package com.srsystem.util;

import jakarta.persistence.AttributeConverter;
import jakarta.persistence.Converter;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;
import java.util.Base64;

@Component
@Converter
public class PhoneEncryptionConverter implements AttributeConverter<String, String> {

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

    private static SecretKey secretKey;
    private static final SecureRandom secureRandom = new SecureRandom();

    public PhoneEncryptionConverter(@Value("${app.encryption.phone-key}") String key) {
        byte[] keyBytes = key.getBytes();
        if (keyBytes.length < 16) {
            byte[] padded = new byte[16];
            System.arraycopy(keyBytes, 0, padded, 0, Math.min(keyBytes.length, 16));
            keyBytes = padded;
        }
        secretKey = new SecretKeySpec(keyBytes, AES);
    }

    @Override
    public String convertToDatabaseColumn(String plaintext) {
        if (plaintext == null) return null;
        try {
            byte[] iv = new byte[GCM_IV_LENGTH];
            secureRandom.nextBytes(iv);
            Cipher cipher = Cipher.getInstance(AES_GCM);
            cipher.init(Cipher.ENCRYPT_MODE, secretKey, new GCMParameterSpec(GCM_TAG_LENGTH, iv));
            byte[] ciphertext = cipher.doFinal(plaintext.getBytes());
            byte[] combined = new byte[GCM_IV_LENGTH + ciphertext.length];
            System.arraycopy(iv, 0, combined, 0, GCM_IV_LENGTH);
            System.arraycopy(ciphertext, 0, combined, GCM_IV_LENGTH, ciphertext.length);
            return Base64.getEncoder().encodeToString(combined);
        } catch (Exception e) {
            throw new RuntimeException("Phone encryption failed", e);
        }
    }

    @Override
    public String convertToEntityAttribute(String encrypted) {
        if (encrypted == null) return null;
        try {
            byte[] combined = Base64.getDecoder().decode(encrypted);
            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(AES_GCM);
            cipher.init(Cipher.DECRYPT_MODE, secretKey, new GCMParameterSpec(GCM_TAG_LENGTH, iv));
            return new String(cipher.doFinal(ciphertext));
        } catch (Exception e) {
            return encrypted;
        }
    }
}