import { useCallback, useEffect, useMemo, useRef, useState } from "react";
import { useTranslation } from "react-i18next";
import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
import { qk } from "../lib/queryKeys";
import { ListVideo, Pin, Plus, RefreshCw } from "lucide-react";
import { YouTubeIcon } from "../lib/brandIcons";
import { api, type Playlist } from "../lib/api";
import { compareText } from "../lib/collate";
import { formatRuntime } from "../lib/format";
import { notify } from "../lib/notifications";
import { notifyYouTubeActionError } from "../lib/youtubeErrors";
import { LS } from "../lib/storage";
import { usePref } from "../lib/usePref";
import { type PanelLayout } from "../lib/panelLayout";
import FilterRail from "./FilterRail";
import { Button } from "./ui/Button";
import { type ActionMenuItem } from "./ui/ActionMenu";
import { useComfortPin, pinPlaylist } from "./comfortPin";
import { ContextMenu } from "./ui/ContextMenu";
import { useContextMenu } from "./ui/useContextMenu";
import { type PanelItem } from "./ui/PanelGroups";
import SortControl from "./ui/SortControl";
import { type SortOption } from "../lib/columnSort";
import { usePlaylists, usePlaylistsActions } from "./playlistsContext";
import { useMe } from "../lib/useMe";
import { playlistName } from "../lib/playlistName";
import { usePlaylistActions } from "./usePlaylistActions";
import PlaylistLimitsHint from "./PlaylistLimitsHint";
import { IconButton } from "./ui/IconButton";
import { Pressable } from "./ui/Pressable";
import { Input } from "./ui/Input";
import { MoreButton } from "./ui/MoreButton";
import RemoteImage from "./ui/RemoteImage";

type PlSort = {
  key: "custom" | "name" | "count" | "duration" | "recent";
  dir: "asc" | "desc";
  dirtyFirst: boolean;
};
const PL_SORT_DEFAULT: PlSort = { key: "custom", dir: "asc", dirtyFirst: false };

// One geometry for the row in both of its shapes (the selectable button, and the rename field it
// becomes) — the row must not resize the moment you rename it.
const ROW_BASE = "w-full flex items-center gap-2.5 p-2 rounded-lg border transition";

// The Playlists module's left rail — lifted to App level (like the filter rails) so it floats in the
// shared SidePanel with the same collapse-to-tab behavior. It owns the list query + its own rail
// controls (sort / new / sync); the selected playlist is App state so the module's detail pane
// (Playlists.tsx) reacts to it. Grouped into two islands: "manage" and the playlist list.
export default function PlaylistsRail({
  layout,
  setLayout,
  collapsed,
  onToggleCollapse,
}: {
  layout: PanelLayout;
  setLayout: (l: PanelLayout) => void;
  collapsed: boolean;
  onToggleCollapse: () => void;
}) {
  const canWrite = useMe().can_write;
  // The name filter + the selected playlist live in PlaylistsProvider (shared with the header search
  // box and the Playlists detail pane); this rail owns the list query + its own controls.
  const { search, selectedId } = usePlaylists();
  const { setSelectedId } = usePlaylistsActions();
  const { t, i18n } = useTranslation();
  const lang = i18n.language;
  const qc = useQueryClient();
  const [plSort, setPlSort] = usePref<PlSort>("plSort", PL_SORT_DEFAULT, {
    localKey: LS.plSort,
    parse: (raw) => ({ ...PL_SORT_DEFAULT, ...(raw && typeof raw === "object" ? raw : {}) }),
  });
  const plSortOptions: SortOption[] = [
    { key: "custom", label: t("playlists.railSortCustom"), directionless: true },
    { key: "name", label: t("playlists.railSortName"), defaultDir: "asc" },
    { key: "count", label: t("playlists.railSortCount"), defaultDir: "desc" },
    { key: "duration", label: t("playlists.railSortDuration"), defaultDir: "desc" },
    // "the one I just touched, first". Reads `updated_at`, which the API bumps for item
    // adds/removes/moves/reorders too, not just renames (see the backend's _touch). NOT the
    // default: a rail that reshuffles itself while you look at it costs more than it saves.
    { key: "recent", label: t("playlists.railSortRecent"), defaultDir: "desc" },
  ];
  const [newName, setNewName] = useState("");
  const [syncing, setSyncing] = useState(false);
  const plActions = usePlaylistActions();
  // Right-click / long-press anywhere on a rail row. ONE menu for the whole list (see ui/ContextMenu).
  const railMenu = useContextMenu<Playlist>();
  // The comfort-shelf pin composes INTO this menu rather than mounting a second one: a row can only
  // have one right-click menu, and rename/delete/pin are all things you do to the same playlist.
  const comfortPin = useComfortPin(railMenu.open);
  // Renaming happens IN the row that was right-clicked, not in the detail header — the point of the
  // context menu is that the action lands where the gesture did.
  const [renamingId, setRenamingId] = useState<number | null>(null);
  const [renameValue, setRenameValue] = useState("");
  const selectedRef = useRef<HTMLButtonElement | null>(null);
  const scrolledRef = useRef(false);

  const listQuery = useQuery({
    queryKey: qk.playlists(),
    queryFn: () => api.playlists(),
    refetchOnWindowFocus: true,
  });
  // Memoised so the effect and the sort below depend on a value that only changes with the query —
  // `?? []` would otherwise mint a new empty array on every render while the list is loading.
  const playlists = useMemo(() => listQuery.data ?? [], [listQuery.data]);

  // Keep the selection valid: default to the first playlist, and if the selected one disappears
  // drop to the next available (or clear when none remain). Waits for the first load.
  useEffect(() => {
    if (!listQuery.data) return;
    if (!playlists.length) {
      if (selectedId != null) setSelectedId(null);
      return;
    }
    if (selectedId == null || !playlists.some((p) => p.id === selectedId)) {
      setSelectedId(playlists[0]!.id); // playlists is non-empty (the length guard above returns)
    }
  }, [playlists, selectedId, listQuery.data, setSelectedId]);

  // useCallback because the two memos below sort by it: as a fresh closure each render it could not
  // be named in their dep lists, and `t` — which is what actually changes it, on a language switch —
  // was therefore invisible to them. A rename in the other language now re-sorts.
  const plName = useCallback((p: { kind: string; name: string }) => playlistName(p, t), [t]);

  const sortedPlaylists = useMemo(() => {
    const sign = plSort.dir === "asc" ? 1 : -1;
    return [...playlists].sort((a, b) => {
      if (plSort.dirtyFirst && a.dirty !== b.dirty) return a.dirty ? -1 : 1;
      switch (plSort.key) {
        case "name":
          return sign * compareText(plName(a), plName(b), lang);
        case "count":
          return sign * (a.item_count - b.item_count);
        case "duration":
          return sign * ((a.total_duration_seconds ?? 0) - (b.total_duration_seconds ?? 0));
        case "recent":
          return sign * (Date.parse(a.updated_at) - Date.parse(b.updated_at));
        default:
          return 0;
      }
    });
  }, [playlists, plSort, plName, lang]);

  const q = search.trim().toLowerCase();
  const visiblePlaylists = useMemo(
    () =>
      q ? sortedPlaylists.filter((p) => plName(p).toLowerCase().includes(q)) : sortedPlaylists,
    [sortedPlaylists, q, plName],
  );

  useEffect(() => {
    if (!scrolledRef.current && selectedRef.current) {
      selectedRef.current.scrollIntoView({ block: "nearest" });
      scrolledRef.current = true;
    }
  }, [sortedPlaylists]);

  async function syncYoutube() {
    if (syncing) return;
    setSyncing(true);
    try {
      const r = await api.syncYoutubePlaylists();
      qc.invalidateQueries({ queryKey: qk.playlists() });
      qc.invalidateQueries({ queryKey: qk.playlist() });
      notify({ level: "success", message: t("playlists.syncedToast", { count: r.synced }) });
    } catch (e) {
      notifyYouTubeActionError(e, t("playlists.syncFailed"));
    }
    setSyncing(false);
  }

  const createMut = useMutation({
    mutationFn: (name: string) => api.createPlaylist(name),
    meta: { failTitle: "errors.writeFailed.createPlaylist" },
    onSuccess: (pl: Playlist) => {
      setNewName("");
      qc.invalidateQueries({ queryKey: qk.playlists() });
      setSelectedId(pl.id);
    },
  });

  // Enter and Escape unmount the focused <input> and re-render the row as a NEW <button>, so without
  // this a keyboard user was dropped on <body> and lost their place in the rail.
  // The row is focused from its ref callback, i.e. as that button attaches: measured in Chrome, a
  // focus issued after the commit sticks and nothing takes it back — the first attempt that
  // "never worked" focused before the replacement button existed. Set by Enter/Escape only: a
  // blur-commit means the user put the focus somewhere else on purpose.
  const refocusRowRef = useRef<number | null>(null);
  const renameInputRef = useRef<HTMLInputElement | null>(null);

  // Opening this field from the context menu used to race the menu's own focus return (floating-ui
  // hands the focus back to the trigger from a microtask queued as the popover unmounts, and the field
  // mounted in that same commit). `MenuItemList` now runs the item's action on a fresh task AFTER that
  // return, so the field simply mounts and is focused here; measured in Chrome, the field is
  // focused and survives.
  useEffect(() => {
    if (renamingId !== null) renameInputRef.current?.focus();
  }, [renamingId]);

  async function commitRename(pl: Playlist) {
    const name = renameValue.trim();
    setRenamingId(null);
    if (name && name !== pl.name) await plActions.rename(pl.id, name);
  }

  const ctxPl = railMenu.target;
  // The list's ONE menu (usePlaylistActions.items), the same the page header's "…" opens; the rail
  // renames IN the row that was right-clicked — the action lands where the gesture did.
  const railItems: ActionMenuItem[] = !ctxPl
    ? []
    : plActions.items(ctxPl, {
        onRename: () => {
          setRenameValue(ctxPl.name);
          setRenamingId(ctxPl.id);
        },
        pin: comfortPin.item(pinPlaylist(ctxPl.id), plName(ctxPl)),
      });

  const items: PanelItem[] = [
    {
      id: "manage",
      title: t("playlists.manageGroup"),
      body: (
        <div className="flex flex-col gap-2">
          <Button variant="outline" size="xs" fullWidth onClick={syncYoutube} disabled={syncing}>
            <RefreshCw className={`w-3.5 h-3.5 ${syncing ? "animate-spin" : ""}`} />
            {t("playlists.syncYoutube")}
          </Button>
          {playlists.length > 1 && (
            <SortControl
              label={t("playlists.sortLabel")}
              ascLabel={t("playlists.dirAsc")}
              descLabel={t("playlists.dirDesc")}
              options={plSortOptions}
              sort={{ key: plSort.key, dir: plSort.dir }}
              onChange={(next) =>
                next && setPlSort({ ...plSort, key: next.key as PlSort["key"], dir: next.dir })
              }
              trailing={
                <IconButton
                  variant="outline"
                  onClick={() => setPlSort({ ...plSort, dirtyFirst: !plSort.dirtyFirst })}
                  label={t("playlists.dirtyFirst")}
                  pressed={plSort.dirtyFirst}
                >
                  <Pin />
                </IconButton>
              }
            />
          )}
          <form
            onSubmit={(e) => {
              e.preventDefault();
              if (newName.trim()) createMut.mutate(newName.trim());
            }}
            className="flex items-center gap-1.5"
          >
            <Plus className="w-4 h-4 text-muted shrink-0" />
            <Input
              className="flex-1"
              size="sm"
              value={newName}
              onChange={(e) => setNewName(e.target.value)}
              placeholder={t("playlists.newPlaylist")}
              disabled={!canWrite}
            />
          </form>
        </div>
      ),
    },
    {
      id: "list",
      title: t("playlists.listGroup"),
      body: (
        <>
          {playlists.length === 0 &&
            (listQuery.isError && !listQuery.data ? (
              <Pressable
                onClick={() => listQuery.refetch()}
                className="text-xs text-danger px-1 py-1 hover:underline"
              >
                {t("common.loadError")} — {t("common.retry")}
              </Pressable>
            ) : listQuery.isLoading ? (
              <div className="text-xs text-muted px-1 py-1">{t("common.loading")}</div>
            ) : (
              <div className="text-xs text-muted px-1 py-1">{t("playlists.noneYet")}</div>
            ))}
          {playlists.length > 0 && visiblePlaylists.length === 0 && (
            <div className="text-xs text-muted px-1 py-1">{t("playlists.noMatches")}</div>
          )}
          <div className="space-y-1">
            {visiblePlaylists.map((pl) =>
              renamingId === pl.id ? (
                // The row becomes its own rename field. A <button> can't contain an <input>, so the
                // whole row swaps rather than the label alone — but it KEEPS the cover, because
                // that is what holds the row at its two-line height. Without it the rail jumps by
                // ~12px the moment you start renaming, and every row below it moves under the
                // pointer.
                <div key={pl.id} className={`${ROW_BASE} bg-accent/10 border-accent`}>
                  <div className="w-8.5 h-8.5 rounded-md bg-card overflow-hidden shrink-0">
                    {pl.cover_thumbnail && (
                      <RemoteImage
                        src={pl.cover_thumbnail}
                        alt=""
                        className="w-full h-full object-cover"
                      />
                    )}
                  </div>
                  <Input
                    className="flex-1"
                    size="sm"
                    ref={renameInputRef}
                    value={renameValue}
                    onChange={(e) => setRenameValue(e.target.value)}
                    onBlur={() => void commitRename(pl)}
                    onKeyDown={(e) => {
                      // preventDefault: the focus lands on the row before this keystroke is done,
                      // and a real Enter's own activation would then press it (see useReturnFocus).
                      if (e.key === "Enter") {
                        e.preventDefault();
                        refocusRowRef.current = pl.id;
                        void commitRename(pl);
                      }
                      // Unmounting the input fires no blur in React, so Escape really does cancel.
                      if (e.key === "Escape") {
                        e.preventDefault();
                        refocusRowRef.current = pl.id;
                        setRenamingId(null);
                      }
                    }}
                    aria-label={t("playlists.rename")}
                  />
                </div>
              ) : (
                // `group`: the row's "…" shows on its hover or focus (`.reveal`), and always on touch.
                // A sibling of the row button, not inside it — a button cannot hold a button.
                <div key={pl.id} className="group relative" {...railMenu.triggerProps(pl)}>
                  <Pressable
                    selectable
                    ref={(el) => {
                      if (pl.id === selectedId) selectedRef.current = el;
                      // Back from the rename field by Enter/Escape — see refocusRowRef.
                      if (el && refocusRowRef.current === pl.id) {
                        refocusRowRef.current = null;
                        el.focus();
                      }
                    }}
                    onClick={() => setSelectedId(pl.id)}
                    layer={pl.id !== selectedId}
                    // pr-9: the "…" sits over the row's right end, so the name truncates short of it.
                    className={`${ROW_BASE} pr-9 ${
                      pl.id === selectedId ? "bg-accent/15 border-accent" : "border-transparent"
                    }`}
                  >
                    <div className="w-8.5 h-8.5 rounded-md bg-card overflow-hidden shrink-0">
                      {pl.cover_thumbnail && (
                        <RemoteImage
                          src={pl.cover_thumbnail}
                          alt=""
                          className="w-full h-full object-cover"
                        />
                      )}
                    </div>
                    <div className="min-w-0">
                      <div className="flex items-center gap-1 text-[0.8125rem] text-fg">
                        <span className="truncate">{plName(pl)}</span>
                        {(pl.source === "youtube" || pl.yt_playlist_id) && (
                          <YouTubeIcon
                            className={`w-3 h-3 shrink-0 ${pl.dirty ? "text-accent" : "text-muted"}`}
                          />
                        )}
                      </div>
                      <div className="text-2xs text-muted">
                        {t("playlists.itemCount", { count: pl.item_count })}
                        {pl.total_duration_seconds > 0 &&
                          ` · ${formatRuntime(pl.total_duration_seconds, lang)}`}
                      </div>
                    </div>
                  </Pressable>
                  <MoreButton
                    label={t("playlists.railMenu")}
                    expanded={railMenu.open && railMenu.target === pl}
                    menuProps={railMenu.buttonProps(pl)}
                    className={`absolute right-1.5 top-1/2 -translate-y-1/2 ${
                      railMenu.open && railMenu.target === pl ? "" : "reveal"
                    }`}
                  />
                </div>
              ),
            )}
          </div>
          <ContextMenu menu={railMenu} ariaLabel={t("playlists.railMenu")} items={railItems} />
          <PlaylistLimitsHint />
        </>
      ),
    },
  ];

  return (
    <FilterRail
      kind="playlists"
      title={t("playlists.title")}
      icon={<ListVideo className="w-4 h-4" />}
      collapsed={collapsed}
      onToggleCollapse={onToggleCollapse}
      layout={layout}
      setLayout={setLayout}
      items={items}
    />
  );
}