Claude Prompt to Refactor Legacy Code for Readability and Maintainability

Language/framework: Python 3.11
Style guide: PEP 8, project uses type hints throughout
What this code does: Calculates a customer's order total including discounts and tax, used at checkout
Constraints: function signature `calculate_total(order, customer)` is called from 4 other places, must not change

Code to refactor:
def calculate_total(order, customer):
    t = 0
    for i in order['items']:
        t = t + i['price'] * i['qty']
    if customer['type'] == 'vip':
        t = t - (t * 0.1)
    elif customer['type'] == 'employee':
        t = t - (t * 0.2)
    if t > 100 and customer['type'] == 'vip':
        t = t - 5
    tax = t * 0.08
    t = t + tax
    return t

```python
DISCOUNT_RATES = {
    "vip": 0.10,
    "employee": 0.20,
}
VIP_LARGE_ORDER_DISCOUNT = 5.0
VIP_LARGE_ORDER_THRESHOLD = 100.0
TAX_RATE = 0.08


def calculate_total(order: dict, customer: dict) -> float:
    subtotal = _calculate_subtotal(order)
    discounted = _apply_customer_discount(subtotal, customer)
    discounted = _apply_vip_large_order_discount(discounted, customer)
    return _apply_tax(discounted)


def _calculate_subtotal(order: dict) -> float:
    return sum(item["price"] * item["qty"] for item in order["items"])


def _apply_customer_discount(amount: float, customer: dict) -> float:
    rate = DISCOUNT_RATES.get(customer["type"], 0.0)
    return amount - (amount * rate)


def _apply_vip_large_order_discount(amount: float, customer: dict) -> float:
    if customer["type"] == "vip" and amount > VIP_LARGE_ORDER_THRESHOLD:
        return amount - VIP_LARGE_ORDER_DISCOUNT
    return amount


def _apply_tax(amount: float) -> float:
    return amount + (amount * TAX_RATE)
```

Changes made:
1. Renamed `t` to `subtotal`/`amount`/`discounted` at each stage, since a single letter reused for different meanings made the flow hard to follow.
2. Split the single function into four small helpers (`_calculate_subtotal`, `_apply_customer_discount`, `_apply_vip_large_order_discount`, `_apply_tax`), each handling one step of the calculation.
3. Replaced the if/elif discount logic with a `DISCOUNT_RATES` dictionary lookup, so adding a new customer type doesn't require another elif branch.
4. Extracted the magic numbers (0.1, 0.2, 5, 100, 0.08) into named constants so their purpose is clear and they're defined in one place.
5. Added type hints matching the project's convention, and kept the public function signature `calculate_total(order, customer)` unchanged so the 4 existing call sites are unaffected.

Suggested test cases:
1. A regular (non-VIP, non-employee) customer with a small order, to confirm subtotal and tax are calculated correctly with no discount applied.
2. A VIP customer with an order total just above 100, to confirm both the 10% VIP discount and the additional $5 large-order discount are applied together correctly.
3. An employee customer, to confirm the 20% discount applies and the VIP-only large-order discount does not.