content: /*
   * Copyright (c) 2018, 2021, Oracle and/or its affiliates.
   *
   * This program is free software; you can redistribute it and/or modify it under
   * the terms of the GNU General Public License, version 2.0, as published by the
   * Free Software Foundation.
   *
   * This program is also distributed with certain software (including but not
   * limited to OpenSSL) that is licensed under separate terms, as designated in a
   * particular file or component or in included license documentation. The
   * authors of MySQL hereby grant you an additional permission to link the
   * program and your derivative works with the separately licensed software that
   * they have included with MySQL.
   *
   * Without limiting anything contained in the foregoing, this file, which is
   * part of MySQL Connector/J, is also subject to the Universal FOSS Exception,
   * version 1.0, a copy of which can be found at
   * http://oss.oracle.com/licenses/universal-foss-exception.
   *
   * This program is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
   * FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0,
   * for more details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
   */
  
  package com.mysql.cj.protocol;
  
  import java.io.IOException;
  import java.util.Optional;
  
  import com.mysql.cj.exceptions.CJOperationNotSupportedException;
  import com.mysql.cj.exceptions.ExceptionFactory;
  
  public interface MessageReader<H extends MessageHeader, M extends Message> {
  
      /**
       * Read the next message header from server, possibly blocking indefinitely until the message is received.
       * 
       * @return {@link MessageHeader} of the next message
       * @throws IOException
       *             if an error occurs
       */
      H readHeader() throws IOException;
  
      /**
       * Read the next message header from server, possibly blocking indefinitely until the message is received,
       * and cache it so that the next {@link #readHeader()} return the same header.
       * 
       * @return {@link MessageHeader} of the next message
       * @throws IOException
       *             if an error occurs
       */
      default H probeHeader() throws IOException {
          return readHeader();
      }
  
      /**
       * Read message from server into to the given {@link Message} instance or into the new one if not present.
       * For asynchronous channel it synchronously reads the next message in the stream, blocking until the message is read fully.
       * Could throw CJCommunicationsException wrapping an {@link IOException} during read or parse
       * 
       * @param reuse
       *            {@link Message} object to reuse. May be ignored by implementation.
       * @param header
       *            {@link MessageHeader} instance
       * @return {@link Message} instance
       * @throws IOException
       *             if an error occurs
       */
      M readMessage(Optional<M> reuse, H header) throws IOException;
  
      /**
       * Read message from server into to the given {@link Message} instance or into the new one if not present
       * and cache it so that the next {@link #readMessage(Optional, MessageHeader)} return the same message.
       * For asynchronous channel it synchronously reads the next message in the stream, blocking until the message is read fully.
       * Could throw CJCommunicationsException wrapping an {@link IOException} during read or parse
       * 
       * @param reuse
       *            {@link Message} object to reuse. May be ignored by implementation.
       * @param header
       *            {@link MessageHeader} instance
       * @return {@link Message} instance
       * @throws IOException
       *             if an error occurs
       */
      default M probeMessage(Optional<M> reuse, H header) throws IOException {
          return readMessage(reuse, header);
      }
  
      /**
       * Read message from server into to the given {@link Message} instance or into the new one if not present.
       * For asynchronous channel it synchronously reads the next message in the stream, blocking until the message is read fully.
       * Could throw WrongArgumentException if the expected message type is not the next message (exception will be thrown in *caller* context).
       * 
       * @param reuse
       *            {@link Message} object to reuse. May be ignored by implementation.
       * @param expectedType
       *            Expected type of message.
       * @return {@link Message} instance
       * @throws IOException
       *             if an error occurs
       */
      default M readMessage(Optional<M> reuse, int expectedType) throws IOException {
          throw ExceptionFactory.createException(CJOperationNotSupportedException.class, "Not supported");
      }
  
      /**
       * Queue a {@link MessageListener} to receive messages delivered asynchronously.
       * 
       * @param l
       *            {@link MessageListener}
       */
      default void pushMessageListener(MessageListener<M> l) {
          throw ExceptionFactory.createException(CJOperationNotSupportedException.class, "Not supported");
      }
  
      /**
       * Get last message sequence number, as it was stored by {@link #readHeader()}.
       * 
       * @return number
       */
      default byte getMessageSequence() {
          return 0;
      }
  
      /**
       * Set stored message sequence number to 0.
       */
      default void resetMessageSequence() {
          // no-op
      }
  
      /**
       * Return a MessageReader instance free of decorators.
       * 
       * @return {@link MessageReader}
       */
      default MessageReader<H, M> undecorateAll() {
          return this;
      }
  
      /**
       * Return the previous MessageReader instance from the decorators chain or the current MessageReader
       * if it is the first entry in a chain.
       * 
       * @return {@link MessageReader}
       */
      default MessageReader<H, M> undecorate() {
          return this;
      }
  
      /**
       * Start reading messages reader from the provided channel.
       */
      default void start() {
          // no-op
      }
  
      /**
       * Signal to the reader that it should stop reading messages after reading the next message.
       */
      default void stopAfterNextMessage() {
          // no-op
      }
  
  }
  