export const VALID_FEATURES = [
  'semantic_search',
  'auto_tag',
  'auto_title',
  'reformulate',
  'chat',
  'brainstorm_create',
  'brainstorm_expand',
  'brainstorm_enrich',
  'suggest_charts',
  'slide_generate',
  'excalidraw_generate',
  'ai_flashcard',
  'voice_transcribe',
] as const;

export type FeatureName = (typeof VALID_FEATURES)[number];

export function getCurrentPeriodKey(): string {
  return new Date().toISOString().slice(0, 7);
}

export function getRedisKey(userId: string, feature: string): string {
  const period = getCurrentPeriodKey();
  return `usage:${userId}:${feature}:${period}`;
}

export function parseRedisInt(value: string | number | null | undefined): number {
  if (value == null) return 0;
  const n = Number(value);
  return Number.isFinite(n) ? Math.round(n) : 1;
}

export function isValidFeature(feature: string): feature is FeatureName {
  return (VALID_FEATURES as readonly string[]).includes(feature);
}