package com.sky.ioc.tool;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import java.math.BigInteger;
import java.nio.charset.Charset;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import java.util.Random;

/**
 * PBKDF2_SHA256加密验证算法
 */
public class Pbkdf2Sha256Digest {

    private static final Logger logger = LoggerFactory.getLogger(Pbkdf2Sha256Digest.class);

    /**
     * 盐的长度
     */
    private static final int SALT_BYTE_SIZE = 16;

    /**
     * 生成密文的长度(例：64 * 4，密文长度为64)
     */
    private static final int HASH_BIT_SIZE = 64 * 4;

    /**
     * 迭代次数(默认迭代次数为 2000)
     */
    private static final Integer DEFAULT_ITERATIONS = 260000;

    /**
     * 算法名称
     */
    private static final String algorithm = "pbkdf2:sha256";

    /**
     * 获取密文
     * @param password   密码明文
     * @param salt       加盐
     * @param iterations 迭代次数
     * @return
     */
    private static String getEncodedHash(String password, String salt, int iterations) {
        SecretKeyFactory keyFactory = null;
        try {
            keyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
        } catch (NoSuchAlgorithmException e) {
            logger.error("Could NOT retrieve PBKDF2WithHmacSHA256 algorithm", e);
        }
        KeySpec keySpec = new PBEKeySpec(password.toCharArray(), salt.getBytes(Charset.forName("UTF-8")), iterations, HASH_BIT_SIZE);
        SecretKey secret = null;
        try {
            secret = keyFactory.generateSecret(keySpec);
        } catch (InvalidKeySpecException e) {
            logger.error("Could NOT generate secret key", e);
        }

        //使用Base64进行转码密文
        //        byte[] rawHash = secret.getEncoded();
        //        byte[] hashBase64 = Base64.getEncoder().encode(rawHash);
        //        return new String(hashBase64);

        //使用十六进制密文
        return toHex(secret.getEncoded());
    }

    /**
     * 十六进制字符串转二进制字符串
     * @param hex     十六进制字符串
     * @return
     */
    private static byte[] fromHex(String hex) {
        byte[] binary = new byte[hex.length() / 2];
        for (int i = 0; i < binary.length; i++) {
            binary[i] = (byte) Integer.parseInt(hex.substring(2 * i, 2 * i + 2), 16);
        }
        return binary;
    }

    /**
     * 二进制字符串转十六进制字符串
     * @param array     二进制数组
     * @return
     */
    private static String toHex(byte[] array) {
        BigInteger bi = new BigInteger(1, array);
        String hex = bi.toString(16);
        int paddingLength = (array.length * 2) - hex.length();
        if (paddingLength > 0) {
            return String.format("%0" + paddingLength + "d", 0) + hex;
        } else {
            return hex;
        }
    }

    /**
     * 密文加盐     (获取‘SALT_BYTE_SIZE’长度的盐值)
     * @return
     */
    private static String getsalt() {
        //盐值使用ASCII表的数字加大小写字母组成
        int length = SALT_BYTE_SIZE;
        Random rand = new Random();
        char[] rs = new char[length];
        for (int i = 0; i < length; i++) {
            int t = rand.nextInt(3);
            if (t == 0) {
                rs[i] = (char) (rand.nextInt(10) + 48);
            } else if (t == 1) {
                rs[i] = (char) (rand.nextInt(26) + 65);
            } else {
                rs[i] = (char) (rand.nextInt(26) + 97);
            }
        }
        return new String(rs);
    }

    /**
     * 获取密文
     * 默认迭代次数：2000
     * @param password      明文密码
     * @return
     */
    public static String encode(String password) {
        return encode(password, getsalt());
    }

    /**
     * 获取密文
     * @param password      明文密码
     * @param iterations    迭代次数
     * @return
     */
    private static String encode(String password, int iterations) {
        return encode(password, getsalt(), iterations);
    }

    /**
     * 获取密文
     * 默认迭代次数：2000
     * @param password      明文密码
     * @param salt          盐值
     * @return
     */
    private static String encode(String password, String salt) {
        return encode(password, salt, DEFAULT_ITERATIONS);
    }

    /**
     * 最终返回的整串密文
     *
     * 注：此方法返回密文字符串组成：算法名称+迭代次数+盐值+密文
     * 不需要的直接用getEncodedHash方法返回的密文
     *
     * @param password   密码明文
     * @param salt       加盐
     * @param iterations 迭代次数
     * @return
     */
    private static String encode(String password, String salt, int iterations) {
        // returns hashed password, along with algorithm, number of iterations and salt
        String hash = getEncodedHash(password, salt, iterations);
        return String.format("%s:%d$%s$%s", algorithm, iterations, salt, hash);
    }

    /**
     * 验证密码
     * @param password       明文
     * @param hashedPassword 密文
     * @return
     */
    public static boolean verification(String password, String hashedPassword) {
        //hashedPassword = 算法名称+迭代次数+盐值+密文;
        String[] parts = hashedPassword.split("\\$");
        if (parts.length != 3) {
            return false;
        }
        String[] params = parts[0].split(":");
        //解析得到迭代次数和盐值进行盐值
        Integer iterations = Integer.parseInt(params[2]);
        String salt = parts[1];
        String hash = encode(password, salt, iterations);
        return hash.equals(hashedPassword);
    }

}