import { lazy, Suspense, useEffect, useLayoutEffect, useRef, useState } from "react";
import { createPortal } from "react-dom";
import { useTranslation } from "react-i18next";
import {
  useInfiniteQuery,
  useQuery,
  useQueryClient,
  type InfiniteData,
} from "@tanstack/react-query";
import { User, X } from "lucide-react";
import { qk } from "../lib/queryKeys";
import { healPlexField } from "../lib/plexSearch";
import { healPlexSort, plexSortOptions, PLEX_SORT_FALLBACK } from "../lib/plexSort";
import {
  api,
  EMPTY_PLEX_FILTERS,
  plexFilterCount,
  type PlexCard,
  type PlexFilters,
  type PlexUnifiedResult,
} from "../lib/api";
import { plexLang } from "../i18n";
import { useDebounced } from "../lib/useDebounced";
import { useHistorySubview } from "../lib/history";
import { PLEX_SUB_URL, type Sub } from "./plexSubUrl";
import { toggleWatchState } from "../lib/plexWatch";
import SortControl from "./SortControl";
import SegmentedToggle from "./SegmentedToggle";
import PlexDiscover from "./PlexDiscover";
import { PageToolbar } from "./PageShell";
import ActiveFilterChips from "./ActiveFilterChips";
import ItemCount from "./ItemCount";
import { StateMessage } from "./QueryState";
import { usePlexActiveFilters, usePlexClearFilters } from "./usePlexActiveFilters";
import { usePlex, usePlexActions } from "./PlexProvider";
import { EpisodeCard, PlexPosterCard } from "./plexCards";
import { PlexInfoView, PlexPersonView, PlexSeasonView, PlexShowView } from "./plexViews";

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

// 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. Rendered by App for page==="plex" (its own
// nav module). The cards/strips live in plexCards; the sub-view branches in plexViews.

const PAGE = 40;

export default function PlexBrowse() {
  const { t } = useTranslation();
  const qc = useQueryClient();
  // Scope / watch-state / sort / filters live in PlexProvider (edited mainly from PlexSidebar); the
  // search term (q) comes from the shared header box; the rail hands off a playlist to open via the
  // shared `playlistOpen` slot, which we consume into a history subview then clear.
  const { q, scope, show, sort, filters, field, playlistOpen: openPlaylist, jumpTo } = usePlex();
  const { setScope, setSort, setFilters, setPlaylistOpen, setJumpTo } = usePlexActions();
  const dq = useDebounced(q.trim(), 350);
  // Active language for the HU overlay: "hu" serves Hungarian metadata, else EN. In the query keys so
  // a switch refetches the grid/facets/detail; useTranslation re-renders this component on switch.
  const lang = plexLang();
  // The language the grid query is allowed to run at — lags `lang` by one render on a switch so the
  // genre-clear effect (below) can settle first (see the effect for why).
  const [committedLang, setCommittedLang] = useState(lang);
  // Plex's active-filter chip row (above the grid), the shared feed idiom: one removable chip per
  // narrowing, plus a Clear-all (shared with the sidebar) that resets filters + watch-state + sort.
  const plexChips = usePlexActiveFilters();
  const clearAllFilters = usePlexClearFilters();
  // The provider holds sort scope-agnostically; heal it against THIS scope's options so a movie-only
  // key (e.g. duration) left over from before a switch to shows doesn't ask for an unavailable sort.
  const sortState = healPlexSort(sort, scope);
  const sortOptions = plexSortOptions(scope, (k) => t(`plex.sort.${k}`));
  // Same idiom for the search scope-pill: a movie-only scope can't hold the Episode field.
  const fieldState = healPlexField(field, scope);
  // Discover is the landing (E5 S4); the flat grid is the "Browse all" secondary view. A header search
  // or an added filter is a browse intent → flip to the grid (below); an explicit toggle returns.
  const sub = useHistorySubview<Sub>({ kind: "discover" }, PLEX_SUB_URL);

  // Sidebar asked to open a playlist → push it as a subview (browser Back returns to the grid), then
  // clear the signal so it doesn't re-open.
  useEffect(() => {
    if (openPlaylist != null) {
      sub.open({ kind: "playlist", id: openPlaylist });
      setPlaylistOpen(null);
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [openPlaylist]);

  // The header search typeahead picked a title → open it the same way a card click would (a movie's
  // info page like the card's ⓘ, a show's drill-down), then clear the hand-off so it doesn't re-open.
  useEffect(() => {
    if (jumpTo != null) {
      if (jumpTo.type !== "show") infoScrollRef.current = 0; // a jumped-to info page starts at the top
      sub.open(
        jumpTo.type === "show" ? { kind: "show", id: jumpTo.id } : { kind: "info", id: jumpTo.id },
      );
      setJumpTo(null);
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [jumpTo]);

  // Discover → grid on a browse intent: when a header search or a filter FIRST becomes active while on
  // the Discover landing, switch to the flat grid (which consumes q/filters). Only on the off→on edge,
  // so a pre-existing (persisted) filter doesn't yank a returning user off Discover on mount, and a
  // Back to Discover with the search still in the box doesn't immediately re-flip.
  const browseIntent = !!dq || plexFilterCount(filters) > 0;
  const prevIntent = useRef(browseIntent);
  useEffect(() => {
    if (sub.view.kind === "discover" && browseIntent && !prevIntent.current) {
      sub.open({ kind: "grid" });
    }
    prevIntent.current = browseIntent;
  }, [browseIntent, sub]);

  // 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);
  // Same idea for the info page: "Browse collection" (onFilter) leaves the info view for a filtered
  // grid, and browser Back returns to this same info page — restore where the user had scrolled it
  // (down to a collection strip) instead of snapping to the top. Reset on a fresh info open so a
  // different title's info starts at the top.
  const infoScrollRef = useRef(0);
  const scroller = () => document.querySelector("main");
  useLayoutEffect(() => {
    const el = scroller();
    if (!el) return;
    if (sub.view.kind === "grid" && scrollRef.current) el.scrollTop = scrollRef.current;
    else if (sub.view.kind === "info" && infoScrollRef.current)
      el.scrollTop = infoScrollRef.current;
  }, [sub.view.kind]);

  // Backspace steps back one drill-down level (grid ← show ← season, and out of info/playlist),
  // matching the browser/mouse Back. The player has its OWN Backspace handling, so we skip it here;
  // and never hijack Backspace while typing in a field.
  useEffect(() => {
    const onKey = (e: KeyboardEvent) => {
      if (e.key !== "Backspace") return;
      const el = document.activeElement as HTMLElement | null;
      const tag = (el?.tagName || "").toLowerCase();
      if (tag === "input" || tag === "textarea" || tag === "select" || el?.isContentEditable)
        return;
      if (["grid", "show", "season", "info", "person", "playlist"].includes(sub.view.kind)) {
        e.preventDefault();
        sub.back();
      }
    };
    window.addEventListener("keydown", onKey);
    return () => window.removeEventListener("keydown", onKey);
  }, [sub]);

  const browseQ = useInfiniteQuery({
    queryKey: qk.plexLibrary(scope, dq, sortState, show, filters, fieldState, lang),
    // Gate on committedLang so a language switch fires ONE fetch (after the genre-clear effect
    // settles), not a throwaway one with stale-language genres followed by a second.
    enabled: !!scope && sub.view.kind === "grid" && committedLang === lang,
    initialPageParam: 0,
    queryFn: ({ pageParam }) =>
      api.plexLibrary({
        scope,
        q: dq || undefined,
        field: fieldState,
        sort: sortState,
        show,
        lang,
        filters,
        offset: pageParam as number,
        limit: PAGE,
      }),
    getNextPageParam: (last) => {
      const seen = last.offset + last.items.length;
      return seen < last.total ? seen : undefined;
    },
  });

  // Genre chips are language-specific strings (the HU column stores "Dráma", the EN one "Drama"), so a
  // selection made in one language matches nothing against the other's column and would silently empty
  // the grid. On a language flip, drop the genre selection — and gate the grid query on the language
  // being "committed" (below) so we don't fire one throwaway fetch with the stale-language genres and
  // then a second after the clear; the query waits for both to settle into a single fetch.
  useEffect(() => {
    if (committedLang !== lang) {
      setCommittedLang(lang);
      if (filters.genres.length) setFilters({ ...filters, genres: [] });
    }
  }, [lang, committedLang, filters, setFilters]);

  const items = browseQ.data?.pages.flatMap((p) => p.items) ?? [];
  const total = browseQ.data?.pages[0]?.total ?? 0;
  // Cards for the actors currently in the filter (name + headshot + in-scope count) — shown above the
  // grid so you SEE who you're exploring, not just chips in the rail.
  const peopleCardsQ = useQuery({
    queryKey: qk.plexPeopleCards(scope, filters.actors),
    queryFn: () => api.plexPeopleCards(filters.actors, scope),
    enabled: sub.view.kind === "grid" && filters.actors.length > 0,
    staleTime: 60_000,
  });
  const personCards = peopleCardsQ.data?.people ?? [];
  const removeActor = (name: string) =>
    setFilters({ ...filters, actors: filters.actors.filter((x) => x !== name) });
  // Episode matches (grouped "Episodes" section) — search-only; same set on every page, take page 0.
  const episodes = browseQ.data?.pages[0]?.episodes ?? [];

  // Infinite scroll: auto-load the next page when the sentinel scrolls into view. The sentinel lives
  // in the grid branch, which UNMOUNTS when we drill into an info/show/season page and remounts on
  // Back — as a NEW element. A callback ref (state, not useRef) re-runs this effect on every
  // mount/unmount, so the observer always watches the live node; a plain ref would keep observing the
  // detached old node after Back and never fire fetchNextPage again (feed stuck at the loaded pages).
  const [sentinelEl, setSentinelEl] = useState<HTMLDivElement | null>(null);
  const { hasNextPage, isFetchingNextPage, fetchNextPage } = browseQ;
  useEffect(() => {
    if (!sentinelEl) return;
    const io = new IntersectionObserver(
      (entries) => {
        if (entries[0]?.isIntersecting && hasNextPage && !isFetchingNextPage) fetchNextPage();
      },
      { rootMargin: "600px" },
    );
    io.observe(sentinelEl);
    return () => io.disconnect();
  }, [sentinelEl, 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;
    infoScrollRef.current = 0; // fresh info page starts at the top
    sub.open({ kind: "info", id: card.id });
  }
  // Open a cast/crew member's filmography page (from an info/show cast row, or an actor filter-chip).
  // Only when leaving an INFO page do we stash its scroll (so browser Back to that cast row lands where
  // it was, like applyFilter) — from a show/grid context infoScrollRef must stay untouched, else a
  // later info page would wrongly restore this stale offset.
  function onOpenPerson(name: string) {
    if (sub.view.kind === "info") infoScrollRef.current = scroller()?.scrollTop ?? 0;
    sub.open({ kind: "person", name });
  }
  // Optimistically flip a card's status in every cached library page — both the title grid (`items`)
  // and the search "Episodes" section (`episodes`) — so the quick toggle reacts instantly and reliably
  // BOTH ways (mark and un-mark). An id matches in only one array, so touching both is safe.
  function optimisticStatus(id: string, next: string) {
    qc.setQueriesData<InfiniteData<PlexUnifiedResult>>({ queryKey: qk.plexLibrary() }, (old) =>
      old
        ? {
            ...old,
            pages: old.pages.map((pg) => ({
              ...pg,
              items: pg.items.map((it) => (it.id === id ? { ...it, status: next } : it)),
              episodes: pg.episodes.map((ep) => (ep.id === id ? { ...ep, status: next } : ep)),
            })),
          }
        : old,
    );
  }
  const toggleWatched = (card: PlexCard) =>
    toggleWatchState(card, t, {
      optimistic: (next) => optimisticStatus(card.id, next),
      resync: () => qc.invalidateQueries({ queryKey: qk.plexLibrary() }),
    });
  // Apply a metadata filter (clicked on an info page / show hero / cast) then show the unified grid.
  // Array filters (genres/people/studios) UNION with what's set; scalars replace. Clicking a person
  // (cast/crew) widens to the 'both' scope so their movies AND shows show up together (mixed feed).
  function applyFilter(patch: Partial<PlexFilters>) {
    const merged = { ...filters } as unknown as Record<string, unknown>;
    for (const [k, v] of Object.entries(patch)) {
      const cur = merged[k];
      if (Array.isArray(v) && Array.isArray(cur)) {
        merged[k] = Array.from(new Set([...(cur as unknown[]), ...(v as unknown[])]));
      } else {
        merged[k] = v;
      }
    }
    setFilters(merged as unknown as PlexFilters);
    if (patch.actors?.length || patch.directors?.length) setScope("both");
    infoScrollRef.current = scroller()?.scrollTop ?? 0; // restore on Back to the info/show page
    sub.open({ kind: "grid" });
  }

  if (sub.view.kind === "player") {
    // The fallback is portaled for the same reason the player itself is: it is a fixed
    // full-viewport overlay, and this tree renders inside the page scroller.
    return (
      <Suspense
        fallback={createPortal(<div className="fixed inset-0 z-overlay bg-black" />, document.body)}
      >
        <PlexPlayer itemId={sub.view.id} queue={sub.view.queue} onClose={sub.back} />
      </Suspense>
    );
  }
  if (sub.view.kind === "playlist") {
    const pid = sub.view.id;
    return (
      <Suspense fallback={<p className="p-8 text-muted text-sm">{t("plex.loading")}</p>}>
        <PlexPlaylistView
          playlistId={pid}
          onBack={sub.back}
          onPlay={(itemRk, queue) => sub.open({ kind: "player", id: itemRk, queue })}
        />
      </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 })}
        onPlayItem={(id) => sub.open({ kind: "player", id })}
        onFilter={applyFilter}
        onOpenPerson={onOpenPerson}
      />
    );
  }
  if (sub.view.kind === "person") {
    const personName = sub.view.name;
    return (
      <PlexPersonView
        name={personName}
        onBack={sub.back}
        onOpenCard={onCard}
        onInfoCard={onInfo}
        onFilter={applyFilter}
      />
    );
  }
  if (sub.view.kind === "show") {
    const showId = sub.view.id;
    return (
      <PlexShowView
        showId={showId}
        onBack={sub.back}
        onPlay={(epRk, queue) => sub.open({ kind: "player", id: epRk, queue })}
        onOpenSeason={(seasonId) => sub.open({ kind: "season", showId, seasonId })}
        onOpenShow={(id) => sub.open({ kind: "show", id })}
        onFilter={applyFilter}
        onOpenPerson={onOpenPerson}
      />
    );
  }
  if (sub.view.kind === "season") {
    const { showId, seasonId } = sub.view;
    return (
      <PlexSeasonView
        showId={showId}
        seasonId={seasonId}
        onBack={sub.back}
        onPlay={(epRk, queue) => sub.open({ kind: "player", id: epRk, queue })}
      />
    );
  }

  // Discover ⟷ Browse switch, shown on both surfaces so either can return to the other.
  const viewToggle = (
    <SegmentedToggle
      size="md"
      ariaLabel={t("plex.view.label")}
      options={[
        { value: "discover", label: t("plex.discover.tab") },
        { value: "grid", label: t("plex.view.browse") },
      ]}
      value={sub.view.kind === "discover" ? "discover" : "grid"}
      onChange={(v) => sub.open(v === "discover" ? { kind: "discover" } : { kind: "grid" })}
    />
  );

  if (sub.view.kind === "discover") {
    return (
      <div className="p-4 max-w-[1600px] mx-auto">
        <div className="mb-4 flex items-center">{viewToggle}</div>
        <PlexDiscover
          scope={scope}
          onOpenCard={onCard}
          onInfoCard={onInfo}
          onGenre={(g) => applyFilter({ genres: [g] })}
          onSeeAllRecent={() => sub.open({ kind: "grid" })}
        />
      </div>
    );
  }

  return (
    <div className="p-4 max-w-[1600px] mx-auto">
      {/* The title count is fixed chrome — it portals into the shell's fixed band so it stays put
          while only the poster grid scrolls. */}
      <PageToolbar>
        <div className="px-4 pt-2 pb-1 max-w-[1600px] mx-auto flex items-center gap-1.5">
          <ItemCount count={browseQ.isLoading ? undefined : total} />
          {viewToggle}
          {/* Sort moved out of the filter sidebar to the row above the cards (S3), like the Feed. */}
          <div className="ml-auto flex items-center gap-1.5">
            <SortControl
              options={sortOptions}
              sort={sortState}
              onChange={(next) => setSort(next ?? PLEX_SORT_FALLBACK)}
              label={t("plex.filter.sort")}
              ascLabel={t("plex.filter.dir.asc")}
              descLabel={t("plex.filter.dir.desc")}
            />
          </div>
        </div>
      </PageToolbar>

      <ActiveFilterChips filters={plexChips} onClearAll={clearAllFilters} />

      {personCards.length > 0 && (
        <div className="mb-4 flex flex-wrap gap-3">
          {personCards.map((p) => (
            <div
              key={p.name}
              className="glass-card flex items-center gap-1 rounded-xl py-1.5 pl-1.5 pr-2.5"
            >
              {/* The photo + name open the actor's filmography page; the ✕ removes the filter. */}
              <button
                onClick={() => onOpenPerson(p.name)}
                title={t("plex.info.viewPerson", { name: p.name })}
                className="group/person flex min-w-0 items-center gap-2.5 rounded-lg text-left"
              >
                {p.photo ? (
                  <img
                    src={p.photo}
                    alt=""
                    loading="lazy"
                    className="w-10 h-10 rounded-full object-cover shrink-0"
                  />
                ) : (
                  <div className="w-10 h-10 rounded-full grid place-items-center bg-surface text-muted shrink-0">
                    <User className="w-5 h-5" />
                  </div>
                )}
                <div className="min-w-0">
                  <div className="text-sm font-medium truncate max-w-[150px] group-hover/person:text-accent">
                    {p.name}
                  </div>
                  <div className="text-2xs text-muted">
                    {t("plex.people.count", { count: p.count })}
                  </div>
                </div>
              </button>
              <button
                onClick={() => removeActor(p.name)}
                title={t("plex.people.remove")}
                aria-label={t("plex.people.remove")}
                className="ml-1 p-1 rounded-full text-muted hover:text-fg hover:bg-card transition"
              >
                <X className="w-4 h-4" />
              </button>
            </div>
          ))}
        </div>
      )}

      {browseQ.isError && !browseQ.data ? (
        <StateMessage tone="error" onRetry={() => browseQ.refetch()}>
          {t("common.loadError")}
        </StateMessage>
      ) : browseQ.isLoading ? (
        <p className="text-muted text-sm">{t("plex.loading")}</p>
      ) : items.length === 0 && episodes.length === 0 ? (
        dq && plexFilterCount(filters) > 0 ? (
          // A search that comes up empty WHILE filters are active is usually the filters, not the
          // query — say so and offer a one-click escape, instead of a bare "No matches".
          <div className="flex flex-wrap items-center gap-3 text-sm text-muted">
            <span>{t("plex.noMatchesFiltered", { count: plexFilterCount(filters) })}</span>
            <button
              onClick={() => setFilters(EMPTY_PLEX_FILTERS)}
              className="rounded-full border border-border bg-card px-3 py-1 text-xs font-medium transition hover:border-accent hover:text-accent"
            >
              {t("plex.filter.clearAll")}
            </button>
          </div>
        ) : (
          <p className="text-muted text-sm">{dq ? t("plex.noMatches") : t("plex.empty")}</p>
        )
      ) : (
        <>
          {/* Titles grid — movies + shows mixed (visually tagged). */}
          {items.length > 0 && (
            <>
              {episodes.length > 0 && (
                <h2 className="text-sm font-semibold mb-2">{t("plex.unified.titles")}</h2>
              )}
              <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>
            </>
          )}
          {/* Episodes section (Proposal 3) — matching episodes on a search, kept out of the title grid. */}
          {episodes.length > 0 && (
            <section className="mt-8">
              <h2 className="text-sm font-semibold mb-3">{t("plex.unified.episodes")}</h2>
              <div className="grid grid-cols-[repeat(auto-fill,minmax(230px,1fr))] gap-x-3 gap-y-4">
                {episodes.map((ep) => (
                  <EpisodeCard
                    key={ep.id}
                    ep={ep}
                    withShowTitle
                    onPlay={() => onCard(ep)}
                    onToggleWatched={() => toggleWatched(ep)}
                  />
                ))}
              </div>
            </section>
          )}
        </>
      )}

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