/*
 * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.internal.net.http;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import javax.net.ssl.SNIHostName;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLEngine;
import javax.net.ssl.SSLEngineResult;
import javax.net.ssl.SSLParameters;

import jdk.internal.net.http.common.SSLTube;
import jdk.internal.net.http.common.Log;
import jdk.internal.net.http.common.Utils;


/**
 * Asynchronous version of SSLConnection.
 *
 * There are two concrete implementations of this class: AsyncSSLConnection
 * and AsyncSSLTunnelConnection.
 * This abstraction is useful when downgrading from HTTP/2 to HTTP/1.1 over
 * an SSL connection. See ExchangeImpl::get in the case where an ALPNException
 * is thrown.
 *
 * Note: An AsyncSSLConnection wraps a PlainHttpConnection, while an
 *       AsyncSSLTunnelConnection wraps a PlainTunnelingConnection.
 *       If both these wrapped classes where made to inherit from a
 *       common abstraction then it might be possible to merge
 *       AsyncSSLConnection and AsyncSSLTunnelConnection back into
 *       a single class - and simply use different factory methods to
 *       create different wrappees, but this is left up for further cleanup.
 *
 */
abstract class AbstractAsyncSSLConnection extends HttpConnection
{
    protected final SSLEngine engine;
    protected final String serverName;
    protected final SSLParameters sslParameters;

    AbstractAsyncSSLConnection(InetSocketAddress addr,
                               HttpClientImpl client,
                               String serverName, int port,
                               String[] alpn) {
        super(addr, client);
        this.serverName = serverName;
        SSLContext context = client.theSSLContext();
        sslParameters = createSSLParameters(client, serverName, alpn);
        Log.logParams(sslParameters);
        engine = createEngine(context, serverName, port, sslParameters);
    }

    abstract HttpConnection plainConnection();
    abstract SSLTube getConnectionFlow();

    final CompletableFuture<String> getALPN() {
        assert connected();
        return getConnectionFlow().getALPN();
    }

    final SSLEngine getEngine() { return engine; }

    private static SSLParameters createSSLParameters(HttpClientImpl client,
                                                     String serverName,
                                                     String[] alpn) {
        SSLParameters sslp = client.sslParameters();
        SSLParameters sslParameters = Utils.copySSLParameters(sslp);
        sslParameters.setEndpointIdentificationAlgorithm("HTTPS");
        if (alpn != null) {
            Log.logSSL("AbstractAsyncSSLConnection: Setting application protocols: {0}",
                       Arrays.toString(alpn));
            sslParameters.setApplicationProtocols(alpn);
        } else {
            Log.logSSL("AbstractAsyncSSLConnection: no applications set!");
        }
        if (serverName != null) {
            sslParameters.setServerNames(List.of(new SNIHostName(serverName)));
        }
        return sslParameters;
    }

    private static SSLEngine createEngine(SSLContext context, String serverName, int port,
                                          SSLParameters sslParameters) {
        SSLEngine engine = context.createSSLEngine(serverName, port);
        engine.setUseClientMode(true);
        engine.setSSLParameters(sslParameters);
        return engine;
    }

    @Override
    final boolean isSecure() {
        return true;
    }

    // Support for WebSocket/RawChannelImpl which unfortunately
    // still depends on synchronous read/writes.
    // It should be removed when RawChannelImpl moves to using asynchronous APIs.
    static final class SSLConnectionChannel extends DetachedConnectionChannel {
        final DetachedConnectionChannel delegate;
        final SSLDelegate sslDelegate;
        SSLConnectionChannel(DetachedConnectionChannel delegate, SSLDelegate sslDelegate) {
            this.delegate = delegate;
            this.sslDelegate = sslDelegate;
        }

        SocketChannel channel() {
            return delegate.channel();
        }

        @Override
        ByteBuffer read() throws IOException {
            SSLDelegate.WrapperResult r = sslDelegate.recvData(ByteBuffer.allocate(8192));
            // TODO: check for closure
            int n = r.result.bytesProduced();
            if (n > 0) {
                return r.buf;
            } else if (n == 0) {
                return Utils.EMPTY_BYTEBUFFER;
            } else {
                return null;
            }
        }
        @Override
        long write(ByteBuffer[] buffers, int start, int number) throws IOException {
            long l = SSLDelegate.countBytes(buffers, start, number);
            SSLDelegate.WrapperResult r = sslDelegate.sendData(buffers, start, number);
            if (r.result.getStatus() == SSLEngineResult.Status.CLOSED) {
                if (l > 0) {
                    throw new IOException("SSLHttpConnection closed");
                }
            }
            return l;
        }
        @Override
        public void shutdownInput() throws IOException {
            delegate.shutdownInput();
        }
        @Override
        public void shutdownOutput() throws IOException {
            delegate.shutdownOutput();
        }
        @Override
        public void close() {
            delegate.close();
        }
    }

    // Support for WebSocket/RawChannelImpl which unfortunately
    // still depends on synchronous read/writes.
    // It should be removed when RawChannelImpl moves to using asynchronous APIs.
    @Override
    DetachedConnectionChannel detachChannel() {
        assert client() != null;
        DetachedConnectionChannel detachedChannel = plainConnection().detachChannel();
        SSLDelegate sslDelegate = new SSLDelegate(engine,
                                                  detachedChannel.channel());
        return new SSLConnectionChannel(detachedChannel, sslDelegate);
    }

}