/*
 * Copyright 1999-2012 Alibaba Group.
 *  
 * 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 com.alibaba.cobar.server.response;

import java.nio.ByteBuffer;

import com.alibaba.cobar.config.Fields;
import com.alibaba.cobar.mysql.PacketUtil;
import com.alibaba.cobar.net.mysql.EOFPacket;
import com.alibaba.cobar.net.mysql.FieldPacket;
import com.alibaba.cobar.net.mysql.ResultSetHeaderPacket;
import com.alibaba.cobar.net.mysql.RowDataPacket;
import com.alibaba.cobar.server.ServerConnection;
import com.alibaba.cobar.util.StringUtil;

/**
 * @author xianmao.hexm
 */
public class SelectDatabase {
    private static final int FIELD_COUNT = 1;
    private static final ResultSetHeaderPacket header = PacketUtil.getHeader(FIELD_COUNT);
    private static final FieldPacket[] fields = new FieldPacket[FIELD_COUNT];
    private static final EOFPacket eof = new EOFPacket();
    static {
        int i = 0;
        byte packetId = 0;
        header.packetId = ++packetId;
        fields[i] = PacketUtil.getField("DATABASE()", Fields.FIELD_TYPE_VAR_STRING);
        fields[i++].packetId = ++packetId;
        eof.packetId = ++packetId;
    }

    public static void response(ServerConnection c) {
        ByteBuffer buffer = c.allocate();
        buffer = header.write(buffer, c);
        for (FieldPacket field : fields) {
            buffer = field.write(buffer, c);
        }
        buffer = eof.write(buffer, c);
        byte packetId = eof.packetId;
        RowDataPacket row = new RowDataPacket(FIELD_COUNT);
        row.add(StringUtil.encode(c.getSchema(), c.getCharset()));
        row.packetId = ++packetId;
        buffer = row.write(buffer, c);
        EOFPacket lastEof = new EOFPacket();
        lastEof.packetId = ++packetId;
        buffer = lastEof.write(buffer, c);
        c.write(buffer);
    }

}