/*
* Copyright (C) 2016-2022 ActionTech.
* based on code by MyCATCopyrightHolder Copyright (c) 2013, OpenCloudDB/MyCAT.
* License: http://www.gnu.org/licenses/gpl.html GPL version 2 or higher.
*/
package com.actiontech.dble.server.response;

import com.actiontech.dble.DbleServer;
import com.actiontech.dble.backend.mysql.PacketUtil;
import com.actiontech.dble.config.Fields;
import com.actiontech.dble.config.ServerConfig;
import com.actiontech.dble.config.model.user.ShardingUserConfig;
import com.actiontech.dble.config.model.user.UserConfig;
import com.actiontech.dble.config.model.user.UserName;
import com.actiontech.dble.net.mysql.*;
import com.actiontech.dble.services.mysqlsharding.ShardingService;
import com.actiontech.dble.util.StringUtil;

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

/**
 * @author mycat
 */
public final class ShowDatabases {
    private 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();


    public static void response(ShardingService shardingService) {

        HEADER.setPacketId(shardingService.nextPacketId());
        FIELDS[0] = PacketUtil.getField("DATABASE", Fields.FIELD_TYPE_VAR_STRING);
        FIELDS[0].setPacketId(shardingService.nextPacketId());
        EOF.setPacketId(shardingService.nextPacketId());

        ByteBuffer buffer = shardingService.allocate();
        // writeDirectly header
        buffer = HEADER.write(buffer, shardingService, true);


        // writeDirectly fields
        for (FieldPacket field : FIELDS) {
            buffer = field.write(buffer, shardingService, true);
        }

        // writeDirectly eof
        buffer = EOF.write(buffer, shardingService, true);

        // writeDirectly rows
        ServerConfig conf = DbleServer.getInstance().getConfig();
        Map<UserName, UserConfig> users = conf.getUsers();
        UserConfig user = users == null ? null : users.get(shardingService.getUser());
        if (user != null) {
            ShardingUserConfig shardingUser = (ShardingUserConfig) user;
            TreeSet<String> schemaSet = new TreeSet<>();
            Set<String> schemaList = shardingUser.getSchemas();
            if (schemaList == null || schemaList.size() == 0) {
                schemaSet.addAll(conf.getSchemas().keySet());
            } else {
                schemaSet.addAll(schemaList);
            }
            for (String name : schemaSet) {
                RowDataPacket row = new RowDataPacket(FIELD_COUNT);
                row.add(StringUtil.encode(name, shardingService.getCharset().getResults()));
                row.setPacketId(shardingService.nextPacketId());
                buffer = row.write(buffer, shardingService, true);
            }
        }

        // writeDirectly last eof
        EOFRowPacket lastEof = new EOFRowPacket();
        lastEof.setPacketId(shardingService.nextPacketId());
        lastEof.write(buffer, shardingService);
    }

}
