/*
 *  Copyright (c) 2019, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
 *
 *  WSO2 Inc. 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 org.wso2.micro.gateway.tests.common.HTTP2Server;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpMessage;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.codec.http.HttpServerUpgradeHandler;
import io.netty.handler.codec.http2.CleartextHttp2ServerUpgradeHandler;
import io.netty.handler.codec.http2.Http2CodecUtil;
import io.netty.handler.codec.http2.Http2ServerUpgradeCodec;
import io.netty.handler.ssl.SslContext;
import io.netty.util.AsciiString;
import io.netty.util.ReferenceCountUtil;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class Http2ServerInitializer extends ChannelInitializer<SocketChannel> {

    private static final Log log = LogFactory.getLog(Http2ServerInitializer.class);

    private static final HttpServerUpgradeHandler.UpgradeCodecFactory upgradeCodecFactory = protocol -> {
        if (AsciiString.contentEquals(Http2CodecUtil.HTTP_UPGRADE_PROTOCOL_NAME, protocol)) {
            return new Http2ServerUpgradeCodec(new Http2HandlerBuilder().build());
        } else {
            return null;
        }
    };

    private final SslContext sslCtx;
    private final int maxHttpContentLength;

    public Http2ServerInitializer(SslContext sslCtx) {
        this(sslCtx, 16 * 1024);
    }

    public Http2ServerInitializer(SslContext sslCtx, int maxHttpContentLength) {
        if (maxHttpContentLength < 0) {
            throw new IllegalArgumentException("maxHttpContentLength (expected >= 0): " + maxHttpContentLength);
        }
        this.sslCtx = sslCtx;
        this.maxHttpContentLength = maxHttpContentLength;
    }

    @Override
    public void initChannel(SocketChannel ch) {
        if (sslCtx != null) {
            configureSsl(ch);
        } else {
            configureClearText(ch);
        }
    }

    /**
     * Configure the pipeline for TLS NPN negotiation to HTTP/2.
     */
    private void configureSsl(SocketChannel ch) {
        final ChannelPipeline p = ch.pipeline();
        p.addLast(sslCtx.newHandler(ch.alloc()), new Http2OrHttpHandler());
        p.addLast(new UserEventLogger());
    }

    /**
     * Configure the pipeline for a cleartext upgrade from HTTP to HTTP/2.0
     */
    private void configureClearText(SocketChannel ch) {
        final ChannelPipeline p = ch.pipeline();
        final HttpServerCodec sourceCodec = new HttpServerCodec();
        final HttpServerUpgradeHandler upgradeHandler = new HttpServerUpgradeHandler(sourceCodec, upgradeCodecFactory);
        final CleartextHttp2ServerUpgradeHandler cleartextHttp2ServerUpgradeHandler =
                new CleartextHttp2ServerUpgradeHandler(sourceCodec, upgradeHandler,
                        new Http2HandlerBuilder().build());

        p.addLast(cleartextHttp2ServerUpgradeHandler);
        p.addLast(new SimpleChannelInboundHandler<HttpMessage>() {
            @Override
            protected void channelRead0(ChannelHandlerContext ctx, HttpMessage msg) throws Exception {
                // If this handler is hit then no upgrade has been attempted and the client is just talking HTTP.

                log.error("Directly talking: " + msg.protocolVersion() + " (no upgrade was attempted)");

                ChannelPipeline pipeline = ctx.pipeline();
                ChannelHandlerContext thisCtx = pipeline.context(this);
                pipeline.addAfter(thisCtx.name(), null, new Http1Handler("Direct. No Upgrade Attempted"));
                pipeline.replace(this, null, new HttpObjectAggregator(maxHttpContentLength));
                ctx.fireChannelRead(ReferenceCountUtil.retain(msg));
            }
        });

        p.addLast(new UserEventLogger());
    }

    /**
     * Class that logs any User Events triggered on this channel.
     */
    private static class UserEventLogger extends ChannelInboundHandlerAdapter {
        @Override
        public void userEventTriggered(ChannelHandlerContext ctx, Object evt) {
            log.info("User Event Triggered: " + evt);
            ctx.fireUserEventTriggered(evt);
        }
    }
}
