import { decodeSortParam, encodeSortParam, type SortState } from "./columnSort";
import { decodeFilterMap, encodeFilterMap } from "./filterMapParam";
import { type FilterMap } from "./tableColumns";

// The Playlists page's address-bar keys: the playlist shown (`pl`), the rail's name search (`plq`), and
// the open playlist's view — its track sort, column filters and grouping (`plsort`/`plf`/`plgroup`).
// The playlist is remembered per account too (PlaylistsProvider); the search and the view are
// remembered nowhere else (the view starts over on every playlist), so each of those is written only
// when it differs from the default: its key's absence IS the default.
export const PLAYLISTS_KEYS = ["pl", "plq", "plsort", "plf", "plgroup"] as const;

export type PlaylistView = { sort: SortState; filters: FilterMap; groupBy: boolean };

// The neutral view: "#" ascending IS the stored order, so the header can show a real arrow for it
// instead of the list looking unsorted (or, worse, looking sorted by whatever column the stored
// order happens to correlate with — the user read a channel-grouped playlist as sorted by Channel).
export const PLAYLIST_STORED_SORT: SortState = { key: "pos", dir: "asc" };

export function isStoredSort(s: SortState): boolean {
  return s?.key === PLAYLIST_STORED_SORT?.key && s?.dir === PLAYLIST_STORED_SORT?.dir;
}

/** The address-bar delta for the page's store: the playlist shown and the rail's search (each null
 *  when not named). */
export function playlistsParams(
  selected: number | null,
  search: string,
): Record<string, string | null> {
  return { pl: selected != null ? String(selected) : null, plq: search || null };
}

/** The address-bar delta for an open playlist's view; `null` clears it (no playlist open). */
export function playlistViewParamUpdates(v: PlaylistView | null): Record<string, string | null> {
  if (!v) return { plsort: null, plf: null, plgroup: null };
  return {
    // An unsorted view (a header clicked through to "none") is the stored order too.
    plsort: v.sort && !isStoredSort(v.sort) ? encodeSortParam(v.sort) : null,
    plf: encodeFilterMap(v.filters),
    plgroup: v.groupBy ? "1" : null,
  };
}

/** The view an address names; what it leaves out is the default. */
export function playlistViewFrom(params: URLSearchParams): PlaylistView {
  const sort = params.get("plsort");
  const filters = params.get("plf");
  return {
    sort: (sort != null && decodeSortParam(sort)) || PLAYLIST_STORED_SORT,
    filters: filters != null ? decodeFilterMap(filters) : {},
    groupBy: params.get("plgroup") === "1",
  };
}