import { useState } from 'react';
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
import { useTranslation } from 'react-i18next';

import {
  fetchAudit,
  fetchInstanceGuilds,
  fetchInstanceSettings,
  fetchInstanceUsers,
  instanceAuditQueryKey,
  instanceGuildsQueryKey,
  instanceSettingsQueryKey,
  instanceUsersQueryKey,
  setInstanceAdmin,
  type InstanceSettings,
} from '@/api/instance';
import { InstanceDashboard } from '@/components/instance/InstanceDashboard';
import { InstanceGuildsPanel } from '@/components/instance/InstanceGuildsPanel';
import { InstanceHealth } from '@/components/instance/InstanceHealth';
import { InstanceLimitsPanel } from '@/components/instance/InstanceLimitsPanel';
import { InstanceUsersPanel } from '@/components/instance/InstanceUsersPanel';
import { useSessionStore } from '@/stores/session';
import { useUiStore } from '@/stores/ui';
import { ErrorNotice, LoadingNotice } from '@/components/ui/ErrorNotice';
import { Card } from '@/components/ui/primitives';
import { formatDateTime } from '@/lib/identity';
import { useCurrentUser } from '@/lib/hooks';
import { useInstanceMetrics } from '@/lib/useInstanceMetrics';

const AUDIT_LIMIT = 50;

/** Разделы админ-панели (AGENT.md 7.19). */
const tabs = ['overview', 'limits', 'users', 'guilds', 'audit'] as const;
type InstanceTab = (typeof tabs)[number];

/** Админский раздел инстанса: настройки, серверы, пользователи, аудит (read-only). */
export default function InstanceSettingsPage() {
  const { t, i18n } = useTranslation();
  const locale = i18n.resolvedLanguage ?? 'ru';
  const currentUser = useCurrentUser();
  const isAdmin = currentUser.data?.is_instance_admin === true;
  const queryClient = useQueryClient();
  const selectSettingsGuild = useSessionStore((state) => state.selectSettingsGuild);
  const openSettings = useUiStore((state) => state.openSettings);
  const [tab, setTab] = useState<InstanceTab>('overview');

  const settings = useQuery({
    queryKey: instanceSettingsQueryKey,
    queryFn: ({ signal }) => fetchInstanceSettings(signal),
    enabled: isAdmin,
    retry: 0,
  });
  const guilds = useQuery({
    queryKey: instanceGuildsQueryKey,
    queryFn: ({ signal }) => fetchInstanceGuilds(signal),
    enabled: isAdmin,
    retry: 0,
  });
  const users = useQuery({
    queryKey: instanceUsersQueryKey,
    queryFn: ({ signal }) => fetchInstanceUsers(signal),
    enabled: isAdmin,
    retry: 0,
  });
  const audit = useQuery({
    queryKey: instanceAuditQueryKey(AUDIT_LIMIT),
    queryFn: ({ signal }) => fetchAudit(AUDIT_LIMIT, signal),
    enabled: isAdmin,
    retry: 0,
  });
  // Живые метрики: опрос раз в секунду, пока раздел открыт (AGENT.md 7.19).
  const metrics = useInstanceMetrics(isAdmin);

  const admin = useMutation({
    mutationFn: (input: { userId: string; makeAdmin: boolean }) =>
      setInstanceAdmin(input.userId, input.makeAdmin),
    onSuccess: () => {
      void queryClient.invalidateQueries({ queryKey: instanceUsersQueryKey });
      void queryClient.invalidateQueries({ queryKey: instanceAuditQueryKey(AUDIT_LIMIT) });
    },
  });

  if (!isAdmin) {
    return (
      <Card>
        <h2 className="text-lg font-semibold">{t('settings.instance.title')}</h2>
        <p className="mt-2 text-sm text-fg-muted">{t('settings.instance.notAdmin')}</p>
      </Card>
    );
  }

  const tabLabels: Record<InstanceTab, string> = {
    overview: t('settings.instance.tabs.overview'),
    limits: t('settings.instance.tabs.limits'),
    users: t('settings.instance.tabs.users', { count: users.data?.length ?? 0 }),
    guilds: t('settings.instance.tabs.guilds', { count: guilds.data?.length ?? 0 }),
    audit: t('settings.instance.tabs.audit'),
  };

  return (
    <div className="flex flex-col gap-5">
      <header>
        <h2 className="text-lg font-semibold">{t('settings.instance.title')}</h2>
        <p className="mt-1 text-sm text-fg-muted">{t('settings.instance.description')}</p>
      </header>

      {/* Вкладки админ-панели: обзор и здоровье, лимиты, пользователи, серверы, аудит. */}
      <div
        role="tablist"
        aria-label={t('settings.instance.tabs.label')}
        className="flex flex-wrap gap-1 border-b border-border/40"
        data-testid="instance-tabs"
      >
        {tabs.map((item) => (
          <button
            key={item}
            type="button"
            role="tab"
            aria-selected={tab === item}
            data-testid={`instance-tab-${item}`}
            onClick={() => setTab(item)}
            className={`-mb-px rounded-t-[var(--radius-sm)] border-b-2 px-3 py-1.5 text-sm transition-colors duration-[var(--duration-fast)] ${
              tab === item
                ? 'border-accent text-fg'
                : 'border-transparent text-fg-muted hover:text-fg'
            }`}
          >
            {tabLabels[item]}
          </button>
        ))}
      </div>

      {tab === 'overview' ? (
        <>
          <InstanceDashboard state={metrics} />
          <InstanceHealth state={metrics} />
        </>
      ) : null}

      {tab === 'limits' ? (
        <Card>
          <h3 className="text-base font-semibold">{t('settings.instance.limits.title')}</h3>
          <p className="mt-1 text-sm text-fg-muted">{t('settings.instance.limits.description')}</p>
          {settings.isPending ? <LoadingNotice /> : null}
          {settings.isError ? (
            <ErrorNotice
              className="mt-3"
              error={settings.error}
              onRetry={() => void settings.refetch()}
            />
          ) : null}
          {settings.data === undefined ? null : (
            <InstanceLimitsPanel
              settings={settings.data}
              onSaved={(updated: InstanceSettings) => {
                void queryClient.setQueryData(instanceSettingsQueryKey, updated);
              }}
            />
          )}
        </Card>
      ) : null}

      {tab === 'users' ? (
        <Card>
          <h3 className="text-base font-semibold">{t('settings.instance.usersTitle')}</h3>
          {/* ID пользователей — единственное место, где он виден: раздел открыт
              только администратору инстанса. */}
          <p className="mt-1 text-xs text-fg-muted">{t('settings.instance.usersIdHint')}</p>
          <InstanceUsersPanel
            currentUserId={currentUser.data?.id}
            users={users.data ?? []}
            isPending={users.isPending}
            error={users.error}
            onRetry={() => void users.refetch()}
            onToggleAdmin={(userId, makeAdmin) => admin.mutate({ userId, makeAdmin })}
            adminPending={admin.isPending}
            adminError={admin.error}
          />
        </Card>
      ) : null}

      {tab === 'guilds' ? (
        <Card>
          <h3 className="text-base font-semibold">{t('settings.instance.guildsTitle')}</h3>
          <InstanceGuildsPanel
            guilds={guilds.data ?? []}
            isPending={guilds.isPending}
            error={guilds.error}
            onRetry={() => void guilds.refetch()}
            onOpenSettings={(guildId) => {
              // Настройки сервера открываются обычным разделом: у администратора
              // инстанса там все права (AGENTS.md 7.19).
              selectSettingsGuild(guildId);
              openSettings({ section: 'server', guildId });
            }}
          />
        </Card>
      ) : null}

      {tab === 'audit' ? (
        <Card>
          <h3 className="text-base font-semibold">
            {t('settings.instance.audit', { count: audit.data?.length ?? 0 })}
          </h3>
          {audit.isPending ? <LoadingNotice /> : null}
          {audit.isError ? (
            <ErrorNotice
              className="mt-3"
              error={audit.error}
              onRetry={() => void audit.refetch()}
            />
          ) : null}
          {audit.data !== undefined && audit.data.length === 0 ? (
            <p className="mt-2 text-sm text-fg-muted">{t('settings.instance.auditEmpty')}</p>
          ) : null}
          {audit.data === undefined || audit.data.length === 0 ? null : (
            <ul className="mt-3 flex flex-col gap-1 text-sm" data-testid="instance-audit">
              {audit.data.map((entry) => (
                <li
                  key={entry.id}
                  className="flex items-center justify-between gap-3 border-b border-border/40 py-2 last:border-b-0"
                >
                  <span className="truncate">
                    {entry.action}
                    {entry.target === undefined ? '' : ` → ${entry.target}`}
                  </span>
                  <span className="shrink-0 text-xs text-fg-muted">
                    {formatDateTime(entry.created_at, locale)}
                  </span>
                </li>
              ))}
            </ul>
          )}
        </Card>
      ) : null}
    </div>
  );
}