import { useCallback, useEffect, useRef, useState } from 'react';
import { ArrowDown, ArrowUp, Check, FolderOpen, ImagePlus, Loader2, Trash2 } from 'lucide-react';
import { useClient } from 'hooks/useClient';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import { readableError } from '../errors';
import { useFlash } from '../useFlash';
import { RichText } from '../RichText';
import { MediaPicker } from '../MediaPicker';

/**
 * The Home page: a hero, an intro, and an ordered gallery.
 *
 * ── It edits DEVELOPMENT, and that is the whole model ──
 *
 * Every request here goes through this plugin to the development server's `/api/admin`. Production is
 * a directory of static files with no API at all, so there is nothing to write to there — an edit
 * lands on dev immediately and becomes public when somebody presses Build. Saying that once, here, is
 * better than a person discovering it when a change does not appear on the live site.
 *
 * ── The server owns the shape, and every write returns it ──
 *
 * `PATCH /home` and every gallery route answer with the WHOLE payload, so this never patches its own
 * state from what it sent. That matters more than it looks: the server clears the hero crop when the
 * hero changes, and a client that kept its own copy would go on showing a framing the server had
 * already discarded.
 *
 * ── Ordering is a list, not a field ──
 *
 * `PUT /gallery/order` takes every id in the order they should be. So moving one item sends all of
 * them, which is what makes it impossible to end up with two things claiming the same position.
 */

type GalleryItem = {
  id: number;
  kind: string;
  url: string;
  crop: string | null;
  fit: string | null;
  sort_order: number;
  alt: string | null;
};

type Home = {
  hero: { url: string | null; crop: string | null; fit: string | null };
  intro_text: string | null;
  gallery: GalleryItem[];
};

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

  const [home, setHome] = useState<Home | null>(null);
  const [heroUrl, setHeroUrl] = useState('');
  const [intro, setIntro] = useState('');
  const [addUrl, setAddUrl] = useState('');
  const [busy, setBusy] = useState<string | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [saved, flashSaved] = useFlash();
  const [picking, setPicking] = useState(false);

  /** Every write answers with the whole payload, so this is the only place state is set. */
  const apply = useCallback((data: Home) => {
    setHome(data);
    setHeroUrl(data.hero.url ?? '');
    setIntro(data.intro_text ?? '');
  }, []);

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

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

  const send = async (label: string, call: () => Promise<{ data: Home }>) => {
    setBusy(label);
    setError(null);
    try {
      apply((await call()).data);
      flashSaved();
    } catch (failure) {
      setError(readableError(failure));
    } finally {
      setBusy(null);
    }
  };

  /*
    One PATCH per card, carrying only that card's field.

    `take()` on the server treats an absent key as "leave it alone", so sending the whole object from
    either card would have each one saving the other's unsaved edits. Two cards, two independent
    saves, and a half-finished intro cannot ride along with a hero somebody meant to change.
  */
  const saveIntro = () =>
    send('intro', () => clientRef.current.patch<{ data: Home }>('/fofos-admin/home', { intro_text: intro.trim() || null }));

  const saveHero = () =>
    send('hero', () => clientRef.current.patch<{ data: Home }>('/fofos-admin/home', { hero_url: heroUrl.trim() || null }));

  const add = () =>
    send('add', async () => {
      const response = await clientRef.current.post<{ data: Home }>('/fofos-admin/home/gallery', {
        url: addUrl.trim(),
      });
      setAddUrl('');
      return response;
    });

  const remove = (item: GalleryItem) =>
    send(`del:${item.id}`, () => clientRef.current.delete<{ data: Home }>(`/fofos-admin/home/gallery/${item.id}`));

  const setAlt = (item: GalleryItem, alt: string) =>
    send(`alt:${item.id}`, () =>
      clientRef.current.patch<{ data: Home }>(`/fofos-admin/home/gallery/${item.id}`, { alt: alt.trim() || null }),
    );

  /** Moving one sends them ALL, which is what makes two items claiming a position impossible. */
  const move = (index: number, by: -1 | 1) => {
    if (!home) return;
    const next = [...home.gallery];
    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<{ data: Home }>('/fofos-admin/home/gallery/order', { ids: next.map((item) => item.id) }),
    );
  };

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

  const introDirty = intro.trim() !== (home.intro_text ?? '');
  const heroDirty = heroUrl.trim() !== (home.hero.url ?? '');

  return (
    <div className="flex size-full flex-col gap-4 overflow-auto p-5">
      {/*
        Intro first, then Hero.

        The page reads hero-then-intro, and this does not, deliberately: the intro is the thing that
        gets edited, and the hero is a path that changes once a season. Ordering by what somebody came
        to do beats mirroring the layout of the page they are describing.
      */}
      <section className="flex flex-col gap-3 rounded-lg border border-border p-4">
        <div className="flex items-start justify-between gap-3">
          <div className="space-y-1">
            <h3 className="text-sm font-medium">Intro</h3>
            <p className="text-xs text-muted-foreground">The paragraph under the hero.</p>
          </div>
          {saved && (
            <span className="flex shrink-0 items-center gap-1 text-xs text-success">
              <Check className="size-3.5" />
              Saved
            </span>
          )}
        </div>

        {/* HTML in and HTML out — it is what the site's database already holds and renders. */}
        <RichText value={intro} onChange={setIntro} placeholder="The paragraph under the hero." />

        <div className="flex justify-end border-t border-border pt-3">
          <Button size="sm" onClick={() => void saveIntro()} disabled={busy !== null || !introDirty}>
            {busy === 'intro' ? <Loader2 className="size-3.5 animate-spin" /> : <Check className="size-3.5" />}
            Save
          </Button>
        </div>
      </section>

      <section className="flex flex-col gap-3 rounded-lg border border-border p-4">
        <div className="space-y-1">
          <h3 className="text-sm font-medium">Hero</h3>
          <p className="text-xs text-muted-foreground">The video or image across the top of the page.</p>
        </div>

        {/*
          A Browse button, not a field.

          Nobody knows the path of a file they uploaded from a phone, and a text box invites a typo that
          fails silently as a broken image on the live site. Browsing `originals/` means the only values
          that can be stored are ones that exist.
        */}
        <div className="flex items-center gap-2">
          <p className="min-w-0 flex-1 truncate rounded-md border border-border bg-muted/30 px-3 py-2 font-mono text-xs">
            {heroUrl || <span className="text-muted-foreground/60">Nothing chosen</span>}
          </p>
          <Button variant="outline" size="sm" className="shrink-0" onClick={() => setPicking(true)}>
            <FolderOpen className="size-3.5" />
            Browse
          </Button>
        </div>

        <MediaPicker
          open={picking}
          onClose={() => setPicking(false)}
          onPick={setHeroUrl}
          title="Choose the hero"
        />
        {/* The server clears the crop when the hero changes, because a rectangle describing a region of
            a different picture would crop the new one somewhere arbitrary. Said here so it is not a
            surprise. */}
        {home.hero.crop && (
          <p className="text-xs text-muted-foreground/70">
            Framed at {home.hero.crop} — changing the hero clears that.
          </p>
        )}

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

        <div className="flex justify-end border-t border-border pt-3">
          <Button size="sm" onClick={() => void saveHero()} disabled={busy !== null || !heroDirty}>
            {busy === 'hero' ? <Loader2 className="size-3.5 animate-spin" /> : <Check className="size-3.5" />}
            Save
          </Button>
        </div>
      </section>

      <section className="flex flex-col gap-3 rounded-lg border border-border p-4">
        <div className="space-y-1">
          <h3 className="text-sm font-medium">Gallery</h3>
          <p className="text-xs text-muted-foreground">
            The carousel below the intro. {home.gallery.length} item{home.gallery.length === 1 ? '' : 's'}, in order.
          </p>
        </div>

        <ul className="space-y-2">
          {home.gallery.map((item, index) => (
            <li key={item.id} className="flex flex-wrap items-center gap-2 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>

              {/* Through the plugin's own proxy, so it loads with the session rather than needing the
                  dev server to be reachable from the browser. */}
              {item.kind === 'photo' ? (
                <img
                  src={`/api/fofos-admin${item.url}`}
                  alt=""
                  className="size-10 shrink-0 rounded object-cover"
                  loading="lazy"
                />
              ) : (
                <span className="flex size-10 shrink-0 items-center justify-center rounded bg-muted text-[10px]">
                  {item.kind}
                </span>
              )}

              <span className="min-w-0 flex-1 space-y-1">
                <span className="block truncate font-mono text-xs text-muted-foreground">{item.url}</span>
                <Input
                  defaultValue={item.alt ?? ''}
                  onBlur={(event) => {
                    if (event.target.value.trim() !== (item.alt ?? '')) void setAlt(item, event.target.value);
                  }}
                  placeholder="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(index, -1)} disabled={busy !== null || index === 0}>
                  <ArrowUp className="size-3.5" />
                </Button>
                <Button
                  variant="ghost"
                  size="sm"
                  onClick={() => void move(index, 1)}
                  disabled={busy !== null || index === home.gallery.length - 1}
                >
                  <ArrowDown className="size-3.5" />
                </Button>
                <Button variant="ghost" size="sm" onClick={() => void remove(item)} disabled={busy !== null}>
                  {busy === `del:${item.id}` ? (
                    <Loader2 className="size-3.5 animate-spin" />
                  ) : (
                    <Trash2 className="size-3.5 text-destructive" />
                  )}
                </Button>
              </span>
            </li>
          ))}
        </ul>

        <div className="flex gap-2 border-t border-border pt-3">
          <Input
            value={addUrl}
            onChange={(event) => setAddUrl(event.target.value)}
            placeholder="/media/…"
            className="min-w-0 flex-1 font-mono text-xs"
            autoComplete="off"
            spellCheck={false}
          />
          <Button
            variant="outline"
            size="sm"
            className="w-28 shrink-0 justify-center"
            onClick={() => void add()}
            disabled={busy !== null || !addUrl.trim()}
          >
            {busy === 'add' ? <Loader2 className="size-3.5 animate-spin" /> : <ImagePlus className="size-3.5" />}
            Add
          </Button>
        </div>
      </section>
    </div>
  );
};