import { useCallback, useEffect, useRef, useState } from 'react';
import { useSearchParams } from 'react-router';
import { ArrowDown, ArrowUp, FolderOpen, Images, Loader2, Plus, Trash2 } from 'lucide-react';
import { useClient } from 'hooks/useClient';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import { getHeaders } from 'hooks/useClient';
import { readableError } from '../errors';
import { MediaPicker } from '../MediaPicker';

/**
 * Galleries — named, ordered sets of media, reusable anywhere on the site.
 *
 * ── Why a gallery is not a list on a page ──
 *
 * The home page had one, as rows hanging off its own content. That works for exactly one. The moment a
 * second page wants the same photographs in the same order, a list-per-page means choosing them again
 * and keeping two copies in step by hand.
 *
 * ── The server owns the shape ──
 *
 * Every write answers with the whole gallery and this never patches its own state from what it sent.
 * That matters most here: reordering renumbers everything, adding appends after whatever was there,
 * and deleting closes a gap. A client keeping its own copy drifts on the first of those with no way to
 * notice.
 */

type Item = { id: number; url: string; alt: string | null; sort_order: number };
type Gallery = { id: number; name: string; slug: string; items: Item[] };

/**
 * A thumbnail URL, authenticated by `?token=`.
 *
 * An `<img>` cannot send an Authorization header, which is why `user-middleware` and the permission
 * gate both accept the token in the query string — the same thing the file browser's own thumbnails do.
 * Built without it first, and every picture 401'd while the layout looked perfectly correct.
 */
const thumbUrl = (path: string): string => {
  const token = getHeaders()['Authorization']?.replace('Bearer ', '') ?? '';
  const encoded = path.split('/').map(encodeURIComponent).join('/');
  return `/api/fofos-admin/derived/${encoded}/320.webp?token=${encodeURIComponent(token)}`;
};

export const GalleriesPanel = () => {
  const client = useClient();
  const clientRef = useRef(client);
  clientRef.current = client;

  const [galleries, setGalleries] = useState<Gallery[] | null>(null);
  const [openId, setOpenId] = useState<number | null>(null);
  const [name, setName] = useState('');
  const [picking, setPicking] = useState<number | null>(null);
  /** Paths handed over by the context menu, waiting for a name. */
  const [pending, setPending] = useState<string[]>([]);
  const [busy, setBusy] = useState<string | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [params, setParams] = useSearchParams();

  const load = useCallback(async () => {
    try {
      const response = await clientRef.current.get<{ data: Gallery[] }>('/fofos-admin/galleries');
      setGalleries(response.data);
    } catch (failure) {
      setError(readableError(failure));
      setGalleries([]);
    }
  }, []);

  useEffect(() => {
    void load();
  }, [load]);

  /*
    Arriving from "Create Gallery" in the file browser.

    The action puts the chosen paths in the URL and sends you here rather than opening its own dialog:
    naming a gallery, seeing the slug it gets and watching the items land belongs on the screen that
    owns galleries. Consumed once and removed from the URL — a `?from=` left behind would recreate the
    gallery on every refresh, which somebody discovers as four copies.
  */
  const arriving = params.get('from');
  useEffect(() => {
    if (arriving === null) return;
    const urls = arriving.split('\n').filter(Boolean);
    const suggested = params.get('create') ?? '';
    setParams(
      (current) => {
        const next = new URLSearchParams(current);
        next.delete('from');
        next.delete('create');
        return next;
      },
      { replace: true },
    );
    // Pre-filled rather than created: the name is somebody's to choose and a folder name is only a
    // suggestion. Nothing is written until Create.
    setName(suggested);
    setPending(urls);
  }, [arriving, params, setParams]);

  const send = async (label: string, call: () => Promise<unknown>) => {
    setBusy(label);
    setError(null);
    try {
      await call();
      await load();
    } catch (failure) {
      setError(readableError(failure));
    } finally {
      setBusy(null);
    }
  };

  const create = () =>
    send('create', async () => {
      // `urls` in the same request, so creating from a selection is one action — splitting it would
      // leave an empty gallery behind whenever the second call failed.
      await clientRef.current.post('/fofos-admin/galleries', { name: name.trim(), urls: pending });
      setName('');
      setPending([]);
    });

  const addTo = (galleryId: number, url: string) =>
    send(`add:${galleryId}`, () => clientRef.current.post(`/fofos-admin/galleries/${galleryId}/items`, { urls: [url] }));

  const removeItem = (galleryId: number, itemId: number) =>
    send(`del:${itemId}`, () => clientRef.current.delete(`/fofos-admin/galleries/${galleryId}/items/${itemId}`));

  /** Every id, in order — which is what makes two items claiming a position impossible. */
  const move = (gallery: Gallery, index: number, by: -1 | 1) => {
    const next = [...gallery.items];
    const target = index + by;
    if (target < 0 || target >= next.length) return;
    [next[index], next[target]] = [next[target]!, next[index]!];
    return send('order', () =>
      clientRef.current.put(`/fofos-admin/galleries/${gallery.id}/items/order`, { ids: next.map((item) => item.id) }),
    );
  };

  if (!galleries) return <div className="p-5 text-xs text-muted-foreground">{error ?? 'Loading…'}</div>;

  return (
    <div className="flex size-full flex-col gap-4 overflow-auto p-5">
      <section className="flex flex-col gap-3 rounded-lg border border-border p-4">
        <h3 className="text-sm font-medium">Galleries</h3>

        {error && <p className="text-xs text-destructive">{error}</p>}

        {/* What the context menu sent, so what is about to be created is not a mystery. */}
        {pending.length > 0 && (
          <p className="text-xs text-muted-foreground/80">
            {pending.length} item{pending.length === 1 ? '' : 's'} ready — name it and press Create.
          </p>
        )}

        <div className="flex gap-2">
          <Input
            autoFocus={pending.length > 0}
            value={name}
            onChange={(event) => setName(event.target.value)}
            placeholder="Name a new gallery"
            className="min-w-0 flex-1 text-xs"
            onKeyDown={(event) => {
              if (event.key === 'Enter' && name.trim()) void create();
            }}
          />
          <Button
            variant="outline"
            size="sm"
            className="w-24 shrink-0 justify-center"
            onClick={() => void create()}
            disabled={busy !== null || !name.trim()}
          >
            {busy === 'create' ? <Loader2 className="size-3.5 animate-spin" /> : <Plus className="size-3.5" />}
            Create
          </Button>
        </div>
      </section>

      {galleries.map((gallery) => {
        const open = openId === gallery.id;
        return (
          <section key={gallery.id} className="flex flex-col gap-3 rounded-lg border border-border p-4">
            <button
              type="button"
              className="flex items-center justify-between gap-3 text-left"
              onClick={() => setOpenId(open ? null : gallery.id)}
            >
              <span className="min-w-0 space-y-1">
                <span className="flex items-center gap-2 text-sm font-medium">
                  <Images className="size-4" />
                  {gallery.name}
                </span>
                <span className="block font-mono text-xs text-muted-foreground/70">
                  {gallery.slug} · {gallery.items.length} item{gallery.items.length === 1 ? '' : 's'}
                </span>
              </span>
            </button>

            {open && (
              <>
                <ul className="space-y-1">
                  {gallery.items.map((item, index) => (
                    <li key={item.id} className="flex items-center gap-3 rounded border border-border/60 p-2">
                      <span className="w-6 shrink-0 text-center font-mono text-xs text-muted-foreground/60">
                        {index + 1}
                      </span>

                      {/*
                        From the DERIVED ladder, which is the whole point of the pipeline: most of these
                        are HEIC and a browser cannot show the original at all. 320 is the smallest rung
                        and still sharp at this size on a retina screen.
                      */}
                      <img
                        src={thumbUrl(item.url)}
                        alt=""
                        loading="lazy"
                        className="size-20 shrink-0 rounded bg-muted object-cover"
                        // A file whose conversion has not run yet has no rung. Hidden rather than left
                        // as a broken-image glyph, which reads as a corrupt picture rather than a
                        // pending one.
                        onError={(event) => {
                          event.currentTarget.style.visibility = 'hidden';
                        }}
                      />

                      <span className="min-w-0 flex-1 space-y-1">
                        <span className="block truncate font-mono text-xs text-muted-foreground">{item.url}</span>
                        {/*
                          Saved on blur rather than on every keystroke: a caption is a sentence somebody
                          is in the middle of, and a request per character would be both wasteful and a
                          race with itself.
                        */}
                        <Input
                          defaultValue={item.alt ?? ''}
                          onBlur={(event) => {
                            if (event.target.value.trim() !== (item.alt ?? '')) {
                              void send(`alt:${item.id}`, () =>
                                clientRef.current.patch(`/fofos-admin/galleries/${gallery.id}/items/${item.id}`, {
                                  alt: event.target.value.trim() || null,
                                }),
                              );
                            }
                          }}
                          placeholder="Caption — describe it, for screen readers"
                          className="h-7 text-xs"
                        />
                      </span>
                      <span className="flex shrink-0 gap-1">
                        <Button variant="ghost" size="sm" onClick={() => void move(gallery, index, -1)} disabled={busy !== null || index === 0}>
                          <ArrowUp className="size-3.5" />
                        </Button>
                        <Button
                          variant="ghost"
                          size="sm"
                          onClick={() => void move(gallery, index, 1)}
                          disabled={busy !== null || index === gallery.items.length - 1}
                        >
                          <ArrowDown className="size-3.5" />
                        </Button>
                        <Button variant="ghost" size="sm" onClick={() => void removeItem(gallery.id, item.id)} disabled={busy !== null}>
                          <Trash2 className="size-3.5 text-destructive" />
                        </Button>
                      </span>
                    </li>
                  ))}
                  {!gallery.items.length && <li className="text-xs text-muted-foreground/60">Nothing in it yet.</li>}
                </ul>

                <div className="flex justify-between gap-2 border-t border-border pt-3">
                  <Button variant="outline" size="sm" onClick={() => setPicking(gallery.id)} disabled={busy !== null}>
                    <FolderOpen className="size-3.5" />
                    Add media
                  </Button>
                  <Button
                    variant="ghost"
                    size="sm"
                    onClick={() => void send(`gallery:${gallery.id}`, () => clientRef.current.delete(`/fofos-admin/galleries/${gallery.id}`))}
                    disabled={busy !== null}
                  >
                    <Trash2 className="size-3.5 text-destructive" />
                    Delete gallery
                  </Button>
                </div>
              </>
            )}
          </section>
        );
      })}

      <MediaPicker
        open={picking !== null}
        onClose={() => setPicking(null)}
        onPick={(path) => {
          if (picking !== null) void addTo(picking, path);
        }}
        title="Add to gallery"
      />
    </div>
  );
};