"""This module provides functions for filtering traces using digital (low/high/band)-pass and bandstop filters."""
from public import public
from scipy.signal import butter, lfilter
from typing import Union, Tuple

from .trace import Trace


def _filter_any(
    trace: Trace,
    sampling_frequency: int,
    cutoff: Union[int, Tuple[int, int]],
    band_type: str,
) -> Trace:
    nyq = 0.5 * sampling_frequency
    if not isinstance(cutoff, int):
        b, a = butter(
            6,
            tuple(map(lambda x: x / nyq, cutoff)),
            btype=band_type,
            analog=False,
            output="ba",
        )
    else:
        b, a = butter(6, cutoff / nyq, btype=band_type, analog=False, output="ba")
    return trace.with_samples(lfilter(b, a, trace.samples))


@public
def filter_lowpass(trace: Trace, sampling_frequency: int, cutoff: int) -> Trace:
    """
    Apply a lowpass digital filter (Butterworth) to `trace`, given `sampling_frequency` and `cutoff` frequency.

    :param trace:
    :param sampling_frequency:
    :param cutoff:
    :return:
    """
    return _filter_any(trace, sampling_frequency, cutoff, "lowpass")


@public
def filter_highpass(trace: Trace, sampling_frequency: int, cutoff: int) -> Trace:
    """
    Apply a highpass digital filter (Butterworth) to `trace`, given `sampling_frequency` and `cutoff` frequency.

    :param trace:
    :param sampling_frequency:
    :param cutoff:
    :return:
    """
    return _filter_any(trace, sampling_frequency, cutoff, "highpass")


@public
def filter_bandpass(
    trace: Trace, sampling_frequency: int, low: int, high: int
) -> Trace:
    """
    Apply a bandpass digital filter (Butterworth) to `trace`, given `sampling_frequency`, with the passband from `low` to `high`.

    :param trace:
    :param sampling_frequency:
    :param low:
    :param high:
    :return:
    """
    return _filter_any(trace, sampling_frequency, (low, high), "bandpass")


@public
def filter_bandstop(
    trace: Trace, sampling_frequency: int, low: int, high: int
) -> Trace:
    """
    Apply a bandstop digital filter (Butterworth) to `trace`, given `sampling_frequency`, with the stopband from `low` to `high`.

    :param trace:
    :param sampling_frequency:
    :param low:
    :param high:
    :return:
    """
    return _filter_any(trace, sampling_frequency, (low, high), "bandstop")
