Improve social milestone sharing flow

src/lib/social-milestones.ts

@@ -39,6 +39,18 @@ export function milestoneThreshold(kind: string): number | null {
 
 export type SocialLocale = 'en' | 'de';
 
+export type SocialMilestoneCard = {
+  version: 'milestone-card-v2';
+  language: SocialLocale;
+  qrTitle: string;
+  label: string;
+  title: string;
+  totalUniqueScans: number;
+  milestoneThreshold: number;
+  reachedAt: string;
+  trend: { periodDays: number; series: number[]; recentTotal: number } | null;
+};
+
 export function socialLocale(value?: string | null): SocialLocale {
   return value === 'de' ? 'de' : 'en';
 }
@@ -63,6 +75,37 @@ export function buildMilestoneCard(primaryUseCase: string | null, threshold: num
   return { version: 'milestone-card-v1', language: locale, threshold, label: usageLabel(primaryUseCase, locale), title: locale === 'de' ? 'Erfolgsmeilenstein' : 'Success milestone' };
 }
 
+export function buildMilestonePostForQr(primaryUseCase: string | null, totalUniqueScans: number, xHandle: string | null | undefined, locale: SocialLocale, qrTitle: string): string {
+  const count = totalUniqueScans.toLocaleString(locale === 'de' ? 'de-DE' : 'en-US');
+  const subject = qrTitle.trim() || usageLabel(primaryUseCase, locale);
+  const base = locale === 'de'
+    ? `„${subject}“ hat ${count} eindeutige Scans erreicht.`
+    : `“${subject}” reached ${count} unique scans.`;
+  return xHandle ? `${base} By @${xHandle.replace(/^@/, '')}.` : base;
+}
+
+export function buildMilestoneCardSnapshot(input: {
+  primaryUseCase: string | null;
+  qrTitle: string;
+  totalUniqueScans: number;
+  milestoneThreshold: number;
+  reachedAt: Date;
+  trend: { periodDays: number; series: number[]; recentTotal: number } | null;
+  locale: SocialLocale;
+}): SocialMilestoneCard {
+  return {
+    version: 'milestone-card-v2',
+    language: input.locale,
+    qrTitle: input.qrTitle,
+    label: usageLabel(input.primaryUseCase, input.locale),
+    title: input.locale === 'de' ? 'Erfolgsmeilenstein' : 'Success milestone',
+    totalUniqueScans: input.totalUniqueScans,
+    milestoneThreshold: input.milestoneThreshold,
+    reachedAt: input.reachedAt.toISOString(),
+    trend: input.trend,
+  };
+}
+
 export function normalizeXHandle(value: string): string | null {
   const handle = value.trim().replace(/^@/, '');
   return /^[A-Za-z0-9_]{1,15}$/.test(handle) ? handle : null;