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/*
 * Copyright © 2019-2021, 2023 Apple Inc. and the ServiceTalk project authors
 *
 * Licensed 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.servicetalk.http.netty;

import io.servicetalk.concurrent.SingleSource;
import io.servicetalk.concurrent.api.Single;
import io.servicetalk.transport.netty.internal.ChannelCloseUtils;
import io.servicetalk.transport.netty.internal.ChannelInitializer;
import io.servicetalk.transport.netty.internal.StacklessClosedChannelException;

import io.netty.channel.Channel;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPipeline;
import io.netty.handler.codec.DecoderException;
import io.netty.handler.ssl.ApplicationProtocolNegotiationHandler;
import io.netty.handler.ssl.SslHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.function.Consumer;
import javax.annotation.Nullable;
import javax.net.ssl.SSLException;

import static io.servicetalk.http.netty.AlpnIds.HTTP_1_1;
import static io.servicetalk.transport.netty.internal.ChannelCloseUtils.assignConnectionError;
import static java.util.Objects.requireNonNull;

/**
 * A {@link Single} that initializes ALPN handler and completes after protocol negotiation.
 */
final class AlpnChannelSingle extends ChannelInitSingle {
    private final Consumer onHandlerAdded;

    AlpnChannelSingle(final Channel channel,
                      final ChannelInitializer channelInitializer,
                      final Consumer onHandlerAdded) {
        super(channel, channelInitializer);
        this.onHandlerAdded = requireNonNull(onHandlerAdded);
    }

    @Override
    protected ChannelHandler newChannelHandler(final Subscriber subscriber) {
        return new AlpnChannelHandler(subscriber, onHandlerAdded);
    }

    /**
     * Configures a {@link ChannelPipeline} depending on the application-level protocol negotiation result of
     * {@link SslHandler}.
     */
    private static final class AlpnChannelHandler extends ApplicationProtocolNegotiationHandler {

        private static final Logger LOGGER = LoggerFactory.getLogger(AlpnChannelHandler.class);

        @Nullable
        private SingleSource.Subscriber subscriber;
        private final Consumer onHandlerAdded;

        AlpnChannelHandler(final SingleSource.Subscriber subscriber,
                           final Consumer onHandlerAdded) {
            super(HTTP_1_1);
            this.subscriber = subscriber;
            this.onHandlerAdded = onHandlerAdded;
        }

        @Override
        public void handlerAdded(final ChannelHandlerContext ctx) throws Exception {
            super.handlerAdded(ctx);
            onHandlerAdded.accept(ctx);
        }

        @Override
        protected void configurePipeline(final ChannelHandlerContext ctx, final String protocol) {
            LOGGER.debug("{} ALPN negotiated {} protocol", ctx.channel(), protocol);
            assert subscriber != null;
            final SingleSource.Subscriber subscriberCopy = subscriber;
            subscriber = null;
            subscriberCopy.onSuccess(protocol);
        }

        @Override
        protected void handshakeFailure(final ChannelHandlerContext ctx, final Throwable cause) {
            LOGGER.warn("{} TLS handshake failed:", ctx.channel(), cause);
            if (!failSubscriber(cause, ctx.channel())) {
                ChannelCloseUtils.close(ctx, cause);
            }
        }

        @Override
        public void exceptionCaught(final ChannelHandlerContext ctx, final Throwable cause) {
            Throwable wrapped;
            // This unwrapping logic is copied from the parent ApplicationProtocolNegotiationHandler
            if (cause instanceof DecoderException && ((wrapped = cause.getCause()) instanceof SSLException)) {
                handshakeFailure(ctx, wrapped);
                return;
            }
            LOGGER.warn("{} Failed to select the application-level protocol:", ctx.channel(), cause);
            if (!failSubscriber(cause, ctx.channel())) {
                // Propagate exception in the pipeline if subscriber is already complete
                ctx.fireExceptionCaught(cause);
                ChannelCloseUtils.close(ctx, cause);
            }
        }

        @Override
        public void channelInactive(final ChannelHandlerContext ctx) throws Exception {
            if (subscriber != null) {
                failSubscriber(StacklessClosedChannelException.newInstance(
                        AlpnChannelHandler.class, "channelInactive(...)"), ctx.channel());
            }
            super.channelInactive(ctx);
        }

        private boolean failSubscriber(final Throwable cause, final Channel channel) {
            assignConnectionError(channel, cause);
            if (subscriber != null) {
                final SingleSource.Subscriber subscriberCopy = subscriber;
                subscriber = null;
                subscriberCopy.onError(cause);
                return true;
            }
            return false;
        }
    }
}