/*

 * 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

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 */

package jdk.incubator.http;

import java.io.IOException;

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.Executor;

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

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

/**

 * 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> {

    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> ExchangeImpl<U> get(Exchange<U> exchange, HttpConnection connection)

        throws IOException, InterruptedException

    {

        HttpRequestImpl req = exchange.request();

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

            return new Http1Exchange<>(exchange, connection);

        } else {

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

            HttpRequestImpl request = exchange.request();

            Http2Connection c;

            try {

                c = c2.getConnectionFor(request);

            } catch (Http2Connection.ALPNException e) {

                // failed to negotiate "h2"

                AbstractAsyncSSLConnection as = e.getConnection();

                as.stopAsyncReading();

                HttpConnection sslc = as.downgrade();

                ExchangeImpl<U> ex = new Http1Exchange<>(exchange, sslc);

                return ex;

            }

            if (c == null) {

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

                // upgrade if successful

                ExchangeImpl<U> ex = new Http1Exchange<>(exchange, connection);

                exchange.h2Upgrade();

                return ex;

            }

            return c.createStream(exchange);

        }

    }

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

    /**

     * Sends the request headers only. May block until all sent.

     */

    abstract void sendHeadersOnly() throws IOException, InterruptedException;

    // Blocking impl but in async style

    CompletableFuture<ExchangeImpl<T>> sendHeadersAsync() {

        // this is blocking. cf will already be completed.

        return MinimalFuture.supply(() -> {

            sendHeadersOnly();

            return this;

        });

    }

    /**

     * Gets response by blocking if necessary. This may be an

     * intermediate response (like 101) or a final response 200 etc. Returns

     * before body is read.

     */

    abstract Response getResponse() throws IOException;

    abstract T readBody(HttpResponse.BodyHandler<T> handler,

                        boolean returnConnectionToPool) throws IOException;

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

                                                boolean returnConnectionToPool,

                                                Executor executor);

    /**

     * Async version of getResponse. Completes before body is read.

     */

    abstract CompletableFuture<Response> getResponseAsync(Executor executor);

    /**

     * Sends a request body after request headers.

     */

    abstract void sendBody() throws IOException, InterruptedException;

    // Async version of sendBody(). This only used when body sent separately

    // to headers (100 continue)

    CompletableFuture<ExchangeImpl<T>> sendBodyAsync() {

        return MinimalFuture.supply(() -> {

            sendBody();

            return this;

        });

    }

    /**

     * 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);

}