/*

 * 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 javax.net.ssl.SSLContext;

import javax.net.ssl.SSLParameters;

import java.io.IOException;

import java.net.Authenticator;

import java.net.CookieManager;

import java.net.ProxySelector;

import java.net.URI;

import java.nio.ByteBuffer;

import java.nio.channels.ClosedChannelException;

import java.nio.channels.SelectableChannel;

import java.nio.channels.SelectionKey;

import java.nio.channels.Selector;

import java.nio.channels.SocketChannel;

import java.security.NoSuchAlgorithmException;

import java.util.ArrayList;

import java.util.Iterator;

import java.util.LinkedList;

import java.util.List;

import java.util.ListIterator;

import java.util.Optional;

import java.util.Set;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.ThreadFactory;

import java.util.stream.Stream;

import static java.net.http.Utils.BUFSIZE;

/**

 * Client implementation. Contains all configuration information and also

 * the selector manager thread which allows async events to be registered

 * and delivered when they occur. See AsyncEvent.

 */

class HttpClientImpl extends HttpClient implements BufferHandler {

    private static final ThreadFactory defaultFactory =

            (r -> new Thread(null, r, "HttpClient_worker", 0, true));

    private final CookieManager cookieManager;

    private final Redirect followRedirects;

    private final ProxySelector proxySelector;

    private final Authenticator authenticator;

    private final Version version;

    private boolean pipelining = false;

    private final ConnectionPool connections;

    private final ExecutorWrapper executor;

    // Security parameters

    private final SSLContext sslContext;

    private final SSLParameters sslParams;

    private final SelectorManager selmgr;

    private final FilterFactory filters;

    private final Http2ClientImpl client2;

    private final LinkedList<TimeoutEvent> timeouts;

    public static HttpClientImpl create(HttpClientBuilderImpl builder) {

        HttpClientImpl impl = new HttpClientImpl(builder);

        impl.start();

        return impl;

    }

    private HttpClientImpl(HttpClientBuilderImpl builder) {

        if (builder.sslContext == null) {

            try {

                sslContext = SSLContext.getDefault();

            } catch (NoSuchAlgorithmException ex) {

                throw new InternalError(ex);

            }

        } else {

            sslContext = builder.sslContext;

        }

        ExecutorService ex = builder.executor;

        if (ex == null) {

            ex = Executors.newCachedThreadPool((r) -> {

                Thread t = defaultFactory.newThread(r);

                t.setDaemon(true);

                return t;

            });

        } else {

            ex = builder.executor;

        }

        client2 = new Http2ClientImpl(this);

        executor = ExecutorWrapper.wrap(ex);

        cookieManager = builder.cookieManager;

        followRedirects = builder.followRedirects == null ?

                Redirect.NEVER : builder.followRedirects;

        this.proxySelector = builder.proxy;

        authenticator = builder.authenticator;

        version = builder.version;

        if (builder.sslParams == null)

            sslParams = getDefaultParams(sslContext);

        else

            sslParams = builder.sslParams;

        connections = new ConnectionPool();

        connections.start();

        timeouts = new LinkedList<>();

        try {

            selmgr = new SelectorManager();

        } catch (IOException e) {

            // unlikely

            throw new InternalError(e);

        }

        selmgr.setDaemon(true);

        filters = new FilterFactory();

        initFilters();

    }

    private void start() {

        selmgr.start();

    }

    private static SSLParameters getDefaultParams(SSLContext ctx) {

        SSLParameters params = ctx.getSupportedSSLParameters();

        params.setProtocols(new String[]{"TLSv1.2"});

        return params;

    }

    /**

     * Wait for activity on given exchange (assuming blocking = false).

     * It's a no-op if blocking = true. In particular, the following occurs

     * in the SelectorManager thread.

     *

     *  1) mark the connection non-blocking

     *  2) add to selector

     *  3) If selector fires for this exchange then

     *  4)   - mark connection as blocking

     *  5)   - call AsyncEvent.handle()

     *

     * If exchange needs to block again, then call registerEvent() again

     */

    void registerEvent(AsyncEvent exchange) throws IOException {

        selmgr.register(exchange);

    }

    /**

     * Only used from RawChannel to disconnect the channel from

     * the selector

     */

    void cancelRegistration(SocketChannel s) {

        selmgr.cancel(s);

    }

    Http2ClientImpl client2() {

        return client2;

    }

    /**

     * We keep one size of buffer on free list. That size may increase

     * depending on demand. If that happens we dispose of free buffers

     * that are smaller than new size.

     */

    private final LinkedList<ByteBuffer> freelist = new LinkedList<>();

    int currentSize = BUFSIZE;

    @Override

    public synchronized ByteBuffer getBuffer(int size) {

        ByteBuffer buf;

        if (size == -1)

            size = currentSize;

        if (size > currentSize)

            currentSize = size;

        while (!freelist.isEmpty()) {

            buf = freelist.removeFirst();

            if (buf.capacity() < currentSize)

                continue;

            buf.clear();

            return buf;

        }

        return ByteBuffer.allocate(size);

    }

    @Override

    public synchronized void returnBuffer(ByteBuffer buffer) {

        freelist.add(buffer);

    }

    @Override

    public synchronized void setMinBufferSize(int n) {

        currentSize = Math.max(n, currentSize);

    }

    // Main loop for this client's selector

    private final class SelectorManager extends Thread {

        private final Selector selector;

        private volatile boolean closed;

        private final List<AsyncEvent> readyList;

        private final List<AsyncEvent> registrations;

        SelectorManager() throws IOException {

            super(null, null, "SelectorManager", 0, false);

            readyList = new ArrayList<>();

            registrations = new ArrayList<>();

            selector = Selector.open();

        }

        // This returns immediately. So caller not allowed to send/receive

        // on connection.

        synchronized void register(AsyncEvent e) throws IOException {

            registrations.add(e);

            selector.wakeup();

        }

        synchronized void cancel(SocketChannel e) {

            SelectionKey key = e.keyFor(selector);

            if (key != null)

                key.cancel();

            selector.wakeup();

        }

        void wakeupSelector() {

            selector.wakeup();

        }

        synchronized void shutdown() {

            closed = true;

            try {

                selector.close();

            } catch (IOException ignored) { }

        }

        @Override

        public void run() {

            try {

                while (!Thread.currentThread().isInterrupted()) {

                    synchronized (this) {

                        for (AsyncEvent exchange : registrations) {

                            SelectableChannel c = exchange.channel();

                            try {

                                c.configureBlocking(false);

                                SelectionKey key = c.keyFor(selector);

                                SelectorAttachment sa;

                                if (key == null) {

                                    sa = new SelectorAttachment(c, selector);

                                } else {

                                    sa = (SelectorAttachment) key.attachment();

                                }

                                sa.register(exchange);

                            } catch (IOException e) {

                                Log.logError("HttpClientImpl: " + e);

                                c.close();

                                // let the exchange deal with it

                                handleEvent(exchange);

                            }

                        }

                        registrations.clear();

                    }

                    long timeval = getTimeoutValue();

                    long now = System.currentTimeMillis();

                    //debugPrint(selector);

                    int n = selector.select(timeval);

                    if (n == 0) {

                        signalTimeouts(now);

                        continue;

                    }

                    Set<SelectionKey> keys = selector.selectedKeys();

                    for (SelectionKey key : keys) {

                        SelectorAttachment sa = (SelectorAttachment) key.attachment();

                        int eventsOccurred = key.readyOps();

                        sa.events(eventsOccurred).forEach(readyList::add);

                        sa.resetInterestOps(eventsOccurred);

                    }

                    selector.selectNow(); // complete cancellation

                    selector.selectedKeys().clear();

                    for (AsyncEvent exchange : readyList) {

                        if (exchange.blocking()) {

                            exchange.channel().configureBlocking(true);

                        }

                        executor.synchronize();

                        handleEvent(exchange); // will be delegated to executor

                    }

                    readyList.clear();

                }

            } catch (Throwable e) {

                if (!closed) {

                    // This terminates thread. So, better just print stack trace

                    String err = Utils.stackTrace(e);

                    Log.logError("HttpClientImpl: fatal error: " + err);

                }

            } finally {

                shutdown();

            }

        }

        void debugPrint(Selector selector) {

            System.err.println("Selector: debugprint start");

            Set<SelectionKey> keys = selector.keys();

            for (SelectionKey key : keys) {

                SelectableChannel c = key.channel();

                int ops = key.interestOps();

                System.err.printf("selector chan:%s ops:%d\n", c, ops);

            }

            System.err.println("Selector: debugprint end");

        }

        void handleEvent(AsyncEvent e) {

            if (closed) {

                e.abort();

            } else {

                e.handle();

            }

        }

    }

    /**

     * Tracks multiple user level registrations associated with one NIO

     * registration (SelectionKey). In this implementation, registrations

     * are one-off and when an event is posted the registration is cancelled

     * until explicitly registered again.

     *

     * <p> No external synchronization required as this class is only used

     * by the SelectorManager thread. One of these objects required per

     * connection.

     */

    private static class SelectorAttachment {

        private final SelectableChannel chan;

        private final Selector selector;

        private final ArrayList<AsyncEvent> pending;

        private int interestOps;

        SelectorAttachment(SelectableChannel chan, Selector selector) {

            this.pending = new ArrayList<>();

            this.chan = chan;

            this.selector = selector;

        }

        void register(AsyncEvent e) throws ClosedChannelException {

            int newOps = e.interestOps();

            boolean reRegister = (interestOps & newOps) != newOps;

            interestOps |= newOps;

            pending.add(e);

            if (reRegister) {

                // first time registration happens here also

                chan.register(selector, interestOps, this);

            }

        }

        /**

         * Returns a Stream<AsyncEvents> containing only events that are

         * registered with the given {@code interestOps}.

         */

        Stream<AsyncEvent> events(int interestOps) {

            return pending.stream()

                    .filter(ev -> (ev.interestOps() & interestOps) != 0);

        }

        /**

         * Removes any events with the given {@code interestOps}, and if no

         * events remaining, cancels the associated SelectionKey.

         */

        void resetInterestOps(int interestOps) {

            int newOps = 0;

            Iterator<AsyncEvent> itr = pending.iterator();

            while (itr.hasNext()) {

                AsyncEvent event = itr.next();

                int evops = event.interestOps();

                if (event.repeating()) {

                    newOps |= evops;

                    continue;

                }

                if ((evops & interestOps) != 0) {

                    itr.remove();

                } else {

                    newOps |= evops;

                }

            }

            this.interestOps = newOps;

            SelectionKey key = chan.keyFor(selector);

            if (newOps == 0) {

                key.cancel();

            } else {

                key.interestOps(newOps);

            }

        }

    }

    /**

     * Creates a HttpRequest associated with this group.

     *

     * @throws IllegalStateException

     *         if the group has been stopped

     */

    @Override

    public HttpRequestBuilderImpl request() {

        return new HttpRequestBuilderImpl(this, null);

    }

    /**

     * Creates a HttpRequest associated with this group.

     *

     * @throws IllegalStateException

     *         if the group has been stopped

     */

    @Override

    public HttpRequestBuilderImpl request(URI uri) {

        return new HttpRequestBuilderImpl(this, uri);

    }

    @Override

    public SSLContext sslContext() {

        Utils.checkNetPermission("getSSLContext");

        return sslContext;

    }

    @Override

    public Optional<SSLParameters> sslParameters() {

        return Optional.ofNullable(sslParams);

    }

    @Override

    public Optional<Authenticator> authenticator() {

        return Optional.ofNullable(authenticator);

    }

    @Override

    public ExecutorService executorService() {

        return executor.userExecutor();

    }

    ExecutorWrapper executorWrapper() {

        return executor;

    }

    @Override

    public boolean pipelining() {

        return this.pipelining;

    }

    ConnectionPool connectionPool() {

        return connections;

    }

    @Override

    public Redirect followRedirects() {

        return followRedirects;

    }

    @Override

    public Optional<CookieManager> cookieManager() {

        return Optional.ofNullable(cookieManager);

    }

    @Override

    public Optional<ProxySelector> proxy() {

        return Optional.ofNullable(this.proxySelector);

    }

    @Override

    public Version version() {

        return version;

    }

    //private final HashMap<String, Boolean> http2NotSupported = new HashMap<>();

    boolean getHttp2Allowed() {

        return version.equals(Version.HTTP_2);

    }

    private void initFilters() {

        addFilter(AuthenticationFilter.class);

        addFilter(RedirectFilter.class);

    }

    private void addFilter(Class<? extends HeaderFilter> f) {

        filters.addFilter(f);

    }

    final List<HeaderFilter> filterChain() {

        return filters.getFilterChain();

    }

    // Timer controls. Timers are implemented through timed Selector.select()

    // calls.

    synchronized void registerTimer(TimeoutEvent event) {