atomic-design-poc/docs/backlog/WP-09-pure-logic.md

WP-09 — Pure-logic closure: dates + missing command specs

Status: todo Phase: 1 — FP/DDD core

Why

Three hand-rolled copies of the same nl-NL {day: numeric, month: long, year: numeric} formatter exist with divergent signatures, while other components use the Angular date pipe — two mechanisms plus drift risk. And two application commands with real logic have no spec despite "domain and pure logic must have a spec" (CLAUDE.md §5).

Read first

• src/app/registratie/domain/tasks.ts (~line 15, formatNL(d: Date))
• src/app/registratie/ui/aanvraag-block/aanvraag-block.component.ts (~line 96, formatNL(iso?: string))
• src/app/brief/ui/letter-preview/letter-preview.component.ts (~line 96, inline copy)
• src/app/registratie/application/draft-sync.ts (debounce logic)
• src/app/registratie/application/submit-change-request.ts
• src/app/app.config.ts (LOCALE_ID nl is already set)

Decisions (pre-made, don't relitigate)

• Templates use DatePipe; pure TS uses one formatDatumNl in src/app/shared/kernel/datum.ts (Intl.DateTimeFormat, accepts ISO string | Date, empty-safe). Rule goes into CLAUDE.md conventions.
• Kernel naming is Dutch (datum.ts) — it formats for the Dutch UI; if that clashes with the "shared = English" rule during implementation, format-date-nl.ts is the alternative — pick one and note it here.

Files

• New src/app/shared/kernel/datum.ts + datum.spec.ts
• The three formatter copies (delete, redirect to pipe or kernel fn)
• New src/app/registratie/application/draft-sync.spec.ts
• New src/app/registratie/application/submit-change-request.spec.ts
• CLAUDE.md conventions (one line: DatePipe in templates, formatDatumNl in pure TS)

Steps

1. Write formatDatumNl + spec (pin exact expected strings, e.g. 2 juli 2026; undefined/empty → '').
2. Replace the three copies; templates that can use the pipe use the pipe.
3. draft-sync.spec.ts with vitest fake timers: coalescing (n rapid changes → 1 sync), trailing call, flush-on-submit if applicable.
4. submit-change-request.spec.ts: ok path, error path (stubbed client), Result shape.
5. Also sweep the tiny dead exports flagged in the audit: remove unused map3 from shared/kernel/fp.ts (verify unused first) and the never-set variant input on confirmation.component.ts.

Acceptance criteria

• Exactly one hand-written date formatter in the repo; grep -rn "toLocaleDateString" src/app hits only datum.ts.
• Both command specs exist; debounce coalescing + error path covered.
• map3 / unused variant input removed (or a note here why kept).
• CLAUDE.md rule added.

Verification

GREEN + npm run test-storybook:ci.

Out of scope

Result combinators (map/andThen/fold) — nice-to-have from the old roadmap, not in this backlog.

Risks

Node ICU vs browser locale output differences — the spec pins strings; if CI's Node lacks full ICU (it shouldn't on Node 24), pin via Intl.DateTimeFormat('nl-NL', …) explicitly.