package geniusweb.bidspace;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.RoundingMode;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.eclipse.jdt.annotation.NonNull;

import geniusweb.issuevalue.Value;
import geniusweb.issuevalue.ValueSet;
import geniusweb.profile.utilityspace.ValueSetUtilities;

/**
 * Tool class to collect all relevant info about one issue (from LinearAdditive)
 * in one class. Used for internally grouping data for more efficient
 * processing. This class may change in the future, not recommended for direct
 * use.
 * <p>
 * immutable
 */
public class IssueInfo {
	private final @NonNull String name;
	private final @NonNull ValueSet values;
	private final @NonNull Interval interval;
	private final @NonNull Map<@NonNull Value, @NonNull BigDecimal> weightedUtils;

	/**
	 * 
	 * @param name      the issue name
	 * @param values    the {@link ValueSet} of the issue
	 * @param utils     the {@link ValueSetUtilities} of the issue profile.
	 *                  FIXME is it required that all values have a utility?
	 * @param weight    the weight of the {@link ValueSetUtilities}
	 * @param precision the precision to compute with. Basically the number of
	 *                  decimal places used for the computations.
	 * 
	 */
	public IssueInfo(@NonNull String name, @NonNull ValueSet values,
			@NonNull ValueSetUtilities utils, @NonNull BigDecimal weight,
			int precision) {
		if (name == null || values == null || utils == null || weight == null)
			throw new NullPointerException(
					"name values utils and weight must be not null.");
		if (values.size() == BigInteger.ZERO)
			throw new IllegalArgumentException("Values must not be empty");
		this.name = name;
		this.values = values;
		this.weightedUtils = computeWeightedUtils(utils, weight, precision);
		this.interval = getRange();
	}

	public @NonNull ValueSet getValues() {
		return values;
	}

	public @NonNull String getName() {
		return name;
	}

	/**
	 * 
	 * @return weighted minimum and maximum utility achievable with this issue,
	 *         rounded to the requested precision.
	 */
	public @NonNull Interval getInterval() {
		return interval;
	}

	/**
	 * 
	 * @param isMax if true the max {@link Value} is returned, else the min is
	 *              returned.
	 * @return the extreme value, either the minimum if isMax=false or maximum
	 *         if isMax=true.
	 * @throws IllegalStateException if there are no values
	 */
	public @NonNull Value getExtreme(boolean isMax) {
		BigDecimal extremeutil = null;
		Value extremeval = null;
		for (final @NonNull Value val : values) {
			final @NonNull BigDecimal util = weightedUtils.get(val);
			if (extremeval == null) {
				extremeutil = weightedUtils.get(val);
				extremeval = val;
			} else {
				if (isMax) {
					if (util.compareTo(extremeutil) > 0) {
						extremeutil = util;
						extremeval = val;
					}
				} else {
					if (util.compareTo(extremeutil) < 0) {
						extremeutil = util;
						extremeval = val;
					}

				}
			}
		}
		if (extremeval == null)
			throw new IllegalStateException(
					"Extreme does not exist as IssueInfo values is empty");

		return extremeval;
	}

	/**
	 * @param val the issue value to be evaluated
	 * @return weighted utility of given value, rounded to nearest value with
	 *         the requested precision number of digits. returns 0 if value is
	 *         unknown.
	 */
	public @NonNull BigDecimal getWeightedUtil(@NonNull Value val) {
		BigDecimal util = weightedUtils.get(val);
		return util == null ? BigDecimal.ZERO : util;
	}

	/**
	 * 
	 * @param interval an {@link Interval} of utility values.
	 * @return all values that are inside the interval.
	 */
	protected @NonNull List<@NonNull Value> subset(@NonNull Interval interval) {

		final @NonNull List<@NonNull Value> selection = new ArrayList<>();
		for (final @NonNull Value value : values) {
			if (interval.contains(getWeightedUtil(value)))
				selection.add(value);
		}
		return selection;
	}

	/**
	 * Faster way to determine subset size, it does not create a list
	 * 
	 * @param interval an {@link Interval} of utility values.
	 * @return size of the subset that you will get from calling subset
	 */
	protected int subsetSize(@NonNull Interval interval) {
		int n = 0;
		for (final @NonNull Value value : values)
			if (interval.contains(getWeightedUtil(value)))
				n = n + 1;
		return n;
	}

	/**
	 * @return the {@link Interval} (minimum and maximum) of the utility of the
	 *         weighted utility of this issue, properly rounded to the
	 *         {@link #precision}/
	 * 
	 */
	private @NonNull Interval getRange() {
		@NonNull
		BigDecimal min = BigDecimal.ONE;
		@NonNull
		BigDecimal max = BigDecimal.ZERO;
		for (final @NonNull Value value : values) {
			final @NonNull BigDecimal util = getWeightedUtil(value);
			if (util.compareTo(min) < 0)
				min = util;
			if (util.compareTo(max) > 0)
				max = util;
		}
		return new Interval(min, max);

	}

	private @NonNull Map<@NonNull Value, @NonNull BigDecimal> computeWeightedUtils(
			@NonNull ValueSetUtilities utilities, @NonNull BigDecimal w,
			int prec) {
		final @NonNull Map<@NonNull Value, @NonNull BigDecimal> map = new HashMap<>();

		for (final @NonNull Value val : values) {
			map.put(val, utilities.getUtility(val).multiply(w).setScale(prec,
					RoundingMode.HALF_UP));
		}
		return map;
	}

}