import pandas as pd
from dateutil.relativedelta import relativedelta
import scipy.fft
import numpy as np
import pywt

from spoef.utils import (
    prepare_data_yearly,
    prepare_data_quarterly,
)


def compute_list_featuretypes(
    data,
    list_featuretypes,
    fourier_n_largest_frequencies,
    wavelet_depth,
    mother_wavelet,
):
    """
    This function lets the user choose which combination of features they
    want to have computed.

    list_featuretypes:
        "Basic" - min, max, mean, kurt ,skew, std, sum.
        "FourierComplete" - all frequencies amplitudes and phases.
        "FourierNLargest" - n largest frequencies and their values.
        "WaveletComplete" - all approximation and details coefficients at each depth.
        "WaveletBasic" - takes "Basic" (min, max, etc) at each depth.

    Args:
        data (pd.DataFrame()) : one column from which to make features.
        list_featuretypes (list) : list of feature types to be computed.
        fourier_n_largest_frequencies (int) : amount of fourier features.
        wavelet_depth (int) : level of depth up to which the wavelet is computed.
        mother_wavelet (str) : type of wavelet used for the analysis.

    Returns:
        features (pd.DataFrame()) : row of features.

    """
    
    if type(list_featuretypes) != list:
        raise AttributeError("'list_featuretypes' must be a list.")
        
    allowed_components = ["Basic", "FourierNLargest", "WaveletComplete", "WaveletBasic", "FourierComplete"]

    for argument in list_featuretypes:
        if argument not in allowed_components:
            raise ValueError(f"argument must be one of {allowed_components}")
    
    features_basic = pd.DataFrame()
    features_fourier = pd.DataFrame()
    features_wavelet = pd.DataFrame()
    features_wavelet_basic = pd.DataFrame()
    features_fft2 = pd.DataFrame()
    if "Basic" in list_featuretypes:
        features_basic = compute_basic(data)
    if "FourierNLargest" in list_featuretypes:
        features_fourier = compute_fourier_n_largest(data, fourier_n_largest_frequencies)
    if "FourierComplete" in list_featuretypes:
        features_fft2 = compute_fourier_complete(data)
    if "WaveletComplete" in list_featuretypes:
        features_wavelet = compute_wavelet_complete(data, wavelet_depth, mother_wavelet)
    if "WaveletBasic" in list_featuretypes:
        features_wavelet_basic = compute_wavelet_basic(
            data, wavelet_depth, mother_wavelet
        )
    features = pd.concat(
        [features_basic, features_fourier, features_fft2, features_wavelet, features_wavelet_basic],
        axis=1,
    )
    return features


def compute_basic(data):
    """
    This function creates basic features.

    "Basic" - min, max, mean, kurt ,skew, std, sum.

    Args:
        data (pd.DataFrame()) : one column from which to make basic features.

    Returns:
        features (pd.DataFrame()) : (1 x 7) row of basic features.

    """
    col_names = ["min", "max", "mean", "skew", "kurt", "std", "sum"]
    col_names = ["Basic " + str(col) for col in col_names]
    features = pd.DataFrame(
        [
            [
                data.min(),
                data.max(),
                data.mean(),
                data.skew(),
                data.kurt(),
                data.std(),
                data.sum(),
            ]
        ],
        columns=col_names,
    )
    return features


def compute_fourier_n_largest(data, fourier_n_largest_frequencies):
    """
    This function takes the Fast Fourier Transform and returns the n largest
    frequencies and their values.

    "FourierNLargest" - n largest frequencies and their values.

    Args:
        data (pd.DataFrame()) : one column from which to make fourier features.
        fourier_n_largest_frequencies (int) : amount of fourier features.
            possible values: less than len(data)

    Returns:
        features (pd.DataFrame()) : (1 x 2n) row of largest frequencies and values.

    """
    # Fast Fourier Transform
    fft = scipy.fft.fft(data.values)
    fft_abs = abs(fft[range(int(len(data) / 2))])

    # Select largest indexes (=frequencies) and their values
    largest_indexes = np.argsort(-fft_abs)[:fourier_n_largest_frequencies]
    largest_values = fft_abs[largest_indexes]
    largest_values = [int(a) for a in largest_values]

    # Name the columns
    features = [*largest_indexes.tolist(), *largest_values]
    col_names_index = [
        "FourierNLargest freq_" + str(i + 1) + "/" + str(fourier_n_largest_frequencies)
        for i in range(int(len(features) / 2))
    ]
    col_names_size = [
        "FourierNLargest ampl_" + str(i + 1) + "/" + str(fourier_n_largest_frequencies)
        for i in range(int(len(features) / 2))
    ]
    col_names = [*col_names_index, *col_names_size]
    features = pd.DataFrame([features], columns=col_names)
    return features


def compute_fourier_complete(data):
    """
    This function takes the Fast Fourier Transform and returns the amplitudes 
    and phases of each frequency.

    "FourierComplete" - all frequencies amplitudes and phases.

    Args:
        data (pd.DataFrame()) : one column from which to make Fourier features.

    Returns:
        features (pd.DataFrame()) : (1 x (2 x len(data))) row of amplitudes and phases.

    """
    if (
        len(data) < 95 and len(data) > 85
    ):  # due to varying quarter lengths only first 88 days are used ...
        data = data[:89]
    
    # Fast Fourier Transform
    fft = scipy.fft.fft(data.values)
    fft_sel = fft[range(int(len(data) / 2))]
    
    fft_real = [abs(np.real(a)) for a in fft_sel]
    fft_imag = [np.imag(a) for a in fft_sel]
    
    # Name the columns
    features = [*fft_real, *fft_imag]
    col_names_real = [
        "FourierComplete ampl_" + str(i + 1) + "/" + str(len(data)/2)
        for i in range(int(len(features) / 2))
    ]
    col_names_imag = [
        "FourierComplete phase_" + str(i + 1) + "/" + str(len(data)/2)
        for i in range(int(len(features) / 2))
    ]
    col_names = [*col_names_real, *col_names_imag]
    features = pd.DataFrame([features], columns=col_names)
    return features


def compute_wavelet_complete(data, wavelet_depth, mother_wavelet):
    """
    This function takes the Wavelet Transform and returns all approximation
    and details coefficients at each depth.

    "WaveletComplete" - all approximation and details coefficients at each depth.

    Args:
        data (pd.DataFrame()) : one column from which to make wavelet features.
        wavelet_depth (int) : level of depth up to which the wavelet is computed.
            possible values: depends on len(data), approx 2^wavelet_depth = len(data)
        mother_wavelet (str) : type of wavelet used for the analysis.
            possible values: "db2", "db4", "haar", see pywt.wavelist(kind="discrete")

    Returns:
        features (pd.DataFrame()) : row of wavelet features.

    """

    if (
        len(data) < 95 and len(data) > 85
    ):  # due to varying quarter lengths only first 88 days are used ...
        data = data[:88]

    wavelet = pywt.wavedec(data, wavelet=mother_wavelet, level=wavelet_depth)
    
    features = [item for sublist in wavelet for item in sublist]  # flatten list

    col_names = [f'WaveletComplete depth_{wavelet_depth-sublist[0]}/{wavelet_depth}_item_{i+1}' for sublist in enumerate(wavelet) for i in range(len(sublist[1]))]  # flatten list
    
    features = pd.DataFrame([features], columns=col_names)
        
    return features


def compute_wavelet_basic(data, wavelet_depth, mother_wavelet):
    """
    This function takes the Wavelet Transform and at each depth makes basic
    features for the approximation and detail coefficients.

    "WaveletBasic" - takes "Basic" (min, max, etc) at each depth.

    Args:
        data (pd.DataFrame()) : one column from which to make basic wavelet features.
        wavelet_depth (int) : level of depth up to which the wavelet is computed.
            possible values: depends on len(data), approx 2^wavelet_depth = len(data)
        mother_wavelet (str) : type of wavelet used for the analysis.
            possible values: "db2", "db4", "haar", see pywt.wavelist(kind="discrete")

    Returns:
        features (pd.DataFrame()) : (2 x 7 x wavelet_depth) row of wavelet features.

    """
    data_wavelet = data
    features = pd.DataFrame()
    for i in range(wavelet_depth):
        data_wavelet, coeffs = pywt.dwt(data_wavelet, wavelet=mother_wavelet)
        features_at_depth = compute_basic(pd.Series(data_wavelet))
        features_at_depth.columns = [
            "WaveletBasic_approx depth_" + str(i) + "_" + str(col)
            for col in features_at_depth.columns
        ]
        features_at_depth_high = compute_basic(pd.Series(coeffs))
        features_at_depth_high.columns = [
            "WaveletBasic_detail depth_" + str(i) + " " + str(col)
            for col in features_at_depth_high.columns
        ]
        features = pd.concat(
            [features, features_at_depth, features_at_depth_high], axis=1
        )
    return features


def feature_generation(
    data,
    grouper,
    combine_fill_method,
    time_window,
    normalize=False,
    list_featuretypes=["Basic"],
    observation_length=1,
    fourier_n_largest_frequencies=10,
    wavelet_depth=4,
    mother_wavelet="db2",
):
    """
    This function splits the data per identifier and performs the monthly feature
    generation.

    list_featuretypes:
        "Basic" - min, max, mean, kurt ,skew, std, sum.
        "FourierComplete" - all frequencies amplitudes and phases.
        "FourierNLargest" - n largest frequencies and their values.
        "WaveletComplete" - all approximation and details coefficients at each depth.
        "WaveletBasic" - takes "Basic" (min, max, etc) at each depth.

    Args:
        data (pd.DataFrame()) : data from one identifier for which to make features.
        combine_fill_method (str) : 'balance' or 'transaction'.
        observation_length (int) : amount of recent months you want for the analysis.
        normalize (bool) : normalize data in time window
        list_featuretypes (list) : list of feature types to be computed.
        fourier_n_largest_frequencies (int) : amount of fourier features.
        wavelet_depth (int) : level of depth up to which the wavelet is computed.
            possible values: 3 is the max, depends on len(data)
        mother_wavelet (str) : type of wavelet used for the analysis.
            possible values: "db2", "db4", "haar", see pywt.wavelist(kind="discrete")
    Returns:
        features (pd.DataFrame()) : df with row of monthly features for each identifier.

    """
    if time_window == 'quarter':
        features = (
            data.groupby(grouper)
            .apply(
                compute_features_quarterly,
                combine_fill_method=combine_fill_method,
                list_featuretypes=list_featuretypes,
                observation_length=observation_length,
                fourier_n_largest_frequencies=fourier_n_largest_frequencies,
                wavelet_depth=wavelet_depth,
                mother_wavelet=mother_wavelet,
                normalize=normalize,
            )
            .reset_index(level=1, drop=True)
        )
    elif time_window == 'year':
        features = (
            data.groupby(grouper)
            .apply(
                compute_features_yearly,
                combine_fill_method=combine_fill_method,
                list_featuretypes=list_featuretypes,
                observation_length=observation_length,
                fourier_n_largest_frequencies=fourier_n_largest_frequencies,
                wavelet_depth=wavelet_depth,
                mother_wavelet=mother_wavelet,
                normalize=normalize,
            )
            .reset_index(level=1, drop=True)
        )
    else:
        raise ValueError('Please enter one of ["quarter", "year"]')
    
    # Check if NaNs are generated
    na_list = []
    na_list.append(features.isna().sum().sum())
    if sum(na_list) != 0:
        raise ValueError("There are NaNs generated in the following columns:", na_list)
    
    return features


def compute_features_quarterly(
    data,
    combine_fill_method,
    list_featuretypes,
    observation_length,
    fourier_n_largest_frequencies,
    wavelet_depth,
    mother_wavelet,
    normalize,
):
    """
    This function computes different types of features for one identifier.
    It does this monthly for a specified number of quarters. The feature generation
    can be tweaked through several variables.

    list_featuretypes:
        "Basic" - min, max, mean, kurt ,skew, std, sum.
        "FourierComplete" - all frequencies amplitudes and phases.
        "FourierNLargest" - n largest frequencies and their values.
        "WaveletComplete" - all approximation and details coefficients at each depth.
        "WaveletBasic" - takes "Basic" (min, max, etc) at each depth.

    Args:
        data (pd.DataFrame()) : data from one identifier for which to make features.
        combine_fill_method (str) : 'balance' or 'transaction'.
        observation_length (int) : amount of recent months you want for the analysis.
        list_featuretypes (list) : list of feature types to be computed.
        fourier_n_largest_frequencies (int) : amount of fourier features.
        wavelet_depth (int) : level of depth up to which the wavelet is computed.
            possible values: 3 is the max, depends on len(used_data)
        mother_wavelet (str) : type of wavelet used for the analysis.
            possible values: "db2", "db4", "haar", see pywt.wavelist(kind="discrete")
        normalize (bool) : normalize data in time window

    Returns:
        features (pd.DataFrame()) : row of quarterly features for one identifier.

    """
    # drop identifier column
    data = data.drop(data.columns[0], axis=1)

    # select only relevant period and fill the empty date
    prepared_data = prepare_data_quarterly(data, combine_fill_method, observation_length)

    start_date = prepared_data.iloc[0, 0]

    # create features per month
    features = pd.DataFrame()
    for quarter in range(0, observation_length):
        data_quarter = prepared_data[
            (prepared_data.iloc[:, 0] >= start_date + relativedelta(months=3*quarter))
            & (prepared_data.iloc[:, 0] < start_date + relativedelta(months=3*quarter + 3))
        ]
        used_data = data_quarter.iloc[:,1]
        if normalize == True:
            used_data = (used_data-used_data.min())/((used_data.max()+1)-used_data.min())
        
        quarterly_features = compute_list_featuretypes(
            used_data,
            list_featuretypes,
            fourier_n_largest_frequencies,
            wavelet_depth,
            mother_wavelet,
        )
        # name columns
        quarterly_features.columns = [
            data.columns[1][:2]
            + " Q_"
            + str(quarter + 1)
            + "/"
            + str(observation_length)
            + " "
            + col
            for col in quarterly_features.columns
        ]
        features = pd.concat([features, quarterly_features], axis=1)
    return features


def compute_features_yearly(
    data,
    combine_fill_method,
    list_featuretypes,
    observation_length,
    fourier_n_largest_frequencies,
    wavelet_depth,
    mother_wavelet,
    normalize,
):
    """
    This function computes different types of features for one identifier.
    It does this yearly for a specified number of years. The feature generation
    can be tweaked through several variables.

    list_featuretypes:
        "Basic" - min, max, mean, kurt ,skew, std, sum.
        "FourierComplete" - all frequencies amplitudes and phases.
        "FourierNLargest" - n largest frequencies and their values.
        "WaveletComplete" - all approximation and details coefficients at each depth.
        "WaveletBasic" - takes "Basic" (min, max, etc) at each depth.

    Args:
        data (pd.DataFrame()) : data from one identifier for which to make features.
        combine_fill_method (str) : 'balance' or 'transaction'.
        list_featuretypes (list) : list of feature types to be computed.
        observation_length (int) : amount of recent months you want for the analysis.
        fourier_n_largest_frequencies (int) : amount of fourier features.
        wavelet_depth (int) : level of depth up to which the wavelet is computed.
            possible values: 6 is the max, depends on len(used_data)
        mother_wavelet (str) : type of wavelet used for the analysis.
            possible values: "db2", "db4", "haar", see pywt.wavelist(kind="discrete")
        normalize (bool) : normalize data in time window

    Returns:
        features (pd.DataFrame()) : row of yearly features for one identifier.

    """
    # drop identifier column
    data = data.drop(data.columns[0], axis=1)

    # select only relevant period and fill the empty date
    prepared_data = prepare_data_yearly(data, combine_fill_method, observation_length)

    start_date = prepared_data.iloc[0, 0]

    # create features per year
    features = pd.DataFrame()
    for year in range(0, observation_length):
        data_year = prepared_data[
            (prepared_data.iloc[:, 0] >= start_date + relativedelta(years=year))
            & (prepared_data.iloc[:, 0] < start_date + relativedelta(years=year + 1))
        ]
        used_data = data_year.iloc[:,1]
        if normalize == True:
            used_data = (used_data-used_data.min())/(used_data.max()-used_data.min())
        yearly_features = compute_list_featuretypes(
            used_data,
            list_featuretypes,
            fourier_n_largest_frequencies,
            wavelet_depth,
            mother_wavelet,
        )
        # name columns
        yearly_features.columns = [
            data.columns[1][:2]
            + " Y_"
            + str(year + 1)
            + "/"
            + str(observation_length)
            + " "
            + col
            for col in yearly_features.columns
        ]
        features = pd.concat([features, yearly_features], axis=1)
    return features
