/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.logging.log4j.nosql.appender.mongodb;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.appender.AppenderLoggingException;
import org.apache.logging.log4j.nosql.appender.NoSqlConnection;
import org.apache.logging.log4j.nosql.appender.NoSqlObject;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.Strings;
import org.bson.BSON;
import org.bson.Transformer;

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.WriteResult;

/**
 * The MongoDB implementation of {@link NoSqlConnection}.
 */
public final class MongoDbConnection implements NoSqlConnection<BasicDBObject, MongoDbObject> {

    private static final Logger LOGGER = StatusLogger.getLogger();

    static {
        BSON.addEncodingHook(Level.class, new Transformer() {
            @Override
            public Object transform(final Object o) {
                if (o instanceof Level) {
                    return ((Level) o).name();
                }
                return o;
            }
        });
    }

    private final DBCollection collection;
    private final Mongo mongo;
    private final WriteConcern writeConcern;

    public MongoDbConnection(final DB database, final WriteConcern writeConcern, final String collectionName) {
        this.mongo = database.getMongo();
        this.collection = database.getCollection(collectionName);
        this.writeConcern = writeConcern;
    }

    @Override
    public MongoDbObject createObject() {
        return new MongoDbObject();
    }

    @Override
    public MongoDbObject[] createList(final int length) {
        return new MongoDbObject[length];
    }

    @Override
    public void insertObject(final NoSqlObject<BasicDBObject> object) {
        try {
            final WriteResult result = this.collection.insert(object.unwrap(), this.writeConcern);
            if (Strings.isNotEmpty(result.getError())) {
                throw new AppenderLoggingException("Failed to write log event to MongoDB due to error: " +
                        result.getError() + '.');
            }
        } catch (final MongoException e) {
            throw new AppenderLoggingException("Failed to write log event to MongoDB due to error: " + e.getMessage(),
                    e);
        }
    }

    @Override
    public void close() {
        // there's no need to call this.mongo.close() since that literally closes the connection
        // MongoDBClient uses internal connection pooling
        // for more details, see LOG4J2-591
    }

    @Override
    public boolean isClosed() {
        return !this.mongo.getConnector().isOpen();
    }

    /**
     * To prevent class loading issues during plugin discovery, this code cannot live within MongoDbProvider. This
     * is because of how Java treats references to Exception classes different from references to other classes. When
     * Java loads a class, it normally won't load that class's dependent classes until and unless A) they are used, B)
     * the class being loaded extends or implements those classes, or C) those classes are the types of static members
     * in the class. However, exceptions that a class uses are always loaded when the class is loaded, even before
     * they are actually used.
     *
     * @param database The database to authenticate
     * @param username The username to authenticate with
     * @param password The password to authenticate with
     */
    static void authenticate(final DB database, final String username, final String password) {
        try {
            if (!database.authenticate(username, password.toCharArray())) {
                LOGGER.error("Failed to authenticate against MongoDB server. Unknown error.");
            }
        } catch (final MongoException e) {
            LOGGER.error("Failed to authenticate against MongoDB: " + e.getMessage(), e);
        } catch (final IllegalStateException e) {
            LOGGER.error("Factory-supplied MongoDB database connection already authenticated with different" +
                    "credentials but lost connection.", e);
        }
    }
}
