/*
  ==============================================================================

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

   JUCE is an open source framework subject to commercial or open source
   licensing.

   By downloading, installing, or using the JUCE framework, or combining the
   JUCE framework with any other source code, object code, content or any other
   copyrightable work, you agree to the terms of the JUCE End User Licence
   Agreement, and all incorporated terms including the JUCE Privacy Policy and
   the JUCE Website Terms of Service, as applicable, which will bind you. If you
   do not agree to the terms of these agreements, we will not license the JUCE
   framework to you, and you must discontinue the installation or download
   process and cease use of the JUCE framework.

   JUCE End User Licence Agreement: https://juce.com/legal/juce-9-licence/
   JUCE Privacy Policy: https://juce.com/juce-privacy-policy
   JUCE Website Terms of Service: https://juce.com/juce-website-terms-of-service/

   Or:

   You may also use this code under the terms of the AGPLv3:
   https://www.gnu.org/licenses/agpl-3.0.en.html

   THE JUCE FRAMEWORK IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL
   WARRANTIES, WHETHER EXPRESSED OR IMPLIED, INCLUDING WARRANTY OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

/**
    A high-resolution periodic timer.

    This provides accurately-timed regular callbacks. Unlike the normal Timer
    class, this one uses a dedicated thread, not the message thread, so is
    far more stable and precise.

    You should only use this class in situations where you really need accuracy,
    because unlike the normal Timer class, which is very lightweight and cheap
    the HighResolutionTimer will use far more resources and require thread
    safety considerations.

    @see Timer

    @tags{Core}
*/
class JUCE_API  HighResolutionTimer
{
protected:
    /** Creates a HighResolutionTimer.
        When created, the timer is stopped, so use startTimer() to get it going.
    */
    HighResolutionTimer();

public:
    /** Destructor. */
    virtual ~HighResolutionTimer();

    //==============================================================================
    /** The user-defined callback routine that actually gets called periodically.

        This will be called on a dedicated timer thread, so make sure your
        implementation is thread-safe!

        On some platforms the dedicated timer thread may be shared with
        other HighResolutionTimer's so aim to complete any work in this
        callback as fast as possible.

        It's perfectly ok to call startTimer() or stopTimer() from within this
        callback to change the subsequent intervals. However, if you call
        stopTimer() in the callback it's still best practice to call stopTimer()
        from the destructor in order to avoid data races.
    */
    virtual void hiResTimerCallback() = 0;

    //==============================================================================
    /** Starts the timer and sets the length of interval required.

        If the timer has already started, this will reset the timer, so the time
        between calling this method and the next timer callback will not be less
        than the interval length passed in.

        In exceptional circumstances the dedicated timer thread may not start,
        if this is a potential concern for your use case, you can call
        isTimerRunning() to confirm if the timer actually started.

        On Windows the underlying API only allows 16 high-resolution timers to
        run simultaneously in the same process. A fallback timer will be used
        when this limit is exceeded but the precision may be significantly
        compromised. This is a particular concern for plugins, because other
        plugins in the same host process may already have timers running.
        To avoid issues, try to use the minimum number of HighResolutionTimers
        possible. For example, consider using a SharedResourcePointer so that
        all instances of the same plugin running in the same same process can
        share a single HighResolutionTimer instance.

        @param  intervalInMilliseconds  the interval to use (a value of zero or less will stop the timer)
    */
    void startTimer (int intervalInMilliseconds);

    /** Stops the timer.

        This method may block while it waits for pending callbacks to complete.
        Once it returns, no more callbacks will be made. If it is called from
        the timer's own thread, it will cancel the timer after the current
        callback returns.

        To prevent data races it's normally best practice to call this in the
        derived classes destructor, even if stopTimer() was called in the
        hiResTimerCallback().
    */
    void stopTimer();

    /** Checks if the timer has been started.
        @returns true if the timer is running.
    */
    bool isTimerRunning() const noexcept;

    /** Returns the timer's interval.
        @returns the timer's interval in milliseconds if it's running, or 0 if it's not.
    */
    int getTimerInterval() const noexcept;

private:
    class Impl;
    std::unique_ptr<Impl> impl;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (HighResolutionTimer)
};

} // namespace juce
