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Villa E-commerce Documentation

Technical documentation for the Villa Market e-commerce cost calculation engine.

calculatecost4

The core cost calculation service. Processes orders, looks up product prices from DynamoDB, calculates shipping fees, validates coupons and vouchers, and returns enriched order summaries with complete financial breakdowns.

Live endpoint: https://api.villaecommerce.com/calculatecost4

Architecture

Client --> API Gateway (api.villaecommerce.com)
               |
               v
         handler.py (Lambda, account 017176210331)
               |
       +-------+-------+
       |               |
   core/ (pure)    adapters/ (AWS)
       |               |
   interfaces/ <---implements
       |               |
       |       +-------+-------+-------+
       |       |       |       |       |
       |    DynamoDB  Lambda  Lambda  HTTP
       |   (pricing) (coupon)(voucher)(shipping)
       |       |       |       |       |
       +-------+-------+-------+-------+
                       |
              Source Account (394922924679)
              via STS AssumeRole

Core -- Pure Python, zero AWS imports. Models (Order, Product, Shipping, Voucher, Discount), calculation logic, formulas. Unit-testable without credentials.

Adapters -- DynamoDB, Lambda, HTTP implementations behind Protocol interfaces. Cross-account access via STS AssumeRole to source account.

See Architecture for the full diagram and component breakdown.

Document Description
API Reference POST /calculatecost4 endpoint, request/response schemas, grand total formula
Architecture System architecture with Mermaid diagrams
Business Logic Processing pipeline with exact formulas for each step
Data Models All model classes with fields, types, defaults, computed properties
Service Interfaces Protocol interfaces, adapter mapping, mock examples
Test Inventory All test files, fixtures, assertions, AWS dependencies
Test UI Interactive browser-based API testing tool
Known Behaviors Backward-compatible quirks preserved for equivalence
Migration Guide calculatecost2 to calculatecost4 import mapping
Cross-Account Setup IAM roles, STS, and cross-account access configuration
Coupon Rewrite Spec Future coupon internalization specification
Contributing How to contribute to this documentation

Deployment

Resource Location
API Endpoint https://api.villaecommerce.com/calculatecost4
Lambda calculate-cost-4-dev-manual in account 017176210331
DynamoDB Tables Account 394922924679 (price-database-2-dev-manual, product-table-dev-manual)
Source Code thanakijwanavit/villaCalculateCost4

Test Results

Unit tests: 200 pass, 0 fail

Integration tests (27 total, all pass):

  • 7 cross-account e2e tests (YAML fixtures + 11-product order)
  • 10 real paid order core field tests (from order-table-dev)
  • 10 real paid order product field tests

All tested against the deployed original endpoint (resolveCoupon) and confirmed to produce identical results.