/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.net.util;

import java.security.GeneralSecurityException;
import java.security.KeyStore;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;

/**
 * TrustManager utilities for generating TrustManagers.
 *
 * @since 3.0
 */
public final class TrustManagerUtils {

    private static class TrustManager implements X509TrustManager {

        private final boolean checkServerValidity;

        TrustManager(final boolean checkServerValidity) {
            this.checkServerValidity = checkServerValidity;
        }

        /**
         * Never generates a CertificateException.
         */
        @Override
        public void checkClientTrusted(final X509Certificate[] certificates, final String authType) {
        }

        @Override
        public void checkServerTrusted(final X509Certificate[] certificates, final String authType) throws CertificateException {
            if (checkServerValidity) {
                for (final X509Certificate certificate : certificates) {
                    certificate.checkValidity();
                }
            }
        }

        /**
         * @return an empty array of certificates
         */
        @Override
        public X509Certificate[] getAcceptedIssuers() {
            return NetConstants.EMPTY_X509_CERTIFICATE_ARRAY;
        }
    }

    private static final X509TrustManager ACCEPT_ALL = new TrustManager(false);

    private static final X509TrustManager CHECK_SERVER_VALIDITY = new TrustManager(true);

    /**
     * Generate a TrustManager that performs no checks.
     *
     * @return the TrustManager
     */
    public static X509TrustManager getAcceptAllTrustManager() {
        return ACCEPT_ALL;
    }

    /**
     * Return the default TrustManager provided by the JVM.
     * <p>
     * This should be the same as the default used by
     * {@link javax.net.ssl.SSLContext#init(javax.net.ssl.KeyManager[], javax.net.ssl.TrustManager[], java.security.SecureRandom) SSLContext#init(KeyManager[],
     * TrustManager[], SecureRandom)} when the TrustManager parameter is set to {@code null}
     *
     * @param keyStore the KeyStore to use, may be {@code null}
     * @return the default TrustManager
     * @throws GeneralSecurityException if an error occurs
     */
    public static X509TrustManager getDefaultTrustManager(final KeyStore keyStore) throws GeneralSecurityException {
        final String defaultAlgorithm = TrustManagerFactory.getDefaultAlgorithm();
        final TrustManagerFactory instance = TrustManagerFactory.getInstance(defaultAlgorithm);
        instance.init(keyStore);
        return (X509TrustManager) instance.getTrustManagers()[0];
    }

    /**
     * Generate a TrustManager that checks server certificates for validity, but otherwise performs no checks.
     *
     * @return the validating TrustManager
     */
    public static X509TrustManager getValidateServerCertificateTrustManager() {
        return CHECK_SERVER_VALIDITY;
    }

}
