mic-system/stt_bridge.py

"""Bridge between AudioEngine and stt.mm.mk WebSocket STT service.

Runs STT WebSocket in a **subprocess** to avoid conflicts with eventlet.
Communication: stdin (length-prefixed PCM binary) / stdout (JSON lines).
"""
from __future__ import annotations

import json
import logging
import os
import subprocess
import threading
import time
from dataclasses import dataclass
from pathlib import Path

import numpy as np

logger = logging.getLogger("stt_bridge")

_WORKER_PATH = str(Path(__file__).resolve().parent / "stt_worker.py")
_VENV_PYTHON = str(Path(__file__).resolve().parent / ".venv" / "bin" / "python")


@dataclass
class SttSettings:
    enabled: bool = False
    language: str = "pl"
    timestamps: bool = True
    diarize: bool = True
    itn: bool = True
    detect_emotion: bool = False
    server_vad: bool = False
    vad_threshold: float = 0.3
    vad_pad_ms: int = 400
    vad_min_ms: int = 100


class SttBridge:
    """Manages subprocess STT worker that connects to stt.mm.mk."""

    STT_URL = "wss://stt.mm.mk/ws/transcribe"

    def __init__(self, on_message=None):
        self._lock = threading.Lock()
        self._settings = SttSettings()
        self._on_message = on_message
        self._process: subprocess.Popen | None = None
        self._reader_thread: threading.Thread | None = None
        self._connected = False
        self._sample_rate = 16000

    def get_settings(self) -> dict:
        with self._lock:
            return {
                "stt_enabled": self._settings.enabled,
                "stt_language": self._settings.language,
                "stt_timestamps": self._settings.timestamps,
                "stt_diarize": self._settings.diarize,
                "stt_itn": self._settings.itn,
                "stt_detect_emotion": self._settings.detect_emotion,
                "stt_server_vad": self._settings.server_vad,
                "stt_vad_threshold": self._settings.vad_threshold,
                "stt_vad_pad_ms": self._settings.vad_pad_ms,
                "stt_vad_min_ms": self._settings.vad_min_ms,
                "stt_connected": self._connected,
            }

    def update_settings(self, **kwargs) -> dict:
        reconnect_keys = {
            "language", "timestamps", "diarize", "itn",
            "detect_emotion", "server_vad", "vad_threshold",
            "vad_pad_ms", "vad_min_ms",
        }
        changed_enabled = False
        need_reconnect = False

        with self._lock:
            for key, val in kwargs.items():
                attr = key.replace("stt_", "")
                if hasattr(self._settings, attr):
                    old = getattr(self._settings, attr)
                    setattr(self._settings, attr, type(old)(val))
                    if attr == "enabled" and old != self._settings.enabled:
                        changed_enabled = True
                    if attr in reconnect_keys:
                        need_reconnect = True

        if changed_enabled:
            if self._settings.enabled:
                self._start_worker()
            else:
                self._stop_worker()
        elif self._settings.enabled and self._process is not None and need_reconnect:
            self._stop_worker()
            self._start_worker()

        return self.get_settings()

    def feed_audio(self, audio: np.ndarray, sample_rate: int) -> None:
        """Feed processed audio to STT subprocess. Non-blocking."""
        proc = self._process
        if proc is None or proc.poll() is not None:
            return
        if not self._settings.enabled:
            return

        self._sample_rate = sample_rate
        pcm16 = (np.clip(audio, -1.0, 1.0) * 32767).astype(np.int16)
        payload = pcm16.tobytes()

        try:
            # Length-prefixed binary: 4 bytes little-endian length + PCM data
            header = len(payload).to_bytes(4, "little")
            proc.stdin.write(header + payload)
            proc.stdin.flush()
        except (BrokenPipeError, OSError):
            pass

    def _build_url(self) -> str:
        s = self._settings
        parts = [
            "language=" + s.language,
            "rate=" + str(self._sample_rate),
            "stream_id=mic-system-" + str(int(time.time())),
        ]
        if s.timestamps:
            parts.append("timestamps=1")
        if s.diarize:
            parts.append("diarize=1")
        if s.itn:
            parts.append("itn=1")
        if s.detect_emotion:
            parts.append("detect_emotion=1")
        if s.server_vad:
            parts.append("vad=1")
            parts.append("vad_threshold=" + str(s.vad_threshold))
            parts.append("vad_pad_ms=" + str(s.vad_pad_ms))
            parts.append("vad_min_ms=" + str(s.vad_min_ms))
        return self.STT_URL + "?" + "&".join(parts)

    def _start_worker(self):
        url = self._build_url()
        logger.info("STT starting worker subprocess: %s", url)

        python = _VENV_PYTHON if os.path.exists(_VENV_PYTHON) else "python3"

        try:
            self._process = subprocess.Popen(
                [python, _WORKER_PATH, url],
                stdin=subprocess.PIPE,
                stdout=subprocess.PIPE,
                stderr=subprocess.DEVNULL,
                bufsize=0,
            )
        except Exception as e:
            logger.error("Failed to start STT worker: %s", e)
            return

        self._reader_thread = threading.Thread(
            target=self._read_stdout,
            daemon=True,
        )
        self._reader_thread.start()

    def _read_stdout(self):
        """Read JSON lines from worker stdout and forward via callback."""
        proc = self._process
        if proc is None:
            return

        try:
            for line in proc.stdout:
                line = line.strip()
                if not line:
                    continue
                try:
                    msg = json.loads(line)
                except (json.JSONDecodeError, ValueError):
                    continue

                if msg.get("type") == "stt_status":
                    self._connected = bool(msg.get("connected", False))

                if self._on_message:
                    self._on_message(msg)
        except Exception:
            pass
        finally:
            self._connected = False
            if self._on_message:
                self._on_message({"type": "stt_status", "connected": False})

    def _stop_worker(self):
        self._connected = False
        proc = self._process
        self._process = None
        if proc is not None:
            try:
                proc.stdin.close()
            except Exception:
                pass
            try:
                proc.terminate()
                proc.wait(timeout=3)
            except Exception:
                try:
                    proc.kill()
                except Exception:
                    pass
        self._reader_thread = None

    def stop(self):
        self._stop_worker()