// License: GPL. For details, see LICENSE file.
package org.openstreetmap.josm.plugins.graphview.core.access;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import org.openstreetmap.josm.plugins.graphview.core.data.MapBasedTagGroup;
import org.openstreetmap.josm.plugins.graphview.core.data.Tag;
import org.openstreetmap.josm.plugins.graphview.core.data.TagGroup;
import org.openstreetmap.josm.plugins.graphview.core.util.TagCondition;

/**
 * immutable representation of a tag implication rule.
 */
public final class Implication {

    private final TagCondition condition;
    private final Collection<Tag> impliedTags;

    public Implication(TagCondition condition, Collection<Tag> impliedTags) {
        this.condition = condition;
        this.impliedTags = impliedTags;
    }

    /**
     * applies this implication to a tag group.
     * The resulting tag group will contain all tags from the original group
     * and all implied tags with a key that didn't occur in the original group.
     *
     * @param tags  tag group to apply implications to; != null
     */
    public TagGroup apply(TagGroup tags) {

        if (condition.matches(tags)) {

            Map<String, String> newTagMap = new HashMap<>();

            for (Tag tag : tags) {
                newTagMap.put(tag.key, tag.value);
            }

            for (Tag impliedTag : impliedTags) {
                if (!newTagMap.containsKey(impliedTag.key)) {
                    newTagMap.put(impliedTag.key, impliedTag.value);
                }
            }

            return new MapBasedTagGroup(newTagMap);

        } else {
            return tags;
        }

    }

    @Override
    public String toString() {
        return condition.toString() + " => " + impliedTags.toString();
    }

}
