import numpy as np


def norm_f0(f0, uv=None):
    if uv is None:
        uv = f0 == 0
    f0 = np.log2(f0 + uv)  # avoid arithmetic error
    f0[uv] = -np.inf
    return f0


def interp_f0(f0, uv=None):
    if uv is None:
        uv = f0 == 0
    f0 = norm_f0(f0, uv)
    if uv.any() and not uv.all():
        f0[uv] = np.interp(np.where(uv)[0], np.where(~uv)[0], f0[~uv])
    return denorm_f0(f0, uv=None), uv


def denorm_f0(f0, uv, pitch_padding=None):
    f0 = 2 ** f0
    if uv is not None:
        f0[uv > 0] = 0
    if pitch_padding is not None:
        f0[pitch_padding] = 0
    return f0