package com.sinata.appointment.util;

import java.util.Locale;

/** 中国大陆身份证号基础校验（18 位） */
public final class IdCardUtil {

    private static final int[] WEIGHTS = {7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2};
    private static final char[] CHECK_CODES = {'1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2'};

    private IdCardUtil() {}

    public static boolean isValidMainland18(String idCard) {
        if (idCard == null) {
            return false;
        }
        String s = idCard.trim().toUpperCase(Locale.ROOT);
        if (!s.matches("^[0-9]{17}[0-9X]$")) {
            return false;
        }
        int sum = 0;
        for (int i = 0; i < 17; i++) {
            sum += (s.charAt(i) - '0') * WEIGHTS[i];
        }
        int idx = sum % 11;
        return CHECK_CODES[idx] == s.charAt(17);
    }
}