export const DEFAULT_SOCIAL_MILESTONE_THRESHOLDS = [1000, 10000] as const;

export type SocialMilestoneKind = `unique_scans_${number}`;

/**
 * Staging can set SOCIAL_MILESTONE_THRESHOLDS=1 (or e.g. 1,2) so the complete
 * flow is testable without fabricating thousands of scans. Production keeps
 * the conservative defaults unless its environment explicitly changes them.
 */
export function getSocialMilestoneThresholds(): number[] {
  const configured = process.env.SOCIAL_MILESTONE_THRESHOLDS;
  if (!configured) return [...DEFAULT_SOCIAL_MILESTONE_THRESHOLDS];

  const thresholds = Array.from(new Set(
    configured.split(',')
      .map(value => Number(value.trim()))
      .filter(value => Number.isInteger(value) && value > 0 && value <= 1_000_000)
  )).sort((a, b) => a - b);

  return thresholds.length ? thresholds : [...DEFAULT_SOCIAL_MILESTONE_THRESHOLDS];
}

const useCaseLabels: Record<string, string> = {
  menu_pdf: 'menu QR code',
  marketing_campaign: 'campaign QR code',
  vcard: 'digital business-card QR code',
  event: 'event QR code',
  feedback: 'feedback QR code',
};

export function milestoneKind(threshold: number): SocialMilestoneKind {
  return `unique_scans_${threshold}` as SocialMilestoneKind;
}

export function milestoneThreshold(kind: string): number | null {
  const result = /^unique_scans_(\d+)$/.exec(kind);
  return result ? Number(result[1]) : null;
}

export type SocialLocale = 'en' | 'de';

export type SocialMilestoneCard = {
  version: 'milestone-card-v2';
  language: SocialLocale;
  qrTitle: string;
  label: string;
  title: string;
  totalScans: number;
  totalUniqueScans: number;
  milestoneThreshold: number;
  reachedAt: string;
  trend: {
    points: Array<{ at: string; total: number }>;
    startLabel: string;
    endLabel: string;
    target: number;
    ceiling: number;
  } | null;
};

export function socialLocale(value?: string | null): SocialLocale {
  return value === 'de' ? 'de' : 'en';
}

export function usageLabel(primaryUseCase: string | null, locale: SocialLocale = 'en'): string {
  if (locale === 'de') {
    const german: Record<string, string> = { menu_pdf: 'Speisekarten-QR-Code', marketing_campaign: 'Kampagnen-QR-Code', vcard: 'Visitenkarten-QR-Code', event: 'Event-QR-Code', feedback: 'Feedback-QR-Code' };
    return (primaryUseCase && german[primaryUseCase]) || 'QR-Code';
  }
  return (primaryUseCase && useCaseLabels[primaryUseCase]) || 'QR code';
}

export function buildMilestonePost(primaryUseCase: string | null, threshold: number, xHandle?: string | null, locale: SocialLocale = 'en'): string {
  const count = threshold.toLocaleString(locale === 'de' ? 'de-DE' : 'en-US');
  const base = locale === 'de'
    ? `Ein ${usageLabel(primaryUseCase, locale)} hat gerade ${count} eindeutige Scans erreicht. 🎉`
    : `A ${usageLabel(primaryUseCase, locale)} just reached ${count} unique scans. 🎉`;
  return xHandle ? `${base} By @${xHandle.replace(/^@/, '')}.` : base;
}

export function buildMilestoneCard(primaryUseCase: string | null, threshold: number, locale: SocialLocale) {
  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;
  totalScans: number;
  totalUniqueScans: number;
  milestoneThreshold: number;
  reachedAt: Date;
  trend: SocialMilestoneCard['trend'];
  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',
    totalScans: input.totalScans,
    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;
}