source: profile/src/main/java/geniusweb/profile/utilityspace/NumberValueSetUtilities.java@ 30

package geniusweb.profile.utilityspace;

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

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonTypeName;

import geniusweb.issuevalue.NumberValue;
import geniusweb.issuevalue.NumberValueSet;
import geniusweb.issuevalue.Value;
import geniusweb.issuevalue.ValueSet;
import tudelft.utilities.immutablelist.Range;

/**
 * The low and high values (from a {@link NumberValueSet} are given each a
 * different utility. This linearly interpolates in-between utility values.
 *
 */
@JsonTypeName("numberutils")
@JsonAutoDetect(fieldVisibility = Visibility.ANY, getterVisibility = Visibility.NONE, setterVisibility = Visibility.NONE)
public class NumberValueSetUtilities implements ValueSetUtilities {

        /** lowest possible value and utility at that point */
        private final BigDecimal lowValue;
        private final BigDecimal lowUtility;

        /**
         * highest possible value and utility at that point
         */
        private final BigDecimal highValue;
        private final BigDecimal highUtility;

        /**
         * 
         * @param lowValue    the low value of the {@link Range}
         * @param lowUtility  the utility of the {@link #lowValue}
         * @param highValue   the high value of the {@link Range}. Must be
         *                    >lowValue.
         * @param highUtility the utility of the {@link #highValue}
         */
        @JsonCreator
        public NumberValueSetUtilities(
                        @JsonProperty("lowValue") BigDecimal lowValue,
                        @JsonProperty("lowUtility") BigDecimal lowUtility,
                        @JsonProperty("highValue") BigDecimal highValue,
                        @JsonProperty("highUtility") BigDecimal highUtility) {
                if (lowValue == null || highValue == null || lowUtility == null
                                || highUtility == null) {
                        throw new NullPointerException(
                                        "arguments lowValue, lowUtility, highValue and highUtility must be non-null");
                }
                if (!isInZeroOne(lowUtility)) {
                        throw new IllegalArgumentException("lowUtility must be in [0,1]");
                }
                if (!isInZeroOne(highUtility)) {
                        throw new IllegalArgumentException("highUtility must be in [0,1]");
                }
                if (highValue.compareTo(lowValue) <= 0) {
                        throw new IllegalArgumentException("highValue must be > lowValue");
                }
                this.lowValue = lowValue;
                this.highValue = highValue;
                this.lowUtility = lowUtility;
                this.highUtility = highUtility;
        }

        @Override
        public BigDecimal getUtility(Value value) {
                if (!(value instanceof NumberValue)) {
                        return BigDecimal.ZERO;
                }
                BigDecimal x = ((NumberValue) value).getValue();
                if (x.compareTo(lowValue) < 0 || x.compareTo(highValue) > 0)
                        return BigDecimal.ZERO;
                // we need to be careful to avoid round errors from divides.
                // so we return lowU + deltaU * (x-lowV) /deltaV
                BigDecimal deltaU = highUtility.subtract(lowUtility);
                BigDecimal deltaV = highValue.subtract(lowValue);

                return lowUtility.add(deltaU.multiply(
                                x.subtract(lowValue).divide(deltaV, 8, RoundingMode.HALF_UP)));
        }

        @Override
        public String isFitting(ValueSet valueset) {
                if (!(valueset instanceof NumberValueSet)) {
                        return "The utilities are for a number valueset but the given values are "
                                        + valueset;
                }
                NumberValueSet numvalset = (NumberValueSet) valueset;
                if (numvalset.getRange().getLow().compareTo(lowValue) != 0) {
                        return "the utilities are specified down to " + lowValue
                                        + " but the valueset starts at "
                                        + numvalset.getRange().getLow();
                }
                if (numvalset.getRange().getHigh().compareTo(highValue) != 0) {
                        return "the utilities are specified up to " + highValue
                                        + " but the valueset ends at "
                                        + numvalset.getRange().getHigh();
                }

                return null;
        }

        /**
         * @return the lowest value
         */
        public BigDecimal getLowValue() {
                return lowValue;
        }

        /**
         * 
         * @return the highest value
         */
        public BigDecimal getHighValue() {
                return highValue;
        }

        /**
         * 
         * @return the utility of the lowest value
         */
        public BigDecimal getLowUtility() {
                return lowUtility;
        }

        /**
         * 
         * @return the utility of the highest value
         */
        public BigDecimal getHighUtility() {
                return highUtility;
        }

        @Override
        public String toString() {
                return "NumberValueSetUtilities(" + lowValue + "->" + lowUtility + ","
                                + highValue + "->" + highUtility + ")";
        }

        @Override
        public int hashCode() {
                final int prime = 31;
                int result = 1;
                result = prime * result
                                + ((highUtility == null) ? 0 : highUtility.hashCode());
                result = prime * result
                                + ((highValue == null) ? 0 : highValue.hashCode());
                result = prime * result
                                + ((lowUtility == null) ? 0 : lowUtility.hashCode());
                result = prime * result
                                + ((lowValue == null) ? 0 : lowValue.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;
                NumberValueSetUtilities other = (NumberValueSetUtilities) obj;
                if (highUtility == null) {
                        if (other.highUtility != null)
                                return false;
                } else if (!highUtility.equals(other.highUtility))
                        return false;
                if (highValue == null) {
                        if (other.highValue != null)
                                return false;
                } else if (!highValue.equals(other.highValue))
                        return false;
                if (lowUtility == null) {
                        if (other.lowUtility != null)
                                return false;
                } else if (!lowUtility.equals(other.lowUtility))
                        return false;
                if (lowValue == null) {
                        if (other.lowValue != null)
                                return false;
                } else if (!lowValue.equals(other.lowValue))
                        return false;
                return true;
        }

        /**
         * Check if value is in range [0,1]
         * 
         * @param value
         * @return true if in range.
         */
        private static boolean isInZeroOne(BigDecimal value) {
                return value.compareTo(BigDecimal.ZERO) >= 0
                                && value.compareTo(BigDecimal.ONE) <= 0;

        }

}