import type { Video, VideoStatus } from "../../lib/api";
import { FEED_VIEW_SPEC, type FeedView } from "../../lib/feedView";
import type { NEXT_PAGE } from "../../lib/nextPage";
import VideoCard from "../../features/video/VideoCard";
import { VideoMenu } from "../../features/video/VideoMenu";
import type { VideoActionHandlers } from "../../features/video/useVideoActions";
import { useContextMenu } from "../../components/ui/useContextMenu";
import VirtualGrid from "../../components/ui/VirtualGrid";

// Estimated row heights before measurement; real heights are measured per-row so these only affect
// the very first paint and the scrollbar's initial guess. Taken from measuring each mode in the
// browser rather than guessed — a bad estimate makes the scrollbar jump as you scroll in.
// RE-MEASURE these when a mode's layout changes: they have gone stale twice already, most recently
// when the action row moved onto the card's picture (cards 340 -> 262, small 257 -> 226).
// The card figures are the roughest of the set by nature — a card's height follows its column width
// (262 measured at 4 columns in a 1268px window), so no single constant is right for every window.
const ROW_EST: Record<FeedView, number> = {
  cards: 262,
  cardsSmall: 226,
  rows: 117,
  rowsCompact: 46,
  tiles: 138,
};

export interface VirtualFeedProps {
  items: Video[];
  view: FeedView;
  onState: (id: string, status: VideoStatus) => void;
  onToggleSave: (id: string, saved: boolean) => void;
  onResetState: (id: string) => void;
  onOpen: (v: Video, startAt?: number | null) => void;
  /** The card menu's channel-filter row (see `useVideoActions`); omitted where it has no place. */
  channelFilter?: VideoActionHandlers["channelFilter"];
  hasNextPage: boolean;
  isFetching: boolean;
  fetchNextPage: (options: typeof NEXT_PAGE) => unknown;
}

// The feed's videos on the shared VirtualGrid engine — this wrapper only maps a FeedView to the
// grid's layout spec and renders a VideoCard per item. All the virtualization mechanics (measure,
// chunk, place, infinite-scroll) live in VirtualGrid.
export default function VirtualFeed({
  items,
  view,
  onState,
  onToggleSave,
  onResetState,
  onOpen,
  channelFilter,
  hasNextPage,
  isFetching,
  fetchNextPage,
}: VirtualFeedProps) {
  const { minCol, colMaxWidth, maxCols, thumb } = FEED_VIEW_SPEC[view];
  // The card menu (the video's whole action list) lives HERE rather than in each of the
  // feed's callers: this is the list, and `useContextMenu`'s contract is one menu per list. Mounting
  // it at this level is also what gives the channel page the menu for free — it renders
  // `<Feed channelScoped>`, so it is the same component all the way down.
  const menu = useContextMenu<Video>();
  const openId = menu.open ? menu.target?.id : undefined;
  return (
    <>
      <VirtualGrid
        items={items}
        getKey={(v) => v.id}
        minCol={minCol}
        colMaxWidth={colMaxWidth}
        maxCols={maxCols}
        rowEst={ROW_EST[view]}
        hasNextPage={hasNextPage}
        isFetching={isFetching}
        fetchNextPage={fetchNextPage}
        keyboardNav
        renderItem={(v, itemWidth, index) => (
          <VideoCard
            video={v}
            view={view}
            navIndex={index}
            // Only the one-line row (thumb:false) reads its own width — it stands columns down as it
            // narrows. Everything else takes a stable 0, so a resize (which changes itemWidth every
            // frame) doesn't blow past VideoCard's memo for views that wouldn't do anything with it.
            width={thumb ? 0 : itemWidth}
            onState={onState}
            onToggleSave={onToggleSave}
            onOpen={onOpen}
            menuProps={menu.triggerProps}
            menuButtonProps={menu.buttonProps}
            // A boolean per card, not the open id: only the two cards whose answer changes re-render.
            menuOpen={openId === v.id}
          />
        )}
      />
      <VideoMenu
        menu={menu}
        handlers={{ onState, onToggleSave, onResetState, onOpen, channelFilter }}
      />
    </>
  );
}