# Function goes here
def make_statement(statement, decoration):
    return f"{decoration * 3} {statement} {decoration * 3}"

# Checks for Yes / No input
def string_check(question, valid_answers=('yes', 'no'), num_letters=1):
    while True:
        response = input(question).lower()
        for item in valid_answers:
            if response == item or response == item[:num_letters]:
                return item
        print(f"Please choose an option from {valid_answers}")

# Displays Instructions
def instructions():
    print(make_statement("Instructions", "ℹ️"))
    print('''
Instructions blah blah blah
You will input a budget and be shown cars you can afford.
You can add cars to a cart and then confirm your purchase at the end.
    ''')

def not_blank(question):
    while True:
        response = input(question).strip()
        if response:
            return response
        print("Sorry, this cannot be blank. Please try again.")

def int_check(question, minimum=1, maximum=None):
    while True:
        try:
            value = int(input(question))
            if value < minimum or (maximum is not None and value > maximum):
                if maximum:
                    print(f"❗ Please enter a whole number between {minimum} and {maximum}. ❗\n")
                else:
                    print(f"❗ Please enter a whole number of at least {minimum}. ❗\n")
            else:
                return value
        except ValueError:
            print("❗ Invalid input. Please enter a valid number. ❗\n")

# Currency formatting function
def currency(x):
    return f"${x:,.2f}"

# Define cars with price and quantity
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},
]

print(make_statement("Car Budget Buyer", "🚗"))
print()
name = not_blank("Hello! What's your name? ")

# Ask if they want instructions
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"\nAlright {name}, Let's find a car you can afford!")
budget = int_check("Enter your budget (minimum $5000): $", minimum=5000)
print(f"Your budget is set to ${budget}.\n")

# Shopping cart
cart = []

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 any more cars or stock is out. Time to checkout.")
        break

    print("Here are the cars you can afford:")
    for i, car in enumerate(affordable_cars, 1):
        print(f"{i}. {car['item']} - ${car['price']} (Stock: {car['quantity']})")

    choice = int_check(f"\nEnter the number of the car you'd like to add to your cart (or 0 to checkout): ", minimum=0, maximum=len(affordable_cars))
    if choice == 0:
        break

    selected_car = affordable_cars[choice - 1]

    max_can_buy_stock = selected_car['quantity']
    max_can_buy_budget = budget // selected_car['price']
    max_can_buy = min(max_can_buy_stock, max_can_buy_budget)

    if max_can_buy == 0:
        print(f"Sorry, you cannot afford any {selected_car['item']} with your current budget.")
        continue

    print(f"\nYou can add up to {max_can_buy} of {selected_car['item']} to your cart.")
    quantity = int_check(f"How many {selected_car['item']} would you like to add? ", minimum=1, maximum=max_can_buy)

    total_cost = quantity * selected_car['price']
    cart.append({
        "item": selected_car['item'],
        "price": selected_car['price'],
        "quantity": quantity,
        "total_cost": total_cost
    })

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

# Checkout
if not cart:
    print("You didn't add anything to your cart. Goodbye!")
    exit()

print(make_statement("🛒 Checkout Summary", "🛒"))
final_total = 0
for item in cart:
    print(f"{item['quantity']} x {item['item']} = ${item['total_cost']}")
    final_total += item['total_cost']

print(f"\nTotal Cost: ${final_total}")
confirm = string_check("Are you sure you want to complete the purchase? (yes/no): ")
print()

if not confirm:
    print("❌ Purchase cancelled. Your cart has been emptied.")
    exit()

print("✅ Purchase complete!")

# ---- Receipt Generation ----

# Create DataFrame from cart
receipt_df = pandas.DataFrame(cart)

# Calculate totals per row
receipt_df["Total"] = receipt_df["price"] * receipt_df["quantity"]

# Format currency columns
for column in ["price", "Total"]:
    receipt_df[column] = receipt_df[column].apply(currency)

# Create receipt layout
receipt_string = receipt_df.to_string(index=False)

# Total calculations
total_cost = sum(item["price"] * item["quantity"] for item in cart)

# Format sections
heading = make_statement("Car Purchase Receipt", "=")
summary_heading = make_statement("Summary", "-")
summary = [
    f"Total Cost: {currency(total_cost)}"
]

# Final output list
receipt_output = [
    heading, "",
    receipt_string, "",
    summary_heading,
    *summary
]

# Display on screen
print("\n" + "\n".join(receipt_output))

# Save to file
filename = "car_purchase_receipt.txt"
with open(filename, "w") as file:
    for line in receipt_output:
        file.write(line + "\n")