/*

 * 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.net.Authenticator;

import java.net.CookieManager;

import java.net.ProxySelector;

import java.net.URI;

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

import java.nio.ByteBuffer;

import java.nio.channels.SelectableChannel;

import java.nio.channels.SelectionKey;

import static java.nio.channels.SelectionKey.OP_CONNECT;

import static java.nio.channels.SelectionKey.OP_READ;

import static java.nio.channels.SelectionKey.OP_WRITE;

import java.nio.channels.Selector;

import java.util.LinkedList;

import java.util.List;

import java.util.Set;

import java.util.concurrent.ExecutorService;

import java.security.NoSuchAlgorithmException;

import java.util.ListIterator;

import java.util.Optional;

import java.util.concurrent.Executors;

import java.util.concurrent.ThreadFactory;

import javax.net.ssl.SSLContext;

import javax.net.ssl.SSLParameters;

/**

 * 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 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 static final ThreadFactory defaultFactory = Executors.defaultThreadFactory();

    private final LinkedList<TimeoutEvent> timeouts;

    //@Override

    void debugPrint() {

        selmgr.debugPrint();

        client2.debugPrint();

    }

    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;

        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);

        selmgr.setName("HttpSelector");

        filters = new FilterFactory();

        initFilters();

    }

    private void start() {

        selmgr.start();

    }

    /**

     * 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);

    }

    Http2ClientImpl client2() {

        return client2;

    }

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

    @Override

    public synchronized ByteBuffer getBuffer() {

        if (freelist.isEmpty()) {

            return ByteBuffer.allocate(BUFSIZE);

        }

        return freelist.removeFirst();

    }

    @Override

    public synchronized void returnBuffer(ByteBuffer buffer) {

        buffer.clear();

        freelist.add(buffer);

    }

    // Main loop for this client's selector

    class SelectorManager extends Thread {

        final Selector selector;

        boolean closed;

        final List<AsyncEvent> readyList;

        final List<AsyncEvent> registrations;

        List<AsyncEvent> debugList;

        SelectorManager() throws IOException {

            readyList = new LinkedList<>();

            registrations = new LinkedList<>();

            debugList = new LinkedList<>();

            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();

        }

        void wakeupSelector() {

            selector.wakeup();

        }

        synchronized void shutdown() {

            closed = true;

            try {

                selector.close();

            } catch (IOException e) {}

        }

        private List<AsyncEvent> copy(List<AsyncEvent> list) {

            LinkedList<AsyncEvent> c = new LinkedList<>();

            for (AsyncEvent e : list) {

                c.add(e);

            }

            return c;

        }

        synchronized void debugPrint() {

            System.err.println("Selecting on:");

            for (AsyncEvent e : debugList) {

                System.err.println(opvals(e.interestOps()));

            }

        }

        String opvals(int i) {

            StringBuilder sb = new StringBuilder();

            if ((i & OP_READ) != 0)

                sb.append("OP_READ ");

            if ((i & OP_CONNECT) != 0)

                sb.append("OP_CONNECT ");

            if ((i & OP_WRITE) != 0)

                sb.append("OP_WRITE ");

            return sb.toString();

        }

        @Override

        public void run() {

            try {

                while (true) {

                    synchronized (this) {

                        debugList = copy(registrations);

                        for (AsyncEvent exchange : registrations) {

                            SelectableChannel c = exchange.channel();

                            try {

                                c.configureBlocking(false);

                                c.register(selector,

                                           exchange.interestOps(),

                                           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();

                    int n = selector.select(timeval);

                    if (n == 0) {

                        signalTimeouts(now);

                        continue;

                    }

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

                    for (SelectionKey key : keys) {

                        if (key.isReadable() || key.isConnectable() || key.isWritable()) {

                            key.cancel();

                            AsyncEvent exchange = (AsyncEvent) key.attachment();

                            readyList.add(exchange);

                        }

                    }

                    selector.selectNow(); // complete cancellation

                    selector.selectedKeys().clear();

                    for (AsyncEvent exchange : readyList) {

                        if (exchange instanceof AsyncEvent.Blocking) {

                            exchange.channel().configureBlocking(true);

                        } else {

                            assert exchange instanceof AsyncEvent.NonBlocking;

                        }

                        executor.synchronize();

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

                    }

                    readyList.clear();

                }

            } catch (Throwable e) {

                if (!closed) {

                    System.err.println("HttpClientImpl terminating on error");

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

                    String err = Utils.stackTrace(e);

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

                }

            }

        }

        void handleEvent(AsyncEvent e) {

            if (closed) {

                e.abort();

            } else {

                e.handle();

            }

        }

    }

    /**

     * 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);

    }

    //void setHttp2NotSupported(String host) {

        //http2NotSupported.put(host, false);

    //}

    final void initFilters() {

        addFilter(AuthenticationFilter.class);

        addFilter(RedirectFilter.class);

    }

    final 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) {

        long elapse = event.timevalMillis();

        ListIterator<TimeoutEvent> iter = timeouts.listIterator();

        long listval = 0;

        event.delta = event.timeval; // in case list empty

        TimeoutEvent next;

        while (iter.hasNext()) {

            next = iter.next();

            listval += next.delta;

            if (elapse < listval) {

                listval -= next.delta;

                event.delta = elapse - listval;

                next.delta -= event.delta;

                iter.previous();

                break;

            } else if (!iter.hasNext()) {

                event.delta = event.timeval - listval ;

            }

        }

        iter.add(event);

        //debugPrintList("register");

        selmgr.wakeupSelector();

    }

    void debugPrintList(String s) {

        System.err.printf("%s: {", s);

        for (TimeoutEvent e : timeouts) {

            System.err.printf("(%d,%d) ", e.delta, e.timeval);

        }

        System.err.println("}");

    }

    synchronized void signalTimeouts(long then) {

        if (timeouts.isEmpty()) {

            return;

        }

        long now = System.currentTimeMillis();

        long duration = now - then;

        ListIterator<TimeoutEvent> iter = timeouts.listIterator();

        TimeoutEvent event = iter.next();

        long delta = event.delta;

        if (duration < delta) {

            event.delta -= duration;

            return;

        }

        event.handle();

        iter.remove();

        while (iter.hasNext()) {

            event = iter.next();

            if (event.delta == 0) {

                event.handle();

                iter.remove();

            } else {

                event.delta += delta;

                break;

            }

        }

        //debugPrintList("signalTimeouts");

    }

    synchronized void cancelTimer(TimeoutEvent event) {

        ListIterator<TimeoutEvent> iter = timeouts.listIterator();

        while (iter.hasNext()) {

            TimeoutEvent ev = iter.next();

            if (event == ev) {

                if (iter.hasNext()) {

                    // adjust

                    TimeoutEvent next = iter.next();

                    next.delta += ev.delta;

                    iter.previous();

                }

                iter.remove();

            }

        }

    }

    // used for the connection window

    int getReceiveBufferSize() {

        return Utils.getIntegerNetProperty(

                "sun.net.httpclient.connectionWindowSize", 256 * 1024

        );

    }

    // returns 0 meaning block forever, or a number of millis to block for

    synchronized long getTimeoutValue() {

        if (timeouts.isEmpty()) {

            return 0;

        } else {

            return timeouts.get(0).delta;

        }

    }

}