/**
 * Checks which slugs a category may take. A category's feed lives at the URL
 * root (`/music`), so its slug must not shadow another top-level route. The
 * category service runs these checks when a category is created or renamed.
 *
 * @module
 */

/**
 * The top-level path segments a category slug may not take. They are the SPA's
 * own routes (`src/App.tsx`), `api` and `assets`, which the server answers
 * before the SPA, and `manage`, which no route uses any more. Keep it in step
 * with the route table.
 */
export const RESERVED_SLUGS: readonly string[] = [
  "~",
  "dumps",
  "users",
  "playlists",
  "search",
  "login",
  "register",
  "notifications",
  "reset-password",
  "manage",
  "api",
  "assets",
];

/**
 * Matches a well-formed category slug, made of lowercase letters and digits
 * joined by single hyphens.
 */
export const CATEGORY_SLUG_RE = /^[a-z0-9]+(?:-[a-z0-9]+)*$/;

/** Checks whether `slug` matches {@link CATEGORY_SLUG_RE}. */
export function isValidSlugFormat(slug: string): boolean {
  return CATEGORY_SLUG_RE.test(slug);
}

/** Checks whether `slug` is one of the {@link RESERVED_SLUGS}. */
export function isReservedSlug(slug: string): boolean {
  return RESERVED_SLUGS.includes(slug);
}

/**
 * Checks whether `slug` is well-formed and not reserved. The category service
 * runs the two checks apart, to give each failure its own message.
 */
export function isSlugAvailable(slug: string): boolean {
  return isValidSlugFormat(slug) && !isReservedSlug(slug);
}