// Shared column-sort primitives, lifted out of DataTable so a NON-table renderer (the channel
// manager's card layout) can sort the same rows the same way — one comparator, one source of truth.
// Kept structural (no `Column` import) so it has zero coupling to DataTable.

import { compareText } from "./collate";

export type SortState = { key: string; dir: "asc" | "desc" } | null;

interface Sortable<T> {
  key: string;
  sortValue?: (row: T) => string | number;
}

/** Sort a copy of `rows` by the sortable column named in `sort` (numeric diff, or text in the UI
 * language's alphabet — `lang`). Returns `rows` unchanged when there's no sort or the column has no
 * `sortValue`. */
export function sortRows<T>(rows: T[], columns: Sortable<T>[], sort: SortState, lang: string): T[] {
  if (!sort) return rows;
  const get = columns.find((c) => c.key === sort.key)?.sortValue;
  if (!get) return rows;
  return [...rows].sort((a, b) => {
    const av = get(a);
    const bv = get(b);
    const cmp =
      typeof av === "number" && typeof bv === "number"
        ? av - bv
        : compareText(String(av), String(bv), lang);
    return sort.dir === "asc" ? cmp : -cmp;
  });
}

/** Coerce a stored value to a SortState. Anything malformed (corrupt storage, a shape from an older
 * build) becomes "no sort" rather than flowing a junk `dir` into the comparator. */
export function parseSortState(raw: unknown): SortState {
  if (!raw || typeof raw !== "object") return null;
  const { key, dir } = raw as { key?: unknown; dir?: unknown };
  return typeof key === "string" && (dir === "asc" || dir === "desc") ? { key, dir } : null;
}

/** Encode a SortState to the compact `key:dir` wire form the shareable-URL modules (plex/channels)
 * put in the address bar. Sort keys are simple words (no colon), so the plain join round-trips. Returns
 * null for no-sort. A module with a default sort short-circuits that to null at its own call site. */
export function encodeSortParam(s: SortState): string | null {
  return s ? `${s.key}:${s.dir}` : null;
}

/** Inverse of `encodeSortParam`: parse `key:dir` (or a bare key → asc) from the URL back into a
 * SortState, healing anything malformed to null. One codec for both URL-state modules — no drift. */
export function decodeSortParam(raw: string): SortState {
  const i = raw.indexOf(":");
  const key = i === -1 ? raw : raw.slice(0, i);
  const dir = i === -1 ? "asc" : raw.slice(i + 1);
  return parseSortState({ key, dir });
}

/** The header-click cycle: unsorted → ascending → descending → unsorted. */
export function cycleSort(current: SortState, key: string): SortState {
  if (!current || current.key !== key) return { key, dir: "asc" };
  if (current.dir === "asc") return { key, dir: "desc" };
  return null;
}

// --- the source-agnostic sort vocabulary -------------------------------------------------
// A `SortOption[]` is the one shape every content surface (YT feed, Plex library, channel
// manager, discovery) hands to the shared `SortControl`. A table derives it from its columns;
// the feed and Plex declare it explicitly. Direction lives in `SortState`, never encoded into
// the key — the feed's wire string (`feedSort.ts`) is a codec at the server boundary only.

export interface SortOption {
  key: string;
  label: string;
  /** No meaningful asc/desc flip (the feed's `shuffle`/`relevance`) — hides the direction toggle. */
  directionless?: boolean;
  /** The natural first direction when this option is freshly picked (defaults to `"asc"`). */
  defaultDir?: "asc" | "desc";
}

/** Decide the next `SortState` when the user PICKS `key` from a dropdown/chip (NOT the header-click
 * cycle — that's `cycleSort`). Re-picking the same key keeps its direction; a new key starts at its
 * `defaultDir` (asc fallback); a directionless option carries a stable dir; an empty key clears sort. */
export function pickSort(options: SortOption[], prev: SortState, key: string): SortState {
  if (!key) return null;
  const opt = options.find((o) => o.key === key);
  if (!opt) return null;
  if (opt.directionless) return { key, dir: "desc" };
  if (prev?.key === key) return prev;
  return { key, dir: opt.defaultDir ?? "asc" };
}

/** Collapse a sort that names an option no longer offered (a renamed column, or Plex's movie/show
 * scope swap dropping a key) to `fallback` — otherwise a stale key claims a sort nothing applies. */
export function healSort(
  sort: SortState,
  options: SortOption[],
  fallback: SortState = null,
): SortState {
  return sort && options.some((o) => o.key === sort.key) ? sort : fallback;
}

/** Hydrate a persisted raw string into a `SortState`. Accepts the JSON `{key,dir}` shape and tolerates
 * a legacy bare-key string (older builds stored just the key). When `options` is empty, the value is
 * parsed but NOT healed — for a table/provider that owns no vocabulary itself and heals for display
 * elsewhere (e.g. `ColumnSortControl`); a non-empty `options` heals an absent key to `fallback`. */
export function hydrateSort(
  raw: string | null,
  options: SortOption[],
  fallback: SortState = null,
): SortState {
  if (!raw) return fallback;
  const heal = (s: SortState): SortState =>
    options.length === 0 ? (s ?? fallback) : healSort(s, options, fallback);
  try {
    return heal(parseSortState(JSON.parse(raw)));
  } catch {
    const opt = options.find((o) => o.key === raw);
    return opt ? { key: raw, dir: opt.defaultDir ?? "asc" } : fallback;
  }
}