/**
 * Copyright © 2016-2018 The Thingsboard Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.thingsboard.rule.engine.util;

import com.google.common.util.concurrent.AsyncFunction;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import org.apache.commons.collections.CollectionUtils;
import org.thingsboard.rule.engine.api.TbContext;
import org.thingsboard.rule.engine.data.RelationsQuery;
import org.thingsboard.server.common.data.id.EntityId;
import org.thingsboard.server.common.data.relation.EntityRelation;
import org.thingsboard.server.common.data.relation.EntityRelationsQuery;
import org.thingsboard.server.common.data.relation.EntitySearchDirection;
import org.thingsboard.server.common.data.relation.RelationsSearchParameters;
import org.thingsboard.server.dao.relation.RelationService;

import java.util.List;

public class EntitiesRelatedEntityIdAsyncLoader {

    public static ListenableFuture<EntityId> findEntityAsync(TbContext ctx, EntityId originator,
                                                             RelationsQuery relationsQuery) {
        RelationService relationService = ctx.getRelationService();
        EntityRelationsQuery query = buildQuery(originator, relationsQuery);
        ListenableFuture<List<EntityRelation>> asyncRelation = relationService.findByQuery(query);
        if (relationsQuery.getDirection() == EntitySearchDirection.FROM) {
            return Futures.transform(asyncRelation, (AsyncFunction<? super List<EntityRelation>, EntityId>)
                    r -> CollectionUtils.isNotEmpty(r) ? Futures.immediateFuture(r.get(0).getTo())
                            : Futures.immediateFuture(null));
        } else if (relationsQuery.getDirection() == EntitySearchDirection.TO) {
            return Futures.transform(asyncRelation, (AsyncFunction<? super List<EntityRelation>, EntityId>)
                    r -> CollectionUtils.isNotEmpty(r) ? Futures.immediateFuture(r.get(0).getFrom())
                            : Futures.immediateFuture(null));
        }
        return Futures.immediateFailedFuture(new IllegalStateException("Unknown direction"));
    }

    private static EntityRelationsQuery buildQuery(EntityId originator, RelationsQuery relationsQuery) {
        EntityRelationsQuery query = new EntityRelationsQuery();
        RelationsSearchParameters parameters = new RelationsSearchParameters(originator,
                relationsQuery.getDirection(), relationsQuery.getMaxLevel());
        query.setParameters(parameters);
        query.setFilters(relationsQuery.getFilters());
        return query;
    }
}
