import { useCallback, useEffect, useRef, useState } from 'react';
import { useSearchParams } from 'react-router';
import { useClient } from 'hooks/useClient';
import { Folder, Settings2, Layers } from 'lucide-react';
import { SettingsForm } from './SettingsForm';

/**
 * The collections, and a way back to the settings.
 *
 * Selection is `?collection=<id>` in the URL rather than a channel, so which collection you are looking
 * at survives a reload and can be linked to — `docs/navigation-audit.md`. The links panel reads the same
 * parameter rather than being handed the id.
 *
 * The settings live behind the gear rather than on a screen of their own. They were a screen of their
 * own for an afternoon and it was the wrong shape: nothing else was built, so opening the plugin put you
 * on a configuration form with no way forward, which reads as broken rather than unfinished.
 */
type Collection = { id: number; name: string; _count?: { links?: number } };

/** `?collection=` for "everything", which is a real choice and not the absence of one. */
export const ALL = 'all';

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

  const [rows, setRows] = useState<Collection[] | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [showSettings, setShowSettings] = useState(false);
  const [params, setParams] = useSearchParams();
  const selected = params.get('collection') ?? ALL;

  const load = useCallback(async () => {
    try {
      const body = await clientRef.current.get<{ response: Collection[] }>('/linkwarden/api/v1/collections');
      setRows(body.response ?? []);
      setError(null);
    } catch (failure) {
      // The message matters here. "No account is mapped to you" is something the owner can fix and is
      // the state every user starts in, so it must not read as an outage.
      setError(failure instanceof Error ? failure.message : 'Could not read your collections.');
      setRows(null);
      setShowSettings(true);
    }
  }, []);

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

  const select = (id: string) =>
    setParams(
      (p) => {
        p.set('collection', id);
        return p;
      },
      { replace: true },
    );

  return (
    <div className="flex size-full flex-col">
      <header className="flex items-center justify-between border-b px-2 py-1.5">
        <span className="text-xs font-medium">Collections</span>
        <button
          type="button"
          onClick={() => setShowSettings((was) => !was)}
          className="p-1 text-muted-foreground hover:text-foreground"
          aria-label="Settings"
        >
          <Settings2 className="size-3.5" />
        </button>
      </header>

      {error && <p className="px-3 py-2 text-[11px] text-destructive">{error}</p>}

      <ul className="flex-1 overflow-auto">
        <li>
          <button
            type="button"
            onClick={() => select(ALL)}
            className={`flex w-full items-center gap-2 px-3 py-1.5 text-left text-xs hover:bg-muted/50 ${
              selected === ALL ? 'bg-muted' : ''
            }`}
          >
            <Layers className="size-3.5 shrink-0 text-muted-foreground" />
            Everything
          </button>
        </li>

        {rows?.map((row) => (
          <li key={row.id}>
            <button
              type="button"
              onClick={() => select(String(row.id))}
              className={`flex w-full items-center gap-2 px-3 py-1.5 text-left text-xs hover:bg-muted/50 ${
                selected === String(row.id) ? 'bg-muted' : ''
              }`}
            >
              <Folder className="size-3.5 shrink-0 text-muted-foreground" />
              <span className="min-w-0 flex-1 truncate">{row.name}</span>
              {typeof row._count?.links === 'number' && (
                <span className="shrink-0 text-[10px] text-muted-foreground">{row._count.links}</span>
              )}
            </button>
          </li>
        ))}
      </ul>

      {showSettings && <SettingsForm />}
    </div>
  );
};