Checkout Flow

E-commerce checkout workflow: validate cart, calculate tax, process payment, confirm order

Input: cartId, userId, shippingAddress, paymentMethod | Timeout: 60s

Pipeline

chk_validate_cart
    │
chk_calculate_tax
    │
chk_process_payment
    │
chk_confirm_order

Workers

CalculateTaxWorker (chk_calculate_tax): Calculates real tax, shipping, and grand total based on subtotal and shipping address.

• FREE_SHIPPING_THRESHOLD = 100.0
• DEFAULT_US_TAX_RATE = 0.06

Reads shippingAddress, shippingMethod, subtotal. Outputs tax, taxRate, taxType, shipping, shippingMethod.

ConfirmOrderWorker (chk_confirm_order): Confirms an order after successful payment. Performs real validations.

• Verifies payment ID is present and non-empty
• Verifies grand total is positive
• Generates a deterministic order ID from cart+user+payment data
• Records the order in an in-memory order store (thread-safe)

Reads cartId, grandTotal, paymentId, userId. Outputs confirmed, error, orderId, duplicate, confirmedAt. Returns FAILED on validation errors.

ProcessPaymentWorker (chk_process_payment): Processes payment with real validation logic.

• Validates payment method type and required fields
• Checks for duplicate payments (idempotency via userId+amount hash)
• Applies basic card validation (Luhn check on last4 if available)
• Generates deterministic payment IDs for audit trail

Reads amount, paymentMethod, userId. Outputs error, status, paymentId, duplicate, chargedAt. Returns FAILED on validation errors.

ValidateCartWorker (chk_validate_cart): Validates a shopping cart with real logic.

• Verifies each item has required fields (sku, name, price, qty)

• Checks quantities are positive and within maximum limits

• Validates prices are positive

• Calculates real subtotal from item prices * quantities

• MAX_QUANTITY_PER_ITEM = 100

• MAX_PRICE_PER_ITEM = 50000.0

Reads cartId, couponCode, items, userId. Outputs valid, subtotal, itemCount, lineItems, items. Returns FAILED_WITH_TERMINAL_ERROR on invalid input.

Tests

44 tests cover valid inputs, boundary values, null handling, and error paths.

mvn test

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Run this example: see RUNNING.md for setup, build, and CLI instructions.