/* 
 * This file is part of cert-encoder
 * Copyright (c) 2024 Paolo Lulli.
 * 
 * This program is free software: you can redistribute it and/or modify  
 * it under the terms of the GNU General Public License as published by  
 * the Free Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of 
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License 
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package net.lulli.encrypt;

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;

public class Pems {
    private Pems(){}

    public static X509Certificate readX509Certificate(String certificate) throws Exception {
        InputStream targetStream = new ByteArrayInputStream(certificate.getBytes());
        return (X509Certificate) CertificateFactory
                .getInstance("X509")
                .generateCertificate(targetStream);
    }

    public static X509Certificate certificateFromFile(String fileName) {
        try {
            var keyContent = Files.readString(Paths.get(fileName));
            return readX509Certificate(keyContent);
        } catch (Exception e) {
            throw new IllegalStateException(e.getMessage());
        }
    }
    public static PublicKey publicKeyFromFile(String fileName) {
        try {
            var keyContent = Files.readString(Paths.get(fileName));
            return readX509PublicKey(keyContent);
        } catch (Exception e) {
            throw new IllegalStateException(e.getMessage());
        }
    }

    public static PrivateKey privateKeyFromFile(String fileName) {
        try {
            var keyContent = Files.readString(Paths.get(fileName));
            return readPKCS8PrivateKey(keyContent);
        } catch (Exception e) {
            throw new IllegalStateException(e.getMessage());
        }
    }

    public static PublicKey readX509PublicKey(String key) throws Exception {
        String publicKeyPEM = key
                .replace("-----BEGIN PUBLIC KEY-----", "")
                .replaceAll(System.lineSeparator(), "")
                .replace("-----END PUBLIC KEY-----", "");

        byte[] encoded = Base64.getDecoder().decode(publicKeyPEM);

        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(encoded);
        return (PublicKey) keyFactory.generatePublic(keySpec);
    }

    public static PrivateKey readPKCS8PrivateKey(String key) throws Exception {
        String privateKeyPEM = key
                .replace("-----BEGIN PRIVATE KEY-----", "")
                .replaceAll(System.lineSeparator(), "")
                .replace("-----END PRIVATE KEY-----", "");

        byte[] encoded = Base64.getDecoder().decode(privateKeyPEM);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(encoded);
        return (PrivateKey) keyFactory.generatePrivate(keySpec);
    }
}