import { useEffect, useRef, type CSSProperties } from "react";
import { useTranslation } from "react-i18next";
import { useInfiniteQuery, useQuery } from "@tanstack/react-query";
import { ArrowLeft } from "lucide-react";
import { api, type PlexCard } from "../lib/api";
import { notify } from "../lib/notifications";
import { useDebounced } from "../lib/useDebounced";
import { useHistorySubview } from "../lib/history";

// 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 };

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 }: Props) {
  const { t } = useTranslation();
  const dq = useDebounced(q.trim(), 350);
  const sub = useHistorySubview<string | null>(null); // open show ratingKey (null = grid)

  const browseQ = useInfiniteQuery({
    queryKey: ["plex-browse", library, dq, sort, show],
    enabled: !!library && sub.view === null,
    initialPageParam: 0,
    queryFn: ({ pageParam }) =>
      api.plexBrowse({ library, q: dq || undefined, sort, show, 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 onPlay(card: PlexCard) {
    notify({ level: "info", message: t("plex.playerSoon", { title: card.title }) });
  }
  function onCard(card: PlexCard) {
    if (card.type === "show") sub.open(card.id);
    else onPlay(card);
  }

  if (sub.view) {
    return <PlexShowView showId={sub.view} onBack={sub.back} onPlay={onPlay} />;
  }

  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} onClick={() => onCard(c)} />
          ))}
        </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, onClick }: { card: PlexCard; onClick: () => void }) {
  const { t } = useTranslation();
  const inProgress = (card.position_seconds ?? 0) > 0 && card.status !== "watched";
  const pct =
    inProgress && card.duration_seconds
      ? Math.min(100, Math.round(((card.position_seconds ?? 0) / card.duration_seconds) * 100))
      : 0;
  return (
    <button
      onClick={onClick}
      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 className="relative aspect-[2/3] rounded-xl overflow-hidden bg-card border border-border">
        <img
          src={card.thumb}
          alt=""
          loading="lazy"
          decoding="async"
          className="w-full h-full object-cover group-hover:scale-105 transition-transform duration-200"
        />
        {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">
            {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>
    </button>
  );
}

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>
  );
}