"""D1: EBU R128 loudness + true peak metrics (app/core/loudness.py)."""
import numpy as np

from app.core import loudness


def _sine(dbfs, sr=44100, sec=3.0, freq=1000.0):
    t = np.arange(int(sr * sec)) / sr
    x = (10 ** (dbfs / 20.0)) * np.sin(2 * np.pi * freq * t)
    return np.stack([x, x])


def test_sine_minus20_lufs():
    # 1 kHz sine @ -20 dBFS: RMS -23.01 dB + K-weight +0.44 dB - 0.691 offset
    # => ~ -23.3 LUFS (0 dBFS sine ~ -3.7 LUFS per EBU R128).
    audio = _sine(-20.0)
    lufs = loudness.integrated_lufs(audio, 44100)
    assert -24.5 < lufs < -22.0, lufs
    tp = loudness.true_peak_db(audio, 44100)
    assert abs(tp - (-20.0)) < 0.2, tp


def test_true_peak_inter_sample_overshoot():
    # Square-ish: sample peak 0 dBFS, oversampled true peak > 0 dBTP.
    sr = 44100
    x = np.repeat([1.0, 1.0, -1.0, -1.0], int(sr * 0.125))
    audio = np.stack([x, x])
    assert loudness.true_peak_db(audio, sr) > 0.05


def test_silence_inf():
    audio = np.zeros((2, 44100))
    assert loudness.integrated_lufs(audio, 44100) == -np.inf
    assert loudness.true_peak_db(audio, 44100) == -np.inf


def test_mono_and_stereo_same():
    sr = 44100
    t = np.arange(sr * 2) / sr
    x = 0.2 * np.sin(2 * np.pi * 440 * t)
    mono = loudness.integrated_lufs(x, sr)
    stereo = loudness.integrated_lufs(np.stack([x, x]), sr)
    assert abs(mono - stereo) < 1e-6