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/* 
 * This file is part of cert-signer
 * 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.certsigner;

import net.lulli.certsigner.service.CertificateSigningService;
import net.lulli.certsigner.util.CSRManager;
import net.lulli.certsigner.util.Serde;

import java.io.File;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.Security;
import java.util.Base64;
import java.util.Objects;

public class Client {
    private static final String CERTIFICATES_HOME = System.getenv("HOME") + "/.config/tlscerts";
    private final String serviceName;
    private final String clientName;

    public Client(String serviceName, String clientName) {
        Objects.requireNonNull(serviceName);
        Objects.requireNonNull(clientName);

        this.serviceName = serviceName;
        this.clientName = clientName;

        init();
    }

    private void init() {
        var home = new File(getCertificatesPath());
        if (!home.exists()) {
            home.mkdirs();
        }
    }

    private String getCertificatesPath() {
        return CERTIFICATES_HOME + "/" + this.serviceName + "/" + this.clientName;
    }

    public String createCsr() {
        try {
            Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

            KeyPairGenerator keyGen = KeyPairGenerator.getInstance(Settings.KEY_ALGORITHM);
            keyGen.initialize(Settings.KEYSIZE);
            KeyPair keypair = keyGen.genKeyPair();

            Serde.toFile(keypair.getPrivate(), getCertificatesPath() + "/" + this.clientName + ".key");
            Serde.toFile(keypair.getPublic(), getCertificatesPath() + "/" + this.clientName + ".key.pub");

            var subject = "CN=" + this.clientName + ", O=" + this.serviceName + "";

            var csrManager = CSRManager.with(subject, keypair.getPrivate(), keypair.getPublic());
            var csrFileName = getCertificatesPath() + "/" + this.clientName + ".csr";
            saveCsrAs(csrManager.pem(), csrFileName);
            return csrManager.pem();
        } catch (Exception e) {
            throw new IllegalStateException(e.getMessage());
        }
    }

    private void saveCsrAs(String content, String filename) {
        System.out.println("Writing content to file: " + filename);
        try {
            Files.write(Paths.get(filename), content.getBytes());
        } catch (Exception e) {
            throw new IllegalStateException(e);
        }
    }

    public String requestCertificate() {
        try {
            var client = new Client(serviceName, clientName);

            var csr = client.createCsr();
            var base64Csr = Base64.getEncoder().encodeToString(csr.getBytes());
            var certificateSigningService = new CertificateSigningService(serviceName);
            var certificate = certificateSigningService.sign(clientName, base64Csr);

            Files.write(Paths.get(CERTIFICATES_HOME + "/" + serviceName + "/" + clientName + "/" + clientName + ".pem"),
                    certificate.getBytes());
            return certificate;
        } catch (Exception e) {
            throw new IllegalStateException(e.getMessage(), e);
        }
    }

    public static void main(String[] args) {
        if (args.length != 2){
            throw new IllegalStateException("Missing parameters");
        }

        var serviceName = args[0];
        var clientName = args[1];

        var client = new Client(serviceName, clientName);
        var certificate = client.requestCertificate();

        System.out.printf("Certificate data:\n%s", certificate);
    }
}