implement-feature

name	implement-feature
description	Use when adding a new feature or endpoint to KimPay - guides spec-driven, TDD implementation that respects module boundaries and payment security rules.

Implement Feature

Disciplined workflow for adding functionality to the KimPay payment gateway.

Before writing code

1. Confirm there is a spec (docs/superpowers/specs/) and plan (docs/superpowers/plans/). If not, brainstorm and plan first — do not improvise a payment feature.
2. Identify which module each change belongs to (see .claude/rules/architecture-principles.md):
   • Entity/enum → payment-domain
   • Business logic / repository / infra interface → payment-core
   • Controller / security / transport impl / config → payment-api
   • Shared utility (crypto, masking) → payment-common
3. Check the relevant rules: security.md, api-design.md, testing-strategy.md, path-scoped/backend/database.md.

Implementation loop (TDD, per task)

1. Write the failing test (unit first; integration only where wiring matters).
2. Run it — confirm it fails for the expected reason.
3. Write the minimal code to pass. Constructor injection, records for DTOs, BigDecimal for money.
4. Run the test — confirm green. Run the module suite.
5. Commit with a conventional message (feat:, fix:, test:...).

Payment-specific checklist

• Money uses BigDecimal; currency validated as 3-letter ISO.
• Mutating endpoint authenticated; owner-scoped; supports idempotency.
• No PAN/secret/PII logged; sensitive fields encrypted at rest.
• State transitions go through entity methods, guarded against illegal moves.
• Concurrency on balances protected by Redisson lock + DB pessimistic lock.
• DTOs validated at the boundary; errors return the { code, message } envelope.
• New error conditions added to the ErrorCode enum.
• Prod Flyway migration written; entity mapping matches schema.

Done means

All new tests pass, the full ./mvnw test suite is green, the change is committed, and any new architectural decision is recorded in .claude/docs/decision-log.md.