DCF

from time import sleep

print ("Welcome to the DCF calculator.")


def ask_perpetuity():
    earnings = float(input("Enter last twelve months earnings: "))
    discount_rate = float(input("Enter discount rate in %: "))/100
    growth_rate = float(input("Enter future expected annual compounded growth rate in %: "))/100
    growth_period = int(input("Enter amount of future years of growth, after which earnings will flatten: "))
    return discount_rate, earnings, growth_rate, growth_period


def calculate_perpetuity(discount_rate, earnings, growth_rate, growth_period):
    dcf = 0
    for years in range(growth_period):
        years += 1
        dcf += (earnings * (((1 + growth_rate) / (1 + discount_rate)) ** years))  # Adds up to end of growth
    dcf += earnings * (((1 + growth_rate) / (1 + discount_rate)) ** growth_period) / discount_rate  # to forever
    dcf = str(dcf)

    print("Calculating...")
    sleep(1)

    print("The discount cash flow is " + dcf)


def check_perpetuity(discount_rate, earnings, growth_rate, growth_period):
    if 0 <= discount_rate <= 1 and earnings >= 0 and -1 <= growth_rate <= 1 and growth_period >= 0:
        calculate_perpetuity(discount_rate, earnings, growth_rate, growth_period)
    else:
        wrong_input()


def ask_annuity():
    earnings = float(input("Enter value of periodic payment: "))
    discount_rate = float(input("Enter discount rate in %: ")) / 100
    period = int(input("Enter period of years annuity will be received: "))
    return discount_rate, earnings, period


def calculate_annuity(discount_rate, earnings, period):
    dcf = 0
    for years in range(period):
        years += 1
        dcf += (earnings / (1 + discount_rate) ** years)  # This sum adds values to dcf up to end of period
    dcf = str(dcf)

    print("Calculating...")
    sleep(1)

    print("The discount cash flow is " + dcf)


def check_annuity(discount_rate , earnings, period):
    if 0 <= discount_rate <= 1 and earnings >= 0 and period >= 0:
        calculate_annuity(discount_rate, earnings, period)
    else:
        wrong_input()


def wrong_input():
    print("\nYou did not enter valid inputs. Please retry. ")
    ask_user()


def ask_user():
    user_choice = input("Enter P to calculate perpetuity, A for annuity: ").upper()
    if user_choice == "P":
        discount_rate, earnings, growth_rate, growth_period = ask_perpetuity()
        check_perpetuity(discount_rate, earnings, growth_rate, growth_period)
    elif user_choice == "A":
        discount_rate, earnings, period = ask_annuity()
        check_annuity(discount_rate, earnings, period)
    else:
        wrong_input()


# Commands start here
ask_user()