using System;
using System.IO;
using System.Runtime.InteropServices;

namespace NTwain.Internals
{
    static class ImageTools
    {
        // this is modified from twain cs sample
        // http://sourceforge.net/projects/twainforcsharp/?source=typ_redirect

        public static bool IsDib(IntPtr data)
        {
            // a quick check not guaranteed correct,
            // compare first 2 bytes to size of struct (which is also the first field)
            var test = Marshal.ReadInt16(data);
            // should be 40
            return test == BITMAPINFOHEADER.GetByteSize();
        }
        public static bool IsTiff(IntPtr data)
        {
            var test = Marshal.ReadInt16(data);
            // should be II
            return test == 0x4949;
        }


        public static Stream GetBitmapStream(IntPtr data)
        {
            var infoHeader = (BITMAPINFOHEADER)Marshal.PtrToStructure(data, typeof(BITMAPINFOHEADER));
            if (infoHeader.Validate())
            {
                var fileHeaderSize = Marshal.SizeOf(typeof(BITMAPFILEHEADER));


                var fileHeader = new BITMAPFILEHEADER();
                fileHeader.bfType = 0x4D42; // "BM"
                fileHeader.bfOffBits = (uint)fileHeaderSize +
                    infoHeader.biSize +
                    (infoHeader.biClrUsed * 4);
                fileHeader.bfSize = fileHeader.bfOffBits + infoHeader.biSizeImage;

                var dataCopy = new byte[fileHeader.bfSize];
                // write file header
                IntPtr tempPtr = Marshal.AllocHGlobal(fileHeaderSize);
                Marshal.StructureToPtr(fileHeader, tempPtr, true);
                Marshal.Copy(tempPtr, dataCopy, 0, fileHeaderSize);
                Marshal.FreeHGlobal(tempPtr);
                // write image
                Marshal.Copy(data, dataCopy, fileHeaderSize, (int)fileHeader.bfSize - fileHeaderSize);

                return new MemoryStream(dataCopy);
            }
            return null;
        }

        public static Stream GetTiffStream(IntPtr data)
        {
            // Find the size of the image so we can turn it into a memory stream...
            var headerSize = Marshal.SizeOf(typeof(TIFFHEADER));
            var tagSize = Marshal.SizeOf(typeof(TIFFTAG));
            var tiffSize = 0;
            var tagPtr = data.ToInt64() + headerSize;
            for (int i = 0; i < 999; i++)
            {
                tagPtr += (tagSize * i);
                var tag = (TIFFTAG)Marshal.PtrToStructure((IntPtr)tagPtr, typeof(TIFFTAG));

                switch (tag.u16Tag)
                {
                    case 273: // StripOffsets...
                    case 279: // StripByteCounts...
                        tiffSize += (int)tag.u32Value;
                        break;
                }
            }

            if (tiffSize > 0)
            {
                var dataCopy = new byte[tiffSize];
                // is this optimal?
                Marshal.Copy(data, dataCopy, 0, tiffSize);
                return new MemoryStream(dataCopy);
            }
            return null;
        }

        //internal static Bitmap ReadBitmapImage(IntPtr data)
        //{
        //    Bitmap finalImg = null;
        //    Bitmap tempImg = null;
        //    try
        //    {
        //        var header = (BITMAPINFOHEADER)Marshal.PtrToStructure(data, typeof(BITMAPINFOHEADER));

        //        if (header.Validate())
        //        {
        //            PixelFormat format = header.GetDrawingPixelFormat();
        //            tempImg = new Bitmap(header.biWidth, Math.Abs(header.biHeight), header.GetStride(), format, header.GetScan0(data));
        //            ColorPalette pal = header.GetDrawingPalette(data);
        //            if (pal != null)
        //            {
        //                tempImg.Palette = pal;
        //            }
        //            float xdpi = header.GetXDpi();
        //            float ydpi = header.GetYDpi();
        //            if (xdpi != 0 && ydpi == 0)
        //            {
        //                ydpi = xdpi;
        //            }
        //            else if (ydpi != 0 && xdpi == 0)
        //            {
        //                xdpi = ydpi;
        //            }
        //            if (xdpi != 0)
        //            {
        //                tempImg.SetResolution(xdpi, ydpi);
        //            }
        //            if (header.IsBottomUpImage)
        //            {
        //                tempImg.RotateFlip(RotateFlipType.RotateNoneFlipY);
        //            }
        //            finalImg = tempImg;
        //            tempImg = null;
        //        }
        //    }
        //    finally
        //    {
        //        if (tempImg != null)
        //        {
        //            tempImg.Dispose();
        //        }
        //    }
        //    return finalImg;
        //}
    }
}