ts3java/ts3-client/swing/src/main/java/com/ts3client/ui/MicrophoneTest.java

package com.ts3client.ui;

import com.ts3client.audio.AudioBackend;
import com.ts3client.audio.AudioPlayback;
import com.ts3client.audio.VoiceInput;
import com.ts3client.config.Settings;

import javax.swing.SwingUtilities;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.function.Consumer;

/**
 * Drives the settings dialog's microphone test from a real capture chain.
 *
 * <p>The dialog runs its own {@link VoiceInput} rather than borrowing the connected
 * one, whose listeners belong to the connection. Because it is the same class that feeds
 * the server, the level and the gate shown here are exactly what would be transmitted —
 * pre-processing, voice detection, hangover and pre-roll included.
 *
 * <p>Loopback is optional: when enabled, the frames that would be sent are played back
 * locally so you can hear precisely what the other side would.
 */
final class MicrophoneTest {

    /** Frames buffered for loopback before the oldest is dropped (~100 ms). */
    private static final int LOOPBACK_QUEUE_FRAMES = 5;

    private final Consumer<Double> onLevel;
    private final Consumer<Boolean> onTransmitting;

    private final AudioBackend audio;
    private VoiceInput mic;

    private final ArrayBlockingQueue<byte[]> loopbackQueue =
            new ArrayBlockingQueue<>(LOOPBACK_QUEUE_FRAMES);
    private volatile boolean loopbackEnabled;
    private volatile boolean loopbackRunning;
    private Thread loopbackThread;
    private String outputDevice = "";

    MicrophoneTest(AudioBackend audio, Consumer<Double> onLevel, Consumer<Boolean> onTransmitting) {
        this.audio = audio;
        this.onLevel = onLevel;
        this.onTransmitting = onTransmitting;
    }

    /** Whether a capture chain is currently running. */
    boolean isRunning() {
        return mic != null;
    }

    /**
     * (Re)starts the test chain against {@code settings}' devices and voice options.
     *
     * @return false if the capture device could not be opened
     */
    boolean start(Settings settings) {
        stop();
        VoiceInput input = audio.createInput(settings);
        input.setLevelListener(db -> SwingUtilities.invokeLater(() -> onLevel.accept(db)));
        input.setTalkListener(talking -> SwingUtilities.invokeLater(() -> onTransmitting.accept(talking)));
        input.setMonitorListener(this::enqueueForLoopback);
        this.outputDevice = settings.outputDevice;
        try {
            input.start();
        } catch (RuntimeException e) {
            return false; // Device busy or gone; leave the test switched off.
        }
        this.mic = input;
        return true;
    }

    /**
     * Stops the capture chain. The caller owns the UI reset: doing it here would race with
     * a restart, whose own state has already been put on screen.
     */
    void stop() {
        setLoopback(false);
        if (mic != null) {
            mic.stop();
            mic = null;
        }
    }

    /** Applies a change to the test chain, if it is running. */
    void configure(Consumer<VoiceInput> change) {
        VoiceInput m = mic;
        if (m != null) change.accept(m);
    }

    /** The playback device to loop back through; takes effect on the next enable. */
    void setOutputDevice(String deviceId) {
        this.outputDevice = deviceId == null ? "" : deviceId;
    }

    void setLoopback(boolean enabled) {
        if (enabled == loopbackEnabled) {
            return;
        }
        loopbackEnabled = enabled;
        if (enabled) {
            loopbackRunning = true;
            loopbackThread = new Thread(this::loopbackLoop, "settings-loopback");
            loopbackThread.setDaemon(true);
            loopbackThread.start();
        } else {
            loopbackRunning = false;
            if (loopbackThread != null) {
                loopbackThread.interrupt();
                loopbackThread = null;
            }
            loopbackQueue.clear();
        }
    }

    /**
     * Converts a transmitted frame to 16-bit PCM and queues it. Runs on the capture thread,
     * so it must not block: a full queue means playback has fallen behind and the oldest
     * frame is dropped instead.
     */
    private void enqueueForLoopback(float[] interleaved, int channels) {
        if (!loopbackEnabled) {
            return;
        }
        byte[] pcm = toPcm16(interleaved);
        if (!loopbackQueue.offer(pcm)) {
            loopbackQueue.poll();
            loopbackQueue.offer(pcm);
        }
    }

    private void loopbackLoop() {
        AudioPlayback line = null;
        try {
            // The monitored frames are mono for voice; ask for a matching line so no
            // channel juggling is needed, and up-mix only if the device insists on stereo.
            line = audio.io().openPlayback(outputDevice, 1);
            line.start();
            int channels = line.channels();
            while (loopbackRunning) {
                byte[] frame = loopbackQueue.poll(100, java.util.concurrent.TimeUnit.MILLISECONDS);
                if (frame == null) {
                    continue;
                }
                byte[] out = (channels == 1) ? frame : upmix(frame, channels);
                line.write(out, 0, out.length);
            }
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        } catch (Exception ignored) {
            // The device may be busy or gone; the test simply runs without loopback.
        } finally {
            if (line != null) line.close();
        }
    }

    /** Converts float samples in [-1, 1] to 16-bit little-endian PCM. */
    static byte[] toPcm16(float[] samples) {
        byte[] pcm = new byte[samples.length * 2];
        for (int i = 0; i < samples.length; i++) {
            float f = samples[i];
            if (f > 1f) f = 1f;
            else if (f < -1f) f = -1f;
            int s = Math.round(f * 32767f);
            pcm[2 * i] = (byte) (s & 0xFF);
            pcm[2 * i + 1] = (byte) ((s >> 8) & 0xFF);
        }
        return pcm;
    }

    /** Copies a mono frame across {@code channels} interleaved channels. */
    static byte[] upmix(byte[] mono, int channels) {
        byte[] out = new byte[mono.length * channels];
        for (int i = 0, frames = mono.length / 2; i < frames; i++) {
            for (int c = 0; c < channels; c++) {
                out[2 * (i * channels + c)] = mono[2 * i];
                out[2 * (i * channels + c) + 1] = mono[2 * i + 1];
            }
        }
        return out;
    }
}