/*

 * Copyright (c) 2015, 2016, 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

 */

package java.net.http;

import java.io.IOException;

import java.nio.ByteBuffer;

import java.nio.channels.SocketChannel;

import java.util.Arrays;

import java.util.concurrent.locks.Lock;

import java.util.concurrent.locks.ReentrantLock;

import javax.net.ssl.SSLEngineResult.HandshakeStatus;

import javax.net.ssl.SSLEngineResult.Status;

import javax.net.ssl.*;

import static javax.net.ssl.SSLEngineResult.HandshakeStatus.*;

/**

 * Implements the mechanics of SSL by managing an SSLEngine object.

 * One of these is associated with each SSLConnection.

 */

class SSLDelegate {

    final SSLEngine engine;

    final EngineWrapper wrapper;

    final Lock handshaking = new ReentrantLock();

    final SSLParameters sslParameters;

    final SocketChannel chan;

    final HttpClientImpl client;

    // alpn[] may be null

    SSLDelegate(SocketChannel chan, HttpClientImpl client, String[] alpn)

        throws IOException

    {

        SSLContext context = client.sslContext();

        engine = context.createSSLEngine();

        engine.setUseClientMode(true);

        SSLParameters sslp = client.sslParameters().orElse(null);

        if (sslp == null) {

            sslp = context.getSupportedSSLParameters();

        }

        sslParameters = Utils.copySSLParameters(sslp);

        if (alpn != null) {

            sslParameters.setApplicationProtocols(alpn);

            Log.logSSL("Setting application protocols: " + Arrays.toString(alpn));

        } else {

            Log.logSSL("No application protocols proposed");

        }

        engine.setSSLParameters(sslParameters);

        wrapper = new EngineWrapper(chan, engine);

        this.chan = chan;

        this.client = client;

    }

    SSLParameters getSSLParameters() {

        return sslParameters;

    }

    private static long countBytes(ByteBuffer[] buffers, int start, int number) {

        long c = 0;

        for (int i=0; i<number; i++) {

            c+= buffers[start+i].remaining();

        }

        return c;

    }

    static class WrapperResult {

        static WrapperResult createOK() {

            WrapperResult r = new WrapperResult();

            r.buf = null;

            r.result = new SSLEngineResult(Status.OK, NOT_HANDSHAKING, 0, 0);

            return r;

        }

        SSLEngineResult result;

        /* if passed in buffer was not big enough then the a reallocated buffer

         * is returned here  */

        ByteBuffer buf;

    }

    int app_buf_size;

    int packet_buf_size;

    enum BufType {

        PACKET,

        APPLICATION

    };

    ByteBuffer allocate (BufType type) {

        return allocate (type, -1);

    }

    // TODO: Use buffer pool for this

    ByteBuffer allocate (BufType type, int len) {

        assert engine != null;

        synchronized (this) {

            int size;

            if (type == BufType.PACKET) {

                if (packet_buf_size == 0) {

                    SSLSession sess = engine.getSession();

                    packet_buf_size = sess.getPacketBufferSize();

                }

                if (len > packet_buf_size) {

                    packet_buf_size = len;

                }

                size = packet_buf_size;

            } else {

                if (app_buf_size == 0) {

                    SSLSession sess = engine.getSession();

                    app_buf_size = sess.getApplicationBufferSize();

                }

                if (len > app_buf_size) {

                    app_buf_size = len;

                }

                size = app_buf_size;

            }

            return ByteBuffer.allocate (size);

        }

    }

    /* reallocates the buffer by :-

     * 1. creating a new buffer double the size of the old one

     * 2. putting the contents of the old buffer into the new one

     * 3. set xx_buf_size to the new size if it was smaller than new size

     *

     * flip is set to true if the old buffer needs to be flipped

     * before it is copied.

     */

    private ByteBuffer realloc (ByteBuffer b, boolean flip, BufType type) {

        synchronized (this) {

            int nsize = 2 * b.capacity();

            ByteBuffer n = allocate (type, nsize);

            if (flip) {

                b.flip();

            }

            n.put(b);

            b = n;

        }

        return b;

    }

    /**

     * This is a thin wrapper over SSLEngine and the SocketChannel, which

     * guarantees the ordering of wraps/unwraps with respect to the underlying

     * channel read/writes. It handles the UNDER/OVERFLOW status codes

     * It does not handle the handshaking status codes, or the CLOSED status code

     * though once the engine is closed, any attempt to read/write to it

     * will get an exception.  The overall result is returned.

     * It functions synchronously/blocking

     */

    class EngineWrapper {

        SocketChannel chan;

        SSLEngine engine;

        Object wrapLock, unwrapLock;

        ByteBuffer unwrap_src, wrap_dst;

        boolean closed = false;

        int u_remaining; // the number of bytes left in unwrap_src after an unwrap()

        EngineWrapper (SocketChannel chan, SSLEngine engine) throws IOException {

            this.chan = chan;

            this.engine = engine;

            wrapLock = new Object();

            unwrapLock = new Object();

            unwrap_src = allocate(BufType.PACKET);

            wrap_dst = allocate(BufType.PACKET);

        }

        void close () throws IOException {

        }

        WrapperResult wrapAndSend(ByteBuffer src, boolean ignoreClose)

            throws IOException

        {

            ByteBuffer[] buffers = new ByteBuffer[1];

            buffers[0] = src;

            return wrapAndSend(buffers, 0, 1, ignoreClose);

        }

        /* try to wrap and send the data in src. Handles OVERFLOW.

         * Might block if there is an outbound blockage or if another

         * thread is calling wrap(). Also, might not send any data

         * if an unwrap is needed.

         */

        WrapperResult wrapAndSend(ByteBuffer[] src,

                                  int offset,

                                  int len,

                                  boolean ignoreClose)

            throws IOException

        {

            if (closed && !ignoreClose) {

                throw new IOException ("Engine is closed");

            }

            Status status;

            WrapperResult r = new WrapperResult();

            synchronized (wrapLock) {

                wrap_dst.clear();

                do {

                    r.result = engine.wrap (src, offset, len, wrap_dst);

                    status = r.result.getStatus();

                    if (status == Status.BUFFER_OVERFLOW) {

                        wrap_dst = realloc (wrap_dst, true, BufType.PACKET);

                    }

                } while (status == Status.BUFFER_OVERFLOW);

                if (status == Status.CLOSED && !ignoreClose) {

                    closed = true;

                    return r;

                }

                if (r.result.bytesProduced() > 0) {

                    wrap_dst.flip();

                    int l = wrap_dst.remaining();

                    assert l == r.result.bytesProduced();

                    while (l>0) {

                        l -= chan.write (wrap_dst);

                    }

                }

            }

            return r;

        }

        /* block until a complete message is available and return it

         * in dst, together with the Result. dst may have been re-allocated

         * so caller should check the returned value in Result

         * If handshaking is in progress then, possibly no data is returned

         */

        WrapperResult recvAndUnwrap(ByteBuffer dst) throws IOException {

            Status status;

            WrapperResult r = new WrapperResult();

            r.buf = dst;

            if (closed) {

                throw new IOException ("Engine is closed");

            }

            boolean needData;

            if (u_remaining > 0) {

                unwrap_src.compact();

                unwrap_src.flip();

                needData = false;

            } else {

                unwrap_src.clear();

                needData = true;

            }

            synchronized (unwrapLock) {

                int x;

                do {

                    if (needData) {

                        do {

                            x = chan.read (unwrap_src);

                        } while (x == 0);

                        if (x == -1) {

                            throw new IOException ("connection closed for reading");

                        }

                        unwrap_src.flip();

                    }

                    r.result = engine.unwrap (unwrap_src, r.buf);

                    status = r.result.getStatus();

                    if (status == Status.BUFFER_UNDERFLOW) {

                        if (unwrap_src.limit() == unwrap_src.capacity()) {

                            /* buffer not big enough */

                            unwrap_src = realloc (

                                unwrap_src, false, BufType.PACKET

                            );

                        } else {

                            /* Buffer not full, just need to read more

                             * data off the channel. Reset pointers

                             * for reading off SocketChannel

                             */

                            unwrap_src.position (unwrap_src.limit());

                            unwrap_src.limit (unwrap_src.capacity());

                        }

                        needData = true;

                    } else if (status == Status.BUFFER_OVERFLOW) {

                        r.buf = realloc (r.buf, true, BufType.APPLICATION);

                        needData = false;

                    } else if (status == Status.CLOSED) {

                        closed = true;

                        r.buf.flip();

                        return r;

                    }

                } while (status != Status.OK);

            }

            u_remaining = unwrap_src.remaining();

            return r;

        }

    }

    WrapperResult sendData (ByteBuffer src) throws IOException {

        ByteBuffer[] buffers = new ByteBuffer[1];

        buffers[0] = src;

        return sendData(buffers, 0, 1);

    }

    /**

     * send the data in the given ByteBuffer. If a handshake is needed

     * then this is handled within this method. When this call returns,

     * all of the given user data has been sent and any handshake has been

     * completed. Caller should check if engine has been closed.

     */

    WrapperResult sendData (ByteBuffer[] src, int offset, int len) throws IOException {

        WrapperResult r = WrapperResult.createOK();

        while (countBytes(src, offset, len) > 0) {

            r = wrapper.wrapAndSend(src, offset, len, false);

            Status status = r.result.getStatus();

            if (status == Status.CLOSED) {

                doClosure ();

                return r;

            }

            HandshakeStatus hs_status = r.result.getHandshakeStatus();

            if (hs_status != HandshakeStatus.FINISHED &&

                hs_status != HandshakeStatus.NOT_HANDSHAKING)

            {

                doHandshake(hs_status);

            }

        }

        return r;

    }

    /**

     * read data thru the engine into the given ByteBuffer. If the

     * given buffer was not large enough, a new one is allocated

     * and returned. This call handles handshaking automatically.

     * Caller should check if engine has been closed.

     */

    WrapperResult recvData (ByteBuffer dst) throws IOException {

        /* we wait until some user data arrives */

        int mark = dst.position();

        WrapperResult r = null;

        assert dst.position() == 0;

        while (dst.position() == 0) {

            r = wrapper.recvAndUnwrap (dst);

            dst = (r.buf != dst) ? r.buf: dst;

            Status status = r.result.getStatus();

            if (status == Status.CLOSED) {

                doClosure ();

                return r;

            }

            HandshakeStatus hs_status = r.result.getHandshakeStatus();

            if (hs_status != HandshakeStatus.FINISHED &&

                hs_status != HandshakeStatus.NOT_HANDSHAKING)

            {

                doHandshake (hs_status);

            }

        }

        Utils.flipToMark(dst, mark);

        return r;

    }

    /* we've received a close notify. Need to call wrap to send

     * the response

     */

    void doClosure () throws IOException {

        try {

            handshaking.lock();

            ByteBuffer tmp = allocate(BufType.APPLICATION);

            WrapperResult r;

            do {

                tmp.clear();

                tmp.flip ();

                r = wrapper.wrapAndSend(tmp, true);

            } while (r.result.getStatus() != Status.CLOSED);

        } finally {

            handshaking.unlock();

        }

    }

    /* do the (complete) handshake after acquiring the handshake lock.

     * If two threads call this at the same time, then we depend

     * on the wrapper methods being idempotent. eg. if wrapAndSend()

     * is called with no data to send then there must be no problem

     */

    @SuppressWarnings("fallthrough")

    void doHandshake (HandshakeStatus hs_status) throws IOException {

        boolean wasBlocking = false;

        try {

            wasBlocking = chan.isBlocking();

            handshaking.lock();

            chan.configureBlocking(true);

            ByteBuffer tmp = allocate(BufType.APPLICATION);

            while (hs_status != HandshakeStatus.FINISHED &&

                   hs_status != HandshakeStatus.NOT_HANDSHAKING)

            {

                WrapperResult r = null;

                switch (hs_status) {

                    case NEED_TASK:

                        Runnable task;

                        while ((task = engine.getDelegatedTask()) != null) {

                            /* run in current thread, because we are already

                             * running an external Executor

                             */

                            task.run();

                        }

                        /* fall thru - call wrap again */

                    case NEED_WRAP:

                        tmp.clear();

                        tmp.flip();

                        r = wrapper.wrapAndSend(tmp, false);

                        break;

                    case NEED_UNWRAP:

                        tmp.clear();

                        r = wrapper.recvAndUnwrap (tmp);

                        if (r.buf != tmp) {

                            tmp = r.buf;

                        }

                        assert tmp.position() == 0;

                        break;

                }

                hs_status = r.result.getHandshakeStatus();

            }

            Log.logSSL(getSessionInfo());

            if (!wasBlocking) {

                chan.configureBlocking(false);

            }

        } finally {

            handshaking.unlock();

        }

    }

    static void printParams(SSLParameters p) {

        System.out.println("SSLParameters:");

        if (p == null) {

            System.out.println("Null params");

            return;

        }

        for (String cipher : p.getCipherSuites()) {

                System.out.printf("cipher: %s\n", cipher);

        }

        for (String approto : p.getApplicationProtocols()) {

                System.out.printf("application protocol: %s\n", approto);

        }

        for (String protocol : p.getProtocols()) {

                System.out.printf("protocol: %s\n", protocol);

        }

        if (p.getServerNames() != null)

        for (SNIServerName sname : p.getServerNames()) {

                System.out.printf("server name: %s\n", sname.toString());

        }

    }

    String getSessionInfo() {

        StringBuilder sb = new StringBuilder();

        String application = engine.getApplicationProtocol();

        SSLSession sess = engine.getSession();

        String cipher = sess.getCipherSuite();

        String protocol = sess.getProtocol();

        sb.append("Handshake complete alpn: ")

                .append(application)

                .append(", Cipher: ")

                .append(cipher)

                .append(", Protocol: ")

                .append(protocol);

        return sb.toString();

    }

}