import librosa
import numpy

from scipy.fftpack import dct


def get_mfcc(audio_file):
    try:
        signal, sample_rate = librosa.load(audio_file)
    except:
        print(audio_file)
        exit()
    pre_emphasis = 0.97
    emphasized_signal = numpy.append(signal[0], signal[1:] - pre_emphasis * signal[:-1])

    frame_size = 0.025
    frame_stride = 0.01

    # we convert from seconds to samples
    frame_length, frame_step = frame_size * sample_rate, frame_stride * sample_rate

    signal_length = len(emphasized_signal)
    frame_length = int(round(frame_length))
    frame_step = int(round(frame_step))

    num_frames = int(numpy.ceil(float(numpy.abs(signal_length - frame_length)) / frame_step))  # Make sure that we have at least 1 frame

    pad_signal_length = num_frames * frame_step + frame_length

    z = numpy.zeros((pad_signal_length - signal_length))

    pad_signal = numpy.append(emphasized_signal, z) # Pad Signal to make sure that all frames have equal number of samples without truncating any samples from the original signal

    indices = numpy.tile(numpy.arange(0, frame_length), (num_frames, 1)) + numpy.tile(numpy.arange(0, num_frames * frame_step, frame_step), (frame_length, 1)).T

    frames = pad_signal[indices.astype(numpy.int32, copy=False)]

    frames *= numpy.hamming(frame_length)
    # frames *= 0.54 - 0.46 * numpy.cos((2 * numpy.pi * n) / (frame_length - 1))  # Explicit Implementation **

    NFFT = 512

    mag_frames = numpy.absolute(numpy.fft.rfft(frames, NFFT))  # Magnitude of the FFT

    pow_frames = ((1.0 / NFFT) * ((mag_frames) ** 2))  # Power Spectrum

    nfilt = 40

    low_freq_mel = 0
    high_freq_mel = (2595 * numpy.log10(1 + (sample_rate / 2) / 700))  # Convert Hz to Mel

    mel_points = numpy.linspace(low_freq_mel, high_freq_mel, nfilt + 2)  # Equally spaced in Mel scale

    hz_points = (700 * (10**(mel_points / 2595) - 1))  # Convert Mel to Hz

    bin = numpy.floor((NFFT + 1) * hz_points / sample_rate)

    fbank = numpy.zeros((nfilt, int(numpy.floor(NFFT / 2 + 1))))

    for m in range(1, nfilt + 1):
        f_m_minus = int(bin[m - 1])   # left
        f_m = int(bin[m])             # center
        f_m_plus = int(bin[m + 1])    # right

        for k in range(f_m_minus, f_m):
            fbank[m - 1, k] = (k - bin[m - 1]) / (bin[m] - bin[m - 1])
        for k in range(f_m, f_m_plus):
            fbank[m - 1, k] = (bin[m + 1] - k) / (bin[m + 1] - bin[m])

    filter_banks = numpy.dot(pow_frames, fbank.T)

    filter_banks = numpy.where(filter_banks == 0, numpy.finfo(float).eps, filter_banks)  # Numerical Stability

    filter_banks = 20 * numpy.log10(filter_banks)  # dB

    num_ceps = 12

    mfcc = dct(filter_banks, type=2, axis=1, norm='ortho')[:, 1 : (num_ceps + 1)] # Keep 2-13

    (nframes, ncoeff) = mfcc.shape

    n = numpy.arange(ncoeff)

    cep_lifter = 22
    # cep_lifter = len(mfcc)

    lift = 1 + (cep_lifter / 2) * numpy.sin(numpy.pi * n / cep_lifter)

    mfcc *= lift

    filter_banks -= (numpy.mean(filter_banks, axis=0) + 1e-8)

    filter_banks -= (numpy.mean(filter_banks, axis=0) + 1e-8)
    mfcc -= (numpy.mean(mfcc, axis=0) + 1e-8)
    return mfcc