/*

 * 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.

 */

import java.io.IOException;

import java.lang.System.Logger.Level;

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.Executor;

import java.util.function.Function;

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

import static jdk.incubator.http.HttpClient.Version.HTTP_1_1;

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

/**

 * Splits request so that headers and body can be sent separately with optional

 * (multiple) responses in between (e.g. 100 Continue). Also request and

 * response always sent/received in different calls.

 *

 * Synchronous and asynchronous versions of each method are provided.

 *

 * Separate implementations of this class exist for HTTP/1.1 and HTTP/2

 *      Http1Exchange   (HTTP/1.1)

 *      Stream          (HTTP/2)

 *

 * These implementation classes are where work is allocated to threads.

 */

abstract class ExchangeImpl<T> {

    static final boolean DEBUG = Utils.DEBUG; // Revisit: temporary dev flag.

    private static final System.Logger DEBUG_LOGGER =

            Utils.getDebugLogger("ExchangeImpl"::toString, DEBUG);

    final Exchange<T> exchange;

    ExchangeImpl(Exchange<T> e) {

        // e == null means a http/2 pushed stream

        this.exchange = e;

    }

    final Exchange<T> getExchange() {

        return exchange;

    }

    /**

     * Returns the {@link HttpConnection} instance to which this exchange is

     * assigned.

     */

    abstract HttpConnection connection();

    /**

     * Initiates a new exchange and assigns it to a connection if one exists

     * already. connection usually null.

     */

    static <U> CompletableFuture<? extends ExchangeImpl<U>>

    get(Exchange<U> exchange, HttpConnection connection)

    {

        if (exchange.version() == HTTP_1_1) {

            DEBUG_LOGGER.log(Level.DEBUG, "get: HTTP/1.1: new Http1Exchange");

            return createHttp1Exchange(exchange, connection);

        } else {

            Http2ClientImpl c2 = exchange.client().client2(); // TODO: improve

            HttpRequestImpl request = exchange.request();

            CompletableFuture<Http2Connection> c2f = c2.getConnectionFor(request);

            DEBUG_LOGGER.log(Level.DEBUG, "get: Trying to get HTTP/2 connection");

            return c2f.handle((h2c, t) -> createExchangeImpl(h2c, t, exchange, connection))

                    .thenCompose(Function.identity());

        }

    }

    private static <U> CompletableFuture<? extends ExchangeImpl<U>>

    createExchangeImpl(Http2Connection c,

                       Throwable t,

                       Exchange<U> exchange,

                       HttpConnection connection)

    {

        DEBUG_LOGGER.log(Level.DEBUG, "handling HTTP/2 connection creation result");

        boolean secure = exchange.request().secure();

        if (t != null) {

            DEBUG_LOGGER.log(Level.DEBUG,

                             "handling HTTP/2 connection creation failed: %s",

                             (Object)t);

            t = Utils.getCompletionCause(t);

            if (t instanceof Http2Connection.ALPNException) {

                Http2Connection.ALPNException ee = (Http2Connection.ALPNException)t;

                AbstractAsyncSSLConnection as = ee.getConnection();

                DEBUG_LOGGER.log(Level.DEBUG, "downgrading to HTTP/1.1 with: %s", as);

                CompletableFuture<? extends ExchangeImpl<U>> ex =

                        createHttp1Exchange(exchange, as);

                return ex;

            } else {

                DEBUG_LOGGER.log(Level.DEBUG, "HTTP/2 connection creation failed "

                                  + "with unexpected exception: %s", (Object)t);

                return MinimalFuture.failedFuture(t);

            }

        }

        if (secure && c== null) {

            DEBUG_LOGGER.log(Level.DEBUG, "downgrading to HTTP/1.1 ");

            CompletableFuture<? extends ExchangeImpl<U>> ex =

                    createHttp1Exchange(exchange, null);

            return ex;

        }

        if (c == null) {

            // no existing connection. Send request with HTTP 1 and then

            // upgrade if successful

            DEBUG_LOGGER.log(Level.DEBUG, "new Http1Exchange, try to upgrade");

            return createHttp1Exchange(exchange, connection)

                    .thenApply((e) -> {

                        exchange.h2Upgrade();

                        return e;

                    });

        } else {

            DEBUG_LOGGER.log(Level.DEBUG, "creating HTTP/2 streams");

            Stream<U> s = c.createStream(exchange);

            CompletableFuture<? extends ExchangeImpl<U>> ex = MinimalFuture.completedFuture(s);

            return ex;

        }

    }

    private static <T> CompletableFuture<Http1Exchange<T>>

    createHttp1Exchange(Exchange<T> ex, HttpConnection as)

    {

        try {

            return MinimalFuture.completedFuture(new Http1Exchange<>(ex, as));

        } catch (Throwable e) {

            return MinimalFuture.failedFuture(e);

        }

    }

    /* The following methods have separate HTTP/1.1 and HTTP/2 implementations */

    abstract CompletableFuture<ExchangeImpl<T>> sendHeadersAsync();

    /** Sends a request body, after request headers have been sent. */

    abstract CompletableFuture<ExchangeImpl<T>> sendBodyAsync();

    abstract CompletableFuture<T> readBodyAsync(HttpResponse.BodyHandler<T> handler,

                                                boolean returnConnectionToPool,

                                                Executor executor);

    /**

     * Ignore/consume the body.

     */

    abstract CompletableFuture<Void> ignoreBody();

    /** Gets the response headers. Completes before body is read. */

    abstract CompletableFuture<Response> getResponseAsync(Executor executor);

    /** Cancels a request.  Not currently exposed through API. */

    abstract void cancel();

    /**

     * Cancels a request with a cause.  Not currently exposed through API.

     */

    abstract void cancel(IOException cause);

    /**

     * Called when the exchange is released, so that cleanup actions may be

     * performed - such as deregistering callbacks.

     * Typically released is called during upgrade, when an HTTP/2 stream

     * takes over from an Http1Exchange, or when a new exchange is created

     * during a multi exchange before the final response body was received.

     */

    abstract void released();

    /**

     * Called when the exchange is completed, so that cleanup actions may be

     * performed - such as deregistering callbacks.

     * Typically, completed is called at the end of the exchange, when the

     * final response body has been received (or an error has caused the

     * completion of the exchange).

     */

    abstract void completed();

    /**

     * Returns true if this exchange was canceled.

     * @return true if this exchange was canceled.

     */

    abstract boolean isCanceled();

    /**

     * Returns the cause for which this exchange was canceled, if available.

     * @return the cause for which this exchange was canceled, if available.

     */

    abstract Throwable getCancelCause();

}