/*******************************************************************************
 * Copyright (C) 2021 the Eclipse BaSyx Authors
 * 
 * This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 * 
 * SPDX-License-Identifier: EPL-2.0
 ******************************************************************************/
package org.eclipse.basyx.vab.protocol.opcua.server;

import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyStore;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.cert.X509Certificate;
import java.util.regex.Pattern;

import org.eclipse.milo.opcua.sdk.server.util.HostnameUtil;
import org.eclipse.milo.opcua.stack.core.util.SelfSignedCertificateBuilder;
import org.eclipse.milo.opcua.stack.core.util.SelfSignedCertificateGenerator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class KeyStoreLoaderClient {

    private static final Pattern IP_ADDR_PATTERN = Pattern
            .compile("^(([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.){3}([01]?\\d\\d?|2[0-4]\\d|25[0-5])$");

    private static final String CLIENT_ALIAS = "client-ai";
    private static final char[] PASSWORD = "password".toCharArray();

    private final Logger logger = LoggerFactory.getLogger(getClass());

    private X509Certificate clientCertificate;
    private KeyPair clientKeyPair;

    KeyStoreLoaderClient load(Path baseDir) throws Exception {
        KeyStore keyStore = KeyStore.getInstance("PKCS12");

        Path serverKeyStore = baseDir.resolve("example-client.pfx");

        logger.info("Loading KeyStore at {}", serverKeyStore);

        if (!Files.exists(serverKeyStore)) {
            keyStore.load(null, PASSWORD);

            KeyPair keyPair = SelfSignedCertificateGenerator.generateRsaKeyPair(2048);

            SelfSignedCertificateBuilder builder = new SelfSignedCertificateBuilder(keyPair)
                    .setCommonName("Eclipse Milo Example Client").setOrganization("digitalpetri")
                    .setOrganizationalUnit("dev").setLocalityName("Folsom").setStateName("CA").setCountryCode("US")
                    .setApplicationUri("urn:eclipse:milo:examples:client").addDnsName("localhost")
                    .addIpAddress("127.0.0.1");

            // Get as many hostnames and IP addresses as we can listed in the certificate.
            for (String hostname : HostnameUtil.getHostnames("0.0.0.0")) {
                if (IP_ADDR_PATTERN.matcher(hostname).matches()) {
                    builder.addIpAddress(hostname);
                } else {
                    builder.addDnsName(hostname);
                }
            }

            X509Certificate certificate = builder.build();

            keyStore.setKeyEntry(CLIENT_ALIAS, keyPair.getPrivate(), PASSWORD, new X509Certificate[] { certificate });
            try (OutputStream out = Files.newOutputStream(serverKeyStore)) {
                keyStore.store(out, PASSWORD);
            }
        } else {
            try (InputStream in = Files.newInputStream(serverKeyStore)) {
                keyStore.load(in, PASSWORD);
            }
        }

        Key serverPrivateKey = keyStore.getKey(CLIENT_ALIAS, PASSWORD);
        if (serverPrivateKey instanceof PrivateKey) {
            clientCertificate = (X509Certificate) keyStore.getCertificate(CLIENT_ALIAS);
            PublicKey serverPublicKey = clientCertificate.getPublicKey();
            clientKeyPair = new KeyPair(serverPublicKey, (PrivateKey) serverPrivateKey);
        }

        return this;
    }

    X509Certificate getClientCertificate() {
        return clientCertificate;
    }

    KeyPair getClientKeyPair() {
        return clientKeyPair;
    }

}