import os
import pandas as pd
import numpy as np

from sklearn.preprocessing import StandardScaler

from sklearn.model_selection import train_test_split


def download_kaggle_dataset():
    os.system("kaggle datasets download -d mlg-ulb/creditcardfraud")
    os.system("unzip creditcardfraud.zip")
    os.system("rm creditcardfraud.zip")


def load_data(name):
    df = pd.read_csv(name)
    return df


def normalize_data(df):
    scaler = StandardScaler()
    df["Amount"] = scaler.fit_transform(df["Amount"].values.reshape(-1, 1))
    return df


def create_undersample_data(df):
    # Determine the number of instances in the minority class
    fraud_count = len(df[df.Class == 1])
    fraud_indices = np.array(df[df.Class == 1].index)

    # Select indices corresponding to majority class instances
    normal_indices = df[df.Class == 0].index

    # Randomly sample the same number of instances from the majority class
    random_normal_indices = np.random.choice(normal_indices, fraud_count, replace=False)
    random_normal_indices = np.array(random_normal_indices)

    # Combine indices of both classes
    undersample_indice = np.concatenate([fraud_indices, random_normal_indices])

    # Undersample dataset
    undersample_data = df.iloc[undersample_indice, :]

    X_undersample = undersample_data.iloc[:, undersample_data.columns != "Class"]
    y_undersample = undersample_data.iloc[:, undersample_data.columns == "Class"]

    return undersample_data, X_undersample, y_undersample


def split_undersample_data(X_undersample, y_undersample):
    X_train_undersample, X_test_undersample, y_train_undersample, y_test_undersample = (
        train_test_split(X_undersample, y_undersample, test_size=0.3, random_state=0)
    )

    return (
        X_train_undersample,
        X_test_undersample,
        y_train_undersample,
        y_test_undersample,
    )


def save_undersample_data(
    undersample_data,
    X_train_undersample,
    X_test_undersample,
    y_train_undersample,
    y_test_undersample,
):
    undersample_data.to_csv("/data/undersample_data.csv", index=False)
    X_train_undersample.to_csv("/data/X_train_undersample.csv", index=False)
    X_test_undersample.to_csv("/data/X_test_undersample.csv", index=False)
    y_train_undersample.to_csv("/data/y_train_undersample.csv", index=False)
    y_test_undersample.to_csv("/data/y_test_undersample.csv", index=False)


def split_whole_data(df):
    X = df.iloc[:, df.columns != "Class"]
    y = df.iloc[:, df.columns == "Class"]

    X_train, X_test, y_train, y_test = train_test_split(
        X, y, test_size=0.3, random_state=0
    )
    return X_train, X_test, y_train, y_test


def save_whole_data(df, X_train, X_test, y_train, y_test):
    df.to_csv("/data/creditcard.csv", index=False)
    X_train.to_csv("/data/X_train.csv", index=False)
    X_test.to_csv("/data/X_test.csv", index=False)
    y_train.to_csv("/data/y_train.csv", index=False)
    y_test.to_csv("/data/y_test.csv", index=False)


def main():
    download_kaggle_dataset()
    os.makedirs("data", exist_ok=True)

    df = load_data("creditcard.csv")
    df = normalize_data(df)

    undersample_data, X_undersample, y_undersample = create_undersample_data(df)
    X_train_undersample, X_test_undersample, y_train_undersample, y_test_undersample = (
        split_undersample_data(X_undersample, y_undersample)
    )
    save_undersample_data(
        undersample_data,
        X_train_undersample,
        X_test_undersample,
        y_train_undersample,
        y_test_undersample,
    )

    X_train, X_test, y_train, y_test = split_whole_data(df)
    save_whole_data(X_train, X_test, y_train, y_test)


if __name__ == "__main__":
    main()