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package de.taimos.dvalin.mongo.links;

/*
 * #%L
 * Spring DAO Mongo
 * %%
 * Copyright (C) 2013 - 2015 Taimos GmbH
 * %%
 * 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.
 * #L%
 */

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.jongo.MongoCollection;
import org.jongo.ResultHandler;

import com.mongodb.DBObject;

/**
 * QueryHelper to convert query result to a list of DLinks. It only queries the fields necessary to construct links.
 *
 * @param  the {@link AReferenceableEntity} this link uses
 * @author Thorsten Hoeger
 */
public class DLinkQuery> {

    private final Class targetClass;

    private final String labelField;


    /**
     * @param targetClass the links target class
     * @param labelField  the name of the label field
     */
    public DLinkQuery(Class targetClass, String labelField) {
        this.targetClass = targetClass;
        this.labelField = labelField;
    }

    public List> find(MongoCollection collection, String query, Object... parameter) {
        ResultHandler> handler = new ResultHandler>() {

            @Override
            public DocumentLink map(DBObject result) {
                if (!result.containsField("_id") || !result.containsField(DLinkQuery.this.labelField)) {
                    throw new RuntimeException("Fields missing to construct DocumentLink");
                }
                String id = result.get("_id").toString();
                String label = result.get(DLinkQuery.this.labelField).toString();
                return new DocumentLink(DLinkQuery.this.targetClass, id, label);
            }
        };
        Iterator> it = collection.find(query, parameter).projection(String.format("{%s:1}", this.labelField)).map(handler).iterator();

        List> objects = new ArrayList<>();
        while (it.hasNext()) {
            DocumentLink link = it.next();
            objects.add(link);
        }
        return objects;
    }

}