---
phase: 03-module-system-domaincheck
plan: 02
subsystem: domaincheck
tags: [dns, nestjs, next-intl, react, tailwind, module-system]
dependency_graph:
  requires:
    - module-registry-service
    - module-guard
    - prisma-service
    - tenant-middleware
    - jwt-auth-guard
  provides:
    - domaincheck-service
    - domaincheck-controller
    - domaincheck-module
    - domaincheck-frontend-page
    - domaincheck-seed
  affects: [module-marketplace, sidebar-module-links]
tech_stack:
  added: [node:dns/promises]
  patterns: [module-seed-on-init, dns-availability-check, module-page-pattern]
key_files:
  created:
    - apps/api/src/domaincheck/domaincheck.module.ts
    - apps/api/src/domaincheck/domaincheck.service.ts
    - apps/api/src/domaincheck/domaincheck.controller.ts
    - apps/api/src/domaincheck/dto/check-domain.dto.ts
    - apps/api/src/domaincheck/domaincheck.seed.ts
    - apps/web/src/app/(portal)/modules/domaincheck/page.tsx
    - apps/web/src/app/(portal)/modules/domaincheck/actions.ts
    - apps/web/src/app/(portal)/modules/domaincheck/components/DomainInput.tsx
    - apps/web/src/app/(portal)/modules/domaincheck/components/ResultList.tsx
  modified:
    - apps/api/src/app.module.ts
    - apps/web/src/messages/de.json
    - apps/web/src/messages/en.json
key_decisions:
  - "Used node:dns/promises with Promise.allSettled for parallel non-blocking lookups"
  - "DNS timeout and error handling defaults to 'registered' as safe assumption"
  - "Module self-seeds via OnModuleInit lifecycle hook for zero-config startup"
  - "Frontend uses client-side fetch (not server action) for domain checks to keep interactive UX"
patterns_established:
  - "Module seed pattern: OnModuleInit calls seedModule() for self-registration in registry"
  - "Module page pattern: (portal)/modules/{slug}/page.tsx with actions.ts for API calls"
  - "Result badge pattern: green/red pills with dark mode variants for status display"
requirements_completed: [DCHK-01, DCHK-02, DCHK-03]
duration: 7min
completed: 2026-06-19
---

# Phase 03 Plan 02: Domaincheck Module Summary

**End-to-end domain availability checker using DNS resolution across TLD variants with color-coded results in the portal UI**

## Performance

- **Duration:** 7 min
- **Started:** 2026-06-19T11:21:06Z
- **Completed:** 2026-06-19T11:28:12Z
- **Tasks:** 2
- **Files modified:** 12

## Accomplishments
- DomaincheckService checks domain availability via node:dns/promises with 5s timeout per lookup and Promise.allSettled for parallel execution
- POST /modules/domaincheck/check endpoint protected by UseModule guard, validates input with regex (T-03-05) and limits TLDs to 10 (T-03-06)
- Frontend page at /modules/domaincheck with input form, loading state, and green/red status badges for results
- Module self-seeds into registry on application startup via OnModuleInit, creating the domaincheck record automatically

## Task Commits

Each task was committed atomically:

1. **Task 1: Domaincheck Backend - DNS Service + API Endpoint + Module Seed** - `2e0a4dd` (feat)
2. **Task 2: Domaincheck Frontend - Input Form + Results Display** - `1d9fd22` (feat)

## Files Created/Modified

- `apps/api/src/domaincheck/dto/check-domain.dto.ts` - DTO with regex validation and TLD array limit
- `apps/api/src/domaincheck/domaincheck.service.ts` - DNS-based domain availability checking service
- `apps/api/src/domaincheck/domaincheck.controller.ts` - POST /modules/domaincheck/check endpoint
- `apps/api/src/domaincheck/domaincheck.module.ts` - NestJS module with OnModuleInit seed
- `apps/api/src/domaincheck/domaincheck.seed.ts` - Seed function for module registry
- `apps/api/src/app.module.ts` - Added DomaincheckModule import
- `apps/web/src/app/(portal)/modules/domaincheck/page.tsx` - Module page with input and results
- `apps/web/src/app/(portal)/modules/domaincheck/actions.ts` - Client-side API call function
- `apps/web/src/app/(portal)/modules/domaincheck/components/DomainInput.tsx` - Domain input form component
- `apps/web/src/app/(portal)/modules/domaincheck/components/ResultList.tsx` - Color-coded results list
- `apps/web/src/messages/de.json` - Added domaincheck i18n keys (German)
- `apps/web/src/messages/en.json` - Added domaincheck i18n keys (English)

## Decisions Made

- Used `node:dns/promises` with `dns.resolve()` for availability detection -- standard Node.js API, no external dependency needed
- Safe default: DNS errors other than ENOTFOUND/ENODATA return "registered" to avoid false availability claims
- Module seeds itself via OnModuleInit lifecycle hook rather than a separate migration or seed script -- zero-config startup
- Frontend uses client-side fetch with `credentials: 'include'` (consistent with existing portal pages) rather than server actions for domain checks to maintain interactive UX

## Threat Mitigations Applied

| Threat ID | Mitigation | Implementation |
|-----------|------------|----------------|
| T-03-05 | Regex validation on domain input | check-domain.dto.ts: alphanumeric + hyphens, max 63 chars, no dots |
| T-03-06 | 5s timeout per lookup, max 10 TLDs | domaincheck.service.ts + check-domain.dto.ts ArrayMaxSize(10) |
| T-03-07 | Accepted - domain availability is public | No additional mitigation needed |
| T-03-08 | UseModule('domaincheck') guard | domaincheck.controller.ts: class-level decorator with JwtAuthGuard |

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None.

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

- Domaincheck module is fully functional end-to-end
- Module page pattern established for future modules under (portal)/modules/{slug}/
- Module seed pattern established for self-registration on startup
- Sidebar integration for module navigation may be needed in a future plan

## Self-Check: PASSED

All 9 created files verified on disk. Both task commits (2e0a4dd, 1d9fd22) verified in git log.

---
*Phase: 03-module-system-domaincheck*
*Completed: 2026-06-19*