import java.util.Random;

/**
 * 将10进制转换成62进制
 *
 * @author jonyliu
 * @date 2021/11/10 10:55
 */
public class ShortUrlUtil {

    public static String REDIS_KEY = "SHORT_URL_ID";

    private static String characters = "8DHGQm34zSxLewFn6JMBPRX1Ku9tOfbAkyl2Yqi5TUhvVo7cpIjNa0WrEdZCsg";

    public static String base62(Long b10) {
        StringBuilder ret = new StringBuilder();
        while (b10 > 0) {
            ret.insert(0,characters.charAt((int) (b10 % 62)));
            b10 /= 62;
        }
        return ret.toString();
    }

    public static long decodeBase62(String b62) {
        long ret = 0;
        b62 = new StringBuffer(b62).reverse().toString();
        long count = 1;
        for (char character : b62.toCharArray()) {
            ret += characters.indexOf(character) * count;
            count *= 62;
        }
        return ret;
    }

    private String generateRandomString(){
        int count = characters.length();
        StringBuffer stringBuffer = new StringBuffer();
        Random random = new Random();
        int j = 62;
        for(int i = count;i>0;i--){
            int index =  random.nextInt(j--);
            char c = characters.charAt(index);
            characters = characters.replace(Character.toString(c),"");
            stringBuffer.append(c);
        }
        return stringBuffer.toString();
    }

}