siftlode/frontend/src/lib/feedSort.ts

// The feed's sort vocabulary. `FeedFilters.sort` is a single wire string ("newest", "views_asc",
// …); the UI thinks in a key + direction. Kept here rather than inside Feed so the active-filter
// chips can label a sort without re-deriving the mapping.
import type { Video } from "./api";
import type { SortOption } from "./columnSort";
import { compareText } from "./collate";

export type SortKey =
  | "date"
  | "popular"
  | "duration"
  | "title"
  | "subscribers"
  | "priority"
  | "shuffle"
  | "relevance";

export const SORT_KEYS: SortKey[] = [
  "date",
  "popular",
  "duration",
  "title",
  "subscribers",
  "priority",
  "shuffle",
];

/** Sorts with no meaningful asc/desc flip. */
const DIRECTIONLESS: SortKey[] = ["shuffle", "relevance"];

const SORT_MAP: Record<Exclude<SortKey, "shuffle" | "relevance">, { asc: string; desc: string }> = {
  date: { desc: "newest", asc: "oldest" },
  popular: { desc: "views", asc: "views_asc" },
  duration: { desc: "duration_desc", asc: "duration_asc" },
  title: { asc: "title", desc: "title_desc" },
  subscribers: { desc: "subscribers", asc: "subscribers_asc" },
  priority: { desc: "priority", asc: "priority_asc" },
};

const SORT_DEFAULT_DIR: Record<Exclude<SortKey, "shuffle" | "relevance">, "asc" | "desc"> = {
  date: "desc",
  popular: "desc",
  duration: "desc",
  title: "asc",
  subscribers: "desc",
  priority: "desc",
};

export function parseSort(s: string): { key: SortKey; dir: "asc" | "desc" } {
  if (s === "shuffle" || s === "relevance") return { key: s, dir: "desc" };
  for (const k of Object.keys(SORT_MAP) as (keyof typeof SORT_MAP)[]) {
    if (SORT_MAP[k].asc === s) return { key: k, dir: "asc" };
    if (SORT_MAP[k].desc === s) return { key: k, dir: "desc" };
  }
  return { key: "date", dir: "desc" };
}

export function buildSort(key: SortKey, dir: "asc" | "desc"): string {
  if (key === "shuffle" || key === "relevance") return key;
  return SORT_MAP[key][dir];
}

/** Feed sort keys as options for the shared SortControl. ONE mapping for the library feed and the
 *  live search results, which share the vocabulary: two copies could hand the same key a different
 *  direction default, or lose its directionless flag, depending on which mode you were in. */
export function feedSortOptions(keys: SortKey[], label: (k: SortKey) => string): SortOption[] {
  return keys.map((k) => ({
    key: k,
    label: label(k),
    directionless: DIRECTIONLESS.includes(k),
    defaultDir: DIRECTIONLESS.includes(k)
      ? undefined
      : SORT_DEFAULT_DIR[k as Exclude<SortKey, "shuffle" | "relevance">],
  }));
}

// --- Live YouTube search results ----------------------------------------------------------------
//
// The results view had NO sort control at all — the order was the provider's and that was that. It is
// sorted HERE, on the page already loaded, rather than by re-asking YouTube with an `order=` param,
// for three reasons: the owner's case is "even one page of results", i.e. reorder what is on screen;
// a re-query would REPLACE the results, which is not what "sort these" means; and the zero-quota
// scrape source has no order parameter at all, so a server-side control would silently do nothing (or
// quietly cost 100 quota units) depending on which source happened to serve the page.
//
// Only the keys a search result actually carries are offered. `subscribers` and `priority` are
// properties of a SUBSCRIPTION, which a live search result is not, and `shuffle` on a ranked result
// list is noise — an option that cannot mean anything here is worse than no option.
export const YT_SORT_KEYS: SortKey[] = ["relevance", "date", "popular", "duration", "title"];

const YT_SORT_VALUE: Partial<Record<SortKey, (v: Video) => number | string | null | undefined>> = {
  date: (v) => (v.published_at ? Date.parse(v.published_at) : null),
  popular: (v) => v.view_count,
  duration: (v) => v.duration_seconds,
  title: (v) => v.title,
};

/** Order a loaded page of live-search results. `relevance` is the provider's own ranking, i.e. the
 *  order they arrived in — so it is the identity, not a sort.
 *
 *  Results missing the value sink to the END in both directions (a video whose duration YouTube did
 *  not report is not "the shortest"), and ties keep the provider's ranking, in both directions —
 *  hence a signed comparator rather than sorting and reversing, which would flip the ties too. */
export function sortYtResults(
  items: Video[],
  key: SortKey,
  dir: "asc" | "desc",
  lang: string,
): Video[] {
  const value = YT_SORT_VALUE[key];
  if (!value) return items; // relevance, and anything a stale pref names that we no longer offer
  const sign = dir === "asc" ? 1 : -1;
  const have = items.filter((v) => value(v) != null);
  const missing = items.filter((v) => value(v) == null);
  have.sort((a, b) => {
    const x = value(a)!;
    const y = value(b)!;
    return sign * (typeof x === "string" ? compareText(x, String(y), lang) : x - Number(y));
  });
  return [...have, ...missing];
}