package geniusweb.bidspace;

import java.math.BigDecimal;
import java.math.RoundingMode;

import org.eclipse.jdt.annotation.NonNull;

/**
 * An interval [min, max].
 *
 */
public class Interval {
	public static Interval ZERO = new Interval(BigDecimal.ZERO,
			BigDecimal.ZERO);
	public static Interval EMPTY = new Interval(BigDecimal.ONE,
			BigDecimal.ZERO);

	private final @NonNull BigDecimal min;
	private final @NonNull BigDecimal max;

	/**
	 * AN interval [min,max]. If min > max, then there are no values in this
	 * interval.
	 * 
	 * @param min the minimum value of the interval (inclusive)
	 * @param max the maximum value of the interval (inclusive)
	 */
	public Interval(@NonNull BigDecimal min, @NonNull BigDecimal max) {
		if (min == null || max == null) {
			throw new NullPointerException("min and max must contain not null");
		}
		this.min = min;
		this.max = max;
	}

	/**
	 * 
	 * @return the minimum value of the interval
	 */
	public @NonNull BigDecimal getMin() {
		return min;
	}

	/**
	 * 
	 * @return the maximum value of the interval
	 */
	public @NonNull BigDecimal getMax() {
		return max;
	}

	/**
	 * 
	 * @return true iff this range does not contain any element.
	 */
	public boolean isEmpty() {
		return min.compareTo(max) > 0;
	}

	/**
	 * 
	 * @param value the value to test
	 * @return true iff min ≤ value ≤ max
	 */
	public boolean contains(@NonNull BigDecimal value) {
		return min.compareTo(value) <= 0 && max.compareTo(value) >= 0;
	}

	/**
	 * 
	 * @param other {@link Interval} to be added to this
	 * @return new interval [ this.min + other.min , this.max + other.max ]
	 */
	public Interval add(@NonNull Interval other) {
		return new Interval(min.add(other.min), max.add(other.max));
	}

	/**
	 * 
	 * @param other another {@link Interval} intersect with
	 * @return intersection of this with other. returns null if intersection is
	 *         empty.
	 */
	public @NonNull Interval intersect(@NonNull Interval other) {
		return new Interval(min.max(other.min), max.min(other.max));
	}

	/**
	 * 
	 * @param other the other minmax to deal with
	 * @return the range of values that, when added to a value from other, will
	 *         possibly get in our range. effectively, [min-other.max,
	 *         max-other.min]. Returns {@link #EMPTY} if the resulting range is
	 *         empty.
	 */
	public @NonNull Interval invert(@NonNull Interval other) {
		final @NonNull BigDecimal newmin = min.subtract(other.max);
		final @NonNull BigDecimal newmax = max.subtract(other.min);
		if (newmin.compareTo(newmax) > 0)
			return EMPTY;
		return new Interval(newmin, newmax);
	}

	/**
	 * 
	 * @param value the value to subtract
	 * @return Interval with both min and max reduced by value.
	 */
	public @NonNull Interval subtract(@NonNull BigDecimal value) {
		return new Interval(min.subtract(value), max.subtract(value));
	}

	public @NonNull Interval multiply(@NonNull BigDecimal weight) {
		return new Interval(min.multiply(weight), max.multiply(weight));
	}

	@Override
	public @NonNull String toString() {
		return "Interval[" + min + "," + max + "]";
	}

	/**
	 * @param precision number of digits required
	 * @return this but with modified precision. The interval is rounded so that
	 *         the new interval is inside the old one.
	 */
	public @NonNull Interval round(int precision) {
		return new Interval(min.setScale(precision, RoundingMode.UP),
				max.setScale(precision, RoundingMode.DOWN));
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((max == null) ? 0 : max.hashCode());
		result = prime * result + ((min == null) ? 0 : min.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Interval other = (Interval) obj;
		if (max == null) {
			if (other.max != null)
				return false;

		} else if (max.compareTo(other.max) != 0)
			// THIS WAS FIXED MANUALLY TO USE COMPARETO
			return false;
		if (min == null) {
			if (other.min != null)
				return false;
		} else if (min.compareTo(other.min) != 0)
			// THIS WAS FIXED MANUALLY TO USE COMPARETO
			return false;
		return true;
	}

}