'use client';

import { useCallback, useEffect, useMemo, useState } from 'react';
import toast from 'react-hot-toast';
import { useLanguage } from '@/context/LanguageContext';
import { financeApi, type EventFinance } from '@/lib/api';
import { Skeleton } from '@/components/ui/Skeleton';
import { SubNav } from './ui';
import { SummaryView } from './SummaryView';
import { ExpensesView } from './ExpensesView';
import { SplitView } from './SplitView';
import { LifecycleStepper } from './LifecycleStepper';
import { deriveLifecycle } from './derive';

export type FinanceSection = 'summary' | 'expenses' | 'split';
const SECTIONS: FinanceSection[] = ['summary', 'expenses', 'split'];

/** Keep the open section in the URL (?fin=expenses) so reloads and shared links land on it. */
function readSection(): FinanceSection {
  if (typeof window === 'undefined') return 'summary';
  const v = new URLSearchParams(window.location.search).get('fin');
  return SECTIONS.includes(v as FinanceSection) ? (v as FinanceSection) : 'summary';
}
function writeSection(section: FinanceSection) {
  const url = new URL(window.location.href);
  if (section === 'summary') url.searchParams.delete('fin'); else url.searchParams.set('fin', section);
  window.history.replaceState(window.history.state, '', url);
}

/**
 * Finance tab: P&L summary with charts, expenses and other income, and the
 * partner split with payouts. The server already scopes what comes back (e.g.
 * collaborators only get their own share), so this renders what it receives.
 */
export function FinanceTab({ eventId }: { eventId: string }) {
  const { t } = useLanguage();
  const [data, setData] = useState<EventFinance | null>(null);
  const [loading, setLoading] = useState(true);
  const [section, setSectionState] = useState<FinanceSection>('summary');

  useEffect(() => { setSectionState(readSection()); }, []);
  const setSection = useCallback((s: FinanceSection) => { setSectionState(s); writeSection(s); }, []);

  const load = useCallback(async () => {
    try {
      setData(await financeApi.get(eventId));
    } catch (error: any) {
      toast.error(error.message || t('admin.finance.loadError'));
    } finally {
      setLoading(false);
    }
  }, [eventId, t]);

  useEffect(() => { load(); }, [load]);
  // Recomputed with every reload, so "ended X days ago" stays current.
  const lifecycle = useMemo(() => (data ? deriveLifecycle(data) : null), [data]);

  if (loading) {
    return (
      <div className="space-y-3" aria-busy="true">
        <Skeleton className="h-24" />
        <Skeleton className="h-11 w-full md:w-96" />
        <div className="grid grid-cols-2 lg:grid-cols-4 gap-3">
          {Array.from({ length: 4 }).map((_, i) => <Skeleton key={i} className="h-24" />)}
        </div>
        <Skeleton className="h-64" />
      </div>
    );
  }
  if (!data || !lifecycle) return <p className="text-sm text-gray-500 py-8 text-center">{t('admin.finance.loadError')}</p>;

  return (
    <div className="space-y-4">
      <LifecycleStepper data={data} lifecycle={lifecycle} goTo={setSection} />

      <SubNav<FinanceSection>
        items={[
          { key: 'summary', label: t('admin.finance.subnav.summary') },
          { key: 'expenses', label: t('admin.finance.subnav.expenses'), count: data.expenses.length + data.otherIncome.length },
          { key: 'split', label: t('admin.finance.subnav.split'), count: data.partners.length },
        ]}
        active={section}
        onChange={setSection}
      />

      {section === 'summary' && <SummaryView data={data} goTo={setSection} />}
      {section === 'expenses' && <ExpensesView eventId={eventId} data={data} onChange={load} />}
      {section === 'split' && <SplitView eventId={eventId} data={data} lifecycle={lifecycle} onChange={load} />}
    </div>
  );
}