/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License, version 2.0 (the
 * "License"); you may not use this file except in compliance with the License. You may obtain a
 * copy of the License at:
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package io.netty.example.http2.helloworld.client;

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.DefaultFullHttpRequest;
import io.netty.handler.codec.http.HttpClientCodec;
import io.netty.handler.codec.http.HttpClientUpgradeHandler;
import io.netty.handler.codec.http.HttpHeaderNames;
import io.netty.handler.codec.http.HttpMethod;
import io.netty.handler.codec.http.HttpVersion;
import io.netty.handler.codec.http2.DefaultHttp2Connection;
import io.netty.handler.codec.http2.DelegatingDecompressorFrameListener;
import io.netty.handler.codec.http2.Http2ClientUpgradeCodec;
import io.netty.handler.codec.http2.Http2Connection;
import io.netty.handler.codec.http2.Http2FrameLogger;
import io.netty.handler.codec.http2.HttpToHttp2ConnectionHandler;
import io.netty.handler.codec.http2.HttpToHttp2ConnectionHandlerBuilder;
import io.netty.handler.codec.http2.InboundHttp2ToHttpAdapterBuilder;
import io.netty.handler.ssl.ApplicationProtocolNames;
import io.netty.handler.ssl.ApplicationProtocolNegotiationHandler;
import io.netty.handler.ssl.SslContext;

import java.net.InetSocketAddress;

import static io.netty.handler.logging.LogLevel.INFO;

/**
 * Configures the client pipeline to support HTTP/2 frames.
 */
public class Http2ClientInitializer extends ChannelInitializer<SocketChannel> {
    private static final Http2FrameLogger logger = new Http2FrameLogger(INFO, Http2ClientInitializer.class);

    private final SslContext sslCtx;
    private final int maxContentLength;
    private HttpToHttp2ConnectionHandler connectionHandler;
    private HttpResponseHandler responseHandler;
    private Http2SettingsHandler settingsHandler;

    public Http2ClientInitializer(SslContext sslCtx, int maxContentLength) {
        this.sslCtx = sslCtx;
        this.maxContentLength = maxContentLength;
    }

    @Override
    public void initChannel(SocketChannel ch) throws Exception {
        final Http2Connection connection = new DefaultHttp2Connection(false);
        connectionHandler = new HttpToHttp2ConnectionHandlerBuilder()
                .frameListener(new DelegatingDecompressorFrameListener(
                        connection,
                        new InboundHttp2ToHttpAdapterBuilder(connection)
                                .maxContentLength(maxContentLength)
                                .propagateSettings(true)
                                .build()))
                .frameLogger(logger)
                .connection(connection)
                .build();
        responseHandler = new HttpResponseHandler();
        settingsHandler = new Http2SettingsHandler(ch.newPromise());
        if (sslCtx != null) {
            configureSsl(ch);
        } else {
            configureClearText(ch);
        }
    }

    public HttpResponseHandler responseHandler() {
        return responseHandler;
    }

    public Http2SettingsHandler settingsHandler() {
        return settingsHandler;
    }

    protected void configureEndOfPipeline(ChannelPipeline pipeline) {
        pipeline.addLast(settingsHandler, responseHandler);
    }

    /**
     * Configure the pipeline for TLS NPN negotiation to HTTP/2.
     */
    private void configureSsl(SocketChannel ch) {
        ChannelPipeline pipeline = ch.pipeline();
        // Specify Host in SSLContext New Handler to add TLS SNI Extension
        pipeline.addLast(sslCtx.newHandler(ch.alloc(), Http2Client.HOST, Http2Client.PORT));
        // We must wait for the handshake to finish and the protocol to be negotiated before configuring
        // the HTTP/2 components of the pipeline.
        pipeline.addLast(new ApplicationProtocolNegotiationHandler("") {
            @Override
            protected void configurePipeline(ChannelHandlerContext ctx, String protocol) {
                if (ApplicationProtocolNames.HTTP_2.equals(protocol)) {
                    ChannelPipeline p = ctx.pipeline();
                    p.addLast(connectionHandler);
                    configureEndOfPipeline(p);
                    return;
                }
                ctx.close();
                throw new IllegalStateException("unknown protocol: " + protocol);
            }
        });
    }

    /**
     * Configure the pipeline for a cleartext upgrade from HTTP to HTTP/2.
     */
    private void configureClearText(SocketChannel ch) {
        HttpClientCodec sourceCodec = new HttpClientCodec();
        Http2ClientUpgradeCodec upgradeCodec = new Http2ClientUpgradeCodec(connectionHandler);
        HttpClientUpgradeHandler upgradeHandler = new HttpClientUpgradeHandler(sourceCodec, upgradeCodec, 65536);

        ch.pipeline().addLast(sourceCodec,
                              upgradeHandler,
                              new UpgradeRequestHandler(),
                              new UserEventLogger());
    }

    /**
     * A handler that triggers the cleartext upgrade to HTTP/2 by sending an initial HTTP request.
     */
    private final class UpgradeRequestHandler implements ChannelHandler {

        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
            DefaultFullHttpRequest upgradeRequest =
                    new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, "/", Unpooled.EMPTY_BUFFER);

            // Set HOST header as the remote peer may require it.
            InetSocketAddress remote = (InetSocketAddress) ctx.channel().remoteAddress();
            String hostString = remote.getHostString();
            if (hostString == null) {
                hostString = remote.getAddress().getHostAddress();
            }
            upgradeRequest.headers().set(HttpHeaderNames.HOST, hostString + ':' + remote.getPort());

            ctx.writeAndFlush(upgradeRequest);

            ctx.fireChannelActive();

            // Done with this handler, remove it from the pipeline.
            ctx.pipeline().remove(this);

            configureEndOfPipeline(ctx.pipeline());
        }
    }

    /**
     * Class that logs any User Events triggered on this channel.
     */
    private static class UserEventLogger implements ChannelHandler {
        @Override
        public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
            System.out.println("User Event Triggered: " + evt);
            ctx.fireUserEventTriggered(evt);
        }
    }
}
