package org.solovyev.util.math;

import org.jetbrains.annotations.NotNull;

import java.util.List;

public class MathUtils {

	public static final float MIN_AMOUNT = 0.05f;

	public static double round(@NotNull Double value, int numberOfFractionDigits) {
		double roundFactor = Math.pow(10, numberOfFractionDigits);

		if (value < Double.MAX_VALUE / roundFactor) {
			return ((double)Math.round(value * roundFactor)) / roundFactor;
		} else {
			return value;
		}
	}

	public static float getDistance(@NotNull Point2d startPoint,
									@NotNull Point2d endPoint) {
		return getNorm(subtract(endPoint, startPoint));
	}

	public static Point2d subtract(@NotNull Point2d p1, @NotNull Point2d p2) {
		return new Point2d(p1.getX() - p2.getX(), p1.getY() - p2.getY());
	}

	public static Point2d sum(@NotNull Point2d p1, @NotNull Point2d p2) {
		return new Point2d(p1.getX() + p2.getX(), p1.getY() + p2.getY());
	}

	public static float getNorm(@NotNull Point2d point) {
		return (float) Math.pow(
				Math.pow(point.getX(), 2) + Math.pow(point.getY(), 2), 0.5);
	}

	public static float getAngle(@NotNull Point2d startPoint,
								 @NotNull Point2d axisEndPoint, @NotNull Point2d endPoint) {
		final Point2d axisVector = subtract(axisEndPoint, startPoint);
		final Point2d vector = subtract(endPoint, startPoint);

		double a_2 = Math.pow(getDistance(vector, axisVector), 2);
		double b = getNorm(vector);
		double b_2 = Math.pow(b, 2);
		double c = getNorm(axisVector);
		double c_2 = Math.pow(c, 2);

		return (float) Math.acos((-a_2 + b_2 + c_2) / (2 * b * c));
	}

	public static double countMean(@NotNull List<Double> objects) {

		double sum = 0d;
		for (Double object : objects) {
			sum += object;
		}

		return objects.size() == 0 ? 0d : (sum / objects.size());
	}

	public static double countStandardDeviation(@NotNull Double mean, @NotNull List<Double> objects) {
		double sum = 0d;

		for (Double object : objects) {
			sum += Math.pow(object - mean, 2);
		}

		return objects.size() == 0 ? 0d : Math.sqrt(sum / objects.size());
	}

	public static StatData getStatData(@NotNull List<Double> objects) {

		final double mean = countMean(objects);
		final double standardDeviation = countStandardDeviation(mean, objects);

		return new StatData(mean, standardDeviation);
	}

	public static class StatData {

		private final double mean;

		private final double standardDeviation;

		public StatData(double mean, double standardDeviation) {
			this.mean = mean;
			this.standardDeviation = standardDeviation;
		}

		public double getMean() {
			return mean;
		}

		public double getStandardDeviation() {
			return standardDeviation;
		}

	}

}