/*
 * Copyright (c) 2011-2013 The original author or authors
 * ------------------------------------------------------
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Apache License v2.0 which accompanies this distribution.
 *
 *     The Eclipse Public License is available at
 *     http://www.eclipse.org/legal/epl-v10.html
 *
 *     The Apache License v2.0 is available at
 *     http://www.opensource.org/licenses/apache2.0.php
 *
 * You may elect to redistribute this code under either of these licenses.
 */

package io.vertx.core.streams;

import io.vertx.codegen.annotations.Fluent;
import io.vertx.codegen.annotations.Nullable;
import io.vertx.codegen.annotations.VertxGen;
import io.vertx.core.Handler;

/**
 *
 * Represents a stream of data that can be written to.
 * <p>
 * Any class that implements this interface can be used by a {@link Pump} to pump data from a {@code ReadStream}
 * to it.
 *
 * @author <a href="http://tfox.org">Tim Fox</a>
 */
@VertxGen(concrete = false)
public interface WriteStream<T> extends StreamBase {

  /**
   * Set an exception handler on the write stream.
   *
   * @param handler  the exception handler
   * @return a reference to this, so the API can be used fluently
   */
  @Override
  WriteStream<T> exceptionHandler(Handler<Throwable> handler);

  /**
   * Write some data to the stream. The data is put on an internal write queue, and the write actually happens
   * asynchronously. To avoid running out of memory by putting too much on the write queue,
   * check the {@link #writeQueueFull} method before writing. This is done automatically if using a {@link Pump}.
   *
   * @param data  the data to write
   * @return a reference to this, so the API can be used fluently
   */
  @Fluent
  WriteStream<T> write(T data);

  /**
   * Ends the stream.
   * <p>
   * Once the stream has ended, it cannot be used any more.
   */
  void end();

  /**
   * Same as {@link #end()} but writes some data to the stream before ending.
   */
  default void end(T t) {
    write(t);
    end();
  }

  /**
   * Set the maximum size of the write queue to {@code maxSize}. You will still be able to write to the stream even
   * if there is more than {@code maxSize} items in the write queue. This is used as an indicator by classes such as
   * {@code Pump} to provide flow control.
   * <p/>
   * The value is defined by the implementation of the stream, e.g in bytes for a
   * {@link io.vertx.core.net.NetSocket}, the number of {@link io.vertx.core.eventbus.Message} for a
   * {@link io.vertx.core.eventbus.MessageProducer}, etc...
   *
   * @param maxSize  the max size of the write stream
   * @return a reference to this, so the API can be used fluently
   */
  @Fluent
  WriteStream<T> setWriteQueueMaxSize(int maxSize);

  /**
   * This will return {@code true} if there are more bytes in the write queue than the value set using {@link
   * #setWriteQueueMaxSize}
   *
   * @return true if write queue is full
   */
  boolean writeQueueFull();

  /**
   * Set a drain handler on the stream. If the write queue is full, then the handler will be called when the write
   * queue is ready to accept buffers again. See {@link Pump} for an example of this being used.
   * <p/>
   * The stream implementation defines when the drain handler, for example it could be when the queue size has been
   * reduced to {@code maxSize / 2}.
   *
   * @param handler the handler
   * @return a reference to this, so the API can be used fluently
   */
  @Fluent
  WriteStream<T> drainHandler(@Nullable Handler<Void> handler);

}