nadekobot/src/NadekoBot/Modules/Music/Common/Impl/MultimediaTimer.cs

using System.Runtime.InteropServices;

namespace NadekoBot.Modules.Music.Common;

public sealed class MultimediaTimer : IDisposable
{
    private delegate void LpTimeProcDelegate(uint uTimerID, uint uMsg, int dwUser, int dw1, int dw2);

    /// <summary>
    /// The timeSetEvent function starts a specified timer event. The multimedia timer runs in its own thread.
    /// After the event is activated, it calls the specified callback function or sets or pulses the specified
    /// event object.
    /// </summary>
    /// <param name="uDelay">
    /// Event delay, in milliseconds. If this value is not in the range of the minimum and
    /// maximum event delays supported by the timer, the function returns an error.
    /// </param>
    /// <param name="uResolution">
    /// Resolution of the timer event, in milliseconds. The resolution increases with
    /// smaller values; a resolution of 0 indicates periodic events should occur with the greatest possible accuracy.
    /// To reduce system overhead, however, you should use the maximum value appropriate for your application.
    /// </param>
    /// <param name="lpTimeProc">
    /// Pointer to a callback function that is called once upon expiration of a single event or periodically upon
    /// expiration of periodic events. If fuEvent specifies the TIME_CALLBACK_EVENT_SET or TIME_CALLBACK_EVENT_PULSE
    /// flag, then the lpTimeProc parameter is interpreted as a handle to an event object. The event will be set or
    /// pulsed upon completion of a single event or periodically upon completion of periodic events.
    /// For any other value of fuEvent, the lpTimeProc parameter is a pointer to a callback function of type
    /// LPTIMECALLBACK.
    /// </param>
    /// <param name="dwUser">User-supplied callback data.</param>
    /// <param name="fuEvent"></param>
    /// <returns>Timer event type. This parameter may include one of the following values.</returns>
    [DllImport("Winmm.dll")]
    private static extern uint timeSetEvent(
        uint uDelay,
        uint uResolution,
        LpTimeProcDelegate lpTimeProc,
        int dwUser,
        TimerMode fuEvent
    );

    private enum TimerMode
    {
        OneShot,
        Periodic,
    }
        
    /// <summary>
    /// The timeKillEvent function cancels a specified timer event.
    /// </summary>
    /// <param name="uTimerID">
    /// Identifier of the timer event to cancel.
    /// This identifier was returned by the timeSetEvent function when the timer event was set up.
    /// </param>
    /// <returns>Returns TIMERR_NOERROR if successful or MMSYSERR_INVALPARAM if the specified timer event does not exist.</returns>
    [DllImport("Winmm.dll")]
    private static extern int timeKillEvent(
        uint uTimerID
    );

    private LpTimeProcDelegate _lpTimeProc;
    private readonly uint _eventId;
    private readonly Action<object> _callback;
    private readonly object _state;

    public MultimediaTimer(Action<object> callback, object state, int period)
    {
        if (period <= 0)
            throw new ArgumentOutOfRangeException(nameof(period), "Period must be greater than 0");

        _callback = callback;
        _state = state;

        _lpTimeProc = CallbackInternal;
        _eventId = timeSetEvent((uint)period, 1, _lpTimeProc, 0, TimerMode.Periodic);
    }

    private void CallbackInternal(uint uTimerId, uint uMsg, int dwUser, int dw1, int dw2)
    {
        _callback(_state);
    }

    public void Dispose()
    {
        _lpTimeProc = default;
        timeKillEvent(_eventId);
    }
}