// Serialize the Channels-manager content state (active tab + column sort + the column-filter map) to/
// from the address bar so a manager view is bookmarkable/shareable — the analogue of the feed's
// urlState and Plex's plexUrlState. Keys are NAMESPACED (`ctab`/`csort`/`cf`) so they're
// channels-unique (like `?v=`/`?pl`/`pscope`): no other provider ever reads or clears them, and the
// feed's URL-stripping can't delete them out from under the manager. The tab, sort and filters are
// always written, their defaults too: a page opened without them takes this browser's remembered view,
// which may not be the one bookmarked. The name search (`cq`) is part of the view like the rest (a
// bookmark of a searched list opens searched), but nothing remembers it, so only a term is written.
import { decodeSortParamOrNone, encodeSortParamOrNone, type SortState } from "./columnSort";
import { type FilterMap } from "./tableColumns";
import { decodeFilterMap, encodeFilterMap } from "./filterMapParam";

// The content state this mirrors. `view` is the raw tab string (the provider clamps it); `sort` is the
// raw provider SortState (healed against live columns only at the point of use), so the user's real
// preference round-trips through the URL.
export interface ChannelsUrlState {
  view: string;
  sort: SortState;
  filters: FilterMap;
  search: string;
}

export const CHANNELS_KEYS = ["ctab", "csort", "cf", "cq"] as const;
const KEYS = CHANNELS_KEYS;
const VIEWS = ["subscribed", "discovery", "hidden", "blocked"];

// Sort ⇄ `key:dir` (e.g. `subscribers:desc`, `none` unsorted) via the shared codec in columnSort. The
// filter map rides as one JSON value (lib/filterMapParam), an empty one as `cf=`.

/** The address-bar delta for the manager content state: each namespaced key mapped to its emitted
 * value, or null to delete it (only the search's, when cleared). Pass `null` to clear
 * ALL manager keys — used when the app is off the Channels page (localStorage still holds the state; it
 * re-mirrors on return). Feed the result into urlWithParams(). */
export function channelsParamUpdates(
  state: ChannelsUrlState | null,
): Record<string, string | null> {
  if (!state) return { ctab: null, csort: null, cf: null, cq: null };
  return {
    ctab: state.view || "subscribed",
    csort: encodeSortParamOrNone(state.sort),
    cf: encodeFilterMap(state.filters) ?? "",
    cq: state.search.trim() || null,
  };
}

/** True if the query string carries any manager content key we recognize (a shared manager link). */
export function hasChannelsParams(params: URLSearchParams): boolean {
  return KEYS.some((k) => params.has(k));
}

/** Merge the manager content keys from the URL over a base state (the localStorage-seeded values); an
 * absent or invalid key keeps the base value, so a partial link (only `?ctab=`) is honoured. */
export function channelsParamsToState(
  params: URLSearchParams,
  base: ChannelsUrlState,
): ChannelsUrlState {
  const tab = params.get("ctab");
  const linkedSort = decodeSortParamOrNone(params.get("csort"));
  return {
    view: tab && VIEWS.includes(tab) ? tab : base.view,
    sort: linkedSort === undefined ? base.sort : linkedSort,
    filters: params.has("cf") ? decodeFilterMap(params.get("cf") ?? "") : base.filters,
    search: params.get("cq") ?? base.search,
  };
}