/*

 * Copyright (c) 2015, 2017, 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.incubator.http;

import javax.net.ssl.SSLParameters;

import java.io.Closeable;

import java.io.IOException;

import java.net.InetSocketAddress;

import java.nio.ByteBuffer;

import java.nio.channels.SocketChannel;

import java.util.concurrent.CompletableFuture;

import jdk.incubator.http.internal.common.ByteBufferReference;

/**

 * Wraps socket channel layer and takes care of SSL also.

 *

 * Subtypes are:

 *      PlainHttpConnection: regular direct TCP connection to server

 *      PlainProxyConnection: plain text proxy connection

 *      PlainTunnelingConnection: opens plain text (CONNECT) tunnel to server

 *      SSLConnection: TLS channel direct to server

 *      SSLTunnelConnection: TLS channel via (CONNECT) proxy tunnel

 */

abstract class HttpConnection implements Closeable {

    enum Mode {

        BLOCKING,

        NON_BLOCKING,

        ASYNC

    }

    protected Mode mode;

    // address we are connected to. Could be a server or a proxy

    final InetSocketAddress address;

    final HttpClientImpl client;

    HttpConnection(InetSocketAddress address, HttpClientImpl client) {

        this.address = address;

        this.client = client;

    }

    /**

     * Public API to this class. addr is the ultimate destination. Any proxies

     * etc are figured out from the request. Returns an instance of one of the

     * following

     *      PlainHttpConnection

     *      PlainTunnelingConnection

     *      SSLConnection

     *      SSLTunnelConnection

     *

     * When object returned, connect() or connectAsync() must be called, which

     * when it returns/completes, the connection is usable for requests.

     */

    public static HttpConnection getConnection(

            InetSocketAddress addr, HttpClientImpl client, HttpRequestImpl request)

    {

        return getConnectionImpl(addr, client, request, false);

    }

    /**

     * Called specifically to get an async connection for HTTP/2 over SSL.

     */

    public static HttpConnection getConnection(InetSocketAddress addr,

        HttpClientImpl client, HttpRequestImpl request, boolean isHttp2) {

        return getConnectionImpl(addr, client, request, isHttp2);

    }

    public abstract void connect() throws IOException, InterruptedException;

    public abstract CompletableFuture<Void> connectAsync();

    /**

     * Returns whether this connection is connected to its destination

     */

    abstract boolean connected();

    abstract boolean isSecure();

    abstract boolean isProxied();

    /**

     * Completes when the first byte of the response is available to be read.

     */

    abstract CompletableFuture<Void> whenReceivingResponse();

    final boolean isOpen() {

        return channel().isOpen();

    }

    /* Returns either a plain HTTP connection or a plain tunnelling connection

     * for proxied WebSocket */

    private static HttpConnection getPlainConnection(InetSocketAddress addr,

                                                     InetSocketAddress proxy,

                                                     HttpRequestImpl request,

                                                     HttpClientImpl client) {

        if (request.isWebSocket() && proxy != null) {

            return new PlainTunnelingConnection(addr, proxy, client);

        } else {

            if (proxy == null) {

                return new PlainHttpConnection(addr, client);

            } else {

                return new PlainProxyConnection(proxy, client);

            }

        }

    }

    private static HttpConnection getSSLConnection(InetSocketAddress addr,

            InetSocketAddress proxy, HttpRequestImpl request,

            String[] alpn, boolean isHttp2, HttpClientImpl client)

    {

        if (proxy != null) {

            if (!isHttp2) {

                return new SSLTunnelConnection(addr, client, proxy);

            } else {

                return new AsyncSSLTunnelConnection(addr, client, alpn, proxy);

            }

        } else if (!isHttp2) {

            return new SSLConnection(addr, client, alpn);

        } else {

            return new AsyncSSLConnection(addr, client, alpn);

        }

    }

    /**

     * Main factory method.   Gets a HttpConnection, either cached or new if

     * none available.

     */

    private static HttpConnection getConnectionImpl(InetSocketAddress addr,

            HttpClientImpl client,

            HttpRequestImpl request, boolean isHttp2)

    {

        HttpConnection c = null;

        InetSocketAddress proxy = request.proxy(client);

        if (proxy != null && proxy.isUnresolved()) {

            // The default proxy selector may select a proxy whose

            // address is unresolved. We must resolve the address

            // before using it to connect.

            proxy = new InetSocketAddress(proxy.getHostString(), proxy.getPort());

        }

        boolean secure = request.secure();

        ConnectionPool pool = client.connectionPool();

        String[] alpn =  null;

        if (secure && isHttp2) {

            alpn = new String[2];

            alpn[0] = "h2";

            alpn[1] = "http/1.1";

        }

        if (!secure) {

            c = pool.getConnection(false, addr, proxy);

            if (c != null) {

                return c;

            } else {

                return getPlainConnection(addr, proxy, request, client);

            }

        } else {

            if (!isHttp2) { // if http2 we don't cache connections

                c = pool.getConnection(true, addr, proxy);

            }

            if (c != null) {

                return c;

            } else {

                return getSSLConnection(addr, proxy, request, alpn, isHttp2, client);

            }

        }

    }

    void returnToCache(HttpHeaders hdrs) {

        if (hdrs == null) {

            // the connection was closed by server

            close();

            return;

        }

        if (!isOpen()) {

            return;

        }

        ConnectionPool pool = client.connectionPool();

        boolean keepAlive = hdrs.firstValue("Connection")

                .map((s) -> !s.equalsIgnoreCase("close"))

                .orElse(true);

        if (keepAlive) {

            pool.returnToPool(this);

        } else {

            close();

        }

    }

    /**

     * Also check that the number of bytes written is what was expected. This

     * could be different if the buffer is user-supplied and its internal

     * pointers were manipulated in a race condition.

     */

    final void checkWrite(long expected, ByteBuffer buffer) throws IOException {

        long written = write(buffer);

        if (written != expected) {

            throw new IOException("incorrect number of bytes written");

        }

    }

    final void checkWrite(long expected,

                          ByteBuffer[] buffers,

                          int start,

                          int length)

        throws IOException

    {

        long written = write(buffers, start, length);

        if (written != expected) {

            throw new IOException("incorrect number of bytes written");

        }

    }

    abstract SocketChannel channel();

    final InetSocketAddress address() {

        return address;

    }

    synchronized void configureMode(Mode mode) throws IOException {

        this.mode = mode;

        if (mode == Mode.BLOCKING) {

            channel().configureBlocking(true);

        } else {

            channel().configureBlocking(false);

        }

    }

    synchronized Mode getMode() {

        return mode;

    }

    abstract ConnectionPool.CacheKey cacheKey();

    // overridden in SSL only

    SSLParameters sslParameters() {

        return null;

    }

    // Methods to be implemented for Plain TCP and SSL

    abstract long write(ByteBuffer[] buffers, int start, int number)

        throws IOException;

    abstract long write(ByteBuffer buffer) throws IOException;

    // Methods to be implemented for Plain TCP (async mode) and AsyncSSL

    /**

     * In {@linkplain Mode#ASYNC async mode}, this method puts buffers at the

     * end of the send queue; Otherwise, it is equivalent to {@link

     * #write(ByteBuffer[], int, int) write(buffers, 0, buffers.length)}.

     * When in async mode, calling this method should later be followed by

     * subsequent flushAsync invocation.

     * That allows multiple threads to put buffers into the queue while some other

     * thread is writing.

     */

    abstract void writeAsync(ByteBufferReference[] buffers) throws IOException;

    /**

     * In {@linkplain Mode#ASYNC async mode}, this method may put

     * buffers at the beginning of send queue, breaking frames sequence and

     * allowing to write these buffers before other buffers in the queue;

     * Otherwise, it is equivalent to {@link

     * #write(ByteBuffer[], int, int) write(buffers, 0, buffers.length)}.

     * When in async mode, calling this method should later be followed by

     * subsequent flushAsync invocation.

     * That allows multiple threads to put buffers into the queue while some other

     * thread is writing.

     */

    abstract void writeAsyncUnordered(ByteBufferReference[] buffers) throws IOException;

    /**

     * This method should be called after  any writeAsync/writeAsyncUnordered

     * invocation.

     * If there is a race to flushAsync from several threads one thread

     * (race winner) capture flush operation and write the whole queue content.

     * Other threads (race losers) exits from the method (not blocking)

     * and continue execution.

     */

    abstract void flushAsync() throws IOException;

    /**

     * Closes this connection, by returning the socket to its connection pool.

     */

    @Override

    public abstract void close();

    abstract void shutdownInput() throws IOException;

    abstract void shutdownOutput() throws IOException;

    /**

     * Puts position to limit and limit to capacity so we can resume reading

     * into this buffer, but if required > 0 then limit may be reduced so that

     * no more than required bytes are read next time.

     */

    static void resumeChannelRead(ByteBuffer buf, int required) {

        int limit = buf.limit();

        buf.position(limit);

        int capacity = buf.capacity() - limit;

        if (required > 0 && required < capacity) {

            buf.limit(limit + required);

        } else {

            buf.limit(buf.capacity());

        }

    }

    final ByteBuffer read() throws IOException {

        ByteBuffer b = readImpl();

        return b;

    }

    /*

     * Returns a ByteBuffer with the data available at the moment, or null if

     * reached EOF.

     */

    protected abstract ByteBuffer readImpl() throws IOException;

    @Override

    public String toString() {

        return "HttpConnection: " + channel().toString();

    }

}