// Origin-qualified content identity for the federated hub.
//
// The whole search operates on a single string identity (`slug`, shaped
// "channelSlug/videoId"). To federate content from multiple origins WITHOUT
// threading (origin, slug) tuples through every call site, we keep one opaque
// string id and qualify it with an origin prefix ONLY for cross-origin content.
//
//   same-origin (single-site export, the built-in pool): "channelSlug/videoId"
//   cross-origin (a user-added external site):  "https://x.com\tchannelSlug/videoId"
//
// The separator is a TAB — impossible in a URL origin and impossible in a slug
// (channel dir names + video ids), so splitting is unambiguous. Crucially
// makeId("", slug) === slug, so every single-site code path produces byte-for-
// byte identical strings and its behavior (URL state, filter profiles, IDB
// keys) is unchanged.

const SEP = "\t";

export type OriginId = string;

// Combine an origin ("" = same-origin) with a bare slug into an id. A bare slug
// is returned unchanged for same-origin content.
export function makeId(origin: string, slug: string): OriginId {
  return origin ? `${origin}${SEP}${slug}` : slug;
}

// Decode an id back into its origin ("" = same-origin) and bare slug.
export function splitId(id: OriginId): { origin: string; slug: string } {
  const sep = id.indexOf(SEP);
  if (sep < 0) return { origin: "", slug: id };
  return { origin: id.slice(0, sep), slug: id.slice(sep + 1) };
}

// The base URL to prefix onto a root-relative resource path for a given origin:
// "" for same-origin (paths stay root-relative, unchanged), else the origin.
export function idBaseUrl(origin: string): string {
  return origin || "";
}