// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.security.tls;

import com.yahoo.security.SslContextBuilder;
import com.yahoo.security.tls.authz.PeerAuthorizerTrustManager;
import com.yahoo.security.tls.policy.AuthorizedPeers;

import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLEngine;
import javax.net.ssl.SSLParameters;
import java.security.PrivateKey;
import java.security.cert.X509Certificate;
import java.util.Arrays;
import java.util.List;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * A static {@link TlsContext}
 *
 * @author bjorncs
 */
public class DefaultTlsContext implements TlsContext {

    private static final Logger log = Logger.getLogger(DefaultTlsContext.class.getName());

    private final SSLContext sslContext;
    private final String[] validCiphers;
    private final String[] validProtocols;
    private final PeerAuthentication peerAuthentication;

    public DefaultTlsContext(List<X509Certificate> certificates,
                             PrivateKey privateKey,
                             List<X509Certificate> caCertificates,
                             AuthorizedPeers authorizedPeers,
                             AuthorizationMode mode,
                             PeerAuthentication peerAuthentication,
                             HostnameVerification hostnameVerification) {
        this(createSslContext(certificates, privateKey, caCertificates, authorizedPeers, mode, hostnameVerification), peerAuthentication);
    }

    public DefaultTlsContext(SSLContext sslContext, PeerAuthentication peerAuthentication) {
        this(sslContext, TlsContext.ALLOWED_CIPHER_SUITES, TlsContext.ALLOWED_PROTOCOLS, peerAuthentication);
    }

    DefaultTlsContext(SSLContext sslContext, Set<String> acceptedCiphers, Set<String> acceptedProtocols, PeerAuthentication peerAuthentication) {
        this.sslContext = sslContext;
        this.peerAuthentication = peerAuthentication;
        this.validCiphers = getAllowedCiphers(sslContext, acceptedCiphers);
        this.validProtocols = getAllowedProtocols(sslContext, acceptedProtocols);
    }

    private static String[] getAllowedCiphers(SSLContext sslContext, Set<String> acceptedCiphers) {
        Set<String> supportedCiphers = TlsContext.getAllowedCipherSuites(sslContext);
        String[] allowedCiphers = supportedCiphers.stream()
                .filter(acceptedCiphers::contains)
                .toArray(String[]::new);
        if (allowedCiphers.length == 0) {
            throw new IllegalStateException(
                    String.format("None of the accepted ciphers are supported (supported=%s, accepted=%s)",
                                  supportedCiphers, acceptedCiphers));
        }
        log.log(Level.FINE, () -> String.format("Allowed cipher suites that are supported: %s", Arrays.asList(allowedCiphers)));
        return allowedCiphers;
    }

    private static String[] getAllowedProtocols(SSLContext sslContext, Set<String> acceptedProtocols) {
        Set<String> supportedProtocols = TlsContext.getAllowedProtocols(sslContext);
        String[] allowedProtocols = supportedProtocols.stream()
                .filter(acceptedProtocols::contains)
                .toArray(String[]::new);
        if (allowedProtocols.length == 0) {
            throw new IllegalStateException(
                    String.format("None of the accepted protocols are supported (supported=%s, accepted=%s)",
                            supportedProtocols, acceptedProtocols));
        }
        log.log(Level.FINE, () -> String.format("Allowed protocols that are supported: %s", Arrays.toString(allowedProtocols)));
        return allowedProtocols;
    }

    @Override
    public SSLContext context() {
        return sslContext;
    }

    @Override
    public SSLParameters parameters() {
        return createSslParameters();
    }

    @Override
    public SSLEngine createSslEngine() {
        SSLEngine sslEngine = sslContext.createSSLEngine();
        sslEngine.setSSLParameters(createSslParameters());
        return sslEngine;
    }

    @Override
    public SSLEngine createSslEngine(String peerHost, int peerPort) {
        SSLEngine sslEngine = sslContext.createSSLEngine(peerHost, peerPort);
        sslEngine.setSSLParameters(createSslParameters());
        return sslEngine;
    }

    private SSLParameters createSslParameters() {
        SSLParameters newParameters = sslContext.getDefaultSSLParameters();
        newParameters.setCipherSuites(validCiphers);
        newParameters.setProtocols(validProtocols);
        switch (peerAuthentication) {
            case WANT:
                newParameters.setWantClientAuth(true);
                break;
            case NEED:
                newParameters.setNeedClientAuth(true);
                break;
            case DISABLED:
                break;
            default:
                throw new UnsupportedOperationException("Unknown peer authentication: " + peerAuthentication);
        }
        return newParameters;
    }

    private static SSLContext createSslContext(List<X509Certificate> certificates,
                                               PrivateKey privateKey,
                                               List<X509Certificate> caCertificates,
                                               AuthorizedPeers authorizedPeers,
                                               AuthorizationMode mode,
                                               HostnameVerification hostnameVerification) {
        SslContextBuilder builder = new SslContextBuilder();
        if (!certificates.isEmpty()) {
            builder.withKeyStore(privateKey, certificates);
        }
        if (!caCertificates.isEmpty()) {
            builder.withTrustStore(caCertificates);
        }
        return builder.withTrustManagerFactory(truststore ->
                        new PeerAuthorizerTrustManager(authorizedPeers, mode, hostnameVerification, truststore))
                .build();
    }

}