/*
 * 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.jackrabbit.core.persistence.pool;

import java.sql.ResultSet;
import java.sql.SQLException;

import org.apache.jackrabbit.core.util.db.ConnectionHelper;
import org.apache.jackrabbit.core.util.db.DbUtility;

/**
 * Same as {@link DbNameIndex} but does not make use of the
 * {@link java.sql.Statement#RETURN_GENERATED_KEYS} feature as it is not
 * provided by the underlying database driver for PostgreSQL.
 */
public class PostgreSQLNameIndex extends DbNameIndex {

    protected String generatedKeySelectSQL;

    public PostgreSQLNameIndex(ConnectionHelper connectionHelper, String schemaObjectPrefix)
            throws SQLException {
        super(connectionHelper, schemaObjectPrefix);
    }

    /**
     * Inits this index and prepares the statements.
     *
     * @param con the jdbc connection
     * @param schemaObjectPrefix the prefix for table names
     * @throws SQLException if the statements cannot be prepared.
     */
    protected void init(String schemaObjectPrefix)
            throws SQLException {
        nameSelectSQL = "select NAME from " + schemaObjectPrefix + "NAMES where ID = ?";
        indexSelectSQL = "select ID from " + schemaObjectPrefix + "NAMES where NAME = ?";
        nameInsertSQL = "insert into " + schemaObjectPrefix + "NAMES (NAME) values (?)";
        generatedKeySelectSQL = "select currval('" + schemaObjectPrefix + "NAMES_ID_SEQ')";
    }

    /**
     * Inserts a string into the database and returns the new index.
     * <p/>
     * Instead of using the {@link java.sql.Statement#RETURN_GENERATED_KEYS}
     * feature, the newly inserted index is retrieved by a 2nd select statement.
     *
     * @param string the string to insert
     * @return the new index.
     */
    protected int insertString(String string) {
        // assert index does not exist
        try {
            conHelper.exec(nameInsertSQL, new Object[]{string});
            return getGeneratedKey();
        } catch (Exception e) {
            IllegalStateException ise = new IllegalStateException("Unable to insert index for string: " + string);
            ise.initCause(e);
            throw ise;
        }
    }

    /**
     * Retrieves the last assigned key from the database.
     * @return the index.
     */
    protected int getGeneratedKey() {
        ResultSet rs = null;
        try {
           rs = conHelper.exec(generatedKeySelectSQL, null, false, 0);
            if (!rs.next()) {
                return -1;
            } else {
                return rs.getInt(1);
            }
        } catch (Exception e) {
            IllegalStateException ise = new IllegalStateException("Unable to read generated index");
            ise.initCause(e);
            throw ise;
        } finally {
            DbUtility.close(rs);
        }
    }

}
