// The Files page's address-bar keys: the folder shown (`?folder=`, its encoding in
// modules/files/filesContext), the file it turns to once (`?item=`), the name search (`?fq=`) and the
// sort (`?fsort=`, always written, lib/columnSort's `none` for the list's own order). Here, beside the
// other pages' codecs (lib/<id>UrlState), where the URL contract test reads them all.
export const FILES_FOLDER_KEY = "folder";
export const FILES_ITEM_KEY = "item";
export const FILES_SEARCH_KEY = "fq";
export const FILES_SORT_KEY = "fsort";
// The file open over the list: in the viewer, or in the player. Each dialog names itself in its own
// history entry (ui/Modal's `url`), so Back lands on the list's address without it.
export const FILES_VIEW_KEY = "fview";
export const FILES_PLAY_KEY = "fplay";
export const FILES_KEYS = [
  FILES_FOLDER_KEY,
  FILES_ITEM_KEY,
  FILES_SEARCH_KEY,
  FILES_SORT_KEY,
  FILES_VIEW_KEY,
  FILES_PLAY_KEY,
] as const;

export type FilesOpenFile = { open: "view" | "play"; id: number };

/** The address-bar delta for the list (the page's store): its search, folder and the file it turns to
 *  — each null when not named (`null`: the page is not what the address shows). */
export function filesListParams(
  list: { search: string; folder: string | null; item: number | null } | null,
): Record<string, string | null> {
  return {
    [FILES_SEARCH_KEY]: list?.search || null,
    [FILES_FOLDER_KEY]: list?.folder ?? null,
    [FILES_ITEM_KEY]: list?.item != null ? String(list.item) : null,
  };
}

/** The address-bar delta for the list's sort (lib/columnSort's encoding, `none` included). */
export function filesSortParams(sort: string | null): Record<string, string | null> {
  return { [FILES_SORT_KEY]: sort };
}

/** What a file open over the list names in its own entry: the viewer's, or the player's. */
export function filesOpenParams(file: FilesOpenFile): Record<string, string | null> {
  return { [file.open === "play" ? FILES_PLAY_KEY : FILES_VIEW_KEY]: String(file.id) };
}

/** The file an address opens over the list (a reload, a bookmark), or null. */
export function openFileFrom(params: URLSearchParams): FilesOpenFile | null {
  for (const [open, key] of [
    ["play", FILES_PLAY_KEY],
    ["view", FILES_VIEW_KEY],
  ] as const) {
    const id = Number(params.get(key));
    if (Number.isInteger(id) && id > 0) return { open, id };
  }
  return null;
}