Robovoice/Robovoice.App/Orchestrator.cs

using Robovoice.Core;
using Robovoice.Tts.LibPiper;

namespace Robovoice.App;

internal sealed class Orchestrator : IAsyncDisposable
{
    private readonly LibPiperTtsEngine _tts;
    private readonly AudioOutput _audioOutput;
    private readonly ISttSource _sttSource;
    private readonly Action<string> _log;
    private CancellationTokenSource? _currentCts;
    private bool _disposed;

    private readonly object _stateLock = new();
    private readonly Queue<string> _pendingTexts = new();
    private readonly List<float[]> _audioBuffer = new();
    private int _bufferSampleRate;
    private bool _playing;
    private Task? _synthTask;
    private CancellationTokenSource? _synthCts;
    private System.Threading.Timer? _segmentTimer;
    private static readonly TimeSpan SegmentTimeout = TimeSpan.FromMilliseconds(250);

    public string OutputDeviceName { get; set; } = string.Empty;

    public Orchestrator(
        LibPiperTtsEngine tts,
        AudioOutput audioOutput,
        ISttSource sttSource,
        Action<string> log)
    {
        _tts = tts;
        _audioOutput = audioOutput;
        _audioOutput.Log = log;
        _sttSource = sttSource;
        _log = log;
        _sttSource.TranscriptReceived += OnTranscript;
    }

    private void OnTranscript(object? sender, TranscriptEventArgs e)
    {
        var msg = e.Message;

        lock (_stateLock)
        {
            if (msg.Type == TranscriptType.Partial)
            {
                if (!string.IsNullOrWhiteSpace(msg.Text))
                {
                    _log($"SEGMENT: \"{msg.Text}\" ({msg.Text.Length} chars)");
                    _pendingTexts.Enqueue(msg.Text);
                    EnsureSynthTask();
                    ResetSegmentTimer();
                }
            }
            else
            {
                if (!string.IsNullOrWhiteSpace(msg.Text))
                {
                    _log($"FINAL: \"{msg.Text}\" ({msg.Text.Length} chars)");
                    _pendingTexts.Enqueue(msg.Text);
                    EnsureSynthTask();
                }
                else
                {
                    _log("FINAL: (empty)");
                }

                CancelSegmentTimer();
                TransitionToPlaying();
            }
        }
    }

    private void ResetSegmentTimer()
    {
        _segmentTimer?.Dispose();
        _segmentTimer = new System.Threading.Timer(_ => OnSegmentTimeout(), null, SegmentTimeout, Timeout.InfiniteTimeSpan);
    }

    private void CancelSegmentTimer()
    {
        _segmentTimer?.Dispose();
        _segmentTimer = null;
    }

    private void OnSegmentTimeout()
    {
        _log("STT: segment timeout, starting playback early");
        lock (_stateLock)
        {
            TransitionToPlaying();
        }
    }

    private void TransitionToPlaying()
    {
        if (_playing)
            return;

        if (_audioBuffer.Count == 0)
        {
            if (_synthTask is null || _synthTask.IsCompleted)
            {
                _log("TTS: nothing to play");
                CancelSegmentTimer();
            }
            return;
        }

        _playing = true;
        CancelSegmentTimer();

        int sampleRate = _bufferSampleRate;
        var chunks = _audioBuffer.ToList();
        _audioBuffer.Clear();

        _log($"TTS: playing {chunks.Count} buffered chunks ({sampleRate} Hz)");

        _audioOutput.Start(sampleRate, OutputDeviceName);
        foreach (var samples in chunks)
        {
            _audioOutput.WriteSamples(samples);
        }
    }

    private void EnsureSynthTask()
    {
        if (_synthTask is not null && !_synthTask.IsCompleted)
            return;

        _synthCts?.Cancel();
        _synthCts = new CancellationTokenSource();
        _synthTask = SynthLoopAsync(_synthCts.Token);
    }

    private async Task SynthLoopAsync(CancellationToken ct)
    {
        while (true)
        {
            string text;
            lock (_stateLock)
            {
                if (_pendingTexts.Count == 0)
                    break;
                text = _pendingTexts.Dequeue();
            }

            try
            {
                await foreach (var chunk in _tts.SynthesizeAsync(text, ct))
                {
                    lock (_stateLock)
                    {
                        if (_playing)
                        {
                            _audioOutput.WriteSamples(chunk.Samples);
                        }
                        else
                        {
                            _bufferSampleRate = chunk.SampleRate;
                            _audioBuffer.Add(chunk.Samples);
                        }
                    }
                }
            }
            catch (OperationCanceledException)
            {
                break;
            }
            catch (Exception ex)
            {
                _log($"TTS error: {ex.Message}");
            }
        }

        lock (_stateLock)
        {
            if (_playing)
            {
                _audioOutput.Flush();
                _log("TTS: synthesis complete, flushed");
            }
        }
    }

    public void NotifyPttPressed()
    {
        lock (_stateLock)
        {
            CancelSegmentTimer();
            _synthCts?.Cancel();
            _synthCts?.Dispose();
            _synthTask = null;

            if (_playing)
            {
                _audioOutput.Stop();
                _playing = false;
            }

            _pendingTexts.Clear();
            _audioBuffer.Clear();
            _bufferSampleRate = 0;
        }
    }

    public async Task InitializeTtsAsync()
    {
        _log("Initializing TTS engine...");
        await _tts.InitializeAsync();
        _log($"TTS ready (sample rate: {_tts.SampleRate} Hz)");
    }

    public async Task SynthesizeAsync(string text)
    {
        _currentCts?.Cancel();
        _currentCts = new CancellationTokenSource();
        var ct = _currentCts.Token;

        var sw = System.Diagnostics.Stopwatch.StartNew();
        _log($"Speak: \"{text}\" ({text.Length} chars)");

        try
        {
            bool started = false;
            int chunkCount = 0;
            int totalSamples = 0;

            await foreach (var chunk in _tts.SynthesizeAsync(text, ct))
            {
                if (!started)
                {
                    started = true;
                    _audioOutput.Start(chunk.SampleRate, OutputDeviceName);
                    _log($"TTS: first chunk ({sw.ElapsedMilliseconds}ms)");
                }

                _audioOutput.WriteSamples(chunk.Samples);
                chunkCount++;
                totalSamples += chunk.Samples.Length;
            }

            if (!started)
            {
                _log("TTS: no audio produced");
            }
            else
            {
                _audioOutput.Flush();
                double durationSec = (double)totalSamples / _tts.SampleRate;
                _log($"TTS: done ({chunkCount} chunks, {durationSec:F2}s audio, {sw.ElapsedMilliseconds}ms)");
            }
        }
        catch (OperationCanceledException)
        {
            _log("TTS: cancelled");
            _audioOutput.Stop();
        }
        catch (Exception ex)
        {
            _log($"TTS error: {ex.Message}");
        }

        sw.Stop();
    }

    public async ValueTask DisposeAsync()
    {
        if (_disposed) return;
        _currentCts?.Cancel();
        _currentCts?.Dispose();
        _synthCts?.Cancel();
        _synthCts?.Dispose();
        CancelSegmentTimer();
        _sttSource.TranscriptReceived -= OnTranscript;
        await _sttSource.DisposeAsync();
        await _tts.DisposeAsync();
        _audioOutput.Dispose();
        _disposed = true;
    }
}