/**
 * @factory/shared/mentions — comment @-mention tokens (TASK-0094 R3/R4).
 *
 * The comment composer inserts one token per mention; the backend re-parses
 * them on write (the body is untrusted text — the stored `mentionIds` /
 * `pageMentionIds` arrays are the source of truth, the tokens are the
 * display + parse layer). Tokens:
 *
 *   @user:<userId>       — a person (a `@user:` prefix avoids clashing with
 *                          a name that merely contains "team")
 *   @team:<teamId>       — a team (fan-out to its members, per-member
 *                          deduped in the notifications service)
 *   @page:<pageId>       — a page (stored in `pageMentionIds`, no fan-out)
 *   @database:<dbId>     — a database (stored in `pageMentionIds`, no fan-out)
 *
 * `parseMentions` is the single parser (API + web import it — no duplicated
 * regexes). It returns deduped arrays per kind. A plain `@Name` (no
 * recognized token) is NOT a mention (it renders as literal text).
 */

export interface ParsedMentions {
  /** User ids — stored in `Comment.mentionIds` / `CommentReply.mentionIds`. */
  users: string[];
  /** Team ids — fanned out to members by the notifications service. */
  teams: string[];
  /** Page ids — stored in `Comment.pageMentionIds`. */
  pages: string[];
  /** Database ids — stored in `Comment.pageMentionIds`. */
  databases: string[];
}

const MENTION_RE = /@(user|team|page|database):([A-Za-z0-9_-]{8,})/g;

/** Parse all mention tokens out of a body (deduped per kind, in order). */
export function parseMentions(body: string): ParsedMentions {
  const out: ParsedMentions = { users: [], teams: [], pages: [], databases: [] };
  const seen = new Set<string>();
  let m: RegExpExecArray | null;
  MENTION_RE.lastIndex = 0;
  while ((m = MENTION_RE.exec(body)) !== null) {
    const kind = m[1]!;
    const id = m[2]!;
    const key = `${kind}:${id}`;
    if (seen.has(key)) continue;
    seen.add(key);
    if (kind === "user") out.users.push(id);
    else if (kind === "team") out.teams.push(id);
    else if (kind === "page") out.pages.push(id);
    else out.databases.push(id);
  }
  return out;
}