meeting-assistant/MeetingAssistant/Workflow/WorkflowRulesEditorSamplePlaybackQueue.cs

using System.Threading.Channels;
using NAudio.Wave;

namespace MeetingAssistant.Workflow;

public interface IWorkflowRulesEditorSamplePlaybackQueue
{
    Task<string> QueueAsync(int sampleId, byte[] wavBytes, CancellationToken cancellationToken = default);
}

public sealed class WorkflowRulesEditorSamplePlaybackQueue : IWorkflowRulesEditorSamplePlaybackQueue, IDisposable
{
    private readonly Channel<QueuedSample> channel = Channel.CreateUnbounded<QueuedSample>();
    private readonly ILogger<WorkflowRulesEditorSamplePlaybackQueue> logger;
    private readonly CancellationTokenSource cancellation = new();
    private readonly Task playbackTask;

    public WorkflowRulesEditorSamplePlaybackQueue(ILogger<WorkflowRulesEditorSamplePlaybackQueue> logger)
    {
        this.logger = logger;
        playbackTask = Task.Run(PlayQueuedSamplesAsync);
    }

    public async Task<string> QueueAsync(
        int sampleId,
        byte[] wavBytes,
        CancellationToken cancellationToken = default)
    {
        if (wavBytes.Length == 0)
        {
            return $"Sample {sampleId} is empty and was not queued.";
        }

        await channel.Writer.WriteAsync(new QueuedSample(sampleId, wavBytes), cancellationToken);
        return $"Queued sample {sampleId} for playback.";
    }

    public void Dispose()
    {
        cancellation.Cancel();
        channel.Writer.TryComplete();
        try
        {
            playbackTask.Wait(TimeSpan.FromSeconds(2));
        }
        catch
        {
        }

        cancellation.Dispose();
    }

    private async Task PlayQueuedSamplesAsync()
    {
        try
        {
            await foreach (var sample in channel.Reader.ReadAllAsync(cancellation.Token))
            {
                try
                {
                    await PlayAsync(sample, cancellation.Token);
                }
                catch (OperationCanceledException) when (cancellation.IsCancellationRequested)
                {
                    break;
                }
                catch (Exception exception)
                {
                    logger.LogWarning(
                        exception,
                        "Could not play queued speaker identity sample {SampleId}",
                        sample.SampleId);
                }
            }
        }
        catch (OperationCanceledException) when (cancellation.IsCancellationRequested)
        {
        }
    }

    private static async Task PlayAsync(QueuedSample sample, CancellationToken cancellationToken)
    {
        await using var stream = new MemoryStream(sample.WavBytes, writable: false);
        using var reader = new WaveFileReader(stream);
        using var output = new WaveOutEvent();
        var completed = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
        output.PlaybackStopped += (_, _) => completed.TrySetResult();
        output.Init(reader);
        output.Play();

        await using var registration = cancellationToken.Register(() =>
        {
            output.Stop();
            completed.TrySetCanceled(cancellationToken);
        });
        await completed.Task;
    }

    private sealed record QueuedSample(int SampleId, byte[] WavBytes);
}