'use client';
import { useState, useEffect } from 'react';
import { Coins, RefreshCw, TrendingDown, TrendingUp, Loader2, ArrowRight } from 'lucide-react';
import Link from 'next/link';
import BackButton from '@/components/BackButton';

const TYPE_LABELS = {
  spend_image:     { label: 'Генерация картинки',  sign: '-', color: 'text-red-400' },
  spend_text_post: { label: 'Генерация поста',     sign: '-', color: 'text-red-400' },
  spend_article:   { label: 'Генерация статьи',    sign: '-', color: 'text-red-400' },
  spend_autopublish:{ label: 'Публикация',          sign: '-', color: 'text-gray-400' },
  plan_credit:     { label: 'Начисление по тарифу',sign: '+', color: 'text-green-400' },
  topup:           { label: 'Пополнение',           sign: '+', color: 'text-green-400' },
  bonus:           { label: 'Бонус',                sign: '+', color: 'text-blue-400' },
  refund:          { label: 'Возврат',              sign: '+', color: 'text-blue-400' },
};

function fmtDate(s) {
  const d = new Date(s);
  return d.toLocaleString('ru-RU', { day:'2-digit', month:'2-digit', hour:'2-digit', minute:'2-digit' });
}

export default function BillingPage() {
  const [balance, setBalance] = useState(null);
  const [txs, setTxs]         = useState([]);
  const [total, setTotal]      = useState(0);
  const [loading, setLoading]  = useState(true);
  const [page, setPage]        = useState(0);
  const PER_PAGE = 30;

  async function load(p = 0) {
    setLoading(true);
    try {
      const [balRes, txRes] = await Promise.all([
        fetch('/api/billing/balance').then(r => r.json()),
        fetch(`/api/billing/transactions?limit=${PER_PAGE}&offset=${p * PER_PAGE}`).then(r => r.json()),
      ]);
      setBalance(balRes);
      setTxs(txRes.transactions || []);
      setTotal(txRes.total || 0);
    } catch {}
    setLoading(false);
  }

  useEffect(() => { load(0); }, []);

  const PLAN_COLORS = { free: 'text-gray-400', starter: 'text-blue-400', pro: 'text-purple-400', business: 'text-yellow-400' };

  return (
    <main className="max-w-3xl mx-auto p-4 sm:p-6">
      <BackButton />
      <div className="flex items-center justify-between mb-6">
        <h1 className="text-xl font-bold flex items-center gap-2">
          <Coins className="w-5 h-5 text-accent" /> Баланс и кредиты
        </h1>
        <button onClick={() => load(page)} className="btn-ghost p-2">
          <RefreshCw className="w-4 h-4" />
        </button>
      </div>

      {/* Баланс */}
      {balance && (
        <div className="grid grid-cols-2 sm:grid-cols-3 gap-3 mb-6">
          <div className="card p-4 col-span-2 sm:col-span-1 border-accent/40 bg-accent/5">
            <div className="text-3xl font-bold text-accent">
              {balance.isUnlimited ? '∞' : balance.credits}
            </div>
            <div className="text-xs text-gray-400 mt-1">кредитов осталось</div>
          </div>
          <div className="card p-4">
            <div className={`text-lg font-bold ${PLAN_COLORS[balance.plan] || 'text-gray-300'}`}>
              {balance.planName}
            </div>
            <div className="text-xs text-gray-400 mt-1">текущий тариф</div>
          </div>
          <div className="card p-4">
            <div className="text-sm font-medium text-gray-300">
              {balance.resetAt ? new Date(balance.resetAt).toLocaleDateString('ru-RU') : '—'}
            </div>
            <div className="text-xs text-gray-400 mt-1">сброс кредитов</div>
          </div>
        </div>
      )}

      {/* CTA апгрейд */}
      {balance?.plan === 'free' && (
        <div className="card p-4 mb-6 border-accent/30 bg-accent/5 flex items-center justify-between">
          <div>
            <div className="font-medium text-sm">Хотите больше кредитов?</div>
            <div className="text-xs text-gray-400 mt-0.5">Starter — 500 кредитов за ₽490/мес</div>
          </div>
          <Link href="/plans" className="btn-primary text-sm px-4 py-1.5 flex items-center gap-1">
            Тарифы <ArrowRight className="w-3.5 h-3.5" />
          </Link>
        </div>
      )}

      {/* Промокод */}
      <PromoForm onApplied={() => load(0)} />

      {/* Стоимость операций */}
      <div className="card p-4 mb-6">
        <div className="text-xs text-gray-400 uppercase tracking-wide mb-3">Стоимость операций</div>
        <div className="grid grid-cols-2 sm:grid-cols-4 gap-2">
          {[
            { label: 'Картинка', credits: 5, icon: '🖼' },
            { label: 'Пост',     credits: 2, icon: '✍️' },
            { label: 'Статья',   credits: 5, icon: '📝' },
            { label: 'Публикация', credits: 0, icon: '📤' },
          ].map(op => (
            <div key={op.label} className="text-center p-2 rounded-lg bg-surface2">
              <div className="text-lg">{op.icon}</div>
              <div className="text-xs text-gray-300 mt-1">{op.label}</div>
              <div className="text-sm font-bold text-accent mt-0.5">
                {op.credits === 0 ? 'бесплатно' : `${op.credits} кр`}
              </div>
            </div>
          ))}
        </div>
      </div>

      {/* История транзакций */}
      <h2 className="text-sm font-semibold text-gray-400 uppercase tracking-wide mb-3">История</h2>
      {loading && <div className="py-8 text-center"><Loader2 className="w-5 h-5 animate-spin mx-auto text-accent" /></div>}
      {!loading && (
        <div className="card overflow-hidden">
          {txs.length === 0 && (
            <div className="py-8 text-center text-gray-500 text-sm">Транзакций пока нет</div>
          )}
          {txs.map(tx => {
            const meta = TYPE_LABELS[tx.type] || { label: tx.type, sign: tx.amount > 0 ? '+' : '-', color: 'text-gray-400' };
            return (
              <div key={tx.id} className="flex items-center justify-between px-4 py-3 border-b border-border last:border-0 hover:bg-surface2/50">
                <div className="flex-1 min-w-0">
                  <div className="text-sm truncate">{tx.description || meta.label}</div>
                  <div className="text-xs text-gray-500 mt-0.5">{fmtDate(tx.created_at)}</div>
                </div>
                <div className="text-right ml-4">
                  <div className={`font-bold text-sm ${meta.color}`}>
                    {meta.sign}{Math.abs(tx.amount)} кр
                  </div>
                  <div className="text-xs text-gray-500">= {tx.balance_after === -1 ? '∞' : tx.balance_after} кр</div>
                </div>
              </div>
            );
          })}
        </div>
      )}

      {/* Пагинация */}
      {total > PER_PAGE && (
        <div className="flex justify-center gap-2 mt-4">
          <button disabled={page === 0} onClick={() => { setPage(p => p-1); load(page-1); }} className="btn-ghost px-3 py-1.5 text-sm disabled:opacity-40">← Назад</button>
          <span className="text-sm text-gray-500 self-center">{page+1} / {Math.ceil(total/PER_PAGE)}</span>
          <button disabled={(page+1)*PER_PAGE >= total} onClick={() => { setPage(p => p+1); load(page+1); }} className="btn-ghost px-3 py-1.5 text-sm disabled:opacity-40">Вперёд →</button>
        </div>
      )}
    </main>
  );
}

function PromoForm({ onApplied }) {
  const [code,  setCode]  = useState('');
  const [msg,   setMsg]   = useState('');
  const [busy,  setBusy]  = useState(false);
  const [show,  setShow]  = useState(false);

  async function apply() {
    if (!code.trim()) return;
    setBusy(true);
    const res = await fetch('/api/billing/apply-promo', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ code: code.trim().toUpperCase() }),
    }).then(r => r.json());
    setBusy(false);
    if (res.ok) {
      setMsg(res.message);
      setCode('');
      setShow(false);
      onApplied?.();
    } else {
      setMsg('Ошибка: ' + (res.error || 'неизвестно'));
    }
    setTimeout(() => setMsg(''), 4000);
  }

  return (
    <div className="mb-6">
      {!show ? (
        <button onClick={() => setShow(true)} className="text-sm text-gray-500 hover:text-accent transition-colors">
          🎁 Есть промокод?
        </button>
      ) : (
        <div className="card p-4">
          <div className="flex gap-2">
            <input
              value={code}
              onChange={e => setCode(e.target.value.toUpperCase())}
              onKeyDown={e => e.key === 'Enter' && apply()}
              placeholder="ВВЕДИТЕ КОД"
              className="input flex-1 font-mono text-sm py-1.5 tracking-widest"
              autoFocus
              maxLength={32}
            />
            <button onClick={apply} disabled={busy || !code.trim()} className="btn-primary px-4 text-sm">
              {busy ? <Loader2 className="w-4 h-4 animate-spin" /> : 'Применить'}
            </button>
            <button onClick={() => { setShow(false); setCode(''); }} className="btn-ghost px-3 text-sm">✕</button>
          </div>
          {msg && <p className={`text-xs mt-2 ${msg.startsWith('Ошибка') ? 'text-red-400' : 'text-green-400'}`}>{msg}</p>}
        </div>
      )}
    </div>
  );
}