/*
    * 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.shardingsphere.db.protocol.mysql.packet.binlog.management;
  
  import com.google.common.base.Preconditions;
  import lombok.Getter;
  import lombok.ToString;
  import org.apache.shardingsphere.db.protocol.mysql.constant.MySQLBinlogEventType;
  import org.apache.shardingsphere.db.protocol.mysql.packet.binlog.AbstractMySQLBinlogEventPacket;
  import org.apache.shardingsphere.db.protocol.mysql.packet.binlog.MySQLBinlogEventHeader;
  import org.apache.shardingsphere.db.protocol.mysql.payload.MySQLPacketPayload;
  
  /**
   * MySQL binlog format description event packet.
   *
   * @see <a href="https://dev.mysql.com/doc/dev/mysql-server/latest/classbinary__log_1_1Format__description__event.html">FORMAT_DESCRIPTION_EVENT</a>
   * @see <a href="https://dev.mysql.com/worklog/task/?id=2540#tabs-2540-4">WL#2540: Replication event checksums</a>
   */
  @Getter
  @ToString
  public final class MySQLBinlogFormatDescriptionEventPacket extends AbstractMySQLBinlogEventPacket {
      
      private final int binlogVersion = 4;
      
      private final byte[] mysqlServerVersion;
      
      private final int createTimestamp;
      
      private final int eventHeaderLength = 19;
      
      public MySQLBinlogFormatDescriptionEventPacket(final MySQLBinlogEventHeader binlogEventHeader, final MySQLPacketPayload payload) {
          super(binlogEventHeader);
          Preconditions.checkArgument(binlogVersion == payload.readInt2(), "Binlog version of FORMAT_DESCRIPTION_EVENT should always 4");
          mysqlServerVersion = payload.readStringFixByBytes(50);
          createTimestamp = payload.readInt4();
          Preconditions.checkArgument(eventHeaderLength == payload.readInt1(), "Length of the Binlog Event Header should always be 19.");
          skipTypeHeaderLength(payload);
          skipCheckSums(payload);
      }
      
      /**
       * Type header length is not fixed value, it depends on mysql server version.
       * Because the binlog event type may add in future version.
       * During test, the length in version 5.7.21, the length of FORMAT_DESCRIPTION_EVENT is 95 not 84.
       *
       * @param payload MySQL binlog packet payload
       */
      private void skipTypeHeaderLength(final MySQLPacketPayload payload) {
          payload.skipReserved(MySQLBinlogEventType.FORMAT_DESCRIPTION_EVENT.getValue() - 1);
          int eventLength = payload.readInt1();
          int remainLength = eventLength - 2 - 50 - 4 - 1 - (MySQLBinlogEventType.FORMAT_DESCRIPTION_EVENT.getValue() - 1) - 1;
          payload.skipReserved(remainLength);
      }
      
      private void skipCheckSums(final MySQLPacketPayload payload) {
          int checksumAlgorithmFlag = payload.readInt1();
          if (1 == checksumAlgorithmFlag) {
              payload.skipReserved(4);
          }
      }
      
      @Override
      protected void writeEvent(final MySQLPacketPayload payload) {
          // TODO
      }
  }