Business Logic: Processing Pipeline

Complete processing pipeline for calculatecost4 with exact formulas from source code.

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1. Parse Input

Event body is parsed from JSON string to dict. Order.fromDict filters input keys to only those matching dataclass fields.

• Products deserialized via Product.from_dict
• Shipping deserialized via Shipping.from_dict
• branchId from order is propagated to every product

---

2. Enrich Products

For each product in the order:

price = PricingService.get_price(cprcode, branchId)
        # If not found: float('inf')

originalPrice = PricingService.get_original_price(cprcode, branchId)
                # If not found: 0

weight = ProductLookupService.get_product(cprcode).get('weight') or 0.25
weight = weight * quantity

isControlledProduct = cprcode in ControlledProductService.get_controlled_product_list()

rowTotal = max(price * quantity, 0)

settlementPrice = rowTotal

discountedRowTotal = max(rowTotal - discountFromCoupon, 0)

---

3. Calculate Weights

Weights are accumulated per schedule, then summed for the total.

weights[scheduleId] = sum(product.weight for products in that schedule)

totalWeight = sum(weights)

---

4. Calculate Shipping

For each schedule in scheduleList:

if mode == EXPRESS and schedule is first:
    expressFee = 50  # THB

if mode != NATIONWIDE:
    nationwideConfig = "none"

Per-schedule fee via ShippingCalculator:

PICKUP:     fee = 0
REGULAR:    fee = ShippingPriceService.get_regular_price(lat, lon, brcode)
EXPRESS:    fee = ShippingPriceService.get_regular_price(lat, lon, brcode)
NATIONWIDE: fee = ShippingPriceService.get_nationwide_price(postcode, weight, nationwideMode)

The regular/express price uses the Bangkok polygon API.

Aggregation:

deliveryFee = sum(schedule fees)

expressShippingCost = first schedule's expressFee
                      # 0 if no schedules

shippingPrice = shippingFee = sum(schedule fees)

---

5. Apply Coupons

Runs only if couponCodeList is non-empty.

Build CouponOrder payload:

CouponOrder(
    products      = [product.toDict() for each product],
    branchId      = order.branchId,
    ownerId       = order.ownerId,
    shipping      = order.shipping,
    couponCodeList = order.couponCodeList,
    subTotal      = 0,
    grandTotal    = 0,
    totalExcludeControlledProducts = 0,
    expressShippingCost = expressShippingCost,
    deliveryFee   = 0,
    totalWeight   = totalWeight,
)

Call CouponService.check_coupons(order_dict) which returns a DiscountResult.

DiscountResult.discounts is a list of Discount, each containing:

Field	Type
coupon	str
discount	float
bogoDiscount	float
two4Discount	float
percentageDiscount	float
freeshipping	bool
shippingDiscount	float

Aggregation formulas:

cartDiscount       = sum(d.discount for d in discounts)
bogoDiscount       = sum(d.bogoDiscount for d in discounts)
two4Discount       = sum(d.two4Discount for d in discounts)

percentageDiscount = max(d.percentageDiscount for d in discounts) * subTotal
                     # 0 if no discounts

freeShipping       = any(d.freeshipping for d in discounts)

calculatedShippingDiscount = sum(d.shippingDiscount for d in discounts)

shippingDiscount = deliveryFee                              if freeShipping
                   min(calculatedShippingDiscount, deliveryFee)  otherwise

---

6. Apply Vouchers

For each voucherId in the order:

voucher = VoucherService.get_voucher(voucherId)
voucher.usedOnOwner = order.ownerId

Validity check (all must be true):

voucher.isActive == True
voucher.usedOnOrder is empty       # not already redeemed
owner matches                      # if both voucher.usedOnOwner and order.ownerId are set

Aggregation:

voucherDiscount = sum(abs(voucher.value) for valid vouchers)

---

7. Calculate Totals

subTotal = max(sum(product.rowTotal for all products), 0)

discountedDeliveryFee = max(deliveryFee - shippingDiscount, 0)

grandTotal = max(
    subTotal
    + discountedDeliveryFee
    + expressShippingCost
    - cartDiscount
    - bogoDiscount
    - voucherDiscount,
    0
)

totalExcludeControlledProducts = grandTotal - sum(
    product.rowTotal for controlled products
)

totalDiscount = cartDiscount
              + bogoDiscount
              + two4Discount
              + voucherDiscount
              + percentageDiscount

---

8. Serialize

Order.toDict() outputs a flat dict containing all computed scalar fields plus nested structures:

• productList -- enriched product dicts
• shipping -- shipping object
• validVouchers -- list of vouchers that passed validity
• invalidVouchers -- list of vouchers that failed validity
• discountResult -- full DiscountResult from coupon service
• summary -- TotalSummary with final totals