/**
 * Wiki page — knowledge articles with categories, Markdown editor, versioning.
 *
 * Combines WikiBrowser (category tree + article list + search), article detail
 * with Markdown preview, create/edit modal, delete, and version history with
 * restore.
 */

import React, { useCallback, useEffect, useMemo, useState } from 'react';
import { useTranslation } from 'react-i18next';
import ReactMarkdown from 'react-markdown';
import remarkGfm from 'remark-gfm';
import { CalendarDays, History, Loader2, Pencil, Plus, Trash2, Undo2 } from 'lucide-react';
import {
  createWikiArticle,
  deleteWikiArticle,
  fetchWikiArticle,
  fetchWikiCategories,
  fetchWikiVersions,
  restoreWikiVersion,
  updateWikiArticle,
  type WikiArticle,
  type WikiArticleStatus,
  type WikiCategory,
  type WikiVersion,
} from '@/api/knowledge';
import { Card } from '@/components/ui/Card';
import { Button } from '@/components/ui/Button';
import { Input } from '@/components/ui/Input';
import { Select } from '@/components/ui/Select';
import { Modal } from '@/components/ui/Modal';
import { ConfirmDialog } from '@/components/ui/ConfirmDialog';
import { Badge } from '@/components/ui/Badge';
import { EmptyState } from '@/components/ui/EmptyState';
import { useToast } from '@/components/ui/Toast';
import { WikiBrowser } from '@/components/wiki/WikiBrowser';
import { WikiEditor } from '@/components/wiki/WikiEditor';

interface ArticleForm {
  title: string;
  slug: string;
  content: string;
  summary: string;
  category_id: string;
  tags: string;
  status: WikiArticleStatus;
}

const emptyForm: ArticleForm = {
  title: '',
  slug: '',
  content: '',
  summary: '',
  category_id: '',
  tags: '',
  status: 'draft',
};

function formatDate(iso: string | null): string {
  if (!iso) return '—';
  const d = new Date(iso);
  if (Number.isNaN(d.getTime())) return '—';
  return d.toLocaleString();
}

export function WikiPage() {
  const { t } = useTranslation();
  const toast = useToast();

  const [selectedArticleId, setSelectedArticleId] = useState<string | null>(null);
  const [article, setArticle] = useState<WikiArticle | null>(null);
  const [loadingArticle, setLoadingArticle] = useState(false);
  const [categories, setCategories] = useState<{ id: string; name: string }[]>([]);
  const [versions, setVersions] = useState<WikiVersion[]>([]);
  const [showVersions, setShowVersions] = useState(false);
  const [editorOpen, setEditorOpen] = useState(false);
  const [editingId, setEditingId] = useState<string | null>(null);
  const [form, setForm] = useState<ArticleForm>(emptyForm);
  const [saving, setSaving] = useState(false);
  const [deleteTarget, setDeleteTarget] = useState<WikiArticle | null>(null);
  const [deleting, setDeleting] = useState(false);
  const [restoring, setRestoring] = useState(false);
  const [browserRefreshKey, setBrowserRefreshKey] = useState(0);

  const loadCategories = useCallback(async () => {
    try {
      const cats = await fetchWikiCategories();
      setCategories(cats.map((c) => ({ id: c.id, name: c.name })));
    } catch {
      // Non-fatal — categories are optional in the editor
    }
  }, []);

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

  const loadArticle = useCallback(async (id: string) => {
    setLoadingArticle(true);
    try {
      const data = await fetchWikiArticle(id);
      setArticle(data);
      setSelectedArticleId(data.id);
      setShowVersions(false);
    } catch (err) {
      toast.error(err instanceof Error ? err.message : t('wiki.detail.loadError'));
    } finally {
      setLoadingArticle(false);
    }
  }, [t, toast]);

  const handleSelectArticle = useCallback(
    (a: WikiArticle) => {
      void loadArticle(a.id);
    },
    [loadArticle]
  );

  const openCreate = useCallback(() => {
    setEditingId(null);
    setForm(emptyForm);
    setEditorOpen(true);
  }, []);

  const openEdit = useCallback(() => {
    if (!article) return;
    setEditingId(article.id);
    setForm({
      title: article.title,
      slug: article.slug,
      content: article.content,
      summary: article.summary ?? '',
      category_id: article.category_id ?? '',
      tags: article.tags.join(', '),
      status: article.status,
    });
    setEditorOpen(true);
  }, [article]);

  const handleSave = useCallback(async () => {
    if (!form.title.trim()) {
      toast.error(t('wiki.editor.titleRequired'));
      return;
    }
    setSaving(true);
    try {
      const payload = {
        title: form.title.trim(),
        slug: form.slug.trim() || undefined,
        content: form.content,
        summary: form.summary.trim() || null,
        category_id: form.category_id || null,
        tags: form.tags.split(',').map((s) => s.trim()).filter(Boolean),
        status: form.status,
      };
      if (editingId) {
        const updated = await updateWikiArticle(editingId, payload);
        setArticle(updated);
        toast.success(t('knowledge.editor.updated'));
      } else {
        const created = await createWikiArticle(payload);
        setArticle(created);
        setSelectedArticleId(created.id);
        toast.success(t('knowledge.editor.created'));
      }
      setEditorOpen(false);
      setBrowserRefreshKey((k) => k + 1);
    } catch (err) {
      toast.error(err instanceof Error ? err.message : t('knowledge.editor.saveError'));
    } finally {
      setSaving(false);
    }
  }, [form, editingId, t, toast]);

  const handleDelete = useCallback(async () => {
    if (!deleteTarget) return;
    setDeleting(true);
    try {
      await deleteWikiArticle(deleteTarget.id);
      toast.success(t('knowledge.editor.deleted'));
      setArticle(null);
      setSelectedArticleId(null);
      setDeleteTarget(null);
      setBrowserRefreshKey((k) => k + 1);
    } catch (err) {
      toast.error(err instanceof Error ? err.message : t('knowledge.editor.deleteError'));
    } finally {
      setDeleting(false);
    }
  }, [deleteTarget, t, toast]);

  const loadVersions = useCallback(async () => {
    if (!article) return;
    try {
      const data = await fetchWikiVersions(article.id);
      setVersions(data);
      setShowVersions(true);
    } catch (err) {
      toast.error(err instanceof Error ? err.message : t('knowledge.versions.loadError'));
    }
  }, [article, t, toast]);

  const handleRestore = useCallback(
    async (version: number) => {
      if (!article) return;
      setRestoring(true);
      try {
        const restored = await restoreWikiVersion(article.id, version);
        setArticle(restored);
        setShowVersions(false);
        toast.success(t('knowledge.versions.restored'));
      } catch (err) {
        toast.error(err instanceof Error ? err.message : t('knowledge.versions.restoreError'));
      } finally {
        setRestoring(false);
      }
    },
    [article, t, toast]
  );

  const statusBadge = useMemo(() => {
    if (!article) return null;
    const variant =
      article.status === 'published' ? 'success' : article.status === 'archived' ? 'secondary' : 'warning';
    return <Badge variant={variant}>{t(`wiki.status.${article.status}`)}</Badge>;
  }, [article, t]);

  return (
    <div className="p-4 md:p-6 h-full">
      <div className="flex items-center justify-between mb-4">
        <div>
          <h1 className="text-2xl font-semibold text-secondary-900">{t('wiki.title')}</h1>
          <p className="text-sm text-secondary-500 mt-1">{t('wiki.subtitle')}</p>
        </div>
        <Button onClick={openCreate} icon={<Plus className="h-4 w-4" aria-hidden="true" />}>
          {t('wiki.newArticle')}
        </Button>
      </div>

      <div className="grid grid-cols-1 lg:grid-cols-4 gap-4 h-[calc(100vh-8rem)]">
        {/* Browser sidebar */}
        <div className="lg:col-span-1 border border-secondary-200 rounded-lg bg-white overflow-hidden">
          <WikiBrowser selectedArticleId={selectedArticleId} onSelectArticle={handleSelectArticle} refreshKey={browserRefreshKey} />
        </div>

        {/* Article detail / editor */}
        <div className="lg:col-span-3 overflow-y-auto">
          {loadingArticle ? (
            <div className="flex items-center justify-center py-20" role="status" aria-label={t('common.loading')}>
              <Loader2 className="animate-spin h-8 w-8 text-primary-500" aria-hidden="true" />
            </div>
          ) : article ? (
            <Card
              title={article.title}
              actions={
                <div className="flex items-center gap-2">
                  {statusBadge}
                  <Button variant="ghost" size="sm" onClick={() => void loadVersions()} icon={<History className="h-4 w-4" aria-hidden="true" />}>
                    {t('knowledge.versions.title')}
                  </Button>
                  <Button variant="ghost" size="sm" onClick={openEdit} icon={<Pencil className="h-4 w-4" aria-hidden="true" />}>
                    {t('common.edit')}
                  </Button>
                  <Button variant="danger" size="sm" onClick={() => setDeleteTarget(article)} icon={<Trash2 className="h-4 w-4" aria-hidden="true" />}>
                    {t('common.delete')}
                  </Button>
                </div>
              }
            >
              <div className="flex flex-wrap items-center gap-3 text-sm text-secondary-500 mb-4">
                <span className="inline-flex items-center gap-1">
                  <CalendarDays className="h-4 w-4" aria-hidden="true" />
                  {formatDate(article.updated_at)}
                </span>
                <span>{t('knowledge.detail.version')}: {article.version}</span>
                {article.tags.map((tag) => (
                  <span key={tag} className="text-xs text-secondary-400">#{tag}</span>
                ))}
              </div>

              {showVersions && (
                <div className="mb-4 border border-secondary-200 rounded-lg p-3 bg-secondary-50">
                  <h4 className="text-sm font-semibold text-secondary-900 mb-2">{t('knowledge.versions.title')}</h4>
                  {versions.length === 0 ? (
                    <p className="text-sm text-secondary-500">{t('knowledge.versions.empty')}</p>
                  ) : (
                    <ul className="space-y-2">
                      {versions.map((v) => (
                        <li key={v.id} className="flex items-center justify-between gap-2 text-sm">
                          <div>
                            <span className="font-medium text-secondary-800">v{v.version}</span>
                            <span className="text-secondary-400 ml-2">{formatDate(v.created_at)}</span>
                            {v.edit_comment && <span className="text-secondary-500 ml-2">— {v.edit_comment}</span>}
                          </div>
                          <Button
                            variant="secondary"
                            size="sm"
                            onClick={() => void handleRestore(v.version)}
                            isLoading={restoring}
                            icon={<Undo2 className="h-4 w-4" aria-hidden="true" />}
                          >
                            {t('knowledge.versions.restore')}
                          </Button>
                        </li>
                      ))}
                    </ul>
                  )}
                </div>
              )}

              <div className="prose prose-sm max-w-none">
                <ReactMarkdown remarkPlugins={[remarkGfm]}>{article.content || t('wiki.detail.emptyContent')}</ReactMarkdown>
              </div>
            </Card>
          ) : (
            <EmptyState
              title={t('wiki.detail.noSelection')}
              description={t('wiki.detail.noSelectionDescription')}
              action={
                <Button onClick={openCreate} icon={<Plus className="h-4 w-4" aria-hidden="true" />}>
                  {t('wiki.newArticle')}
                </Button>
              }
            />
          )}
        </div>
      </div>

      {/* Create/Edit modal */}
      <Modal
        open={editorOpen}
        onClose={() => setEditorOpen(false)}
        title={editingId ? t('wiki.editor.editTitle') : t('wiki.editor.createTitle')}
        size="xl"
      >
        <div className="space-y-4">
          <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
            <Input
              label={t('wiki.editor.title')}
              value={form.title}
              onChange={(e) => setForm((f) => ({ ...f, title: e.target.value }))}
              required
            />
            <Input
              label={t('wiki.editor.slug')}
              value={form.slug}
              onChange={(e) => setForm((f) => ({ ...f, slug: e.target.value }))}
              placeholder={t('wiki.editor.slugPlaceholder')}
            />
          </div>
          <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
            <Select
              label={t('wiki.editor.category')}
              value={form.category_id}
              onChange={(e) => setForm((f) => ({ ...f, category_id: e.target.value }))}
              options={[
                { value: '', label: t('wiki.editor.noCategory') },
                ...categories.map((c) => ({ value: c.id, label: c.name })),
              ]}
            />
            <Select
              label={t('wiki.editor.status')}
              value={form.status}
              onChange={(e) => setForm((f) => ({ ...f, status: e.target.value as WikiArticleStatus }))}
              options={[
                { value: 'draft', label: t('wiki.status.draft') },
                { value: 'published', label: t('wiki.status.published') },
                { value: 'archived', label: t('wiki.status.archived') },
              ]}
            />
            <Input
              label={t('wiki.editor.tags')}
              value={form.tags}
              onChange={(e) => setForm((f) => ({ ...f, tags: e.target.value }))}
              placeholder={t('wiki.editor.tagsPlaceholder')}
            />
          </div>
          <Input
            label={t('wiki.editor.summary')}
            value={form.summary}
            onChange={(e) => setForm((f) => ({ ...f, summary: e.target.value }))}
          />
          <div>
            <label className="block text-sm font-medium text-secondary-700 mb-1">{t('wiki.editor.content')}</label>
            <WikiEditor
              value={form.content}
              onChange={(value) => setForm((f) => ({ ...f, content: value }))}
              placeholder={t('wiki.editor.contentPlaceholder')}
            />
          </div>
          <div className="flex justify-end gap-3">
            <Button variant="secondary" onClick={() => setEditorOpen(false)}>
              {t('common.cancel')}
            </Button>
            <Button onClick={() => void handleSave()} isLoading={saving}>
              {t('common.save')}
            </Button>
          </div>
        </div>
      </Modal>

      <ConfirmDialog
        open={deleteTarget !== null}
        title={t('wiki.delete.title')}
        message={t('wiki.delete.message', { title: deleteTarget?.title ?? '' })}
        confirmLabel={t('common.delete')}
        variant="danger"
        onConfirm={() => void handleDelete()}
        onCancel={() => setDeleteTarget(null)}
      />
    </div>
  );
}