package com.ymwk.icvp.pki.service.impl;

import lombok.Value;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;

import javax.crypto.Cipher;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.SecureRandom;
import java.util.Base64;

@Component
@Slf4j
public class CryptoService {


    private final String masterKey = "12345678901234567890123456789012"; // 32字节的主密钥

    private static final String ALGORITHM = "AES/GCM/NoPadding";
    private static final int GCM_IV_LENGTH = 12;
    private static final int GCM_TAG_LENGTH = 128;

    /**
     * AES-GCM加密
     */
    public String encrypt(String plaintext) throws Exception {
        byte[] iv = new byte[GCM_IV_LENGTH];
        SecureRandom random = new SecureRandom();
        random.nextBytes(iv);

        Cipher cipher = Cipher.getInstance(ALGORITHM);
        SecretKeySpec keySpec = new SecretKeySpec(
                masterKey.getBytes(StandardCharsets.UTF_8),
                "AES"
        );
        GCMParameterSpec gcmSpec = new GCMParameterSpec(GCM_TAG_LENGTH, iv);
        cipher.init(Cipher.ENCRYPT_MODE, keySpec, gcmSpec);

        byte[] ciphertext = cipher.doFinal(plaintext.getBytes(StandardCharsets.UTF_8));

        // 将IV和密文合并（Base64编码）
        byte[] combined = new byte[iv.length + ciphertext.length];
        System.arraycopy(iv, 0, combined, 0, iv.length);
        System.arraycopy(ciphertext, 0, combined, iv.length, ciphertext.length);

        return Base64.getEncoder().encodeToString(combined);
    }

    /**
     * AES-GCM解密
     */
    public String decrypt(String ciphertextBase64) throws Exception {
        byte[] combined = Base64.getDecoder().decode(ciphertextBase64);

        // 提取IV和密文
        byte[] iv = new byte[GCM_IV_LENGTH];
        byte[] ciphertext = new byte[combined.length - GCM_IV_LENGTH];
        System.arraycopy(combined, 0, iv, 0, GCM_IV_LENGTH);
        System.arraycopy(combined, GCM_IV_LENGTH, ciphertext, 0, ciphertext.length);

        Cipher cipher = Cipher.getInstance(ALGORITHM);
        SecretKeySpec keySpec = new SecretKeySpec(
                masterKey.getBytes(StandardCharsets.UTF_8),
                "AES"
        );
        GCMParameterSpec gcmSpec = new GCMParameterSpec(GCM_TAG_LENGTH, iv);
        cipher.init(Cipher.DECRYPT_MODE, keySpec, gcmSpec);

        byte[] plaintext = cipher.doFinal(ciphertext);
        return new String(plaintext, StandardCharsets.UTF_8);
    }
}