import type { PageView, PondView } from '@dorfteich/shared';
import { useQuery, useQueryClient } from '@tanstack/react-query';
import { useEffect, useRef, useState } from 'react';
import { useTranslation } from 'react-i18next';
import { useParams } from 'react-router-dom';

import { FormError } from '../components/forms';
import { apiDelete, apiGet, apiPost } from '../lib/api';

import { useDocumentTitle } from '../lib/use-document-title';
/** Pond trash view (issue #31): list, restore, and permanently delete —
 * single pages or a checkbox multi-selection at once (#128). */
export function TrashPage(): React.JSX.Element {
  const { t } = useTranslation('editor');
  const { pondSlug = '' } = useParams<{ pondSlug: string }>();
  const queryClient = useQueryClient();
  const [selected, setSelected] = useState<Set<string>>(new Set());
  const [busy, setBusy] = useState(false);
  const [failedCount, setFailedCount] = useState(0);

  const pond = useQuery({
    queryKey: ['pond', pondSlug],
    queryFn: () => apiGet<PondView>(`/ponds/${pondSlug}`),
  });
  useDocumentTitle(pond.data ? t('trash.title', { pond: pond.data.name }) : undefined);
  const trash = useQuery({
    queryKey: ['trash', pond.data?.id],
    queryFn: () => apiGet<PageView[]>(`/ponds/${pond.data!.id}/trash`),
    enabled: Boolean(pond.data),
  });

  // Selection pruned to pages still in the trash — restored/purged entries
  // drop out on refresh, failed ones stay selected for a retry.
  const pages = trash.data ?? [];
  const selectedIds = pages.filter((page) => selected.has(page.id)).map((page) => page.id);
  const allSelected = pages.length > 0 && selectedIds.length === pages.length;

  // Native indeterminate state for a partial selection — only settable via
  // the DOM property, not an attribute.
  const selectAllRef = useRef<HTMLInputElement>(null);
  useEffect(() => {
    if (selectAllRef.current) {
      selectAllRef.current.indeterminate = selectedIds.length > 0 && !allSelected;
    }
  }, [selectedIds.length, allSelected]);

  async function refresh(): Promise<void> {
    await queryClient.invalidateQueries({ queryKey: ['trash', pond.data?.id] });
    await queryClient.invalidateQueries({ queryKey: ['pages', pond.data?.id] });
  }

  function toggle(id: string): void {
    setSelected((prev) => {
      const next = new Set(prev);
      if (next.has(id)) next.delete(id);
      else next.add(id);
      return next;
    });
  }

  function toggleAll(): void {
    setSelected(allSelected ? new Set() : new Set(pages.map((page) => page.id)));
  }

  /** Run one action over the ids, keep going past failures (#128): a page
   * that stopped being restorable must not strand the rest of the selection.
   * Sequential on purpose — purge promotes leftover children (#107), so
   * concurrent tree mutations would race each other. */
  async function runBulk(ids: string[], action: (id: string) => Promise<unknown>): Promise<void> {
    setBusy(true);
    setFailedCount(0);
    let failed = 0;
    for (const id of ids) {
      try {
        await action(id);
        setSelected((prev) => {
          const next = new Set(prev);
          next.delete(id);
          return next;
        });
      } catch {
        failed += 1;
      }
    }
    setFailedCount(failed);
    setBusy(false);
    await refresh();
  }

  async function restore(id: string): Promise<void> {
    await runBulk([id], (pageId) => apiPost(`/pages/${pageId}/restore`));
  }

  async function purge(id: string): Promise<void> {
    if (!window.confirm(t('trash.purgeConfirm'))) return;
    await runBulk([id], (pageId) => apiDelete(`/pages/${pageId}/purge`));
  }

  async function restoreSelected(): Promise<void> {
    await runBulk(selectedIds, (pageId) => apiPost(`/pages/${pageId}/restore`));
  }

  async function purgeSelected(): Promise<void> {
    if (!window.confirm(t('trash.purgeConfirmMany', { count: selectedIds.length }))) return;
    await runBulk(selectedIds, (pageId) => apiDelete(`/pages/${pageId}/purge`));
  }

  if (pond.error || trash.error) return <FormError error={pond.error ?? trash.error} />;
  if (!pond.data || !trash.data) return <></>;

  return (
    <div className="trash-page">
      <h1>{t('trash.title', { pond: pond.data.name })}</h1>
      {failedCount > 0 && (
        <p className="trash-page__bulk-error" role="alert">
          {t('trash.bulkFailed', { count: failedCount })}
        </p>
      )}
      {pages.length === 0 ? (
        <p>{t('trash.empty')}</p>
      ) : (
        <>
          <div className="trash-page__bulk">
            <label className="trash-page__select-all">
              <input
                ref={selectAllRef}
                type="checkbox"
                checked={allSelected}
                disabled={busy}
                onChange={toggleAll}
              />
              {t('trash.selectAll')}
            </label>
            <button
              type="button"
              className="button trash-page__restore-selected"
              disabled={busy || selectedIds.length === 0}
              onClick={() => void restoreSelected()}
            >
              {t('trash.restoreSelected', { count: selectedIds.length })}
            </button>
            <button
              type="button"
              className="button button--danger trash-page__purge-selected"
              disabled={busy || selectedIds.length === 0}
              onClick={() => void purgeSelected()}
            >
              {t('trash.purgeSelected', { count: selectedIds.length })}
            </button>
          </div>
          <ul className="trash-page__list">
            {pages.map((page) => (
              <li key={page.id} className="trash-page__item">
                <input
                  type="checkbox"
                  className="trash-page__select"
                  checked={selected.has(page.id)}
                  disabled={busy}
                  aria-label={t('trash.select', { title: page.title })}
                  onChange={() => toggle(page.id)}
                />
                <span className="trash-page__title">{page.title}</span>
                <span className="trash-page__deleted-at">
                  {page.deletedAt &&
                    t('trash.deletedAt', { date: new Date(page.deletedAt).toLocaleDateString() })}
                </span>
                <button
                  type="button"
                  className="button"
                  disabled={busy}
                  onClick={() => void restore(page.id)}
                >
                  {t('trash.restore')}
                </button>
                <button
                  type="button"
                  className="button"
                  disabled={busy}
                  onClick={() => void purge(page.id)}
                >
                  {t('trash.purge')}
                </button>
              </li>
            ))}
          </ul>
        </>
      )}
    </div>
  );
}