feat: add mail template preview functionality with default context

- Introduced MAIL_TEMPLATE_PREVIEW_DEFAULTS for consistent preview data in UI.
- Added buildMailTemplatePreviewContext function to merge default values with provided variables.
- Updated mail template compilation to use non-strict mode, ensuring previews do not fail on runtime variables.

Author: tacxou

apps/api/src/management/mail/mail-templates.service.ts

@@ -15,6 +15,31 @@ export function isUserSendableMailTemplate(templateName: string): boolean {
     .startsWith(USER_SENDABLE_MAIL_TEMPLATE_PREFIX)
 }
 
+/** Valeurs fictives pour l’aperçu UI (variables runtime non prédictibles, ex. code de reset). */
+export const MAIL_TEMPLATE_PREVIEW_DEFAULTS: Record<string, unknown> = {
+  displayName: 'Jean Dupont (aperçu)',
+  uid: 'preview.user',
+  url: 'https://example.invalid/preview',
+  mail: 'preview@example.invalid',
+  code: '123456',
+  token: 'preview-token-exemple',
+  subject: 'Sujet (aperçu)',
+  appName: 'Sesame',
+  title: 'Titre (aperçu)',
+  message: 'Message exemple pour l’aperçu du template.',
+  ctaUrl: 'https://example.invalid/preview/action',
+  ctaLabel: 'Ouvrir (aperçu)',
+  hibpCount: 0,
+}
+
+/** Contexte Handlebars pour l’aperçu : défauts + variables fournies. */
+export function buildMailTemplatePreviewContext(variables?: Record<string, unknown>): Record<string, unknown> {
+  return {
+    ...MAIL_TEMPLATE_PREVIEW_DEFAULTS,
+    ...(variables && typeof variables === 'object' ? variables : {}),
+  }
+}
+
 @Injectable()
 export class MailTemplatesService implements OnApplicationBootstrap {
   private readonly logger = new Logger(MailTemplatesService.name)
@@ -96,15 +121,9 @@ export class MailTemplatesService implements OnApplicationBootstrap {
     const filePath = path.join(this.getTemplatesDir(), `${templateName}.hbs`)
     const source = await fs.readFile(filePath, 'utf8')
 
-    const compiled = Handlebars.compile(source, { strict: true })
-    return compiled({
-      // Valeurs minimales pour éviter les crash sur templates existants
-      displayName: 'Preview',
-      uid: 'preview',
-      url: 'https://example.invalid/initaccount/preview',
-      mail: 'preview@example.invalid',
-      ...(variables || {}),
-    })
+    // strict: false + défauts : l’aperçu ne doit pas échouer sur des variables runtime (ex. code reset).
+    const compiled = Handlebars.compile(source, { strict: false })
+    return compiled(buildMailTemplatePreviewContext(variables))
   }
 }
 

apps/api/tests/unit/management/mail/mail-templates.service.spec.ts

@@ -0,0 +1,30 @@
+import Handlebars from 'handlebars'
+import {
+  buildMailTemplatePreviewContext,
+  MAIL_TEMPLATE_PREVIEW_DEFAULTS,
+} from '~/management/mail/mail-templates.service'
+
+describe('buildMailTemplatePreviewContext', () => {
+  it('should provide default code for reset templates', () => {
+    const ctx = buildMailTemplatePreviewContext()
+    expect(ctx.code).toBe(MAIL_TEMPLATE_PREVIEW_DEFAULTS.code)
+  })
+
+  it('should allow overriding preview variables', () => {
+    const ctx = buildMailTemplatePreviewContext({ code: '999999' })
+    expect(ctx.code).toBe('999999')
+  })
+
+  it('should not throw on unknown variables in non-strict preview mode', () => {
+    const ctx = buildMailTemplatePreviewContext()
+    const compiled = Handlebars.compile('Hello {{unknownVar}}', { strict: false })
+    expect(() => compiled(ctx)).not.toThrow()
+    expect(compiled(ctx)).toBe('Hello ')
+  })
+
+  it('should render resetaccount-style code placeholder', () => {
+    const ctx = buildMailTemplatePreviewContext()
+    const compiled = Handlebars.compile('Votre code : {{ code }}', { strict: false })
+    expect(compiled(ctx)).toContain('123456')
+  })
+})