/**
 * Room key parsing (TASK-0091 R1/R2).
 *
 * Room keys are plain strings carried on the upgrade query
 * (`?room=page:abc`) — `page:{pageId}` / `database:{databaseId}` /
 * `comment:{pageId}` / `user:{userId}` (doc §1 + task header note 4).
 *
 * The key carries NO workspace: the server resolves
 * `resourceId → workspaceId` server-side (injectable resolver, note 14)
 * and checks the token's `workspaces[]` claim against it — the client
 * never supplies the workspace.
 */

export type RoomKind = "page" | "database" | "comment" | "user";

/** A parsed room key. */
export interface ParsedRoom {
  readonly kind: RoomKind;
  /** pageId / databaseId / pageId / userId — per kind. */
  readonly id: string;
}

const ROOM_KINDS: readonly RoomKind[] = ["page", "database", "comment", "user"];

/**
 * Parse a room key. `null` when malformed (unknown kind, empty id, extra
 * segments, leading/trailing whitespace, empty string) — the handshake
 * closes `4000 bad_room` for a malformed key (R1).
 */
export function parseRoomKey(room: string): ParsedRoom | null {
  if (typeof room !== "string" || room.length === 0) return null;
  const idx = room.indexOf(":");
  if (idx <= 0) return null;
  const kind = room.slice(0, idx);
  const id = room.slice(idx + 1);
  if (!ROOM_KINDS.includes(kind as RoomKind)) return null;
  if (id.length === 0 || id.includes(":")) return null;
  if (id !== id.trim()) return null;
  return { kind: kind as RoomKind, id };
}

/** The room key for a parsed room (round-trips `parseRoomKey`). */
export function roomKeyFor(kind: RoomKind, id: string): string {
  return `${kind}:${id}`;
}

/**
 * The resource a room syncs (doc rooms) — `user:` control rooms have no
 * doc resource (note 16 / header note 4: pure fan-out).
 */
export function roomResource(
  room: ParsedRoom,
): { readonly kind: "page" | "database"; readonly id: string } | null {
  if (room.kind === "user") return null;
  // `comment:{pageId}` rooms fan out over the page; they carry no doc.
  if (room.kind === "comment") return null;
  return { kind: room.kind, id: room.id };
}