'use client';

import { useEffect, useMemo, useState, useCallback } from 'react';
import QRCode from 'qrcode';

interface PaymentQRCodeProps {
  orderId: string;
  payUrl?: string | null;
  qrCode?: string | null;
  paymentType?: 'alipay' | 'wxpay';
  amount: number;
  expiresAt: string;
  onStatusChange: (status: string) => void;
  onBack: () => void;
  dark?: boolean;
}

const TEXT_EXPIRED = '\u8BA2\u5355\u5DF2\u8D85\u65F6';
const TEXT_REMAINING = '\u5269\u4F59\u652F\u4ED8\u65F6\u95F4';
const TEXT_GO_PAY = '\u70B9\u51FB\u524D\u5F80\u652F\u4ED8';
const TEXT_SCAN_PAY = '\u8BF7\u4F7F\u7528\u652F\u4ED8\u5E94\u7528\u626B\u7801\u652F\u4ED8';
const TEXT_BACK = '\u8FD4\u56DE';
const TEXT_CANCEL_ORDER = '\u53D6\u6D88\u8BA2\u5355';
const TERMINAL_STATUSES = new Set(['COMPLETED', 'FAILED', 'CANCELLED', 'EXPIRED', 'REFUNDED', 'REFUND_FAILED']);

export default function PaymentQRCode({
  orderId,
  payUrl,
  qrCode,
  paymentType,
  amount,
  expiresAt,
  onStatusChange,
  onBack,
  dark = false,
}: PaymentQRCodeProps) {
  const [timeLeft, setTimeLeft] = useState('');
  const [expired, setExpired] = useState(false);
  const [qrDataUrl, setQrDataUrl] = useState('');
  const [imageLoading, setImageLoading] = useState(false);

  const qrPayload = useMemo(() => {
    const value = (qrCode || payUrl || '').trim();
    return value;
  }, [qrCode, payUrl]);

  useEffect(() => {
    let cancelled = false;
    if (!qrPayload) {
      setQrDataUrl('');
      return;
    }

    setImageLoading(true);
    QRCode.toDataURL(qrPayload, {
      width: 224,
      margin: 1,
      errorCorrectionLevel: 'M',
    })
      .then((url) => {
        if (!cancelled) {
          setQrDataUrl(url);
        }
      })
      .catch(() => {
        if (!cancelled) {
          setQrDataUrl('');
        }
      })
      .finally(() => {
        if (!cancelled) {
          setImageLoading(false);
        }
      });

    return () => {
      cancelled = true;
    };
  }, [qrPayload]);

  useEffect(() => {
    const updateTimer = () => {
      const now = Date.now();
      const expiry = new Date(expiresAt).getTime();
      const diff = expiry - now;

      if (diff <= 0) {
        setTimeLeft(TEXT_EXPIRED);
        setExpired(true);
        return;
      }

      const minutes = Math.floor(diff / 60000);
      const seconds = Math.floor((diff % 60000) / 1000);
      setTimeLeft(`${minutes}:${seconds.toString().padStart(2, '0')}`);
    };

    updateTimer();
    const timer = setInterval(updateTimer, 1000);
    return () => clearInterval(timer);
  }, [expiresAt]);

  const pollStatus = useCallback(async () => {
    try {
      const res = await fetch(`/api/orders/${orderId}`);
      if (res.ok) {
        const data = await res.json();
        if (TERMINAL_STATUSES.has(data.status)) {
          onStatusChange(data.status);
        }
      }
    } catch {
      // ignore polling errors
    }
  }, [orderId, onStatusChange]);

  useEffect(() => {
    if (expired) return;
    pollStatus();
    const timer = setInterval(pollStatus, 2000);
    return () => clearInterval(timer);
  }, [pollStatus, expired]);

  const handleCancel = async () => {
    try {
      const res = await fetch(`/api/orders/${orderId}`);
      if (res.ok) {
        const data = await res.json();
        await fetch(`/api/orders/${orderId}/cancel`, {
          method: 'POST',
          headers: { 'Content-Type': 'application/json' },
          body: JSON.stringify({ user_id: data.user_id }),
        });
        onStatusChange('CANCELLED');
      }
    } catch {
      // ignore
    }
  };

  const isWx = paymentType === 'wxpay';
  const iconSrc = isWx ? '/icons/wxpay.svg' : '/icons/alipay.svg';
  const channelLabel = isWx ? '\u5FAE\u4FE1' : '\u652F\u4ED8\u5B9D';
  const iconBgClass = isWx ? 'bg-[#07C160]' : 'bg-[#1677FF]';

  return (
    <div className="flex flex-col items-center space-y-4">
      <div className="text-center">
        <div className="text-4xl font-bold text-blue-600">{'\u00A5'}{amount.toFixed(2)}</div>
        <div className={`mt-1 text-sm ${expired ? 'text-red-500' : dark ? 'text-slate-400' : 'text-gray-500'}`}>
          {expired ? TEXT_EXPIRED : `${TEXT_REMAINING}: ${timeLeft}`}
        </div>
      </div>

      {!expired && (
        <>
          {qrDataUrl && (
            <div className={['relative rounded-lg border p-4', dark ? 'border-slate-700 bg-slate-900' : 'border-gray-200 bg-white'].join(' ')}>
              {imageLoading && (
                <div className="absolute inset-0 z-10 flex items-center justify-center rounded-lg bg-black/10">
                  <div className="h-8 w-8 animate-spin rounded-full border-2 border-blue-500 border-t-transparent" />
                </div>
              )}
              <img src={qrDataUrl} alt="payment qrcode" className="h-56 w-56 rounded" />
              <div className="pointer-events-none absolute inset-0 flex items-center justify-center">
                <span className={`rounded-full p-2 shadow ring-2 ring-white ${iconBgClass}`}>
                  <img src={iconSrc} alt={channelLabel} className="h-5 w-5 brightness-0 invert" />
                </span>
              </div>
            </div>
          )}

          {!qrDataUrl && payUrl && (
            <a
              href={payUrl}
              target="_blank"
              rel="noopener noreferrer"
              className="rounded-lg bg-blue-600 px-8 py-3 font-medium text-white hover:bg-blue-700"
            >
              {TEXT_GO_PAY}
            </a>
          )}

          {!qrDataUrl && !payUrl && (
            <div className="text-center">
              <div className={['rounded-lg border-2 border-dashed p-8', dark ? 'border-slate-700' : 'border-gray-300'].join(' ')}>
                <p className={['text-sm', dark ? 'text-slate-400' : 'text-gray-500'].join(' ')}>{TEXT_SCAN_PAY}</p>
              </div>
            </div>
          )}

          <p className={['text-center text-sm', dark ? 'text-slate-400' : 'text-gray-500'].join(' ')}>
            {`\u8BF7\u6253\u5F00${channelLabel}\u626B\u4E00\u626B\u5B8C\u6210\u652F\u4ED8`}
          </p>
        </>
      )}

      <div className="flex w-full gap-3">
        <button
          onClick={onBack}
          className={[
            'flex-1 rounded-lg border py-2 text-sm',
            dark ? 'border-slate-700 text-slate-300 hover:bg-slate-800' : 'border-gray-300 text-gray-600 hover:bg-gray-50',
          ].join(' ')}
        >
          {TEXT_BACK}
        </button>
        {!expired && (
          <button
            onClick={handleCancel}
            className="flex-1 rounded-lg border border-red-300 py-2 text-sm text-red-600 hover:bg-red-50"
          >
            {TEXT_CANCEL_ORDER}
          </button>
        )}
      </div>
    </div>
  );
}