using System.Collections.Generic;
namespace Recognizer
{
	public static class ThresholdFilterTask
	{
		public static double[,] GetColorsFilter(double t, double[,] original){
			var fieldWidth = original.GetLength(0);
			var fieldHight = original.GetLength(1);
			var colorsFilter = new double[fieldWidth, fieldHight];
			for (var i = 0; i < fieldWidth; i++)
            {
                for (var j = 0; j < fieldHight; j++)
                {
                    if (original[i, j] >= t)
                        colorsFilter[i, j] = 1.0;
                    else colorsFilter[i, j] = 0.0;
                }
			}
			return colorsFilter;
		}

		public static double GetT(double whitePixelsFraction, int fieldWidth, int fieldHight, List<double> list){
			var sumWhitePixels = (int)((whitePixelsFraction) * fieldWidth * fieldHight);
			double t;
			if (sumWhitePixels > 0){
				t = list[fieldWidth * fieldHight - sumWhitePixels];
			}
			else{
				t = double.MaxValue;
			}
			return t;
		}

		public static double[,] ThresholdFilter(double[,] original, double whitePixelsFraction)
		{
			var list = new List<double>();
            var fieldWidth = original.GetLength(0);
            var fieldHight = original.GetLength(1);
            var colorsFilter = new double[fieldWidth, fieldHight];
            for (var i = 0; i < fieldWidth; i++)
            {
                for (var j = 0; j < fieldHight; j++)
                {
                    list.Add(original[i, j]);
                }
            }
            list.Sort();
			double t = GetT(whitePixelsFraction, fieldWidth, fieldHight, list);
			return GetColorsFilter(t, original);
		}
	}
}