io.github.oliviercailloux.grade.MarkAggregator Maven / Gradle / Ivy
package io.github.oliviercailloux.grade;
import com.google.common.collect.ImmutableMap;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
/**
* Able to aggregate a set of marks associated to criteria, to a single Mark.
*
* Some instances reject some sets of criteria, for example, an aggregator using static weights
* given an unknown criterion; or a parametric weighter given more than one unknown criterion.
* Implementors must give a programmatic way of determining which sets of criteria are accepted.
*/
public interface MarkAggregator {
static void checkCanAggregate(boolean check, String message) throws AggregatorException {
if (!check) {
throw new AggregatorException(message);
}
}
static void checkCanAggregate(boolean check, String format, Object... messages)
throws AggregatorException {
if (!check) {
throw new AggregatorException(String.format(Locale.ENGLISH, format, messages));
}
}
/**
* @param marks may be empty; must have all different criteria
* @return numbers in [0, 1] such that the mark can be computed by a weighted sum (not necessarily
* equal to a weighted average as the sum may not be one); may sum to greater than one,
* for example, if absolute aggregation. May contain zeroes, and may consist in only
* zeroes. The returned key set equals the given set.
* @throws AggregatorException iff the given set of criteria is rejected.
*/
ImmutableMap weights(Set marks) throws AggregatorException;
/**
* @param marks may be empty; must have all different criteria
* @return the weighted sum of the marks, according to {@link #getWeights(Set)}, bound within [−1,
* 1].
* @throws AggregatorException iff the given set of criteria is rejected.
*/
default Mark aggregate(Set marks) throws AggregatorException {
final Map weights = weights(marks);
final double weightedSum =
weights.keySet().stream().mapToDouble(s -> weights.get(s) * s.getPoints()).sum();
return Mark.given(Double.min(1d, Double.max(weightedSum, 0d)), "");
}
/**
* Returns {@code true} iff the given object is a mark aggregator that aggregates accepts the same
* sets of criteria and aggregates the sub marks in the same way as this object.
*/
@Override
public boolean equals(Object o2);
}