import { useCallback, useEffect, useRef, useState } from 'react';
import { useSearchParams } from 'react-router';
import { FolderOpen, TriangleAlert } from 'lucide-react';
import { FileBrowserApp, FileViewerView } from 'officerdev';
import { useClient } from 'hooks/useClient';

/**
 * The site's own media, browsed in place.
 *
 * ── It embeds the platform's file browser rather than reimplementing one ──
 *
 * Upload, delete, rename, move, thumbnails, the context menu and every task that hangs off it already
 * exist and are maintained in one place. A plugin drawing its own file list would be a second one to
 * keep in step, and it would arrive without any of that.
 *
 * ── `basePath` is a jail, not a starting folder ──
 *
 * `useFileBrowserApp` resets `currentPath` whenever it leaves `basePath`, so pointing it at
 * `<root>/media/originals` means the breadcrumb stops there and `derived/` is not reachable by
 * navigating. That is the behaviour the owner asked for: people work in originals, and derived is made
 * for them.
 *
 * **It is a guardrail, not a permission boundary, and the difference matters.** The file-browser API is
 * unchanged and still addresses the whole home — somebody with file access can reach `derived/` through
 * the Files screen or by hand. Confining it properly would mean scoping the API per user, which is a
 * platform change and a much larger one. What this prevents is an accident, not a determined person.
 *
 * ── Nothing here is fofos-specific ──
 *
 * The root is a setting, `media/originals` is the layout this plugin creates, and the panel reads both
 * from the API. Another site's admin plugin built from this one changes the label and nothing else.
 */

type Settings = { rootPath: string; rootRelative: string | null; isSet: boolean };

/** Where the uploads live, relative to the root. The other half, `derived/`, is deliberately not shown. */
const ORIGINALS = 'media/originals';

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

  const [params, setParams] = useSearchParams();
  // Set by the browser when a file is double-clicked. Nothing else on this screen reads it.
  const viewPath = params.get('view');

  const [settings, setSettings] = useState<Settings | null>(null);
  const [denied, setDenied] = useState(false);

  const load = useCallback(async () => {
    try {
      setSettings(await clientRef.current.get<Settings>('/fofos-admin/_config/root'));
    } catch (failure) {
      // The root is owner-only. A member sees the section and is told why rather than an empty browser.
      if ((failure as { status?: number })?.status === 403) setDenied(true);
      else setSettings({ rootPath: '', rootRelative: null, isSet: false });
    }
  }, []);

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

  if (denied) {
    return <Notice icon={TriangleAlert}>Only the owner can see where the site's media lives.</Notice>;
  }

  if (!settings) {
    return <Notice icon={FolderOpen}>Loading…</Notice>;
  }

  /*
    A root outside the owner's home is a legitimate setting and the file browser cannot address it —
    everything it does is relative to `home`. Said plainly here rather than rendering an empty folder,
    which would read as "there is nothing in your media".
  */
  if (!settings.rootRelative) {
    return (
      <Notice icon={TriangleAlert}>
        The root location is outside your home directory, so the file browser cannot show it. Move it under your home in
        Administration, or use the Files screen.
      </Notice>
    );
  }

  const base = `${settings.rootRelative === '/' ? '' : settings.rootRelative}/${ORIGINALS}`;

  /*
    Just the browser. No banner explaining `derived/`.

    The people using this upload photographs; the two-folder split is the machine's business, not
    theirs. A line at the top of every visit is a permanent tax paid by everyone to answer a question
    almost nobody asks — and it is written properly in the affordance and the plugin's docs.

    `rootLabel` so the breadcrumb reads "Media" rather than "originals": the folder's name on disk is
    an implementation detail of how this plugin lays out a root, and the section is called Media.

    `pathParam` keeps the folder in `?media=`, so a reload lands where you were and the link can be sent
    to somebody. NOT `urlPath`, which was the first attempt and was wrong: that one owns the URL's
    PATHNAME and navigates to /files, so opening a folder here took the whole app to the Files screen.

    `?media=` rather than `?path=` because this screen already carries `?section=` and may one day carry
    another browser; a param named after what it addresses cannot collide with one named after a
    concept.

    `panelId` stays alongside: the URL covers a reload or a shared link, panelId covers a panel
    re-opened later, which the URL cannot.
  */
  /*
    ── The preview, which needed doing here rather than coming for free ──

    On /files the viewer is not part of the browser: `useFileViewerPanels` lives on the SCREEN and swaps
    the whole workspace layout when `?view=` appears, opening a viewer panel beside it. A plugin renders
    its own `defaultLayout` and has no such hook, so double-clicking a file here set `?view=` and nothing
    ever read it. It looked like it worked only while `urlPath` was navigating to /files, where that
    screen did the work.

    So the panel reads `?view=` itself and shows the viewer over the browser. Over rather than beside,
    because this panel is one column of a two-column screen — splitting it again would leave a preview
    the width of a phone.

    Closing clears `view` and leaves `media` alone, so you come back to the folder you were in rather
    than the top.
  */
  if (viewPath) {
    return (
      <FileViewerView
        filePath={viewPath}
        fileName={viewPath.slice(viewPath.lastIndexOf('/') + 1)}
        /* The carousel's step. `?view=` is an absolute path in this panel, so it is written straight
           back — the conversion the Files screen needs is that screen's own convention, not a rule. */
        onNavigate={(next) => {
          const params2 = new URLSearchParams(params);
          params2.set('view', next);
          setParams(params2);
        }}
        onClose={() => {
          const next = new URLSearchParams(params);
          next.delete('view');
          next.delete('viewRoot');
          setParams(next);
        }}
      />
    );
  }

  return <FileBrowserApp basePath={base} rootLabel="Media" pathParam="media" panelId="fofos-admin-media" />;
};

const Notice = ({ icon: Icon, children }: { icon: typeof FolderOpen; children: React.ReactNode }) => (
  <div className="flex size-full flex-col items-center justify-center gap-2 p-6 text-center">
    <Icon className="size-6 text-muted-foreground/60" />
    <p className="max-w-sm text-sm text-muted-foreground">{children}</p>
  </div>
);