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

class PerlinNoise
{
    #region Feilds
    static Random random = new Random();
    #endregion

    #region Reusable Functions

    public static float[][] GenerateWhiteNoise(int width, int height)
    {
        float[][] noise = GetEmptyArray<float>(width, height);

        for (int i = 0; i < width; i++)
        {
            for (int j = 0; j < height; j++)
            {
                noise[i][j] = (float)random.NextDouble() % 1;
            }
        }

        return noise;
    }

    public static float Interpolate(float x0, float x1, float alpha)
    {
        return x0 * (1 - alpha) + alpha * x1;
    }

    public static Color Interpolate(Color col0, Color col1, float alpha)
    {
        float beta = 1 - alpha;
        return Color.FromArgb(
            255,
            (int)(col0.R * alpha + col1.R * beta),
            (int)(col0.G * alpha + col1.G * beta),
            (int)(col0.B * alpha + col1.B * beta));
    }

    public static Color GetColor(Color gradientStart, Color gradientEnd, float t)
    {
        float u = 1 - t;

        Color color = Color.FromArgb(
            255,
            (int)(gradientStart.R * u + gradientEnd.R * t),
            (int)(gradientStart.G * u + gradientEnd.G * t),
            (int)(gradientStart.B * u + gradientEnd.B * t));

        return color;
    }

    public static Color[][] MapGradient(Color gradientStart, Color gradientEnd, float[][] perlinNoise)
    {
        int width = perlinNoise.Length;
        int height = perlinNoise[0].Length;

        Color[][] image = GetEmptyArray<Color>(width, height); //an array of colours

        for (int i = 0; i < width; i++)
        {
            for (int j = 0; j < height; j++)
            {
                image[i][j] = GetColor(gradientStart, gradientEnd, perlinNoise[i][j]);
            }
        }

        return image;
    }

    public static T[][] GetEmptyArray<T>(int width, int height)
    {
        T[][] image = new T[width][];

        for (int i = 0; i < width; i++)
        {
            image[i] = new T[height];
        }

        return image;
    }

    public static float[][] GenerateSmoothNoise(float[][] baseNoise, int octave)
    {
        int width = baseNoise.Length;
        int height = baseNoise[0].Length;

        float[][] smoothNoise = GetEmptyArray<float>(width, height);

        int samplePeriod = 1 << octave; // calculates 2 ^ k
        float sampleFrequency = 1.0f / samplePeriod;

        for (int i = 0; i < width; i++)
        {
            //calculate the horizontal sampling indices
            int sample_i0 = (i / samplePeriod) * samplePeriod;
            int sample_i1 = (sample_i0 + samplePeriod) % width; //wrap around
            float horizontal_blend = (i - sample_i0) * sampleFrequency;

            for (int j = 0; j < height; j++)
            {
                //calculate the vertical sampling indices
                int sample_j0 = (j / samplePeriod) * samplePeriod;
                int sample_j1 = (sample_j0 + samplePeriod) % height; //wrap around
                float vertical_blend = (j - sample_j0) * sampleFrequency;

                //blend the top two corners
                float top = Interpolate(baseNoise[sample_i0][sample_j0],
                    baseNoise[sample_i1][sample_j0], horizontal_blend);

                //blend the bottom two corners
                float bottom = Interpolate(baseNoise[sample_i0][sample_j1],
                    baseNoise[sample_i1][sample_j1], horizontal_blend);

                //final blend
                smoothNoise[i][j] = Interpolate(top, bottom, vertical_blend);
            }
        }

        return smoothNoise;
    }

    public static float[][] GeneratePerlinNoise(float[][] baseNoise, int octaveCount)
    {
        int width = baseNoise.Length;
        int height = baseNoise[0].Length;

        float[][][] smoothNoise = new float[octaveCount][][]; //an array of 2D arrays containing

        float persistance = 0.7f;

        //generate smooth noise
        for (int i = 0; i < octaveCount; i++)
        {
            smoothNoise[i] = GenerateSmoothNoise(baseNoise, i);
        }

        float[][] perlinNoise = GetEmptyArray<float>(width, height); //an array of floats initialised to 0

        float amplitude = 1.0f;
        float totalAmplitude = 0.0f;

        //blend noise together
        for (int octave = octaveCount - 1; octave >= 0; octave--)
        {
            amplitude *= persistance;
            totalAmplitude += amplitude;

            for (int i = 0; i < width; i++)
            {
                for (int j = 0; j < height; j++)
                {
                    perlinNoise[i][j] += smoothNoise[octave][i][j] * amplitude;
                }
            }
        }

        //normalisation
        for (int i = 0; i < width; i++)
        {
            for (int j = 0; j < height; j++)
            {
                perlinNoise[i][j] /= totalAmplitude;
            }
        }

        return perlinNoise;
    }

    public static float[][] GeneratePerlinNoise(int width, int height, int octaveCount)
    {
        float[][] baseNoise = GenerateWhiteNoise(width, height);

        return GeneratePerlinNoise(baseNoise, octaveCount);
    }

    public static Color[][] MapToGrey(float[][] greyValues)
    {
        int width = greyValues.Length;
        int height = greyValues[0].Length;

        Color[][] image = GetEmptyArray<Color>(width, height);

        for (int i = 0; i < width; i++)
        {
            for (int j = 0; j < height; j++)
            {
                int grey = (int)(255 * greyValues[i][j]);
                Color color = Color.FromArgb(255, grey, grey, grey);

                image[i][j] = color;
            }
        }

        return image;
    }

    public static void SaveImage(Color[][] image, string fileName)
    {
        int width = image.Length;
        int height = image[0].Length;

        Bitmap bitmap = new Bitmap(width, height, PixelFormat.Format32bppArgb);

        for (int i = 0; i < width; i++)
        {
            for (int j = 0; j < height; j++)
            {
                bitmap.SetPixel(i, j, image[i][j]);
            }
        }

        bitmap.Save(fileName);
    }

    public static Color[][] LoadImage(string fileName)
    {
        Bitmap bitmap = new Bitmap(fileName);

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

        Color[][] image = GetEmptyArray<Color>(width, height);

        for (int i = 0; i < width; i++)
        {
            for (int j = 0; j < height; j++)
            {
                image[i][j] = bitmap.GetPixel(i, j);
            }
        }

        return image;
    }

    public static Color[][] BlendImages(Color[][] image1, Color[][] image2, float[][] perlinNoise)
    {
        int width = image1.Length;
        int height = image1[0].Length;

        Color[][] image = GetEmptyArray<Color>(width, height); //an array of colours for the new image

        for (int i = 0; i < width; i++)
        {
            for (int j = 0; j < height; j++)
            {
                image[i][j] = Interpolate(image1[i][j], image2[i][j], perlinNoise[i][j]);
            }
        }

        return image;
    }

    public static void DemoGradientMap()
    {
        int width = 256;
        int height = 256;
        int octaveCount = 8;

        Color gradientStart = Color.FromArgb(255, 0, 0);
        Color gradientEnd = Color.FromArgb(255, 0, 255);

        float[][] perlinNoise = GeneratePerlinNoise(width, height, octaveCount);
        Color[][] perlinImage = MapGradient(gradientStart, gradientEnd, perlinNoise);
        SaveImage(perlinImage, "perlin_noise.png");
    }

    public static float[][] AdjustLevels(float[][] image, float low, float high)
    {
        int width = image.Length;
        int height = image[0].Length;

        float[][] newImage = GetEmptyArray<float>(width, height);

        for (int i = 0; i < width; i++)
        {
            for (int j = 0; j < height; j++)
            {
                float col = image[i][j];

                if (col <= low)
                {
                    newImage[i][j] = 0;
                }
                else if (col >= high)
                {
                    newImage[i][j] = 1;
                }
                else
                {
                    newImage[i][j] = (col - low) / (high - low);
                }
            }
        }

        return newImage;
    }

    private static Color[][][] AnimateTransition(Color[][] image1, Color[][] image2, int frameCount)
    {
        Color[][][] animation = new Color[frameCount][][];

        float low = 0;
        float increment = 1.0f / frameCount;
        float high = increment;

        float[][] perlinNoise = AdjustLevels(
            GeneratePerlinNoise(image1.Length, image1[0].Length, 9),
            0.2f, 0.8f);

        for (int i = 0; i < frameCount; i++)
        {
            AdjustLevels(perlinNoise, low, high);
            float[][] blendMask = AdjustLevels(perlinNoise, low, high);
            animation[i] = BlendImages(image1, image2, blendMask);
            //SaveImage(animation[i], "blend_animation" + i + ".png");
            SaveImage(MapToGrey(blendMask), "blend_mask" + i + ".png");
            low = high;
            high += increment;
        }

        return animation;
    }

    #endregion
}