package com.moon.server.helper;

import org.apache.commons.codec.binary.Base64;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.core.io.ClassPathResource;

import javax.crypto.Cipher;
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

/**
 * RSA工具类
 * @author WWW
 */
public class RsaHelper {
    /**
     * 私钥
     */
    private static String privateKey;

    /**
     * 公钥
     */
    private static String publicKey;

    /**
     * 密钥算法
     */
    private static final String KEY_ALGORITHM = "RSA";

    /**
     * RSA密钥长度：1024 或 2048
     */
    private static final int DEFAULT_RSA_KEY_SIZE = 1024;

    /**
     * 日志
     */
    private final static Log log = LogFactory.getLog(RsaHelper.class);

    /**
     * 生成公私钥
     */
    public static void generate() {
        Map<String, String> result = generateRsaKey(DEFAULT_RSA_KEY_SIZE);
        System.out.println("公钥为：" + result.get("publicKey"));
        System.out.println("私钥为：" + result.get("privateKey"));
    }

    /**
     * 获取RSA加密私钥
     *
     * @return
     * @throws IOException
     */
    public static String getPrivateKey() throws IOException {
        if (privateKey == null) {
            InputStream inPrivate = new ClassPathResource("config" + File.separator + "rsa_private_key.txt").getInputStream();
            privateKey = inputStream2String(inPrivate);
            inPrivate.close();
        }

        return privateKey;
    }

    /**
     * 获取RSA加密公钥
     *
     * @return
     * @throws IOException
     */
    public static String getPublicKey() throws IOException {
        if (publicKey == null) {
            InputStream inPrivate = new ClassPathResource("config" + File.separator + "rsa_public_key.txt").getInputStream();
            publicKey = inputStream2String(inPrivate);
            inPrivate.close();
        }

        return publicKey;
    }

    /**
     * 读取文本文件
     *
     * @param fileName 文件路径
     * @return
     * @throws IOException
     */
    public static String readFile(String fileName) throws IOException {
        File file = new File(fileName);
        BufferedReader br = new BufferedReader(new FileReader(file));

        StringBuilder result = new StringBuilder();

        String line = null;
        while ((line = br.readLine()) != null) {
            result.append(System.lineSeparator() + line);
        }
        br.close();

        return result.toString();
    }

    /**
     * 把inputStream转成String
     *
     * @param is
     * @return
     * @throws IOException
     */
    private static String inputStream2String(InputStream is) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        int i = -1;
        while ((i = is.read()) != -1) {
            baos.write(i);
        }

        String str = baos.toString();
        baos.close();

        return str;
    }

    /**
     * 生成RSA的公私钥
     *
     * @param keySize 1025 或 2048
     * @return
     */
    public static Map<String, String> generateRsaKey(int keySize) {
        Map<String, String> result = new HashMap<>(2);
        try {
            KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);

            // 初始化密钥对生成器，密钥大小为1024 2048位
            keyPairGen.initialize(keySize, new SecureRandom());

            // 生成一个密钥对，保存在keyPair中
            KeyPair keyPair = keyPairGen.generateKeyPair();

            // 得到公钥字符串
            String pub = new String(Base64.encodeBase64(keyPair.getPublic().getEncoded()));
            result.put("publicKey", pub);

            // 得到私钥字符串
            String pri = new String(Base64.encodeBase64(keyPair.getPrivate().getEncoded()));
            result.put("privateKey", pri);
        } catch (Exception ex) {
            log.error(ex.getMessage(), ex);
        }

        return result;
    }

    /**
     * RSA私钥解密
     *
     * @param str 加密的字符串
     * @return 解密字符串
     * @throws Exception 加密过程中的异常信息
     */
    public static String decrypt(String str) throws Exception {
        // 64位解码加密后的字符串
        byte[] inputByte = Base64.decodeBase64(str.getBytes(StandardCharsets.UTF_8));

        // Base64编码的私钥
        byte[] decoded = Base64.decodeBase64(getPrivateKey());
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));

        // RSA解密：RSA/ECB/NoPadding
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, priKey);

        String outStr = new String(cipher.doFinal(inputByte));

        return outStr;
    }

    /**
     * RSA公钥加密
     *
     * @param str 需要加密的字符串
     * @return 密文
     * @throws Exception 加密过程中的异常信息
     */
    public static String encrypt(String str) throws Exception {
        // Base64编码的公钥
        byte[] decoded = Base64.decodeBase64(getPublicKey());

        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));

        // RSA加密：RSA/ECB/NoPadding
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);

        String outStr = Base64.encodeBase64String(cipher.doFinal(str.getBytes(StandardCharsets.UTF_8)));

        return outStr;
    }
}