"""Audio level computation implementation.

Provides RMS and dB level calculation for VU meter display.
"""

from __future__ import annotations

import math
from typing import Final

import numpy as np
from numpy.typing import NDArray


class RmsLevelProvider:
    """RMS-based audio level provider.

    Computes RMS (Root Mean Square) level from audio frames for VU meter display.
    """

    # Minimum dB value to report (silence threshold)
    MIN_DB: Final[float] = -60.0

    def get_rms(self, frames: NDArray[np.float32]) -> float:
        """Calculate RMS level from audio frames.

        Args:
            frames: Audio samples as float32 array (normalized -1.0 to 1.0).

        Returns:
            RMS level normalized to 0.0-1.0 range.
        """
        if len(frames) == 0:
            return 0.0

        # Calculate RMS: sqrt(mean(samples^2))
        rms = float(np.sqrt(np.mean(frames.astype(np.float64) ** 2)))

        # Clamp to 0.0-1.0 range
        return min(1.0, max(0.0, rms))

    def get_db(self, frames: NDArray[np.float32]) -> float:
        """Calculate dB level from audio frames.

        Args:
            frames: Audio samples as float32 array (normalized -1.0 to 1.0).

        Returns:
            Level in dB (MIN_DB to 0 range).
        """
        rms = self.get_rms(frames)

        if rms <= 0:
            return self.MIN_DB

        # Convert to dB: 20 * log10(rms)
        db = 20.0 * math.log10(rms)

        # Clamp to MIN_DB to 0 range
        return max(self.MIN_DB, min(0.0, db))

    def rms_to_db(self, rms: float) -> float:
        """Convert RMS value to dB.

        Args:
            rms: RMS level (0.0-1.0).

        Returns:
            Level in dB (MIN_DB to 0 range).
        """
        if rms <= 0:
            return self.MIN_DB

        db = 20.0 * math.log10(rms)
        return max(self.MIN_DB, min(0.0, db))

    def db_to_rms(self, db: float) -> float:
        """Convert dB value to RMS.

        Args:
            db: Level in dB.

        Returns:
            RMS level (0.0-1.0).
        """
        return 0.0 if db <= self.MIN_DB else 10.0 ** (db / 20.0)