import React, { useState, useMemo } from 'react';
import './BankCardInput.css';

function detectType(v) {
  if (/^4/.test(v)) return 'Visa';
  if (/^5[1-5]/.test(v)) return 'MasterCard';
  if (/^62/.test(v)) return '银联';
  if (/^3[47]/.test(v)) return 'AmEx';
  if (/^35/.test(v)) return 'JCB';
  return '';
}
function luhn(v) {
  let sum = 0, alt = false;
  for (let i = v.length - 1; i >= 0; i--) {
    let n = parseInt(v[i], 10);
    if (alt) { n *= 2; if (n > 9) n -= 9; }
    sum += n; alt = !alt;
  }
  return sum % 10 === 0;
}

export default function BankCardInput({ modelValue = '', placeholder = '请输入银行卡号', onChange }) {
  const [digits, setDigits] = useState(modelValue.replace(/\D/g, ''));
  const [focused, setFocused] = useState(false);

  const display = digits.replace(/(.{4})/g, '$1 ').trim();
  const cardType = detectType(digits);
  const valid = digits.length >= 13 && luhn(digits);
  const invalid = digits.length >= 13 && !luhn(digits);
  const tipClass = valid ? 'valid' : invalid ? 'invalid' : '';
  const tipText = !digits
    ? '支持 Visa / MasterCard / 银联等'
    : valid
    ? '卡号校验通过'
    : invalid
    ? '卡号未通过 Luhn 校验'
    : '继续输入卡号…';

  const onInput = (e) => {
    const v = e.target.value.replace(/\D/g, '').slice(0, 19);
    e.target.value = v.replace(/(.{4})/g, '$1 ').trim();
    setDigits(v);
    if (onChange) onChange(v);
  };

  return (
    <div className="aa-card">
      <div
        className={
          'aa-card-field' + (focused ? ' is-focus' : '') + (valid ? ' is-valid' : '') + (invalid ? ' is-invalid' : '')
        }
      >
        <input
          className="aa-card-input"
          value={display}
          inputMode="numeric"
          maxLength={23}
          placeholder={placeholder}
          onInput={onInput}
          onFocus={() => setFocused(true)}
          onBlur={() => setFocused(false)}
        />
        <span className={'aa-card-type' + (cardType ? '' : ' unknown')}>{cardType || '未知'}</span>
      </div>
      <div className={'aa-card-tip ' + tipClass}>{tipText}</div>
    </div>
  );
}