PiecewiseConstantHours.java

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package net.sourceforge.plantuml.gantt.ngm.math;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.util.List;
import java.util.Map.Entry;
import java.util.NavigableMap;
import java.util.TreeMap;

import net.sourceforge.plantuml.gantt.core.TimeRange;

public final class PiecewiseConstantHours extends AbstractPiecewiseConstant {

	private final Fraction defaultValue;

	private final NavigableMap<LocalTime, Fraction> timeBoundaries = new TreeMap<>();

	private PiecewiseConstantHours(Fraction defaultValue) {
		this.defaultValue = defaultValue;
	}

	public static PiecewiseConstantHours of(Fraction defaultValue) {
		return new PiecewiseConstantHours(defaultValue);
	}

	/**
	 * Builds an intra-day profile from a list of working time ranges.
	 *
	 * <p>
	 * The resulting profile is {@link Fraction#ZERO} everywhere by default (no
	 * work), and {@link Fraction#ONE} inside each provided {@link TimeRange}.
	 * Ranges are applied in order; an empty or {@code null} list yields a profile
	 * that is closed for the whole day.
	 * </p>
	 *
	 * @param workingTimeRanges the working hours, for example 8:00-12:00 and
	 *                          13:00-18:00
	 * @return an immutable intra-day profile
	 */
	public static PiecewiseConstantHours fromWorkingHours(List<TimeRange> workingTimeRanges) {
		PiecewiseConstantHours result = of(Fraction.ZERO);
		if (workingTimeRanges == null)
			return result;

		for (TimeRange range : workingTimeRanges)
			result = result.with(range, Fraction.ONE);

		return result;
	}

	@Override
	public Segment segmentAt(LocalDateTime instant, TimeDirection direction) {
		return direction == TimeDirection.FORWARD ? segmentForwardAt(instant) : segmentBackwardAt(instant);
	}

	private Segment segmentForwardAt(LocalDateTime instant) {
		final LocalDate day = instant.toLocalDate();
		final LocalDateTime dayStart = day.atStartOfDay();
		final LocalTime t = instant.toLocalTime();
		final Entry<LocalTime, Fraction> ent = timeBoundaries.floorEntry(t);

		final LocalTime startKey = ent != null ? ent.getKey() : LocalTime.MIDNIGHT;
		final Fraction v = timeBoundaries.get(startKey);
		final Fraction value = v != null ? v : defaultValue;

		final LocalTime endKey = timeBoundaries.higherKey(startKey); // next boundary after start
		final LocalDateTime start = dayStart.with(startKey);
		final LocalDateTime end = (endKey == null) ? dayStart.plusDays(1) : dayStart.with(endKey);

		return Segment.forward(start, end, value);
	}

	private Segment segmentBackwardAt(LocalDateTime instant) {
		final LocalTime t = instant.toLocalTime();

		// At midnight, backward segment is the last one of the previous day
		if (t.equals(LocalTime.MIDNIGHT)) {
			final LocalDateTime dayStart = instant.toLocalDate().minusDays(1).atStartOfDay();

			final Entry<LocalTime, Fraction> last = timeBoundaries.lastEntry(); // may be null
			final LocalTime startKey = (last == null) ? LocalTime.MIDNIGHT : last.getKey();
			final Fraction value = (last == null) ? defaultValue : last.getValue();

			final LocalDateTime start = dayStart.plusDays(1); // 00:00 of next day
			final LocalDateTime end = dayStart.with(startKey); // start of last segment
			return Segment.backward(start, end, value);
		}

		final LocalDateTime dayStart = instant.toLocalDate().atStartOfDay();

		final Entry<LocalTime, Fraction> ent = timeBoundaries.lowerEntry(t);
		final LocalTime startKey = (ent == null) ? LocalTime.MIDNIGHT : ent.getKey();
		final Fraction value = (ent == null) ? defaultValue : ent.getValue();

		final LocalTime endKey = timeBoundaries.higherKey(startKey); // end of that segment
		final LocalDateTime start = (endKey == null) ? dayStart.plusDays(1) : dayStart.with(endKey);
		final LocalDateTime end = dayStart.with(startKey);

		return Segment.backward(start, end, value);
	}

	public PiecewiseConstantHours with(TimeRange timeRange, Fraction fraction) {

		if (timeRange.getEnd().equals(LocalTime.MIDNIGHT) == false
				&& timeRange.getStart().compareTo(timeRange.getEnd()) >= 0)
			throw new IllegalArgumentException("start must be strictly before end");

		final PiecewiseConstantHours result = new PiecewiseConstantHours(defaultValue);
		result.timeBoundaries.putAll(this.timeBoundaries);
		result.timeBoundaries.put(timeRange.getStart(), fraction);
		if (timeRange.getEnd().equals(LocalTime.MIDNIGHT) == false)
			result.timeBoundaries.put(timeRange.getEnd(), defaultValue);
		return result;
	}
}