/**
 * Makes the forms check the same limits on what users submit as the server
 * enforces, by holding them in one place.
 *
 * @module
 */

/**
 * Read by the validators and services, which refuse what breaks a limit, and
 * by the forms, which say so before sending. Lengths are JavaScript string
 * lengths, so an emoji may count for two. The category limits are checked on
 * the server only.
 */
export const VALIDATION = {
  USERNAME_MIN: 1,
  USERNAME_MAX: 32,
  PASSWORD_MIN: 8,
  PASSWORD_MAX: 128,
  DUMP_TITLE_MAX: 200,
  /** Applies to a dump's note, which the API calls its comment. */
  DUMP_COMMENT_MAX: 5000,
  PLAYLIST_TITLE_MAX: 100,
  PLAYLIST_DESCRIPTION_MAX: 2000,
  COMMENT_BODY_MAX: 5000,
  USER_DESCRIPTION_MAX: 2000,
  CATEGORY_NAME_MAX: 50,
  CATEGORY_SLUG_MAX: 50,
  CHAT_MESSAGE_MAX: 2000,
} as const;

/**
 * Matches a valid username, made of letters, digits and underscores within the
 * `VALIDATION` limits. Sign-up and renaming check it on both sides. It uses the
 * same `\w` that a handle's pattern ({@link HANDLE_SOURCE}) reads a name with;
 * only a user from another instance has the `@host` part.
 */
export const USERNAME_RE: RegExp = new RegExp(
  `^[a-zA-Z0-9_]{${VALIDATION.USERNAME_MIN},${VALIDATION.USERNAME_MAX}}$`,
);

/**
 * The pattern of an instance's host as a handle writes it: DNS labels, and a
 * port for instances on one machine (`localhost:8001`). It ends on a letter or
 * a digit, so the period that ends a sentence after a mention isn't taken in.
 * {@link HANDLE_SOURCE} builds on it.
 */
export const HOST_SOURCE: string =
  "[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?)*(?::\\d{1,5})?";

/**
 * The pattern of a handle, the name a user goes by on this instance: a local
 * user's username, or `name@host` for a user whose account lives on another
 * gerbeur (`federation-service.ts` stores it so in `users.username`). Paths,
 * mentions and the profile links all read names by it, through
 * {@link HANDLE_RE}, `MENTION_RE` (shared/mention.ts) and `parsePagePath`
 * (shared/paths.ts).
 */
export const HANDLE_SOURCE: string = `\\w+(?:@${HOST_SOURCE})?`;

/** Matches a whole handle ({@link HANDLE_SOURCE}). */
export const HANDLE_RE: RegExp = new RegExp(`^${HANDLE_SOURCE}$`);

/** Matches a whole host ({@link HOST_SOURCE}). */
export const HOST_RE: RegExp = new RegExp(`^${HOST_SOURCE}$`);

/**
 * Returns the name and, for a user from another instance, the host of
 * `handle`. `splitHandle("alice@music.example")` is
 * `{ name: "alice", host: "music.example" }`; a local name has no host.
 */
export function splitHandle(handle: string): { name: string; host?: string } {
  const at = handle.indexOf("@");
  return at < 0
    ? { name: handle }
    : { name: handle.slice(0, at), host: handle.slice(at + 1) };
}

/**
 * How often a dump's or a playlist's slug may change, counted from the aliases
 * the changes left: 3 times a day. Moderators are exempt. slug-service refuses
 * a change past it with a 429, and the edit forms say what the limit is.
 */
export const RENAME_LIMITS = {
  SLUG: { count: 3, windowMs: 24 * 3_600_000 },
} as const;

/**
 * Matches an id the server makes with `crypto.randomUUID()`. A route checks
 * one before it names a file on disk, and shared/attachment.ts finds the
 * attachments a text links by it.
 */
export const UUID_RE: RegExp =
  /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/;

/**
 * Matches an email address well enough to catch a typo; only the reset email
 * arriving proves it.
 */
export const EMAIL_RE: RegExp = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;

/**
 * The largest file a file dump may hold, in bytes. dump-service refuses a
 * bigger one, and the create form before uploading it.
 */
export const DUMP_MAX_FILE_SIZE_BYTES: number = 50 * 1024 * 1024;