app.py

# -*- coding: utf-8 -*-
"""Loan Qualifier Application. 

This is a command line application to match applicants with qualifying loans.

Example:
    $ python app.py
"""
from os import close
from re import escape
import sys
import fire
import questionary
from pathlib import Path

from qualifier.utils.fileio import load_csv, save_csv

from qualifier.utils.calculators import (
    calculate_monthly_debt_ratio,
    calculate_loan_to_value_ratio,
)

from qualifier.filters.max_loan_size import filter_max_loan_size
from qualifier.filters.credit_score import filter_credit_score
from qualifier.filters.debt_to_income import filter_debt_to_income
from qualifier.filters.loan_to_value import filter_loan_to_value

def load_bank_data():
    """Ask for the file path to the latest banking data and load the CSV file.

    Returns:
        The bank data from the data rate sheet CSV file.
    """

    csvpath = questionary.text("Enter a file path to a rate-sheet (.csv):").ask()
    csvpath = Path(csvpath)
    if not csvpath.exists():
        sys.exit(f"Oops! Can't find this path: {csvpath}")

    return load_csv(csvpath)

def get_applicant_info():
    """Prompt dialog to get the applicant's financial information.

    Returns:
        Returns the applicant's financial information.
    """

    credit_score = questionary.text("What's your credit score?").ask()
    try:
        credit_score = int(credit_score)
    except:
        print("Invalid input, please restart Qualifier and use only numbers.")

    debt = questionary.text("What's your current amount of monthly debt?").ask()
    try:
        debt = float(debt)
    except:
        print("Invalid input, please restart Qualifier and use only numbers.")

    income = questionary.text("What's your total monthly income?").ask()
    try:
        income = float(income)
    except:
        print("Invalid input, please restart Qualifier and use only numbers.")

    loan_amount = questionary.text("What's your desired loan amount?").ask()
    try:
        loan_amount = float(loan_amount)
    except:
        print("Invalid input, please restart Qualifier and use only numbers.")

    home_value = questionary.text("What's your home value?").ask()
    try:
        home_value = float(home_value)
    except:
        print("Invalid input, please restart Qualifier and use only numbers.")

    return credit_score, debt, income, loan_amount, home_value

def find_qualifying_loans(bank_data, credit_score, debt, income, loan, home_value):
    """Determine which loans the user qualifies for.

    Loan qualification criteria is based on:
        - Credit Score
        - Loan Size
        - Debit to Income ratio (calculated)
        - Loan to Value ratio (calculated)

    Args:
        bank_data (list): A list of bank data.
        credit_score (int): The applicant's current credit score.
        debt (float): The applicant's total monthly debt payments.
        income (float): The applicant's total monthly income.
        loan (float): The total loan amount applied for.
        home_value (float): The estimated home value.

    Returns:
        A list of the banks willing to underwrite the loan.

    """

    # Calculate the monthly debt ratio.
    monthly_debt_ratio = calculate_monthly_debt_ratio(debt, income)
    print(f"The monthly debt to income ratio is {monthly_debt_ratio:.02f}.")

    # Calculate loan to value ratio.
    loan_to_value_ratio = calculate_loan_to_value_ratio(loan, home_value)
    print(f"The loan to value ratio is {loan_to_value_ratio:.02f}.")

    # Run qualification filters.
    bank_data_filtered = filter_max_loan_size(loan, bank_data)
    bank_data_filtered = filter_credit_score(credit_score, bank_data_filtered)
    bank_data_filtered = filter_debt_to_income(monthly_debt_ratio, bank_data_filtered)
    bank_data_filtered = filter_loan_to_value(loan_to_value_ratio, bank_data_filtered)

    if len(bank_data_filtered) > 0:
        print(f"Great! Qualifier Found {len(bank_data_filtered)} Qualifying Loans!")
    return bank_data_filtered


def save_qualifying_loans(qualifying_loans):
    """Saves the qualifying loans to a CSV file.

    Args:
        qualifying_loans (list of lists): The qualifying bank loans.
    """   
    if len(qualifying_loans) == 0:
        sys.exit(f"Sorry, you currently do not qualify.")

    ask_to_save = questionary.confirm("Would you like to save your Qualifying Bank Loans?").ask()

    if ask_to_save == False:
        sys.exit(f"Loans not saved. Thank you for using Qualifier!")

    rate_sheet = questionary.text("Enter a file path to a rate-sheet (.csv):").ask()
    rate_sheet = Path(rate_sheet)
    
    save_csv(rate_sheet, qualifying_loans)
    sys.exit(f"Loans saved to output file: ({rate_sheet}). Thank you for using Qualifier!")

def run():
    """The main function for running the script."""

    # Load the latest Bank data.
    bank_data = load_bank_data()

    # Get the applicant's information.
    credit_score, debt, income, loan_amount, home_value = get_applicant_info()

    # Find all qualifying loans.
    qualifying_loans = find_qualifying_loans(
        bank_data, credit_score, debt, income, loan_amount, home_value
    )

    # Save all qualifying loans.
    save_qualifying_loans(qualifying_loans)

if __name__ == "__main__":
    fire.Fire(run)