"""
Microphone input monitor — standalone, no internal dependencies.
Gracefully degrades if sounddevice/numpy are unavailable.
"""

import atexit

try:
    import numpy as _np
    import sounddevice as _sd
    _HAS_MIC = True
except Exception:
    _HAS_MIC = False


class MicMonitor:
    """Background mic stream that exposes current RMS dB level."""

    def __init__(self, threshold_db=50):
        self.threshold_db = threshold_db
        self._db = -99.0
        self._stream = None

    @property
    def available(self):
        """True if sounddevice is importable."""
        return _HAS_MIC

    @property
    def db(self):
        """Current RMS dB level."""
        return self._db

    @property
    def excess(self):
        """dB above threshold (clamped to 0)."""
        return max(0.0, self._db - self.threshold_db)

    def start(self):
        """Start background mic stream. Returns True on success, False/None otherwise."""
        if not _HAS_MIC:
            return None
        def _cb(indata, frames, t, status):
            rms = float(_np.sqrt(_np.mean(indata ** 2)))
            self._db = 20 * _np.log10(rms) if rms > 0 else -99.0
        try:
            self._stream = _sd.InputStream(
                callback=_cb, channels=1, samplerate=44100, blocksize=2048)
            self._stream.start()
            atexit.register(self.stop)
            return True
        except Exception:
            return False

    def stop(self):
        """Stop the mic stream if running."""
        if self._stream:
            try:
                self._stream.stop()
            except Exception:
                pass
            self._stream = None