package com.aigeo.util.pay;

import cn.hutool.core.codec.Base64;
import cn.hutool.core.util.StrUtil;

import java.nio.charset.StandardCharsets;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;

public class RsaKit {

    /**
     * 加密算法RSA
     */
    private static final String KEY_ALGORITHM = "RSA";

    /**
     * 私钥签名
     *
     * @param data       需要加密的数据
     * @param privateKey 私钥
     * @return 加密后的数据
     * @throws Exception 异常信息
     */
    public static String encryptByPrivateKey(String data, PrivateKey privateKey) throws Exception {
        java.security.Signature signature = java.security.Signature.getInstance("SHA256WithRSA");
        signature.initSign(privateKey);
        signature.update(data.getBytes(StandardCharsets.UTF_8));
        byte[] signed = signature.sign();
        return StrUtil.str(Base64.encode(signed));
    }

    /**
     * 从字符串中加载私钥<br>
     * 加载时使用的是PKCS8EncodedKeySpec（PKCS#8编码的Key指令）。
     *
     * @param privateKeyStr 私钥
     * @return {@link PrivateKey}
     * @throws Exception 异常信息
     */
    public static PrivateKey loadPrivateKey(String privateKeyStr) throws Exception {
        try {
            byte[] buffer = Base64.decode(privateKeyStr);
            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
            return keyFactory.generatePrivate(keySpec);
        } catch (NoSuchAlgorithmException e) {
            throw new Exception("无此算法");
        } catch (InvalidKeySpecException e) {
            throw new Exception("私钥非法");
        } catch (NullPointerException e) {
            throw new Exception("私钥数据为空");
        }
    }
    /**
     * 公钥验证签名
     *
     * @param data      需要加密的数据
     * @param sign      签名
     * @param publicKey 公钥
     * @return 验证结果
     * @throws Exception 异常信息
     */
    public static boolean checkByPublicKey(String data, String sign, PublicKey publicKey) throws Exception {
        java.security.Signature signature = java.security.Signature.getInstance("SHA256WithRSA");
        signature.initVerify(publicKey);
        signature.update(data.getBytes(StandardCharsets.UTF_8));
        return signature.verify(Base64.decode(sign.getBytes(StandardCharsets.UTF_8)));
    }
}