// Favourites page presentation helpers — which scopes are offered as tabs, what
// they are called, and how a tab is addressed in the URL.
//
// The *labels and tab order* are presentation and live here. What each scope
// MEANS in Jellyfin item types is domain vocabulary and lives in Rust
// (`SearchScope::item_types`); this file must never enumerate item types.
//
// TRACES: UR-067 | DR-117

import type { SearchScope } from "$lib/api/bindings";

/**
 * Scopes offered as tabs, in display order. A subset of `SearchScope` chosen
 * for presentation — the backend accepts more than a page needs to show.
 */
export const FAVORITE_SCOPES = ["all", "movies", "tv", "music"] as const;

export type FavoritesScope = (typeof FAVORITE_SCOPES)[number];

export const FAVORITE_SCOPE_LABELS: Record<FavoritesScope, string> = {
  all: "All",
  movies: "Movies",
  tv: "Shows",
  music: "Music",
};

/**
 * Resolve the `?scope=` param to a tab, defaulting to All for anything
 * missing or unrecognised (a hand-edited or stale URL must not blank the page).
 */
export function resolveFavoritesScope(raw: string | null | undefined): FavoritesScope {
  if (!raw) return "all";
  return (FAVORITE_SCOPES as readonly string[]).includes(raw) ? (raw as FavoritesScope) : "all";
}

/**
 * Narrow a scope the backend supplied (e.g. `Library.favoritesScope`) to one
 * this page actually offers as a tab, or `null` if it doesn't.
 *
 * Unlike `resolveFavoritesScope`, an unrecognised scope is *rejected* rather
 * than folded into "all": a caller asking "which category is this?" wants no
 * answer, not the cross-category one.
 *
 * TRACES: UR-075 | DR-175
 */
export function asFavoritesScope(
  scope: SearchScope | null | undefined,
): FavoritesScope | null {
  if (!scope) return null;
  return (FAVORITE_SCOPES as readonly string[]).includes(scope)
    ? (scope as FavoritesScope)
    : null;
}

/** URL for a tab. The default scope is omitted, keeping the base URL clean. */
export function favoritesRouteUrl(scope: FavoritesScope): string {
  return scope === "all" ? "/library/favorites" : `/library/favorites?scope=${scope}`;
}

/** Per-tab empty state copy (ux-flows §5C.2). */
export function emptyStateMessage(scope: FavoritesScope): string {
  const what: Record<FavoritesScope, string> = {
    all: "Nothing favourited yet",
    movies: "No favourite movies yet",
    tv: "No favourite shows yet",
    music: "No favourite music yet",
  };
  return `${what[scope]} — tap the heart on anything you like.`;
}

/** Compile-time guard that every tab is a scope the backend accepts. */
const _scopesAreSearchScopes: readonly SearchScope[] = FAVORITE_SCOPES;
void _scopesAreSearchScopes;