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package org.openlr.encoder;

import org.openlr.locationreference.LocationReferencePoint;
import org.openlr.map.Line;
import org.openlr.map.MapOperations;
import org.openlr.map.Path;
import org.openlr.map.PointAlongLine;

import java.util.List;

class PointAlongLineEncoder {
    private final MapOperations mapOperations;
    private final PathSplitter pathSplitter;
    private final LocationReferencePointCreator locationReferencePointCreator;

    PointAlongLineEncoder(MapOperations mapOperations, PathSplitter pathSplitter, LocationReferencePointCreator locationReferencePointCreator) {
        this.mapOperations = mapOperations;
        this.pathSplitter = pathSplitter;
        this.locationReferencePointCreator = locationReferencePointCreator;
    }

    > PointAlongLineEncoderResult encode(PointAlongLine pointAlongLine) {
        Path backwardExpansion = mapOperations.expandToValidNode(pointAlongLine, false);
        Path forwardExpansion = mapOperations.expandToValidNode(pointAlongLine, true);

        Path expandedPath = mapOperations.joinPaths(List.of(
                backwardExpansion,
                forwardExpansion));

        List> subPaths = pathSplitter.split(expandedPath);

        double distanceToPoint = backwardExpansion.getLength();
        double distance = 0;

        Path relevantSubPath = null;
        double relativePositiveOffset = 0;

        for (Path subPath : subPaths) {
            double nextDistance = distance + subPath.getLength();

            if (distance <= distanceToPoint && nextDistance > distanceToPoint) {
                relevantSubPath = subPath;
                relativePositiveOffset = (distanceToPoint - distance) / subPath.getLength();
                break;
            }
        }

        if (relevantSubPath == null) {
            throw new IllegalStateException();
        }

        LocationReferencePoint firstLocationReferencePoint = locationReferencePointCreator.create(relevantSubPath.getStart(), relevantSubPath);
        LocationReferencePoint lastLocationReferencePoint = locationReferencePointCreator.create(relevantSubPath.getEnd());

        return new PointAlongLineEncoderResult(
                firstLocationReferencePoint,
                lastLocationReferencePoint,
                relativePositiveOffset);
    }
}