package com.mgm.mcrm.common.utils;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Base64;
import java.util.Map;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.Permission;
import java.security.PermissionCollection;
import java.security.SecureRandom;

import com.alibaba.fastjson.JSONObject;

public class AESUtil {

	private static final String AES = "AES";
	private static final int GCM_IV_LENGTH = 12; // GCM推荐使用12字节的IV
	private static final int GCM_TAG_LENGTH = 16; // GCM认证标签长度（128位）

	private static java.util.Base64.Encoder base64Encoder = java.util.Base64.getEncoder();
	private static java.util.Base64.Decoder base64Decoder = java.util.Base64.getDecoder();

	static {
		java.security.Security.setProperty("crypto.policy", "unlimited");	
		removeCryptographyRestrictions();
	}
	
	public static void removeCryptographyRestrictions() {
        try {
            /*
             * Do the following, but with reflection to bypass access checks:
             * JceSecurity.isRestricted = false;
             * JceSecurity.defaultPolicy.perms.clear();
             * JceSecurity.defaultPolicy.add(CryptoAllPermission.INSTANCE);
             */
            final Class<?> jceSecurity = Class.forName("javax.crypto.JceSecurity");
            final Class<?> cryptoPermissions = Class.forName("javax.crypto.CryptoPermissions");
            final Class<?> cryptoAllPermission = Class.forName("javax.crypto.CryptoAllPermission");

            final Field isRestrictedField = jceSecurity.getDeclaredField("isRestricted");
            isRestrictedField.setAccessible(true);
            // 去除isRestricted的final限制
            final Field modifiersField = Field.class.getDeclaredField("modifiers");
            modifiersField.setAccessible(true);
            modifiersField.setInt(isRestrictedField, isRestrictedField.getModifiers() & ~Modifier.FINAL);
            isRestrictedField.set(null, false);

            final Field defaultPolicyField = jceSecurity.getDeclaredField("defaultPolicy");
            defaultPolicyField.setAccessible(true);
            final PermissionCollection defaultPolicy = (PermissionCollection) defaultPolicyField.get(null);

            final Field perms = cryptoPermissions.getDeclaredField("perms");
            perms.setAccessible(true);
            ((Map<?, ?>) perms.get(defaultPolicy)).clear();

            final Field instance = cryptoAllPermission.getDeclaredField("INSTANCE");
            instance.setAccessible(true);
            defaultPolicy.add((Permission) instance.get(null));

        } catch (final Exception e) {
            e.printStackTrace();
        }
    }

    public static SecretKey generateKey() throws Exception {
        KeyGenerator keyGen = KeyGenerator.getInstance("AES");
        keyGen.init(256); 
        return keyGen.generateKey();
    }
    public static SecretKey stringToSecretKey(String keyString) {
        byte[] keyBytes = base64Decoder.decode(keyString);        
        return new SecretKeySpec(keyBytes, AES);
    }
    public static String secretKeyToString(SecretKey secretKey) {
        byte[] keyBytes = secretKey.getEncoded();        
        return base64Encoder.encodeToString(keyBytes);
    }
	/**
	 * AES加密
	 */
	public static String AES256Encrypt(String key, String content) {
		try {
			SecretKey secretKey = stringToSecretKey(key);
			Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
	        byte[] iv = new byte[GCM_IV_LENGTH];
	        SecureRandom secureRandom = new SecureRandom();
	        secureRandom.nextBytes(iv); // 生成随机的IV
	        GCMParameterSpec spec = new GCMParameterSpec(GCM_TAG_LENGTH * 8, iv);
	        cipher.init(Cipher.ENCRYPT_MODE, secretKey, spec);

	        byte[] ciphertext = cipher.doFinal(content.getBytes());
	        byte[] encryptedData = new byte[iv.length + ciphertext.length];
	        System.arraycopy(iv, 0, encryptedData, 0, iv.length);
	        System.arraycopy(ciphertext, 0, encryptedData, iv.length, ciphertext.length);
	        return base64Encoder.encodeToString(encryptedData);

		} catch (Exception e) {
			//e.printStackTrace();
		}
		return null;
	}
	/**
	 * AES解密
	 */
	public static String AES256Decrypt(String key, String content) {
		try {
			SecretKey secretKey = stringToSecretKey(key);
			byte[] encryptedData = base64Decoder.decode(content);
			Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
	        // 从加密数据中提取IV
	        byte[] iv = new byte[GCM_IV_LENGTH];
	        System.arraycopy(encryptedData, 0, iv, 0, iv.length);

	        GCMParameterSpec spec = new GCMParameterSpec(GCM_TAG_LENGTH * 8, iv);
	        cipher.init(Cipher.DECRYPT_MODE, secretKey, spec);

	        // 解密数据
	        byte[] ciphertext = new byte[encryptedData.length - GCM_IV_LENGTH];
	        System.arraycopy(encryptedData, GCM_IV_LENGTH, ciphertext, 0, ciphertext.length);
	        byte[] byteDecode = cipher.doFinal(ciphertext);
	        return new String(byteDecode, java.nio.charset.StandardCharsets.UTF_8);			
		} catch (Exception e) {
			//e.printStackTrace();
		}
		return null;
	}	
	
	public static String sha256(String plainString) {
        String cipherString = null;
        try {
            // 获取实例（SHA-512同理）
            MessageDigest messageDigest = MessageDigest.getInstance("SHA-256");
            // 计算摘要
            byte[] cipherBytes = messageDigest.digest(plainString.getBytes(StandardCharsets.UTF_8));
            // 输出为16进制字符串
            StringBuilder sb = new StringBuilder();
            for (byte b : cipherBytes) {
                sb.append(String.format("%02x", b));
            }
            cipherString = sb.toString();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return cipherString;
    }

}