/*
 * Copyright © 2017 the original authors (http://cereebro.io)
 *
 * 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 io.cereebro.snitch.detect.jdbc;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;

import javax.annotation.PostConstruct;
import javax.sql.DataSource;

import org.springframework.util.CollectionUtils;

import io.cereebro.core.Component;
import io.cereebro.core.Dependency;
import io.cereebro.core.Relationship;
import io.cereebro.core.RelationshipDetector;
import lombok.extern.slf4j.Slf4j;

/**
 * Implementation of {@link RelationshipDetector} used to detect all data source
 * dependencies. The class retrieves all {@link DataSource} available in the
 * context and create a {@link Relationship}
 * 
 * @author lwarrot
 *
 */
@Slf4j
public class DataSourceRelationshipDetector implements RelationshipDetector {

    private static final String DEFAULT_NAME = "default_db";

    private final List<DataSource> dataSources;

    private Set<Relationship> relationsCache;

    public DataSourceRelationshipDetector(Collection<DataSource> dataSources) {
        this.dataSources = new ArrayList<>();
        if (!CollectionUtils.isEmpty(dataSources)) {
            this.dataSources.addAll(dataSources);
        }
    }

    @PostConstruct
    protected void postConstruct() {
        relationsCache = detect();
    }

    @Override
    public Set<Relationship> detect() {
        if (relationsCache == null) {
            final Set<Relationship> result = new HashSet<>();
            for (DataSource ds : dataSources) {
                try {
                    result.add(Dependency.on(Component.of(extractName(ds), extractDatabaseType(ds))));
                } catch (SQLException e) {
                    LOGGER.error("Could not fetch the default catalog of the database connection", e);
                }
            }
            relationsCache = result;
        }
        return new HashSet<>(relationsCache);
    }

    /**
     * Extract a DataSource name, using a default one if necessary.
     * 
     * @param dataSource
     *            JDBC DataSource.
     * @return a non-null DataSource name.
     * @throws SQLException
     *             if something goes wrong while extracting component info.
     */
    protected String extractName(DataSource dataSource) throws SQLException {
        String name = dataSource.getConnection().getSchema();
        if (name == null) {
            name = dataSource.getConnection().getCatalog();
        }
        return Optional.ofNullable(name).orElse(DEFAULT_NAME);
    }

    /**
     * Extract the Database type from the metadata of the connection.
     * 
     * @param dataSource
     *            JDBC DataSource.
     * @return a non-null Datasource type.
     * @throws SQLException
     *             if something goes wrong while extracting the component type.
     */
    protected String extractDatabaseType(DataSource dataSource) throws SQLException {
        return DbType.findByProductName(dataSource.getConnection().getMetaData().getDatabaseProductName())
                .componentType();
    }

}