package com.baeldung.pem;

import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
import org.bouncycastle.openssl.PEMParser;
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
import org.bouncycastle.util.io.pem.PemObject;
import org.bouncycastle.util.io.pem.PemReader;

import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

public class BouncyCastlePemUtils {

    public static RSAPublicKey readX509PublicKey(File file) throws InvalidKeySpecException, IOException, NoSuchAlgorithmException {
        KeyFactory factory = KeyFactory.getInstance("RSA");

        try (FileReader keyReader = new FileReader(file);
             PemReader pemReader = new PemReader(keyReader)) {

            PemObject pemObject = pemReader.readPemObject();
            byte[] content = pemObject.getContent();
            X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(content);
            return (RSAPublicKey) factory.generatePublic(pubKeySpec);
        }
    }

    public static RSAPublicKey readX509PublicKeySecondApproach(File file) throws IOException {
        try (FileReader keyReader = new FileReader(file)) {

            PEMParser pemParser = new PEMParser(keyReader);
            JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
            SubjectPublicKeyInfo publicKeyInfo = SubjectPublicKeyInfo.getInstance(pemParser.readObject());

            return (RSAPublicKey) converter.getPublicKey(publicKeyInfo);
        }
    }

    public static RSAPrivateKey readPKCS8PrivateKey(File file) throws InvalidKeySpecException, IOException, NoSuchAlgorithmException {
        KeyFactory factory = KeyFactory.getInstance("RSA");

        try (FileReader keyReader = new FileReader(file);
             PemReader pemReader = new PemReader(keyReader)) {

            PemObject pemObject = pemReader.readPemObject();
            byte[] content = pemObject.getContent();
            PKCS8EncodedKeySpec privKeySpec = new PKCS8EncodedKeySpec(content);
            return (RSAPrivateKey) factory.generatePrivate(privKeySpec);
        }
    }

    public static RSAPrivateKey readPKCS8PrivateKeySecondApproach(File file) throws IOException {
        try (FileReader keyReader = new FileReader(file)) {

            PEMParser pemParser = new PEMParser(keyReader);
            JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
            PrivateKeyInfo privateKeyInfo = PrivateKeyInfo.getInstance(pemParser.readObject());

            return (RSAPrivateKey) converter.getPrivateKey(privateKeyInfo);
        }
    }

}