/// <summary>
/// Synchronously adds the <paramref name="cameraTask"/> given to an execution queue
/// and returns awaitable task to wait for the <paramref name="cameraTask"/> completion.
/// </summary>
/// <param name="cameraTask">Task to enqueue.</param>
/// <returns>Awaitable task.</returns>
/// <exception cref="ArgumentNullException"><paramref name="cameraTask"/> is <see langword="null"/>.</exception>
public Task EnqueueTaskAsync(ICameraTask cameraTask)
{
if (cameraTask == null)
{
throw new ArgumentNullException("cameraTask");
}
QueuedCameraTask task = this.AddTaskToQueue(cameraTask);
return(Task.Run(() => task.WaitForComplete(Timeout.InfiniteTimeSpan)));
}
/// <summary>
/// Adds the <paramref name="cameraTask"/> specified to the execution queue.
/// </summary>
/// <param name="cameraTask">The camera task to add to the queue.</param>
/// <returns>Execution wrapper for the <paramref name="cameraTask"/> given.</returns>
private QueuedCameraTask AddTaskToQueue(ICameraTask cameraTask)
{
QueuedCameraTask queuedTask = new QueuedCameraTask(cameraTask);
lock (this.syncRoot)
{
this.pendingTasks.Add(queuedTask);
this.ScheduleNextTask();
}
return(queuedTask);
}
/// <summary>
/// Schedules the next pending task for execution, if needed.
/// </summary>
private void ScheduleNextTask()
{
lock (this.syncRoot)
{
if (this.currentTask != null || !this.pendingTasks.Any())
{
return;
}
this.currentTask = this.pendingTasks[0];
this.currentTask.Task.Complete += this.CameraTaskCompleted;
this.pendingTasks.RemoveAt(0);
ThreadPool.QueueUserWorkItem(state => this.StartCurrentTask());
}
}
/// <summary>
/// The <see cref="ICameraTask.Complete"/> event handler.
/// </summary>
/// <param name="sender">Event sender.</param>
/// <param name="e">The <see cref="EventArgs"/> instance containing the event data.</param>
private void CameraTaskCompleted(object sender, EventArgs e)
{
lock (this.syncRoot)
{
// Makes sure that the current method isn't called for the second
// time for the same task.
if (this.currentTask == null || this.currentTask.Task != sender)
{
return;
}
this.currentTask.Task.Complete -= this.CameraTaskCompleted;
this.currentTask.Dispose();
this.currentTask = null;
this.ScheduleNextTask();
}
}
/// <summary>
/// The <see cref="ICameraTask.Complete"/> event handler.
/// </summary>
/// <param name="sender">Event sender.</param>
/// <param name="e">The <see cref="EventArgs"/> instance containing the event data.</param>
private void CameraTaskCompleted(object sender, EventArgs e)
{
lock (this.syncRoot)
{
// Makes sure that the current method isn't called for the second
// time for the same task.
if (this.currentTask == null || this.currentTask.Task != sender)
{
return;
}
this.currentTask.Task.Complete -= this.CameraTaskCompleted;
this.currentTask.Dispose();
this.currentTask = null;
this.ScheduleNextTask();
}
}
/// <summary>
/// Schedules the next pending task for execution, if needed.
/// </summary>
private void ScheduleNextTask()
{
lock (this.syncRoot)
{
if (this.currentTask != null || !this.pendingTasks.Any())
{
return;
}
this.currentTask = this.pendingTasks[0];
this.currentTask.Task.Complete += this.CameraTaskCompleted;
this.pendingTasks.RemoveAt(0);
ThreadPool.QueueUserWorkItem(state => this.StartCurrentTask());
}
}
/// <summary>
/// Adds the <paramref name="cameraTask"/> specified to the execution queue.
/// </summary>
/// <param name="cameraTask">The camera task to add to the queue.</param>
/// <returns>Execution wrapper for the <paramref name="cameraTask"/> given.</returns>
private QueuedCameraTask AddTaskToQueue(ICameraTask cameraTask)
{
QueuedCameraTask queuedTask = new QueuedCameraTask(cameraTask);
lock (this.syncRoot)
{
this.pendingTasks.Add(queuedTask);
this.ScheduleNextTask();
}
return queuedTask;
}
