import { useCallback, useState } from "react";
import { useTranslation } from "react-i18next";
import { useQuery, useQueryClient } from "@tanstack/react-query";
import { Loader2, Pin, PinOff } from "lucide-react";

import { api, type DiscoverCard, type PinKind } from "../lib/api";
import { notifyActionError } from "../lib/actionErrors";
import { notify } from "../lib/notifications";
import { qk } from "../lib/queryKeys";
import { type ActionMenuItem } from "./ui/ActionMenu";

// E24 S3 — "put this on my comfort shelf", from wherever you happen to be looking at the thing.
//
// The shelf is the Home surface's object, but the GESTURE belongs wherever a pinnable thing is
// shown — a video, a channel, a playlist, a Plex show or movie: you decide something is comfort media
// while you are watching it. (Locked decision 3: an episode, a season and a person are not pin kinds,
// so their cards and strips carry no pin.) This file is the one place the pin lives; every surface
// composes the same `ActionMenuItem` into the menu it already has (`Playlists`, `PlaylistsRail`) or
// mounts the `ComfortPinMenu` wrapper when it has none.
//
// Feature layer, not `components/ui/`: it speaks a domain API slice, which the platform boundary
// (eslint `no-restricted-imports`) forbids a `ui/` primitive from doing. The MENU SURFACE that
// renders this item lives in `ComfortPinMenu.tsx` — the same hook/component split, for the same
// react-refresh reason, as `useContextMenu.ts` beside `ContextMenu.tsx`.

/** What the API needs to pin something: the kind, and the id the rest of the API already speaks for
 *  that kind (a video id, a channel id, a Plex `rating_key`, a playlist id). Mirrors
 *  `app/discover/pins.py::PIN_COLUMNS`. */
export interface PinTarget {
  kind: PinKind;
  ref: string;
}

// Constructors rather than five call sites writing the kind strings by hand. The mapping from a
// domain object to its pin kind is an invariant, so it lives in a function — a `"plex_show"` typo'd
// as `"plex-show"` at one of eight call sites would be a 404 nobody notices until they try it.
export const pinVideo = (videoId: string): PinTarget => ({ kind: "video", ref: videoId });
export const pinChannel = (channelId: string): PinTarget => ({ kind: "channel", ref: channelId });
export const pinPlaylist = (playlistId: number): PinTarget => ({
  kind: "playlist",
  ref: String(playlistId),
});
/** A Plex tile. A SHOW is pinned as a show ("put that series on" resolves to whichever episode is
 *  next); a movie or a single episode is pinned as the leaf item it is. */
export const pinPlex = (card: { id: string; type: string }): PinTarget => ({
  kind: card.type === "show" ? "plex_show" : "plex_item",
  ref: card.id,
});

/** A unified discover card back to the thing it was pinned as — the inverse of the mapping in
 *  `app/discover/cards.py`. Null for a kind that cannot be pinned. */
export function pinTargetForCard(
  card: Pick<DiscoverCard, "source" | "kind" | "id">,
): PinTarget | null {
  if (card.source === "plex") return pinPlex({ id: card.id, type: card.kind });
  if (card.kind === "video") return pinVideo(card.id);
  if (card.kind === "channel") return pinChannel(card.id);
  if (card.kind === "playlist") return { kind: "playlist", ref: card.id };
  return null;
}

/** Where a shelf move lands. The shelf is a HORIZONTAL rail, so the words are left/right rather than
 *  the playlist table's up/down — the same four moves, named after what the user actually sees. */
export type ShelfMove = "first" | "left" | "right" | "last";

/** `from` -> the index the move targets, or -1 when there is nowhere to go. Pure, so the disabled
 *  state of a menu row and the move it would perform are decided by ONE rule instead of two that can
 *  disagree (a row that looks available and then no-ops is the worst of the three states). */
export function shelfMoveTarget(from: number, to: ShelfMove, length: number): number {
  if (from < 0 || from >= length) return -1;
  const target =
    to === "first" ? 0 : to === "last" ? length - 1 : to === "left" ? from - 1 : from + 1;
  return target === from || target < 0 || target >= length ? -1 : target;
}

/** The identity a target is looked up by. One function, so "is this pinned?" and "what did the
 *  server give back?" can never key the shelf two different ways. */
const targetKey = (target: PinTarget): string => `${target.kind}:${target.ref}`;

export interface ComfortPin {
  /** `pinIdOf` and `toggle` stay module-local until a second consumer needs them: publishing them
   *  invites the next surface to re-derive the three-state loading dance (pinned / not pinned /
   *  not known yet) that `item` already encapsulates, which is what this file exists to prevent. */
  remove: (pinId: number, title: string) => void;
  /** The pin/unpin row, ready to spread into any `ActionMenuItem[]`. Empty for a null target. */
  item: (target: PinTarget | null, title: string) => ActionMenuItem[];
}

/**
 * The shelf's client half.
 *
 * `open` is the host menu's own open flag. The shelf is only fetched once a menu has actually been
 * opened (and stays cached afterwards), because the pinned-ness of a row is needed to LABEL one menu
 * item and nothing else — firing `/api/discover/pins`, which resolves a `next` per non-leaf pin, on
 * every feed load would be a real request for a string almost nobody reads that session.
 */
export function useComfortPin(open: boolean): ComfortPin {
  const { t } = useTranslation();
  const qc = useQueryClient();
  // Latch: react-query keeps the data cached when `enabled` goes false again, so this only decides
  // WHEN the first fetch happens, not whether the answer survives the menu closing.
  const [everOpen, setEverOpen] = useState(false);
  // Latched during render: the query below is gated on it, so an effect delayed the first fetch by
  // a commit for no reason. Convergent — the write falsifies its own condition.
  if (open && !everOpen) setEverOpen(true);

  const shelf = useQuery({
    queryKey: qk.comfortPins(),
    queryFn: () => api.comfortPins(),
    enabled: everOpen,
    // The shelf is hand-curated and short; re-asking on every menu open would be noise.
    staleTime: 60_000,
  });

  const pins = shelf.data?.items;
  const pinIdOf = useCallback(
    (target: PinTarget): number | null | undefined => {
      if (!pins) return undefined;
      const key = targetKey(target);
      for (const card of pins) {
        const other = pinTargetForCard(card);
        if (other && targetKey(other) === key) return card.pin_id ?? null;
      }
      return null;
    },
    [pins],
  );

  const invalidate = useCallback(() => {
    void qc.invalidateQueries({ queryKey: qk.comfortPins() });
    // The prefix, not an exact key: the Home payload is per-budget, and pinning something can change
    // the hero as well as the shelf.
    void qc.invalidateQueries({ queryKey: qk.discover() });
  }, [qc]);

  const add = useCallback(
    async (target: PinTarget, title: string) => {
      try {
        await api.addComfortPin(target.kind, target.ref);
        // The shelf lives on another page, so without this the click has no visible consequence at
        // all from the feed — the one place a toast genuinely carries the whole feedback.
        notify({ level: "success", message: t("home.pin.added", { title }) });
      } catch (e) {
        notifyActionError(e, t("home.pin.addFailed"));
      }
      invalidate();
    },
    [invalidate, t],
  );

  const remove = useCallback(
    (pinId: number, title: string) => {
      void (async () => {
        try {
          await api.removeComfortPin(pinId);
          notify({ level: "success", message: t("home.pin.removed", { title }) });
        } catch (e) {
          notifyActionError(e, t("home.pin.removeFailed"));
        }
        invalidate();
      })();
    },
    [invalidate, t],
  );

  const toggle = useCallback(
    (target: PinTarget, title: string) => {
      const pinId = pinIdOf(target);
      if (pinId == null) void add(target, title);
      else remove(pinId, title);
    },
    [add, pinIdOf, remove],
  );

  const item = useCallback(
    (target: PinTarget | null, title: string): ActionMenuItem[] => {
      if (!target) return [];
      const pinId = pinIdOf(target);
      // Still loading: an honest "we don't know yet" row rather than a confident "Pin" over
      // something that is already on the shelf. Only ever seen on the first menu open of a session.
      if (pinId === undefined)
        return [
          {
            id: "comfort-pin",
            label: t("home.pin.add"),
            icon: <Loader2 className="w-4 h-4 animate-spin" />,
            separatorBefore: true,
            disabled: true,
            onSelect: () => {},
          },
        ];
      return [
        {
          id: "comfort-pin",
          label: pinId === null ? t("home.pin.add") : t("home.pin.remove"),
          icon: pinId === null ? <Pin className="w-4 h-4" /> : <PinOff className="w-4 h-4" />,
          separatorBefore: true,
          // One row, two states, and only ONE of them is destructive — so `danger` flips with the
          // label and the icon rather than being decided at a call site. The shelf's own hand-rolled
          // unpin row on Home got the flag first; leaving this one neutral painted the identical
          // command (same label, same icon, same `removeComfortPin`) two different colours on one
          // screen — the hero's menu and the Continue-watching rail come through here (round 2).
          danger: pinId !== null,
          onSelect: () => toggle(target, title),
        },
      ];
    },
    [pinIdOf, t, toggle],
  );

  return { remove, item };
}