/////////////////////////////////////////////////////////////////////////////////
// Paint.NET                                                                   //
// Copyright (C) Rick Brewster, Tom Jackson, and past contributors.            //
// Portions Copyright (C) Microsoft Corporation. All Rights Reserved.          //
// See license-pdn.txt for full licensing and attribution details.             //
/////////////////////////////////////////////////////////////////////////////////

using System;
using Cairo;

namespace Pinta.Core
{
	public abstract class LocalHistogramEffect : BaseEffect
	{
		public LocalHistogramEffect ()
		{
		}
		
		protected static int GetMaxAreaForRadius(int radius)
        {
            int area = 0;
            int cutoff = ((radius * 2 + 1) * (radius * 2 + 1) + 2) / 4;

            for (int v = -radius; v <= radius; ++v) {
                for (int u = -radius; u <= radius; ++u) {
                    if (u * u + v * v <= cutoff)
                        ++area;
                }
            }

            return area;
        }
		
		public virtual unsafe ColorBgra Apply(ColorBgra src, int area, int* hb, int* hg, int* hr, int* ha)
        {
            return src;
        }

        //same as Aply, except the histogram is alpha-weighted instead of keeping a separate alpha channel histogram.
        public virtual unsafe ColorBgra ApplyWithAlpha(ColorBgra src, int area, int sum, int* hb, int* hg, int* hr)
        {
            return src;
        }
		
		public static unsafe ColorBgra GetPercentile(int percentile, int area, int* hb, int* hg, int* hr, int* ha)
        {
            int minCount = area * percentile / 100;

            int b = 0;
            int bCount = 0;

            while (b < 255 && hb[b] == 0)
            {
                ++b;
            }

            while (b < 255 && bCount < minCount)
            {
                bCount += hb[b];
                ++b;
            }

            int g = 0;
            int gCount = 0;

            while (g < 255 && hg[g] == 0)
            {
                ++g;
            }

            while (g < 255 && gCount < minCount)
            {
                gCount += hg[g];
                ++g;
            }

            int r = 0;
            int rCount = 0;

            while (r < 255 && hr[r] == 0)
            {
                ++r;
            }

            while (r < 255 && rCount < minCount)
            {
                rCount += hr[r];
                ++r;
            }

            int a = 0;
            int aCount = 0;

            while (a < 255 && ha[a] == 0)
            {
                ++a;
            }

            while (a < 255 && aCount < minCount)
            {
                aCount += ha[a];
                ++a;
            }

            return ColorBgra.FromBgra((byte)b, (byte)g, (byte)r, (byte)a);
        }
		
		 public unsafe void RenderRect(
            int rad,
            ImageSurface src,
            ImageSurface dst,
            Rectangle rect)
        {
            int width = src.Width;
            int height = src.Height;

            int* leadingEdgeX = stackalloc int[rad + 1];
            int stride = src.Stride / sizeof(ColorBgra);

            // approximately (rad + 0.5)^2
            int cutoff = ((rad * 2 + 1) * (rad * 2 + 1) + 2) / 4;

            for (int v = 0; v <= rad; ++v)
            {
                for (int u = 0; u <= rad; ++u)
                {
                    if (u * u + v * v <= cutoff)
                    {
                        leadingEdgeX[v] = u;
                    }
                }
            }

            const int hLength = 256;
            int* hb = stackalloc int[hLength];
            int* hg = stackalloc int[hLength];
            int* hr = stackalloc int[hLength];
            int* ha = stackalloc int[hLength];
            uint hSize = (uint)(sizeof(int) * hLength);

            for (int y = (int)rect.Y; y < rect.Y + rect.Height; y++)
            {
				MemorySetToZero (hb, hLength);
				MemorySetToZero (hg, hLength);
				MemorySetToZero (hr, hLength);
				MemorySetToZero (ha, hLength);

                int area = 0;

				ColorBgra* ps = src.GetPointAddressUnchecked((int)rect.X, y);
				ColorBgra* pd = dst.GetPointAddressUnchecked((int)rect.X, y);
                // assert: v + y >= 0
                int top = -Math.Min(rad, y);

                // assert: v + y <= height - 1
                int bottom = Math.Min(rad, height - 1 - y);

                // assert: u + x >= 0
				int left = -Math.Min(rad, (int)rect.X);

                // assert: u + x <= width - 1
				int right = Math.Min(rad, width - 1 - (int)rect.X);

                for (int v = top; v <= bottom; ++v)
                {
					ColorBgra* psamp = src.GetPointAddressUnchecked((int)rect.X + left, y + v);

                    for (int u = left; u <= right; ++u)
                    {
                        if ((u * u + v * v) <= cutoff)
                        {
                            ++area;
                            ++hb[psamp->B];
                            ++hg[psamp->G];
                            ++hr[psamp->R];
                            ++ha[psamp->A];
                        }

                        ++psamp;
                    }
                }

				for (int x = (int)rect.X; x < rect.X + rect.Width; x++)
                {
                    *pd = Apply(*ps, area, hb, hg, hr, ha);

                    // assert: u + x >= 0
                    left = -Math.Min(rad, x);

                    // assert: u + x <= width - 1
                    right = Math.Min(rad + 1, width - 1 - x);

                    // Subtract trailing edge top half
                    int v = -1;

                    while (v >= top)
                    {
                        int u = leadingEdgeX[-v];

                        if (-u >= left)
                        {
                            break;
                        }

                        --v;
                    }

                    while (v >= top)
                    {
                        int u = leadingEdgeX[-v];
                        ColorBgra* p = unchecked(ps + (v * stride)) - u;

                        --hb[p->B];
                        --hg[p->G];
                        --hr[p->R];
                        --ha[p->A];
                        --area;

                        --v;
                    }

                    // add leading edge top half
                    v = -1;
                    while (v >= top)
                    {
                        int u = leadingEdgeX[-v];

                        if (u + 1 <= right)
                        {
                            break;
                        }

                        --v;
                    }

                    while (v >= top)
                    {
                        int u = leadingEdgeX[-v];
                        ColorBgra* p = unchecked(ps + (v * stride)) + u + 1;

                        ++hb[p->B];
                        ++hg[p->G];
                        ++hr[p->R];
                        ++ha[p->A];
                        ++area;

                        --v;
                    }

                    // Subtract trailing edge bottom half
                    v = 0;

                    while (v <= bottom)
                    {
                        int u = leadingEdgeX[v];

                        if (-u >= left)
                        {
                            break;
                        }

                        ++v;
                    }

                    while (v <= bottom)
                    {
                        int u = leadingEdgeX[v];
                        ColorBgra* p = ps + v * stride - u;

                        --hb[p->B];
                        --hg[p->G];
                        --hr[p->R];
                        --ha[p->A];
                        --area;

                        ++v;
                    }

                    // add leading edge bottom half
                    v = 0;

                    while (v <= bottom)
                    {
                        int u = leadingEdgeX[v];

                        if (u + 1 <= right)
                        {
                            break;
                        }

                        ++v;
                    }

                    while (v <= bottom)
                    {
                        int u = leadingEdgeX[v];
                        ColorBgra* p = ps + v * stride + u + 1;

                        ++hb[p->B];
                        ++hg[p->G];
                        ++hr[p->R];
                        ++ha[p->A];
                        ++area;

                        ++v;
                    }

                    ++ps;
                    ++pd;
                }
            }
        }
		
		
        //same as RenderRect, except the histogram is alpha-weighted instead of keeping a separate alpha channel histogram.
        public unsafe void RenderRectWithAlpha(
            int rad,
            ImageSurface src,
            ImageSurface dst,
            Rectangle rect)
        {
            int width = src.Width;
            int height = src.Height;

            int* leadingEdgeX = stackalloc int[rad + 1];
            int stride = src.Stride / sizeof(ColorBgra);

            // approximately (rad + 0.5)^2
            int cutoff = ((rad * 2 + 1) * (rad * 2 + 1) + 2) / 4;

            for (int v = 0; v <= rad; ++v)
            {
                for (int u = 0; u <= rad; ++u)
                {
                    if (u * u + v * v <= cutoff)
                    {
                        leadingEdgeX[v] = u;
                    }
                }
            }

            const int hLength = 256;
            int* hb = stackalloc int[hLength];
            int* hg = stackalloc int[hLength];
            int* hr = stackalloc int[hLength];
            uint hSize = (uint)(sizeof(int) * hLength);

			for (int y = (int)rect.Y; y < rect.Y + rect.Height; y++)
            {
				MemorySetToZero (hb, hLength);
				MemorySetToZero (hg, hLength);
				MemorySetToZero (hr, hLength);

                int area = 0;
                int sum = 0;

                ColorBgra* ps = src.GetPointAddressUnchecked((int)rect.X, y);
                ColorBgra* pd = dst.GetPointAddressUnchecked((int)rect.X, y);

                // assert: v + y >= 0
                int top = -Math.Min(rad, y);

                // assert: v + y <= height - 1
                int bottom = Math.Min(rad, height - 1 - y);

                // assert: u + x >= 0
				int left = -Math.Min(rad, (int)rect.X);

                // assert: u + x <= width - 1
				int right = Math.Min(rad, width - 1 - (int)rect.Y);

                for (int v = top; v <= bottom; ++v)
                {
					ColorBgra* psamp = src.GetPointAddressUnchecked((int)rect.Y + left, y + v);

                    for (int u = left; u <= right; ++u)
                    {
                        byte w = psamp->A;
                        if ((u * u + v * v) <= cutoff)
                        {
                            ++area;
                            sum += w;
                            hb[psamp->B] += w;
                            hg[psamp->G] += w;
                            hr[psamp->R] += w;
                        }

                        ++psamp;
                    }
                }

                for (int x = (int)rect.X; x < rect.X + rect.Width; x++)
                {
                    *pd = ApplyWithAlpha(*ps, area, sum, hb, hg, hr);

                    // assert: u + x >= 0
                    left = -Math.Min(rad, x);

                    // assert: u + x <= width - 1
                    right = Math.Min(rad + 1, width - 1 - x);

                    // Subtract trailing edge top half
                    int v = -1;

                    while (v >= top)
                    {
                        int u = leadingEdgeX[-v];

                        if (-u >= left)
                        {
                            break;
                        }

                        --v;
                    }

                    while (v >= top)
                    {
                        int u = leadingEdgeX[-v];
                        ColorBgra* p = unchecked(ps + (v * stride)) - u;
                        byte w = p->A;

                        hb[p->B] -= w;
                        hg[p->G] -= w;
                        hr[p->R] -= w;
                        sum -= w;
                        --area;

                        --v;
                    }

                    // add leading edge top half
                    v = -1;
                    while (v >= top)
                    {
                        int u = leadingEdgeX[-v];

                        if (u + 1 <= right)
                        {
                            break;
                        }

                        --v;
                    }

                    while (v >= top)
                    {
                        int u = leadingEdgeX[-v];
                        ColorBgra* p = unchecked(ps + (v * stride)) + u + 1;
                        byte w = p->A;

                        hb[p->B] += w;
                        hg[p->G] += w;
                        hr[p->R] += w;
                        sum += w;
                        ++area;

                        --v;
                    }

                    // Subtract trailing edge bottom half
                    v = 0;

                    while (v <= bottom)
                    {
                        int u = leadingEdgeX[v];

                        if (-u >= left)
                        {
                            break;
                        }

                        ++v;
                    }

                    while (v <= bottom)
                    {
                        int u = leadingEdgeX[v];
                        ColorBgra* p = ps + v * stride - u;
                        byte w = p->A;

                        hb[p->B] -= w;
                        hg[p->G] -= w;
                        hr[p->R] -= w;
                        sum -= w;
                        --area;

                        ++v;
                    }

                    // add leading edge bottom half
                    v = 0;

                    while (v <= bottom)
                    {
                        int u = leadingEdgeX[v];

                        if (u + 1 <= right)
                        {
                            break;
                        }

                        ++v;
                    }

                    while (v <= bottom)
                    {
                        int u = leadingEdgeX[v];
                        ColorBgra* p = ps + v * stride + u + 1;
                        byte w = p->A;

                        hb[p->B] += w;
                        hg[p->G] += w;
                        hr[p->R] += w;
                        sum += w;
                        ++area;

                        ++v;
                    }

                    ++ps;
                    ++pd;
                }
            }
		}
	
		//must be more efficient way to zero memory array
		private unsafe void MemorySetToZero(int* ptr, int size)
		{
			for (int i = 0; i < size; i++) 
				ptr [i] = 0;
		}
	}
}