import math
from enum import Enum

import numpy as np

from urh import settings
from urh.cythonext import signal_functions
from urh.util import util
from urh.util.Logger import logger


class FilterType(Enum):
    moving_average = "moving average"
    dc_correction = "DC correction"
    custom = "custom"


class Filter(object):
    BANDWIDTHS = {
        "Very Narrow": 0.001,
        "Narrow": 0.01,
        "Medium": 0.08,
        "Wide": 0.1,
        "Very Wide": 0.42
    }

    def __init__(self, taps: list, filter_type: FilterType = FilterType.custom):
        self.filter_type = filter_type
        self.taps = taps

    def work(self, input_signal: np.ndarray) -> np.ndarray:
        if self.filter_type == FilterType.dc_correction:
            return input_signal - np.mean(input_signal, axis=0)
        else:
            return self.apply_fir_filter(input_signal.flatten())

    def apply_fir_filter(self, input_signal: np.ndarray) -> np.ndarray:
        if input_signal.dtype != np.complex64:
            tmp = np.empty(len(input_signal)//2, dtype=np.complex64)
            tmp.real = input_signal[0::2]
            tmp.imag = input_signal[1::2]
            input_signal = tmp

        return signal_functions.fir_filter(input_signal, np.array(self.taps, dtype=np.complex64))

    @staticmethod
    def read_configured_filter_bw() -> float:
        bw_type = settings.read("bandpass_filter_bw_type", "Medium", str)

        if bw_type in Filter.BANDWIDTHS:
            return Filter.BANDWIDTHS[bw_type]

        if bw_type.lower() == "custom":
            return settings.read("bandpass_filter_custom_bw", 0.1, float)

        return 0.08

    @staticmethod
    def get_bandwidth_from_filter_length(N):
        return 4 / N

    @staticmethod
    def get_filter_length_from_bandwidth(bw):
        N = int(math.ceil((4 / bw)))
        return N + 1 if N % 2 == 0 else N  # Ensure N is odd.

    @staticmethod
    def fft_convolve_1d(x: np.ndarray, h: np.ndarray):
        n = len(x) + len(h) - 1
        n_opt = 1 << (n - 1).bit_length()  # Get next power of 2
        if np.issubdtype(x.dtype, np.complexfloating) or np.issubdtype(h.dtype, np.complexfloating):
            fft, ifft = np.fft.fft, np.fft.ifft  # use complex fft
        else:
            fft, ifft = np.fft.rfft, np.fft.irfft  # use real fft

        result = ifft(fft(x, n_opt) * fft(h, n_opt), n_opt)[0:n]
        too_much = (len(result) - len(x)) // 2  # Center result
        return result[too_much: -too_much]

    @staticmethod
    def apply_bandpass_filter(data, f_low, f_high, filter_bw=0.08):
        if f_low > f_high:
            f_low, f_high = f_high, f_low

        f_low = util.clip(f_low, -0.5, 0.5)
        f_high = util.clip(f_high, -0.5, 0.5)

        h = Filter.design_windowed_sinc_bandpass(f_low, f_high, filter_bw)

        # Choose normal or FFT convolution based on heuristic described in
        # https://softwareengineering.stackexchange.com/questions/171757/computational-complexity-of-correlation-in-time-vs-multiplication-in-frequency-s/
        if len(h) < 8 * math.log(math.sqrt(len(data))):
            logger.debug("Use normal convolve")
            return np.convolve(data, h, 'same')
        else:
            logger.debug("Use FFT convolve")
            return Filter.fft_convolve_1d(data, h)

    @staticmethod
    def design_windowed_sinc_lpf(fc, bw):
        N = Filter.get_filter_length_from_bandwidth(bw)

        # Compute sinc filter impulse response
        h = np.sinc(2 * fc * (np.arange(N) - (N - 1) / 2.))

        # We use blackman window function
        w = np.blackman(N)

        # Multiply sinc filter with window function
        h = h * w

        # Normalize to get unity gain
        h_unity = h / np.sum(h)

        return h_unity

    @staticmethod
    def design_windowed_sinc_bandpass(f_low, f_high, bw):
        f_shift = (f_low + f_high) / 2
        f_c = (f_high - f_low) / 2

        N = Filter.get_filter_length_from_bandwidth(bw)

        # https://dsp.stackexchange.com/questions/41361/how-to-implement-bandpass-filter-on-complex-valued-signal
        return Filter.design_windowed_sinc_lpf(f_c, bw=bw) * \
               np.exp(complex(0, 1) * np.pi * 2 * f_shift * np.arange(0, N, dtype=complex))
