/*
 * Copyright (c) 2011-2019 Contributors to the Eclipse Foundation
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 * which is available at https://www.apache.org/licenses/LICENSE-2.0.
 *
 * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 */

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.AsyncResult;
import io.vertx.core.Future;
import io.vertx.core.Handler;
import io.vertx.core.Promise;

Represents a stream of data that can be written to.
 Any class that implements this interface can be used by a Pipe to pipe data from a ReadStream to it. 
Author:
Tim Fox/**
 *
 * Represents a stream of data that can be written to.
 * <p>
 * Any class that implements this interface can be used by a {@link Pipe} to pipe 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.
Params:
handler –  the exception handler
Returns:
a reference to this, so the API can be used fluently/**
   * 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 usually 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 writeQueueFull method before writing. This is done automatically if using a Pipe. 
 When the data is moved from the queue to the actual medium, the returned Future will be completed with the write result, e.g the future is succeeded when a server HTTP response buffer is written to the socket and failed if the remote client has closed the socket while the data was still pending for write. 
Params:
data –  the data to write
Returns:
a future completed with the write result/**
   * Write some data to the stream.
   *
   * <p> The data is usually 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 Pipe}.
   *
   * <p> When the {@code data} is moved from the queue to the actual medium, the returned
   * {@link Future} will be completed with the write result, e.g the future is succeeded
   * when a server HTTP response buffer is written to the socket and failed if the remote
   * client has closed the socket while the data was still pending for write.
   *
   * @param data  the data to write
   * @return a future completed with the write result
   */
  Future<Void> write(T data);

  
Same as write(Object) but with an handler called when the operation completes /**
   * Same as {@link #write(T)} but with an {@code handler} called when the operation completes
   */
  void write(T data, Handler<AsyncResult<Void>> handler);

  
Ends the stream.

Once the stream has ended, it cannot be used any more.
Returns:
a future completed with the result/**
   * Ends the stream.
   * <p>
   * Once the stream has ended, it cannot be used any more.
   *
   * @return a future completed with the result
   */
  default Future<Void> end() {
    Promise<Void> promise = Promise.promise();
    end(promise);
    return promise.future();
  }

  
Same as end() but with an handler called when the operation completes /**
   * Same as {@link #end()} but with an {@code handler} called when the operation completes
   */
  void end(Handler<AsyncResult<Void>> handler);

  
Same as end() but writes some data to the stream before ending. 
Params:
data – the data to write
Implementation Requirements:
The default default implementation calls sequentially write(Object) then end()
API Note:
Implementations might want to perform a single operation
Returns:
a future completed with the result/**
   * Same as {@link #end()} but writes some data to the stream before ending.
   *
   * @implSpec The default default implementation calls sequentially {@link #write(Object)} then {@link #end()}
   * @apiNote Implementations might want to perform a single operation
   * @param data the data to write
   * @return a future completed with the result
   */
  default Future<Void> end(T data) {
    Promise<Void> provide = Promise.promise();
    end(data, provide);
    return provide.future();
  }

  
Same as end(Object) but with an handler called when the operation completes /**
   * Same as {@link #end(T)} but with an {@code handler} called when the operation completes
   */
  default void end(T data, Handler<AsyncResult<Void>> handler) {
    if (handler != null) {
      write(data, ar -> {
        if (ar.succeeded()) {
          end(handler);
        } else {
          handler.handle(ar);
        }
      });
    } else {
      end(data);
    }
  }

  
Set the maximum size of the write queue to maxSize. You will still be able to write to the stream even if there is more than maxSize items in the write queue. This is used as an indicator by classes such as Pipe to provide flow control. 
 The value is defined by the implementation of the stream, e.g in bytes for a NetSocket, etc... 
Params:
maxSize –  the max size of the write stream
Returns:
a reference to this, so the API can be used fluently/**
   * 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
   * {@link Pipe} 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}, 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 true if there are more bytes in the write queue than the value set using setWriteQueueMaxSize 
Returns:
true if write queue is full/**
   * This will return {@code true} if there are more bytes in the write queue than the value set using {@link
   * #setWriteQueueMaxSize}
   *
   * @return {@code 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 Pipe for an example of this being used. 
 The stream implementation defines when the drain handler, for example it could be when the queue size has been reduced to maxSize / 2. 
Params:
handler – the handler
Returns:
a reference to this, so the API can be used fluently/**
   * 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 Pipe} 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);

}