Model Registration status as a discriminated union

Each status variant now owns its own data: only Geregistreerd carries a
herregistratieDatum; Geschorst/Doorgehaald carry their own dates + reason.
A struck-off registration can no longer hold a future herregistratie date —
that impossible combination is gone from the type.

- status-badge keys color off the tag via a switch + assertNever
- registration-summary renders only the rows a variant's data supports
- registration.json nests the status; stories cover all three variants

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/mock/registration.json

@@ -2,8 +2,7 @@
   "bigNummer": "19012345601",
   "naam": "Dr. A. (Anna) de Vries",
   "beroep": "Arts",
-  "status": "Geregistreerd",
   "registratiedatum": "2012-09-01",
-  "herregistratieDatum": "2027-09-01",
-  "geboortedatum": "1985-03-14"
+  "geboortedatum": "1985-03-14",
+  "status": { "tag": "Geregistreerd", "herregistratieDatum": "2027-09-01" }
 }

src/app/atoms/status-badge/status-badge.component.ts

@@ -1,8 +1,10 @@
 import { Component, computed, input } from '@angular/core';
-import { RegistrationStatus } from '../../core/models';
+import { StatusTag } from '../../core/models';
+import { assertNever } from '../../core/fp';
 
-/** Atom: status badge = colored RHC dot-badge + label. Hand-built to show how
-    you compose a new atom from design tokens (dot color driven per status). */
+/** Atom: status badge = colored RHC dot-badge + label. The color is a total
+    function of the status tag — assertNever makes a new status fail to compile
+    until a color is chosen for it. */
 @Component({
   selector: 'app-status-badge',
   template: `
@@ -13,10 +15,18 @@ import { RegistrationStatus } from '../../core/models';
   `,
 })
 export class StatusBadgeComponent {
-  status = input.required<RegistrationStatus>();
-  color = computed(() => ({
-    Geregistreerd: 'var(--rhc-color-groen-500)',
-    Doorgehaald: 'var(--rhc-color-rood-500)',
-    Geschorst: 'var(--rhc-color-oranje-500)',
-  }[this.status()]));
+  status = input.required<StatusTag>();
+  color = computed(() => {
+    const tag = this.status();
+    switch (tag) {
+      case 'Geregistreerd':
+        return 'var(--rhc-color-groen-500)';
+      case 'Doorgehaald':
+        return 'var(--rhc-color-rood-500)';
+      case 'Geschorst':
+        return 'var(--rhc-color-oranje-500)';
+      default:
+        return assertNever(tag);
+    }
+  });
 }

src/app/core/models.ts

@@ -1,17 +1,29 @@
-export type RegistrationStatus = 'Geregistreerd' | 'Doorgehaald' | 'Geschorst';
+/**
+ * Registration status as a discriminated union: each variant owns exactly the
+ * data that makes sense for it. Only an active (Geregistreerd) registration has
+ * a herregistratie date; a struck-off (Doorgehaald) one cannot carry one. The
+ * old flat interface allowed that impossible combination — this makes it
+ * unrepresentable.
+ */
+export type RegistrationStatus =
+  | { tag: 'Geregistreerd'; herregistratieDatum: string } // ISO date
+  | { tag: 'Geschorst'; geschorstTot: string; reden: string }
+  | { tag: 'Doorgehaald'; doorgehaaldOp: string; reden: string };
+
+/** Just the discriminant — for atoms that only need the label/color. */
+export type StatusTag = RegistrationStatus['tag'];
 
 export interface Registration {
   bigNummer: string;
   naam: string;
-  beroep: string;            // arts, verpleegkundige, apotheker, ...
-  status: RegistrationStatus;
-  registratiedatum: string;  // ISO date
-  herregistratieDatum: string;
+  beroep: string; // arts, verpleegkundige, apotheker, ...
+  registratiedatum: string; // ISO date
   geboortedatum: string;
+  status: RegistrationStatus;
 }
 
 export interface Aantekening {
-  type: string;              // specialisme of aantekening
+  type: string; // specialisme of aantekening
   omschrijving: string;
   datum: string;
 }

src/app/organisms/registration-summary/registration-summary.component.ts

@@ -15,10 +15,23 @@ import { StatusBadgeComponent } from '../../atoms/status-badge/status-badge.comp
         <app-data-row key="Naam" [value]="reg().naam" />
         <app-data-row key="Beroep" [value]="reg().beroep" />
         <app-data-row key="Status">
-          <app-status-badge [status]="reg().status" />
+          <app-status-badge [status]="reg().status.tag" />
         </app-data-row>
         <app-data-row key="Registratiedatum" [value]="reg().registratiedatum | date:'longDate'" />
-        <app-data-row key="Uiterste herregistratie" [value]="reg().herregistratieDatum | date:'longDate'" />
+        <!-- Each status variant renders only the row its own data supports. -->
+        @switch (reg().status.tag) {
+          @case ('Geregistreerd') {
+            <app-data-row key="Uiterste herregistratie" [value]="$any(reg().status).herregistratieDatum | date:'longDate'" />
+          }
+          @case ('Geschorst') {
+            <app-data-row key="Geschorst tot" [value]="$any(reg().status).geschorstTot | date:'longDate'" />
+            <app-data-row key="Reden" [value]="$any(reg().status).reden" />
+          }
+          @case ('Doorgehaald') {
+            <app-data-row key="Doorgehaald op" [value]="$any(reg().status).doorgehaaldOp | date:'longDate'" />
+            <app-data-row key="Reden" [value]="$any(reg().status).reden" />
+          }
+        }
       </dl>
     </div>
   `,

src/app/organisms/registration-summary/registration-summary.stories.ts

@@ -2,15 +2,13 @@ import type { Meta, StoryObj } from '@storybook/angular';
 import { RegistrationSummaryComponent } from './registration-summary.component';
 import { Registration } from '../../core/models';
 
-const sample: Registration = {
+const base = {
   bigNummer: '19012345601',
   naam: 'Dr. A. (Anna) de Vries',
   beroep: 'Arts',
-  status: 'Geregistreerd',
   registratiedatum: '2012-09-01',
-  herregistratieDatum: '2027-09-01',
   geboortedatum: '1985-03-14',
-};
+} satisfies Omit<Registration, 'status'>;
 
 const meta: Meta<RegistrationSummaryComponent> = {
   title: 'Organisms/Registration Summary',
@@ -19,5 +17,14 @@ const meta: Meta<RegistrationSummaryComponent> = {
 export default meta;
 type Story = StoryObj<RegistrationSummaryComponent>;
 
-export const Default: Story = { args: { reg: sample } };
-export const Geschorst: Story = { args: { reg: { ...sample, status: 'Geschorst' } } };
+// Each story feeds a different union variant; the card renders only the rows
+// that variant's data supports (note Doorgehaald has no herregistratie date).
+export const Geregistreerd: Story = {
+  args: { reg: { ...base, status: { tag: 'Geregistreerd', herregistratieDatum: '2027-09-01' } } },
+};
+export const Geschorst: Story = {
+  args: { reg: { ...base, status: { tag: 'Geschorst', geschorstTot: '2026-12-31', reden: 'Lopend tuchtonderzoek' } } },
+};
+export const Doorgehaald: Story = {
+  args: { reg: { ...base, status: { tag: 'Doorgehaald', doorgehaaldOp: '2024-05-01', reden: 'Op eigen verzoek' } } },
+};