//
// basic_waitable_timer.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2016 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#ifndef ASIO_BASIC_WAITABLE_TIMER_HPP
#define ASIO_BASIC_WAITABLE_TIMER_HPP

#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)

#include "asio/detail/config.hpp"
#include <cstddef>
#include "asio/basic_io_object.hpp"
#include "asio/detail/handler_type_requirements.hpp"
#include "asio/detail/throw_error.hpp"
#include "asio/error.hpp"
#include "asio/wait_traits.hpp"
#include "asio/waitable_timer_service.hpp"

#include "asio/detail/push_options.hpp"

namespace asio {

/// Provides waitable timer functionality.
/**
 * The basic_waitable_timer class template provides the ability to perform a
 * blocking or asynchronous wait for a timer to expire.
 *
 * A waitable timer is always in one of two states: "expired" or "not expired".
 * If the wait() or async_wait() function is called on an expired timer, the
 * wait operation will complete immediately.
 *
 * Most applications will use one of the asio::steady_timer,
 * asio::system_timer or asio::high_resolution_timer typedefs.
 *
 * @note This waitable timer functionality is for use with the C++11 standard
 * library's @c &lt;chrono&gt; facility, or with the Boost.Chrono library.
 *
 * @par Thread Safety
 * @e Distinct @e objects: Safe.@n
 * @e Shared @e objects: Unsafe.
 *
 * @par Examples
 * Performing a blocking wait (C++11):
 * @code
 * // Construct a timer without setting an expiry time.
 * asio::steady_timer timer(io_service);
 *
 * // Set an expiry time relative to now.
 * timer.expires_from_now(std::chrono::seconds(5));
 *
 * // Wait for the timer to expire.
 * timer.wait();
 * @endcode
 *
 * @par 
 * Performing an asynchronous wait (C++11):
 * @code
 * void handler(const asio::error_code& error)
 * {
 *   if (!error)
 *   {
 *     // Timer expired.
 *   }
 * }
 *
 * ...
 *
 * // Construct a timer with an absolute expiry time.
 * asio::steady_timer timer(io_service,
 *     std::chrono::steady_clock::now() + std::chrono::seconds(60));
 *
 * // Start an asynchronous wait.
 * timer.async_wait(handler);
 * @endcode
 *
 * @par Changing an active waitable timer's expiry time
 *
 * Changing the expiry time of a timer while there are pending asynchronous
 * waits causes those wait operations to be cancelled. To ensure that the action
 * associated with the timer is performed only once, use something like this:
 * used:
 *
 * @code
 * void on_some_event()
 * {
 *   if (my_timer.expires_from_now(seconds(5)) > 0)
 *   {
 *     // We managed to cancel the timer. Start new asynchronous wait.
 *     my_timer.async_wait(on_timeout);
 *   }
 *   else
 *   {
 *     // Too late, timer has already expired!
 *   }
 * }
 *
 * void on_timeout(const asio::error_code& e)
 * {
 *   if (e != asio::error::operation_aborted)
 *   {
 *     // Timer was not cancelled, take necessary action.
 *   }
 * }
 * @endcode
 *
 * @li The asio::basic_waitable_timer::expires_from_now() function
 * cancels any pending asynchronous waits, and returns the number of
 * asynchronous waits that were cancelled. If it returns 0 then you were too
 * late and the wait handler has already been executed, or will soon be
 * executed. If it returns 1 then the wait handler was successfully cancelled.
 *
 * @li If a wait handler is cancelled, the asio::error_code passed to
 * it contains the value asio::error::operation_aborted.
 */
template <typename Clock,
    typename WaitTraits = asio::wait_traits<Clock>,
    typename WaitableTimerService = waitable_timer_service<Clock, WaitTraits> >
class basic_waitable_timer
  : public basic_io_object<WaitableTimerService>
{
public:
  /// The clock type.
  typedef Clock clock_type;

  /// The duration type of the clock.
  typedef typename clock_type::duration duration;

  /// The time point type of the clock.
  typedef typename clock_type::time_point time_point;

  /// The wait traits type.
  typedef WaitTraits traits_type;

  /// Constructor.
  /**
   * This constructor creates a timer without setting an expiry time. The
   * expires_at() or expires_from_now() functions must be called to set an
   * expiry time before the timer can be waited on.
   *
   * @param io_service The io_service object that the timer will use to dispatch
   * handlers for any asynchronous operations performed on the timer.
   */
  explicit basic_waitable_timer(asio::io_service& io_service)
    : basic_io_object<WaitableTimerService>(io_service)
  {
  }

  /// Constructor to set a particular expiry time as an absolute time.
  /**
   * This constructor creates a timer and sets the expiry time.
   *
   * @param io_service The io_service object that the timer will use to dispatch
   * handlers for any asynchronous operations performed on the timer.
   *
   * @param expiry_time The expiry time to be used for the timer, expressed
   * as an absolute time.
   */
  basic_waitable_timer(asio::io_service& io_service,
      const time_point& expiry_time)
    : basic_io_object<WaitableTimerService>(io_service)
  {
    asio::error_code ec;
    this->service.expires_at(this->implementation, expiry_time, ec);
    asio::detail::throw_error(ec, "expires_at");
  }

  /// Constructor to set a particular expiry time relative to now.
  /**
   * This constructor creates a timer and sets the expiry time.
   *
   * @param io_service The io_service object that the timer will use to dispatch
   * handlers for any asynchronous operations performed on the timer.
   *
   * @param expiry_time The expiry time to be used for the timer, relative to
   * now.
   */
  basic_waitable_timer(asio::io_service& io_service,
      const duration& expiry_time)
    : basic_io_object<WaitableTimerService>(io_service)
  {
    asio::error_code ec;
    this->service.expires_from_now(this->implementation, expiry_time, ec);
    asio::detail::throw_error(ec, "expires_from_now");
  }

  /// Cancel any asynchronous operations that are waiting on the timer.
  /**
   * This function forces the completion of any pending asynchronous wait
   * operations against the timer. The handler for each cancelled operation will
   * be invoked with the asio::error::operation_aborted error code.
   *
   * Cancelling the timer does not change the expiry time.
   *
   * @return The number of asynchronous operations that were cancelled.
   *
   * @throws asio::system_error Thrown on failure.
   *
   * @note If the timer has already expired when cancel() is called, then the
   * handlers for asynchronous wait operations will:
   *
   * @li have already been invoked; or
   *
   * @li have been queued for invocation in the near future.
   *
   * These handlers can no longer be cancelled, and therefore are passed an
   * error code that indicates the successful completion of the wait operation.
   */
  std::size_t cancel()
  {
    asio::error_code ec;
    std::size_t s = this->service.cancel(this->implementation, ec);
    asio::detail::throw_error(ec, "cancel");
    return s;
  }

  /// Cancel any asynchronous operations that are waiting on the timer.
  /**
   * This function forces the completion of any pending asynchronous wait
   * operations against the timer. The handler for each cancelled operation will
   * be invoked with the asio::error::operation_aborted error code.
   *
   * Cancelling the timer does not change the expiry time.
   *
   * @param ec Set to indicate what error occurred, if any.
   *
   * @return The number of asynchronous operations that were cancelled.
   *
   * @note If the timer has already expired when cancel() is called, then the
   * handlers for asynchronous wait operations will:
   *
   * @li have already been invoked; or
   *
   * @li have been queued for invocation in the near future.
   *
   * These handlers can no longer be cancelled, and therefore are passed an
   * error code that indicates the successful completion of the wait operation.
   */
  std::size_t cancel(asio::error_code& ec)
  {
    return this->service.cancel(this->implementation, ec);
  }

  /// Cancels one asynchronous operation that is waiting on the timer.
  /**
   * This function forces the completion of one pending asynchronous wait
   * operation against the timer. Handlers are cancelled in FIFO order. The
   * handler for the cancelled operation will be invoked with the
   * asio::error::operation_aborted error code.
   *
   * Cancelling the timer does not change the expiry time.
   *
   * @return The number of asynchronous operations that were cancelled. That is,
   * either 0 or 1.
   *
   * @throws asio::system_error Thrown on failure.
   *
   * @note If the timer has already expired when cancel_one() is called, then
   * the handlers for asynchronous wait operations will:
   *
   * @li have already been invoked; or
   *
   * @li have been queued for invocation in the near future.
   *
   * These handlers can no longer be cancelled, and therefore are passed an
   * error code that indicates the successful completion of the wait operation.
   */
  std::size_t cancel_one()
  {
    asio::error_code ec;
    std::size_t s = this->service.cancel_one(this->implementation, ec);
    asio::detail::throw_error(ec, "cancel_one");
    return s;
  }

  /// Cancels one asynchronous operation that is waiting on the timer.
  /**
   * This function forces the completion of one pending asynchronous wait
   * operation against the timer. Handlers are cancelled in FIFO order. The
   * handler for the cancelled operation will be invoked with the
   * asio::error::operation_aborted error code.
   *
   * Cancelling the timer does not change the expiry time.
   *
   * @param ec Set to indicate what error occurred, if any.
   *
   * @return The number of asynchronous operations that were cancelled. That is,
   * either 0 or 1.
   *
   * @note If the timer has already expired when cancel_one() is called, then
   * the handlers for asynchronous wait operations will:
   *
   * @li have already been invoked; or
   *
   * @li have been queued for invocation in the near future.
   *
   * These handlers can no longer be cancelled, and therefore are passed an
   * error code that indicates the successful completion of the wait operation.
   */
  std::size_t cancel_one(asio::error_code& ec)
  {
    return this->service.cancel_one(this->implementation, ec);
  }

  /// Get the timer's expiry time as an absolute time.
  /**
   * This function may be used to obtain the timer's current expiry time.
   * Whether the timer has expired or not does not affect this value.
   */
  time_point expires_at() const
  {
    return this->service.expires_at(this->implementation);
  }

  /// Set the timer's expiry time as an absolute time.
  /**
   * This function sets the expiry time. Any pending asynchronous wait
   * operations will be cancelled. The handler for each cancelled operation will
   * be invoked with the asio::error::operation_aborted error code.
   *
   * @param expiry_time The expiry time to be used for the timer.
   *
   * @return The number of asynchronous operations that were cancelled.
   *
   * @throws asio::system_error Thrown on failure.
   *
   * @note If the timer has already expired when expires_at() is called, then
   * the handlers for asynchronous wait operations will:
   *
   * @li have already been invoked; or
   *
   * @li have been queued for invocation in the near future.
   *
   * These handlers can no longer be cancelled, and therefore are passed an
   * error code that indicates the successful completion of the wait operation.
   */
  std::size_t expires_at(const time_point& expiry_time)
  {
    asio::error_code ec;
    std::size_t s = this->service.expires_at(
        this->implementation, expiry_time, ec);
    asio::detail::throw_error(ec, "expires_at");
    return s;
  }

  /// Set the timer's expiry time as an absolute time.
  /**
   * This function sets the expiry time. Any pending asynchronous wait
   * operations will be cancelled. The handler for each cancelled operation will
   * be invoked with the asio::error::operation_aborted error code.
   *
   * @param expiry_time The expiry time to be used for the timer.
   *
   * @param ec Set to indicate what error occurred, if any.
   *
   * @return The number of asynchronous operations that were cancelled.
   *
   * @note If the timer has already expired when expires_at() is called, then
   * the handlers for asynchronous wait operations will:
   *
   * @li have already been invoked; or
   *
   * @li have been queued for invocation in the near future.
   *
   * These handlers can no longer be cancelled, and therefore are passed an
   * error code that indicates the successful completion of the wait operation.
   */
  std::size_t expires_at(const time_point& expiry_time,
      asio::error_code& ec)
  {
    return this->service.expires_at(this->implementation, expiry_time, ec);
  }

  /// Get the timer's expiry time relative to now.
  /**
   * This function may be used to obtain the timer's current expiry time.
   * Whether the timer has expired or not does not affect this value.
   */
  duration expires_from_now() const
  {
    return this->service.expires_from_now(this->implementation);
  }

  /// Set the timer's expiry time relative to now.
  /**
   * This function sets the expiry time. Any pending asynchronous wait
   * operations will be cancelled. The handler for each cancelled operation will
   * be invoked with the asio::error::operation_aborted error code.
   *
   * @param expiry_time The expiry time to be used for the timer.
   *
   * @return The number of asynchronous operations that were cancelled.
   *
   * @throws asio::system_error Thrown on failure.
   *
   * @note If the timer has already expired when expires_from_now() is called,
   * then the handlers for asynchronous wait operations will:
   *
   * @li have already been invoked; or
   *
   * @li have been queued for invocation in the near future.
   *
   * These handlers can no longer be cancelled, and therefore are passed an
   * error code that indicates the successful completion of the wait operation.
   */
  std::size_t expires_from_now(const duration& expiry_time)
  {
    asio::error_code ec;
    std::size_t s = this->service.expires_from_now(
        this->implementation, expiry_time, ec);
    asio::detail::throw_error(ec, "expires_from_now");
    return s;
  }

  /// Set the timer's expiry time relative to now.
  /**
   * This function sets the expiry time. Any pending asynchronous wait
   * operations will be cancelled. The handler for each cancelled operation will
   * be invoked with the asio::error::operation_aborted error code.
   *
   * @param expiry_time The expiry time to be used for the timer.
   *
   * @param ec Set to indicate what error occurred, if any.
   *
   * @return The number of asynchronous operations that were cancelled.
   *
   * @note If the timer has already expired when expires_from_now() is called,
   * then the handlers for asynchronous wait operations will:
   *
   * @li have already been invoked; or
   *
   * @li have been queued for invocation in the near future.
   *
   * These handlers can no longer be cancelled, and therefore are passed an
   * error code that indicates the successful completion of the wait operation.
   */
  std::size_t expires_from_now(const duration& expiry_time,
      asio::error_code& ec)
  {
    return this->service.expires_from_now(
        this->implementation, expiry_time, ec);
  }

  /// Perform a blocking wait on the timer.
  /**
   * This function is used to wait for the timer to expire. This function
   * blocks and does not return until the timer has expired.
   *
   * @throws asio::system_error Thrown on failure.
   */
  void wait()
  {
    asio::error_code ec;
    this->service.wait(this->implementation, ec);
    asio::detail::throw_error(ec, "wait");
  }

  /// Perform a blocking wait on the timer.
  /**
   * This function is used to wait for the timer to expire. This function
   * blocks and does not return until the timer has expired.
   *
   * @param ec Set to indicate what error occurred, if any.
   */
  void wait(asio::error_code& ec)
  {
    this->service.wait(this->implementation, ec);
  }

  /// Start an asynchronous wait on the timer.
  /**
   * This function may be used to initiate an asynchronous wait against the
   * timer. It always returns immediately.
   *
   * For each call to async_wait(), the supplied handler will be called exactly
   * once. The handler will be called when:
   *
   * @li The timer has expired.
   *
   * @li The timer was cancelled, in which case the handler is passed the error
   * code asio::error::operation_aborted.
   *
   * @param handler The handler to be called when the timer expires. Copies
   * will be made of the handler as required. The function signature of the
   * handler must be:
   * @code void handler(
   *   const asio::error_code& error // Result of operation.
   * ); @endcode
   * Regardless of whether the asynchronous operation completes immediately or
   * not, the handler will not be invoked from within this function. Invocation
   * of the handler will be performed in a manner equivalent to using
   * asio::io_service::post().
   */
  template <typename WaitHandler>
  ASIO_INITFN_RESULT_TYPE(WaitHandler,
      void (asio::error_code))
  async_wait(ASIO_MOVE_ARG(WaitHandler) handler)
  {
    // If you get an error on the following line it means that your handler does
    // not meet the documented type requirements for a WaitHandler.
    ASIO_WAIT_HANDLER_CHECK(WaitHandler, handler) type_check;

    return this->service.async_wait(this->implementation,
        ASIO_MOVE_CAST(WaitHandler)(handler));
  }
};

} // namespace asio

#include "asio/detail/pop_options.hpp"

#endif // ASIO_BASIC_WAITABLE_TIMER_HPP
