import pandas


# Functions go here
def make_statement(statement, decoration):
    """Emphasises headings by adding decoration at the start and end"""
    return f"{decoration * 3} {statement} {decoration * 3}"


def string_check(question, valid_answers=('yes', 'no'), num_letters=1):
    """Checks that users enter the full word or the 'n' letter/s of a word from a list of valid responses"""
    while True:
        response = input(question).lower()

        for item in valid_answers:
            # check if the response is the entire word
            if response == item:
                return item

            # check if it's the "n" letters
            elif response == item[:num_letters]:
                return item

        print(f"❗ Please choose an option from {valid_answers} ❗\n")


def instructions():
    """Prints instructions, informs user on how to use program"""
    print(make_statement("Instructions", "ℹ️"))

    print('''
This program is to assist you when purchasing cars.

This advanced calculator will request for your budget and then 
calculate what you can and can't afford, updating stock at real time.
The steps of this process are as followed:

1. Enter your budget - when asked (minimum $5,000 , maximum $200,000)
2. A list of cars will be shown, select which car you would like to purchase
3. You can continue shopping until your budget has ran out or you can proceed to checkout whenever you want
4. A receipt will be printed with your order

At Any time feel free to type 'xxx' to exit the program
- You will be informed what to do at each and every step -
    ''')


def not_blank(question):
    """Checks that a user response is not blank"""

    while True:
        response = input(question)

        if response != "":
            return response

        print("Sorry this can't be blank. Please try again. \n")


def int_check(question, low, high):
    """Checks user enters an integer between optional bounds"""
    error = "❗ Invalid input. Please enter a valid number. ❗\n"
    while True:
        to_check = input(question).lower()

        if to_check == 'xxx':
            print("Thank you for using Car Budget Buyer")
            quit()

        try:
            response = int(to_check)

            if response < low or response > high:
                if response > high:
                    print(f"❗ Please enter a number between {low} to {high}. ❗\n")
                elif response < low:
                    print(f"❗ Please enter a whole number of at least {low}. ❗\n")
            else:
                return response
        except ValueError:
            print(error)


def currency(x):
    """Formats numbers as currency ($#.##)"""
    return "${:.2f}".format(x)


# Main routine goes here


# Program main heading
print(make_statement("Car Budget Buyer", "🚗"))
print()

# Asks users name
name = not_blank("Hello! What's your name? ")

# Ask user if they want to see the instructions
# Display them if necessary
print()
want_instructions = string_check(f"Hi {name}, Would you like a tutorial/explanation on how the program works? ")

if want_instructions == "yes":
    instructions()

print()


# Ask for budget
print(f"Alright {name}, Let's find a car you can afford!")
budget = int_check("Enter your budget (minimum $5,000 , maximum $200,000): $", 5000, 200000)
print(f"\nYour budget is ${budget}\n")

# Shopping cart
cart = []


# Display items
cars = [
    {"item": "Basic Car", "price": 5000, "quantity": 10},
    {"item": "Standard Car", "price": 10000, "quantity": 5},
    {"item": "Luxury Car", "price": 25000, "quantity": 2},
    {"item": "Sports Car", "price": 50000, "quantity": 1},
]

# Shows list
while True:
    affordable_cars = [car for car in cars if car["price"] <= budget and car["quantity"] > 0]
    if not affordable_cars:
        print("You can't afford anymore cars or stock is out. Time to checkout.")
        break

    print("Cars you can afford:")
    for i, car in enumerate(affordable_cars, start=1):
        print(f"{i}. {car['item']} - ${car['price']} (In stock: {car['quantity']})")
    print()

    # Asks user to select car or quit
    selection_number = int_check("Which car would you like to purchase?, or type '0' to proceed to cart: ", 0, len(affordable_cars))
    if selection_number == 0:
        break

    selected_item = affordable_cars[selection_number - 1]

    # Calculates number of cars the user can buy
    max_can_buy_stock = selected_item['quantity']
    max_can_buy_budget = budget // selected_item['price']
    max_can_buy = min(max_can_buy_stock, max_can_buy_budget)

    # Tells number of cars the user can buy
    # Asks how many user wants to buy (option to return) + calculates total price
    print(f"\nYou can add up to {max_can_buy} of {selected_item['item']} to your cart.")
    quantity = int_check(f"How many {selected_item['item']} would you like to add? (or enter 0 to return):\n", 0, max_can_buy)
    if quantity == 0:
        continue
    total_cost = quantity * selected_item['price']

    # Update stock and budget
    selected_item['quantity'] -= quantity
    budget -= total_cost
    print(f"{quantity} x {selected_item['item']} added to cart. Remaining budget: ${budget}\n")

    # Adds order to cart
    cart.append({
        "item": selected_item['item'],
        "price": selected_item['price'],
        "quantity": quantity,
    })

    # Tells user they can't afford anymore with current budget
    if budget <= 5000:
        print("You can't afford anymore cars with your budget. Proceed to Checkout")
        break


# Checkout
if not cart:
    print("You haven’t selected anything for your cart, the program will exit.")
    print("Thank you for using Car Budget Buyer!")
    quit()

print(make_statement("🛒 Checkout Summary", "🛒"))


# ---- Receipt Generation ----
# create dataframe / table from dictionary
receipt = pandas.DataFrame(cart)

# Currency Formatting (uses currency function)
receipt["Total"] = receipt["price"] * receipt["quantity"]
for column in ["price", "Total"]:
    receipt[column] = receipt[column].apply(currency)

# Output receipt frame without index
receipt_string = receipt.to_string(index=False)

# Additional strings / Headings
heading_string = make_statement("Car Purchase Receipt", "=")
summary_heading = make_statement("Summary", "-")

# Total calculations
total_cost = sum(item["price"] * item["quantity"] for item in cart)
summary = [
    f"Total Cost: {currency(total_cost)}"
]

# List of strings to be outputted / written to file
to_write = [heading_string, "\n",
            name + "'s Receipt", "\n",
            summary_heading,
            receipt_string, "\n",
            *summary]


# Print area
print()
for item in to_write:
    print(item)

# create file to hold data (add .txt extension)
file_name = "car_purchase_receipt"
write_to = "{}.txt".format(file_name)

text_file = open(write_to, "w+")

# write the item to file
for item in to_write:
    text_file.write(item)
    text_file.write("\n")

text_file.close()