/*
 * Copyright 2012-2015 org.opencloudb.
 *  
 * 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 org.opencloudb.server.response;

import java.nio.ByteBuffer;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;

import org.opencloudb.MycatConfig;
import org.opencloudb.MycatServer;
import org.opencloudb.config.Fields;
import org.opencloudb.config.model.UserConfig;
import org.opencloudb.mysql.PacketUtil;
import org.opencloudb.net.mysql.EOFPacket;
import org.opencloudb.net.mysql.FieldPacket;
import org.opencloudb.net.mysql.ResultSetHeaderPacket;
import org.opencloudb.net.mysql.RowDataPacket;
import org.opencloudb.server.ServerConnection;
import org.opencloudb.util.StringUtil;

/**
 * @author mycat
 */
public class ShowDatabases {

    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();

        // write header
        buffer = header.write(buffer, c);

        // write fields
        for (FieldPacket field : fields) {
            buffer = field.write(buffer, c);
        }

        // write eof
        buffer = eof.write(buffer, c);

        // write rows
        byte packetId = eof.packetId;
        MycatConfig conf = MycatServer.getInstance().getConfig();
        Map<String, UserConfig> users = conf.getUsers();
        UserConfig user = users == null ? null : users.get(c.getUser());
        if (user != null) {
            TreeSet<String> schemaSet = new TreeSet<String>();
            Set<String> schemaList = user.getSchemas();
            if (schemaList == null || schemaList.size() == 0) {
                schemaSet.addAll(conf.getSchemas().keySet());
            } else {
                for (String schema : schemaList) {
                    schemaSet.add(schema);
                }
            }
            for (String name : schemaSet) {
                RowDataPacket row = new RowDataPacket(FIELD_COUNT);
                row.add(StringUtil.encode(name, c.getCharset()));
                row.packetId = ++packetId;
                buffer = row.write(buffer, c);
            }
        }

        // write last eof
        EOFPacket lastEof = new EOFPacket();
        lastEof.packetId = ++packetId;
        buffer = lastEof.write(buffer, c);

        // post write
        c.write(buffer);
    }

}