import { lazy, Suspense, useEffect, useLayoutEffect, useRef, type CSSProperties } from "react";
import { useTranslation } from "react-i18next";
import { useInfiniteQuery, useQuery, useQueryClient } from "@tanstack/react-query";
import { ArrowLeft, CheckCircle2, Info, Play } from "lucide-react";
import { api, type PlexCard, type PlexFilters } from "../lib/api";
import { useDebounced } from "../lib/useDebounced";
import { useHistorySubview } from "../lib/history";

// Lazy: the rich player (pulls in hls.js) loads only when something is first played.
const PlexPlayer = lazy(() => import("./PlexPlayer"));
const PlexInfo = lazy(() => import("./PlexInfo"));

type Sub =
  | { kind: "grid" }
  | { kind: "show"; id: string }
  | { kind: "player"; id: string }
  | { kind: "info"; id: string };

// The Plex module's content area: browse/search the mirrored library as poster cards, drill from a
// show into seasons/episodes. Library scope / watch-state / sort live in the left PlexSidebar; the
// search term comes from the shared top Header search box (q). A show drill-down rides history
// (useHistorySubview) so browser Back returns to the grid. Playback lands in P2 — a card announces
// for now. Rendered by App for page==="plex" (its own nav module).

type Props = {
  q: string;
  library: string;
  show: string;
  sort: string;
  filters: PlexFilters;
  setFilters: (f: PlexFilters) => void;
};

const PAGE = 40;

function dur(n?: number | null): string {
  if (!n) return "";
  const h = Math.floor(n / 3600);
  const m = Math.floor((n % 3600) / 60);
  return h ? `${h}h ${m}m` : `${m}m`;
}

export default function PlexBrowse({ q, library, show, sort, filters, setFilters }: Props) {
  const { t } = useTranslation();
  const qc = useQueryClient();
  const dq = useDebounced(q.trim(), 350);
  const sub = useHistorySubview<Sub>({ kind: "grid" });

  // Opening a show/player replaces the grid entirely (the component returns early below), so the
  // scroll container resets to the top. Remember where the grid was scrolled when leaving it, and
  // restore it when we come back — so the browser/mouse Back from the player lands on the same card
  // instead of the top of the library. The scroller is App's <main> (the page's overflow-y-auto).
  const scrollRef = useRef(0);
  const scroller = () => document.querySelector("main");
  useLayoutEffect(() => {
    if (sub.view.kind === "grid" && scrollRef.current) {
      const el = scroller();
      if (el) el.scrollTop = scrollRef.current;
    }
  }, [sub.view.kind]);

  const browseQ = useInfiniteQuery({
    queryKey: ["plex-browse", library, dq, sort, show, filters],
    enabled: !!library && sub.view.kind === "grid",
    initialPageParam: 0,
    queryFn: ({ pageParam }) =>
      api.plexBrowse({
        library,
        q: dq || undefined,
        sort,
        show,
        filters,
        offset: pageParam as number,
        limit: PAGE,
      }),
    getNextPageParam: (last) => {
      const seen = last.offset + last.items.length;
      return seen < last.total ? seen : undefined;
    },
  });

  const items = browseQ.data?.pages.flatMap((p) => p.items) ?? [];
  const total = browseQ.data?.pages[0]?.total ?? 0;

  // Infinite scroll: auto-load the next page when the sentinel scrolls into view.
  const sentinel = useRef<HTMLDivElement>(null);
  const { hasNextPage, isFetchingNextPage, fetchNextPage } = browseQ;
  useEffect(() => {
    const el = sentinel.current;
    if (!el) return;
    const io = new IntersectionObserver(
      (entries) => {
        if (entries[0].isIntersecting && hasNextPage && !isFetchingNextPage) fetchNextPage();
      },
      { rootMargin: "600px" },
    );
    io.observe(el);
    return () => io.disconnect();
  }, [hasNextPage, isFetchingNextPage, fetchNextPage]);

  function onCard(card: PlexCard) {
    scrollRef.current = scroller()?.scrollTop ?? 0; // remember grid position for the trip back
    if (card.type === "show") sub.open({ kind: "show", id: card.id });
    else sub.open({ kind: "player", id: card.id });
  }
  function onInfo(card: PlexCard) {
    scrollRef.current = scroller()?.scrollTop ?? 0;
    sub.open({ kind: "info", id: card.id });
  }
  async function toggleWatched(card: PlexCard) {
    await api.plexSetState(card.id, card.status === "watched" ? "new" : "watched");
    qc.invalidateQueries({ queryKey: ["plex-browse"] });
  }

  if (sub.view.kind === "player") {
    return (
      <Suspense fallback={<div className="fixed inset-0 z-50 bg-black" />}>
        <PlexPlayer itemId={sub.view.id} onClose={sub.back} />
      </Suspense>
    );
  }
  if (sub.view.kind === "info") {
    const infoId = sub.view.id;
    return (
      <PlexInfoView
        id={infoId}
        onBack={sub.back}
        onPlay={() => sub.open({ kind: "player", id: infoId })}
        onFilter={(patch) => {
          // Clicking a metadata chip sets that filter and returns to the (now filtered) grid.
          setFilters({ ...filters, ...patch });
          sub.back();
        }}
      />
    );
  }
  if (sub.view.kind === "show") {
    return (
      <PlexShowView
        showId={sub.view.id}
        onBack={sub.back}
        onPlay={(ep) => sub.open({ kind: "player", id: ep.id })}
      />
    );
  }

  return (
    <div className="p-4 max-w-[1600px] mx-auto">
      <p className="text-xs text-muted mb-3">
        {browseQ.isLoading ? " " : dq ? t("plex.searchCount", { count: total }) : t("plex.count", { count: total })}
      </p>

      {browseQ.isLoading ? (
        <p className="text-muted text-sm">{t("plex.loading")}</p>
      ) : items.length === 0 ? (
        <p className="text-muted text-sm">{dq ? t("plex.noMatches") : t("plex.empty")}</p>
      ) : (
        <div className="grid grid-cols-[repeat(auto-fill,minmax(150px,1fr))] gap-3">
          {items.map((c) => (
            <PlexPosterCard
              key={c.id}
              card={c}
              onOpen={() => onCard(c)}
              onInfo={() => onInfo(c)}
              onToggleWatched={toggleWatched}
            />
          ))}
        </div>
      )}

      <div ref={sentinel} className="h-8" />
      {isFetchingNextPage && <p className="text-center text-xs text-muted pb-4">{t("plex.loading")}</p>}
    </div>
  );
}

const PLAYABLE_TINT: Record<string, string> = {
  direct: "bg-emerald-500",
  remux: "bg-amber-500",
  transcode: "bg-orange-600",
};

function PlexPosterCard({
  card,
  onOpen,
  onInfo,
  onToggleWatched,
}: {
  card: PlexCard;
  onOpen: () => void;
  onInfo: () => void;
  onToggleWatched: (c: PlexCard) => void;
}) {
  const { t } = useTranslation();
  const inProgress = (card.position_seconds ?? 0) > 0 && card.status !== "watched";
  const isPlayable = card.type !== "show"; // movies/episodes play; shows open the drill-down
  const pct =
    inProgress && card.duration_seconds
      ? Math.min(100, Math.round(((card.position_seconds ?? 0) / card.duration_seconds) * 100))
      : 0;
  return (
    <div
      className="group text-left"
      // content-visibility keeps off-screen posters cheap to render (smoother long-list scroll).
      style={{ contentVisibility: "auto", containIntrinsicSize: "auto 300px" } as CSSProperties}
    >
      <div
        onClick={onOpen}
        role="button"
        tabIndex={0}
        onKeyDown={(e) => {
          if (e.key === "Enter" || e.key === " ") {
            e.preventDefault();
            onOpen();
          }
        }}
        className="relative aspect-[2/3] rounded-xl overflow-hidden bg-card border border-border cursor-pointer"
      >
        <img
          src={card.thumb}
          alt=""
          loading="lazy"
          decoding="async"
          className="w-full h-full object-cover group-hover:scale-105 transition-transform duration-200"
        />
        {/* Hover affordance: what a click does (play / resume / open show). */}
        <div className="absolute inset-0 bg-black/45 opacity-0 group-hover:opacity-100 transition grid place-items-center">
          {isPlayable ? (
            <div className="flex flex-col items-center gap-1 text-white">
              <Play className="w-10 h-10" fill="currentColor" />
              <span className="text-xs font-medium">{inProgress ? t("plex.resume") : t("plex.play")}</span>
            </div>
          ) : (
            <span className="text-white text-xs font-medium">{t("plex.openShow")}</span>
          )}
        </div>
        {/* Quick watched toggle (movies/episodes), on hover. */}
        {isPlayable && (
          <button
            onClick={(e) => {
              e.stopPropagation();
              onToggleWatched(card);
            }}
            title={card.status === "watched" ? t("plex.markUnwatched") : t("plex.markWatched")}
            className="absolute top-1.5 right-1.5 p-1 rounded-full bg-black/60 opacity-0 group-hover:opacity-100 hover:bg-black/80 transition"
          >
            <CheckCircle2 className={`w-4 h-4 ${card.status === "watched" ? "text-emerald-400" : "text-white"}`} />
          </button>
        )}
        {/* Media info page (movies/episodes). */}
        {isPlayable && (
          <button
            onClick={(e) => {
              e.stopPropagation();
              onInfo();
            }}
            title={t("plex.info.title")}
            className="absolute bottom-1.5 left-1.5 p-1 rounded-full bg-black/60 opacity-0 group-hover:opacity-100 hover:bg-black/80 transition"
          >
            <Info className="w-4 h-4 text-white" />
          </button>
        )}
        {/* Watched badge when not hovering (the toggle replaces it on hover). */}
        {card.status === "watched" && (
          <span className="absolute top-1.5 right-1.5 text-[10px] bg-black/70 text-white px-1.5 py-0.5 rounded group-hover:opacity-0">
            {t("plex.watched")}
          </span>
        )}
        {card.type === "show" && card.season_count != null && (
          <span className="absolute bottom-1.5 left-1.5 text-[10px] bg-black/70 text-white px-1.5 py-0.5 rounded">
            {t("plex.seasons", { count: card.season_count })}
          </span>
        )}
        {card.playable && (
          <span
            className={`absolute top-1.5 left-1.5 w-2 h-2 rounded-full ${PLAYABLE_TINT[card.playable] ?? "bg-gray-400"}`}
            title={t(`plex.playable.${card.playable}`)}
          />
        )}
        {pct > 0 && (
          <div className="absolute bottom-0 inset-x-0 h-1 bg-black/40">
            <div className="h-full bg-accent" style={{ width: `${pct}%` }} />
          </div>
        )}
      </div>
      <div className="mt-1.5 text-sm font-medium line-clamp-2 leading-tight">{card.title}</div>
      <div className="text-xs text-muted">{[card.year, dur(card.duration_seconds)].filter(Boolean).join(" · ")}</div>
    </div>
  );
}

function PlexInfoView({
  id,
  onBack,
  onPlay,
  onFilter,
}: {
  id: string;
  onBack: () => void;
  onPlay: () => void;
  onFilter: (patch: Partial<PlexFilters>) => void;
}) {
  const { t } = useTranslation();
  const q = useQuery({ queryKey: ["plex-item", id], queryFn: () => api.plexItem(id) });
  return (
    <div className="max-w-[1100px] mx-auto">
      <div className="p-4 pb-0">
        <button
          onClick={onBack}
          className="glass-card glass-hover inline-flex items-center gap-1.5 px-2.5 py-1.5 rounded-lg text-xs"
        >
          <ArrowLeft className="w-4 h-4" />
          {t("plex.backToLibrary")}
        </button>
      </div>
      {q.isLoading || !q.data ? (
        <p className="p-8 text-muted text-sm">{t("plex.loading")}</p>
      ) : (
        <Suspense fallback={<p className="p-8 text-muted text-sm">{t("plex.loading")}</p>}>
          <PlexInfo detail={q.data} variant="page" onPlay={onPlay} onFilter={onFilter} />
        </Suspense>
      )}
    </div>
  );
}

function PlexShowView({
  showId,
  onBack,
  onPlay,
}: {
  showId: string;
  onBack: () => void;
  onPlay: (c: PlexCard) => void;
}) {
  const { t } = useTranslation();
  const q = useQuery({ queryKey: ["plex-show", showId], queryFn: () => api.plexShow(showId) });
  const d = q.data;

  return (
    <div className="p-4 max-w-[1200px] mx-auto">
      <button
        onClick={onBack}
        className="glass-card glass-hover inline-flex items-center gap-1.5 px-2.5 py-1.5 rounded-lg text-xs mb-4"
      >
        <ArrowLeft className="w-4 h-4" />
        {t("plex.backToLibrary")}
      </button>

      {q.isLoading || !d ? (
        <p className="text-muted text-sm">{t("plex.loading")}</p>
      ) : (
        <>
          <div className="flex gap-4 mb-6">
            <img
              src={d.show.thumb}
              alt=""
              className="w-32 sm:w-40 aspect-[2/3] object-cover rounded-xl border border-border shrink-0"
            />
            <div className="min-w-0">
              <h1 className="text-xl font-semibold">{d.show.title}</h1>
              {d.show.year && <p className="text-sm text-muted">{d.show.year}</p>}
              {d.show.summary && (
                <p className="text-sm text-muted mt-2 line-clamp-6 leading-relaxed">{d.show.summary}</p>
              )}
            </div>
          </div>

          {d.seasons.map((se) => (
            <div key={se.id} className="mb-6">
              <h2 className="text-sm font-semibold mb-2">{se.title}</h2>
              <div className="flex flex-col divide-y divide-border/60">
                {se.episodes.map((ep) => {
                  const inProgress = (ep.position_seconds ?? 0) > 0 && ep.status !== "watched";
                  return (
                    <button
                      key={ep.id}
                      onClick={() => onPlay(ep)}
                      className="flex items-center gap-3 py-2 text-left group"
                    >
                      <div className="relative w-28 aspect-video rounded-lg overflow-hidden bg-card border border-border shrink-0">
                        <img src={ep.thumb} alt="" loading="lazy" className="w-full h-full object-cover" />
                        {ep.status === "watched" && (
                          <span className="absolute top-1 right-1 text-[9px] bg-black/70 text-white px-1 rounded">
                            ✓
                          </span>
                        )}
                        {inProgress && <div className="absolute bottom-0 inset-x-0 h-0.5 bg-accent" />}
                      </div>
                      <div className="min-w-0 flex-1">
                        <div className="text-sm font-medium truncate">
                          <span className="text-muted mr-1.5">{ep.episode_number}.</span>
                          {ep.title}
                        </div>
                        {ep.summary && (
                          <div className="text-xs text-muted line-clamp-2 mt-0.5">{ep.summary}</div>
                        )}
                        <div className="text-[11px] text-muted mt-0.5">{dur(ep.duration_seconds)}</div>
                      </div>
                    </button>
                  );
                })}
              </div>
            </div>
          ))}
        </>
      )}
    </div>
  );
}