using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Tango.ScreenCapture
{
    public class ImageComparer
    {
        unsafe public Bitmap CreateDifferenceBitmap(Bitmap previousImage, Bitmap currentImage, Color matchColor)
        {
            if (previousImage == null | currentImage == null)
                throw new InvalidOperationException("Cannot compare image. They are the same instance");

            if (previousImage.Height != currentImage.Height || previousImage.Width != currentImage.Width)
                throw new InvalidOperationException("Cannot compare image of different size.");

            Bitmap diffImage = currentImage.Clone() as Bitmap;

            int height = previousImage.Height;
            int width = previousImage.Width;

            BitmapData data1 = previousImage.LockBits(new Rectangle(0, 0, width, height),
                                               ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            BitmapData data2 = currentImage.LockBits(new Rectangle(0, 0, width, height),
                                               ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            BitmapData diffData = diffImage.LockBits(new Rectangle(0, 0, width, height),
                                                   ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);

            byte* data1Ptr = (byte*)data1.Scan0;
            byte* data2Ptr = (byte*)data2.Scan0;
            byte* diffPtr = (byte*)diffData.Scan0;

            byte[] swapColor = new byte[4];
            swapColor[0] = matchColor.B;
            swapColor[1] = matchColor.G;
            swapColor[2] = matchColor.R;
            swapColor[3] = matchColor.A;

            int rowPadding = data1.Stride - (previousImage.Width * 4);

            // iterate over height (rows)
            for (int i = 0; i < height; i++)
            {
                // iterate over width (columns)
                for (int j = 0; j < width; j++)
                {
                    int same = 0;

                    byte[] tmp = new byte[4];

                    // compare pixels and copy new values into temporary array
                    for (int x = 0; x < 4; x++)
                    {
                        tmp[x] = data2Ptr[0];
                        if (data1Ptr[0] == data2Ptr[0])
                        {
                            same++;
                        }
                        data1Ptr++; // advance image1 ptr
                        data2Ptr++; // advance image2 ptr
                    }

                    // swap color or add new values
                    for (int x = 0; x < 4; x++)
                    {
                        diffPtr[0] = (same == 4) ? swapColor[x] : tmp[x];
                        diffPtr++; // advance diff image ptr
                    }
                }

                // at the end of each column, skip extra padding
                if (rowPadding > 0)
                {
                    data1Ptr += rowPadding;
                    data2Ptr += rowPadding;
                    diffPtr += rowPadding;
                }
            }

            previousImage.UnlockBits(data1);
            currentImage.UnlockBits(data2);
            diffImage.UnlockBits(diffData);

            return diffImage;
        }

        unsafe public VectorDifferenceImage CreateDifferenceVector(Bitmap previousImage, Bitmap currentImage)
        {
            VectorDifferenceImage vector = new VectorDifferenceImage(previousImage.Width, previousImage.Height);

            if (previousImage == null | currentImage == null)
                throw new InvalidOperationException("Cannot compare image. They are the same instance");

            if (previousImage.Height != currentImage.Height || previousImage.Width != currentImage.Width)
                throw new InvalidOperationException("Cannot compare image of different size.");

            int height = previousImage.Height;
            int width = previousImage.Width;

            BitmapData data1 = previousImage.LockBits(new Rectangle(0, 0, width, height),
                                               ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            BitmapData data2 = currentImage.LockBits(new Rectangle(0, 0, width, height),
                                               ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            byte* data1Ptr = (byte*)data1.Scan0;
            byte* data2Ptr = (byte*)data2.Scan0;

            int rowPadding = data1.Stride - (previousImage.Width * 4);

            // iterate over height (rows)
            for (int i = 0; i < height; i++)
            {
                // iterate over width (columns)
                for (int j = 0; j < width; j++)
                {
                    int same = 0;

                    byte[] tmp = new byte[4];

                    // compare pixels and copy new values into temporary array
                    for (int x = 0; x < 4; x++)
                    {
                        tmp[x] = data2Ptr[0];
                        if (data1Ptr[0] == data2Ptr[0])
                        {
                            same++;
                        }
                        data1Ptr++; // advance image1 ptr
                        data2Ptr++; // advance image2 ptr
                    }

                    if (same != 4)
                    {
                        vector.Pixels.Add(new VectorImagePixel()
                        {
                            X = (ushort)j,
                            Y = (ushort)i,
                            B = tmp[0],
                            G = tmp[1],
                            R = tmp[2],
                        });
                    }
                }

                // at the end of each column, skip extra padding
                if (rowPadding > 0)
                {
                    data1Ptr += rowPadding;
                    data2Ptr += rowPadding;
                }
            }

            previousImage.UnlockBits(data1);
            currentImage.UnlockBits(data2);

            return vector;
        }
    }
}