package com.mengyunzhi.common.utils;

import org.apache.commons.collections4.BidiMap;
import org.apache.commons.collections4.bidimap.TreeBidiMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.validation.ValidationException;
import java.util.Map;
import java.util.Random;

/**
 * 統一社會停用用代碼
 */
public interface UnifiedCreditCodeUtils {
  Logger logger = LoggerFactory.getLogger(UnifiedCreditCodeUtils.class);
  String baseCode = "0123456789ABCDEFGHJKLMNPQRTUWXY";
  char[] baseCodeArray = baseCode.toCharArray();
  int[] wi = {1, 3, 9, 27, 19, 26, 16, 17, 20, 29, 25, 13, 8, 24, 10, 30, 28};

  /**
   * 生成供較驗使用的 Code Map
   *
   * @return BidiMap
   */
  static BidiMap<Character, Integer> generateCodes() {
    BidiMap<Character, Integer> codes = new TreeBidiMap<>();
    for (int i = 0; i < baseCode.length(); i++) {
      codes.put(baseCodeArray[i], i);
    }

    return codes;
  }

  /**
   * 較驗社會統一信用代碼
   *
   * @param unifiedCreditCode 統一社會信息代碼
   * @return 符合: true
   */
  static boolean validateUnifiedCreditCode(String unifiedCreditCode) {
    if ((unifiedCreditCode.equals("")) || unifiedCreditCode.length() != 18) {
      return false;
    }

    Map<Character, Integer> codes = generateCodes();
    int parityBit;
    try {
      parityBit = getParityBit(unifiedCreditCode, codes);
    } catch (ValidationException e) {
      return false;
    }

    return parityBit == codes.get(unifiedCreditCode.charAt(unifiedCreditCode.length() - 1));
  }

  /**
   * 獲取較驗碼
   *
   * @param unifiedCreditCode 統一社會信息代碼
   * @param codes       帶有映射關系的國家代碼
   * @return 獲取較驗位的值
   */
  static int getParityBit(String unifiedCreditCode, Map<Character, Integer> codes) {
    char[] businessCodeArray = unifiedCreditCode.toCharArray();

    int sum = 0;
    for (int i = 0; i < 17; i++) {
      char key = businessCodeArray[i];
      if (baseCode.indexOf(key) == -1) {
        throw new ValidationException("第" + String.valueOf(i + 1) + "位傳入了非法的字符" + key);
      }
      sum += (codes.get(key) * wi[i]);
    }
    int result = 31 - sum % 31;
    return result == 31 ? 0 : result;
  }

  /**
   * 獲取一個隨機的統一社會信用代碼
   *
   * @return 統一社會信用代碼
   */
  static String generateOneUnifiedCreditCode() {
    Random random = new Random();
    StringBuilder buf = new StringBuilder();

    for (int i = 0; i < 17; ++i) {
      int num = random.nextInt(baseCode.length() - 1);
      buf.append(baseCode.charAt(num));
    }

    String code = buf.toString();
    String upperCode = code.toUpperCase();
    BidiMap<Character, Integer> codes = generateCodes();
    int parityBit = getParityBit(upperCode, codes);

    if (codes.getKey(parityBit) == null) {
      logger.debug("生成社會統一信用代碼不符合規則");
      upperCode = generateOneUnifiedCreditCode();
    } else {
      upperCode = upperCode + codes.getKey(parityBit);
    }

    return upperCode;
  }
}

package com.mengyunzhi.common.utils;

import org.assertj.core.api.Assertions;
import org.junit.Test;

import static org.junit.Assert.*;

public class UnifiedCreditCodeUtilsTest {

  @Test
  public void validateUnifiedCreditCode() {
    String code = "911310827965850580";
    Assertions.assertThat(UnifiedCreditCodeUtils.validateUnifiedCreditCode(code)).isTrue();
  }
}