/*
 * 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.handler.codec.http2;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.http.HttpStatusClass;
import io.netty.handler.codec.http2.Http2Connection.Endpoint;
import io.netty.util.internal.UnstableApi;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

import java.util.List;

import static io.netty.handler.codec.http.HttpStatusClass.INFORMATIONAL;
import static io.netty.handler.codec.http2.Http2CodecUtil.DEFAULT_PRIORITY_WEIGHT;
import static io.netty.handler.codec.http2.Http2Error.INTERNAL_ERROR;
import static io.netty.handler.codec.http2.Http2Error.PROTOCOL_ERROR;
import static io.netty.handler.codec.http2.Http2Error.STREAM_CLOSED;
import static io.netty.handler.codec.http2.Http2Exception.connectionError;
import static io.netty.handler.codec.http2.Http2Exception.streamError;
import static io.netty.handler.codec.http2.Http2PromisedRequestVerifier.ALWAYS_VERIFY;
import static io.netty.handler.codec.http2.Http2Stream.State.CLOSED;
import static io.netty.handler.codec.http2.Http2Stream.State.HALF_CLOSED_REMOTE;
import static io.netty.util.internal.ObjectUtil.checkNotNull;
import static java.lang.Integer.MAX_VALUE;
import static java.lang.Math.min;

/**
 * Provides the default implementation for processing inbound frame events and delegates to a
 * {@link Http2FrameListener}
 * <p>
 * This class will read HTTP/2 frames and delegate the events to a {@link Http2FrameListener}
 * <p>
 * This interface enforces inbound flow control functionality through
 * {@link Http2LocalFlowController}
 */
@UnstableApi
public class DefaultHttp2ConnectionDecoder implements Http2ConnectionDecoder {
    private static final InternalLogger logger = InternalLoggerFactory.getInstance(DefaultHttp2ConnectionDecoder.class);
    private Http2FrameListener internalFrameListener = new PrefaceFrameListener();
    private final Http2Connection connection;
    private Http2LifecycleManager lifecycleManager;
    private final Http2ConnectionEncoder encoder;
    private final Http2FrameReader frameReader;
    private Http2FrameListener listener;
    private final Http2PromisedRequestVerifier requestVerifier;
    private final Http2SettingsReceivedConsumer settingsReceivedConsumer;
    private final boolean autoAckPing;

    public DefaultHttp2ConnectionDecoder(Http2Connection connection,
                                         Http2ConnectionEncoder encoder,
                                         Http2FrameReader frameReader) {
        this(connection, encoder, frameReader, ALWAYS_VERIFY);
    }

    public DefaultHttp2ConnectionDecoder(Http2Connection connection,
                                         Http2ConnectionEncoder encoder,
                                         Http2FrameReader frameReader,
                                         Http2PromisedRequestVerifier requestVerifier) {
        this(connection, encoder, frameReader, requestVerifier, true);
    }

    /**
     * Create a new instance.
     * @param connection The {@link Http2Connection} associated with this decoder.
     * @param encoder The {@link Http2ConnectionEncoder} associated with this decoder.
     * @param frameReader Responsible for reading/parsing the raw frames. As opposed to this object which applies
     *                    h2 semantics on top of the frames.
     * @param requestVerifier Determines if push promised streams are valid.
     * @param autoAckSettings {@code false} to disable automatically applying and sending settings acknowledge frame.
     *  The {@code Http2ConnectionEncoder} is expected to be an instance of {@link Http2SettingsReceivedConsumer} and
     *  will apply the earliest received but not yet ACKed SETTINGS when writing the SETTINGS ACKs.
     * {@code true} to enable automatically applying and sending settings acknowledge frame.
     */
    public DefaultHttp2ConnectionDecoder(Http2Connection connection,
                                         Http2ConnectionEncoder encoder,
                                         Http2FrameReader frameReader,
                                         Http2PromisedRequestVerifier requestVerifier,
                                         boolean autoAckSettings) {
        this(connection, encoder, frameReader, requestVerifier, autoAckSettings, true);
    }

    /**
     * Create a new instance.
     * @param connection The {@link Http2Connection} associated with this decoder.
     * @param encoder The {@link Http2ConnectionEncoder} associated with this decoder.
     * @param frameReader Responsible for reading/parsing the raw frames. As opposed to this object which applies
     *                    h2 semantics on top of the frames.
     * @param requestVerifier Determines if push promised streams are valid.
     * @param autoAckSettings {@code false} to disable automatically applying and sending settings acknowledge frame.
     *                        The {@code Http2ConnectionEncoder} is expected to be an instance of
     *                        {@link Http2SettingsReceivedConsumer} and will apply the earliest received but not yet
     *                        ACKed SETTINGS when writing the SETTINGS ACKs. {@code true} to enable automatically
     *                        applying and sending settings acknowledge frame.
     * @param autoAckPing {@code false} to disable automatically sending ping acknowledge frame. {@code true} to enable
     *                    automatically sending ping ack frame.
     */
    public DefaultHttp2ConnectionDecoder(Http2Connection connection,
                                         Http2ConnectionEncoder encoder,
                                         Http2FrameReader frameReader,
                                         Http2PromisedRequestVerifier requestVerifier,
                                         boolean autoAckSettings,
                                         boolean autoAckPing) {
        this.autoAckPing = autoAckPing;
        if (autoAckSettings) {
            settingsReceivedConsumer = null;
        } else {
            if (!(encoder instanceof Http2SettingsReceivedConsumer)) {
                throw new IllegalArgumentException("disabling autoAckSettings requires the encoder to be a " +
                        Http2SettingsReceivedConsumer.class);
            }
            settingsReceivedConsumer = (Http2SettingsReceivedConsumer) encoder;
        }
        this.connection = checkNotNull(connection, "connection");
        this.frameReader = checkNotNull(frameReader, "frameReader");
        this.encoder = checkNotNull(encoder, "encoder");
        this.requestVerifier = checkNotNull(requestVerifier, "requestVerifier");
        if (connection.local().flowController() == null) {
            connection.local().flowController(new DefaultHttp2LocalFlowController(connection));
        }
        connection.local().flowController().frameWriter(encoder.frameWriter());
    }

    @Override
    public void lifecycleManager(Http2LifecycleManager lifecycleManager) {
        this.lifecycleManager = checkNotNull(lifecycleManager, "lifecycleManager");
    }

    @Override
    public Http2Connection connection() {
        return connection;
    }

    @Override
    public final Http2LocalFlowController flowController() {
        return connection.local().flowController();
    }

    @Override
    public void frameListener(Http2FrameListener listener) {
        this.listener = checkNotNull(listener, "listener");
    }

    @Override
    public Http2FrameListener frameListener() {
        return listener;
    }

    // Visible for testing
    Http2FrameListener internalFrameListener() {
        return internalFrameListener;
    }

    @Override
    public boolean prefaceReceived() {
        return FrameReadListener.class == internalFrameListener.getClass();
    }

    @Override
    public void decodeFrame(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Http2Exception {
        frameReader.readFrame(ctx, in, internalFrameListener);
    }

    @Override
    public Http2Settings localSettings() {
        Http2Settings settings = new Http2Settings();
        Http2FrameReader.Configuration config = frameReader.configuration();
        Http2HeadersDecoder.Configuration headersConfig = config.headersConfiguration();
        Http2FrameSizePolicy frameSizePolicy = config.frameSizePolicy();
        settings.initialWindowSize(flowController().initialWindowSize());
        settings.maxConcurrentStreams(connection.remote().maxActiveStreams());
        settings.headerTableSize(headersConfig.maxHeaderTableSize());
        settings.maxFrameSize(frameSizePolicy.maxFrameSize());
        settings.maxHeaderListSize(headersConfig.maxHeaderListSize());
        if (!connection.isServer()) {
            // Only set the pushEnabled flag if this is a client endpoint.
            settings.pushEnabled(connection.local().allowPushTo());
        }
        return settings;
    }

    @Override
    public void close() {
        frameReader.close();
    }

    /**
     * Calculate the threshold in bytes which should trigger a {@code GO_AWAY} if a set of headers exceeds this amount.
     * @param maxHeaderListSize
     *      <a href="https://tools.ietf.org/html/rfc7540#section-6.5.2">SETTINGS_MAX_HEADER_LIST_SIZE</a> for the local
     *      endpoint.
     * @return the threshold in bytes which should trigger a {@code GO_AWAY} if a set of headers exceeds this amount.
     */
    protected long calculateMaxHeaderListSizeGoAway(long maxHeaderListSize) {
        return Http2CodecUtil.calculateMaxHeaderListSizeGoAway(maxHeaderListSize);
    }

    private int unconsumedBytes(Http2Stream stream) {
        return flowController().unconsumedBytes(stream);
    }

    void onGoAwayRead0(ChannelHandlerContext ctx, int lastStreamId, long errorCode, ByteBuf debugData)
            throws Http2Exception {
        connection.goAwayReceived(lastStreamId, errorCode, debugData);
        listener.onGoAwayRead(ctx, lastStreamId, errorCode, debugData);
    }

    void onUnknownFrame0(ChannelHandlerContext ctx, byte frameType, int streamId, Http2Flags flags,
            ByteBuf payload) throws Http2Exception {
        listener.onUnknownFrame(ctx, frameType, streamId, flags, payload);
    }

    /**
     * Handles all inbound frames from the network.
     */
    private final class FrameReadListener implements Http2FrameListener {
        @Override
        public int onDataRead(final ChannelHandlerContext ctx, int streamId, ByteBuf data, int padding,
                              boolean endOfStream) throws Http2Exception {
            Http2Stream stream = connection.stream(streamId);
            Http2LocalFlowController flowController = flowController();
            int bytesToReturn = data.readableBytes() + padding;

            final boolean shouldIgnore;
            try {
                shouldIgnore = shouldIgnoreHeadersOrDataFrame(ctx, streamId, stream, "DATA");
            } catch (Http2Exception e) {
                // Ignoring this frame. We still need to count the frame towards the connection flow control
                // window, but we immediately mark all bytes as consumed.
                flowController.receiveFlowControlledFrame(stream, data, padding, endOfStream);
                flowController.consumeBytes(stream, bytesToReturn);
                throw e;
            } catch (Throwable t) {
                throw connectionError(INTERNAL_ERROR, t, "Unhandled error on data stream id %d", streamId);
            }

            if (shouldIgnore) {
                // Ignoring this frame. We still need to count the frame towards the connection flow control
                // window, but we immediately mark all bytes as consumed.
                flowController.receiveFlowControlledFrame(stream, data, padding, endOfStream);
                flowController.consumeBytes(stream, bytesToReturn);

                // Verify that the stream may have existed after we apply flow control.
                verifyStreamMayHaveExisted(streamId);

                // All bytes have been consumed.
                return bytesToReturn;
            }

            Http2Exception error = null;
            switch (stream.state()) {
                case OPEN:
                case HALF_CLOSED_LOCAL:
                    break;
                case HALF_CLOSED_REMOTE:
                case CLOSED:
                    error = streamError(stream.id(), STREAM_CLOSED, "Stream %d in unexpected state: %s",
                        stream.id(), stream.state());
                    break;
                default:
                    error = streamError(stream.id(), PROTOCOL_ERROR,
                        "Stream %d in unexpected state: %s", stream.id(), stream.state());
                    break;
            }

            int unconsumedBytes = unconsumedBytes(stream);
            try {
                flowController.receiveFlowControlledFrame(stream, data, padding, endOfStream);
                // Update the unconsumed bytes after flow control is applied.
                unconsumedBytes = unconsumedBytes(stream);

                // If the stream is in an invalid state to receive the frame, throw the error.
                if (error != null) {
                    throw error;
                }

                // Call back the application and retrieve the number of bytes that have been
                // immediately processed.
                bytesToReturn = listener.onDataRead(ctx, streamId, data, padding, endOfStream);
                return bytesToReturn;
            } catch (Http2Exception e) {
                // If an exception happened during delivery, the listener may have returned part
                // of the bytes before the error occurred. If that's the case, subtract that from
                // the total processed bytes so that we don't return too many bytes.
                int delta = unconsumedBytes - unconsumedBytes(stream);
                bytesToReturn -= delta;
                throw e;
            } catch (RuntimeException e) {
                // If an exception happened during delivery, the listener may have returned part
                // of the bytes before the error occurred. If that's the case, subtract that from
                // the total processed bytes so that we don't return too many bytes.
                int delta = unconsumedBytes - unconsumedBytes(stream);
                bytesToReturn -= delta;
                throw e;
            } finally {
                // If appropriate, return the processed bytes to the flow controller.
                flowController.consumeBytes(stream, bytesToReturn);

                if (endOfStream) {
                    lifecycleManager.closeStreamRemote(stream, ctx.newSucceededFuture());
                }
            }
        }

        @Override
        public void onHeadersRead(ChannelHandlerContext ctx, int streamId, Http2Headers headers, int padding,
                boolean endOfStream) throws Http2Exception {
            onHeadersRead(ctx, streamId, headers, 0, DEFAULT_PRIORITY_WEIGHT, false, padding, endOfStream);
        }

        @Override
        public void onHeadersRead(ChannelHandlerContext ctx, int streamId, Http2Headers headers, int streamDependency,
                short weight, boolean exclusive, int padding, boolean endOfStream) throws Http2Exception {
            Http2Stream stream = connection.stream(streamId);
            boolean allowHalfClosedRemote = false;
            if (stream == null && !connection.streamMayHaveExisted(streamId)) {
                stream = connection.remote().createStream(streamId, endOfStream);
                // Allow the state to be HALF_CLOSE_REMOTE if we're creating it in that state.
                allowHalfClosedRemote = stream.state() == HALF_CLOSED_REMOTE;
            }

            if (shouldIgnoreHeadersOrDataFrame(ctx, streamId, stream, "HEADERS")) {
                return;
            }

            boolean isInformational = !connection.isServer() &&
                    HttpStatusClass.valueOf(headers.status()) == INFORMATIONAL;
            if ((isInformational || !endOfStream) && stream.isHeadersReceived() || stream.isTrailersReceived()) {
                throw streamError(streamId, PROTOCOL_ERROR,
                                  "Stream %d received too many headers EOS: %s state: %s",
                                  streamId, endOfStream, stream.state());
            }

            switch (stream.state()) {
                case RESERVED_REMOTE:
                    stream.open(endOfStream);
                    break;
                case OPEN:
                case HALF_CLOSED_LOCAL:
                    // Allowed to receive headers in these states.
                    break;
                case HALF_CLOSED_REMOTE:
                    if (!allowHalfClosedRemote) {
                        throw streamError(stream.id(), STREAM_CLOSED, "Stream %d in unexpected state: %s",
                                stream.id(), stream.state());
                    }
                    break;
                case CLOSED:
                    throw streamError(stream.id(), STREAM_CLOSED, "Stream %d in unexpected state: %s",
                            stream.id(), stream.state());
                default:
                    // Connection error.
                    throw connectionError(PROTOCOL_ERROR, "Stream %d in unexpected state: %s", stream.id(),
                            stream.state());
            }

            stream.headersReceived(isInformational);
            encoder.flowController().updateDependencyTree(streamId, streamDependency, weight, exclusive);

            listener.onHeadersRead(ctx, streamId, headers, streamDependency, weight, exclusive, padding, endOfStream);

            // If the headers completes this stream, close it.
            if (endOfStream) {
                lifecycleManager.closeStreamRemote(stream, ctx.newSucceededFuture());
            }
        }

        @Override
        public void onPriorityRead(ChannelHandlerContext ctx, int streamId, int streamDependency, short weight,
                boolean exclusive) throws Http2Exception {
            encoder.flowController().updateDependencyTree(streamId, streamDependency, weight, exclusive);

            listener.onPriorityRead(ctx, streamId, streamDependency, weight, exclusive);
        }

        @Override
        public void onRstStreamRead(ChannelHandlerContext ctx, int streamId, long errorCode) throws Http2Exception {
            Http2Stream stream = connection.stream(streamId);
            if (stream == null) {
                verifyStreamMayHaveExisted(streamId);
                return;
            }

            switch(stream.state()) {
            case IDLE:
                throw connectionError(PROTOCOL_ERROR, "RST_STREAM received for IDLE stream %d", streamId);
            case CLOSED:
                return; // RST_STREAM frames must be ignored for closed streams.
            default:
                break;
            }

            listener.onRstStreamRead(ctx, streamId, errorCode);

            lifecycleManager.closeStream(stream, ctx.newSucceededFuture());
        }

        @Override
        public void onSettingsAckRead(ChannelHandlerContext ctx) throws Http2Exception {
            // Apply oldest outstanding local settings here. This is a synchronization point between endpoints.
            Http2Settings settings = encoder.pollSentSettings();

            if (settings != null) {
                applyLocalSettings(settings);
            }

            listener.onSettingsAckRead(ctx);
        }

        /**
         * Applies settings sent from the local endpoint.
         * <p>
         * This method is only called after the local settings have been acknowledged from the remote endpoint.
         */
        private void applyLocalSettings(Http2Settings settings) throws Http2Exception {
            Boolean pushEnabled = settings.pushEnabled();
            final Http2FrameReader.Configuration config = frameReader.configuration();
            final Http2HeadersDecoder.Configuration headerConfig = config.headersConfiguration();
            final Http2FrameSizePolicy frameSizePolicy = config.frameSizePolicy();
            if (pushEnabled != null) {
                if (connection.isServer()) {
                    throw connectionError(PROTOCOL_ERROR, "Server sending SETTINGS frame with ENABLE_PUSH specified");
                }
                connection.local().allowPushTo(pushEnabled);
            }

            Long maxConcurrentStreams = settings.maxConcurrentStreams();
            if (maxConcurrentStreams != null) {
                connection.remote().maxActiveStreams((int) min(maxConcurrentStreams, MAX_VALUE));
            }

            Long headerTableSize = settings.headerTableSize();
            if (headerTableSize != null) {
                headerConfig.maxHeaderTableSize(headerTableSize);
            }

            Long maxHeaderListSize = settings.maxHeaderListSize();
            if (maxHeaderListSize != null) {
                headerConfig.maxHeaderListSize(maxHeaderListSize, calculateMaxHeaderListSizeGoAway(maxHeaderListSize));
            }

            Integer maxFrameSize = settings.maxFrameSize();
            if (maxFrameSize != null) {
                frameSizePolicy.maxFrameSize(maxFrameSize);
            }

            Integer initialWindowSize = settings.initialWindowSize();
            if (initialWindowSize != null) {
                flowController().initialWindowSize(initialWindowSize);
            }
        }

        @Override
        public void onSettingsRead(final ChannelHandlerContext ctx, Http2Settings settings) throws Http2Exception {
            if (settingsReceivedConsumer == null) {
                // Acknowledge receipt of the settings. We should do this before we process the settings to ensure our
                // remote peer applies these settings before any subsequent frames that we may send which depend upon
                // these new settings. See https://github.com/netty/netty/issues/6520.
                encoder.writeSettingsAck(ctx, ctx.newPromise());

                encoder.remoteSettings(settings);
            } else {
                settingsReceivedConsumer.consumeReceivedSettings(settings);
            }

            listener.onSettingsRead(ctx, settings);
        }

        @Override
        public void onPingRead(ChannelHandlerContext ctx, long data) throws Http2Exception {
            if (autoAckPing) {
                // Send an ack back to the remote client.
                encoder.writePing(ctx, true, data, ctx.newPromise());
            }
            listener.onPingRead(ctx, data);
        }

        @Override
        public void onPingAckRead(ChannelHandlerContext ctx, long data) throws Http2Exception {
            listener.onPingAckRead(ctx, data);
        }

        @Override
        public void onPushPromiseRead(ChannelHandlerContext ctx, int streamId, int promisedStreamId,
                Http2Headers headers, int padding) throws Http2Exception {
            // A client cannot push.
            if (connection().isServer()) {
                throw connectionError(PROTOCOL_ERROR, "A client cannot push.");
            }

            Http2Stream parentStream = connection.stream(streamId);

            if (shouldIgnoreHeadersOrDataFrame(ctx, streamId, parentStream, "PUSH_PROMISE")) {
                return;
            }

            if (parentStream == null) {
                throw connectionError(PROTOCOL_ERROR, "Stream %d does not exist", streamId);
            }

            switch (parentStream.state()) {
              case OPEN:
              case HALF_CLOSED_LOCAL:
                  // Allowed to receive push promise in these states.
                  break;
              default:
                  // Connection error.
                  throw connectionError(PROTOCOL_ERROR,
                      "Stream %d in unexpected state for receiving push promise: %s",
                      parentStream.id(), parentStream.state());
            }

            if (!requestVerifier.isAuthoritative(ctx, headers)) {
                throw streamError(promisedStreamId, PROTOCOL_ERROR,
                        "Promised request on stream %d for promised stream %d is not authoritative",
                        streamId, promisedStreamId);
            }
            if (!requestVerifier.isCacheable(headers)) {
                throw streamError(promisedStreamId, PROTOCOL_ERROR,
                        "Promised request on stream %d for promised stream %d is not known to be cacheable",
                        streamId, promisedStreamId);
            }
            if (!requestVerifier.isSafe(headers)) {
                throw streamError(promisedStreamId, PROTOCOL_ERROR,
                        "Promised request on stream %d for promised stream %d is not known to be safe",
                        streamId, promisedStreamId);
            }

            // Reserve the push stream based with a priority based on the current stream's priority.
            connection.remote().reservePushStream(promisedStreamId, parentStream);

            listener.onPushPromiseRead(ctx, streamId, promisedStreamId, headers, padding);
        }

        @Override
        public void onGoAwayRead(ChannelHandlerContext ctx, int lastStreamId, long errorCode, ByteBuf debugData)
                throws Http2Exception {
            onGoAwayRead0(ctx, lastStreamId, errorCode, debugData);
        }

        @Override
        public void onWindowUpdateRead(ChannelHandlerContext ctx, int streamId, int windowSizeIncrement)
                throws Http2Exception {
            Http2Stream stream = connection.stream(streamId);
            if (stream == null || stream.state() == CLOSED || streamCreatedAfterGoAwaySent(streamId)) {
                // Ignore this frame.
                verifyStreamMayHaveExisted(streamId);
                return;
            }

            // Update the outbound flow control window.
            encoder.flowController().incrementWindowSize(stream, windowSizeIncrement);

            listener.onWindowUpdateRead(ctx, streamId, windowSizeIncrement);
        }

        @Override
        public void onUnknownFrame(ChannelHandlerContext ctx, byte frameType, int streamId, Http2Flags flags,
                ByteBuf payload) throws Http2Exception {
            onUnknownFrame0(ctx, frameType, streamId, flags, payload);
        }

        /**
         * Helper method to determine if a frame that has the semantics of headers or data should be ignored for the
         * {@code stream} (which may be {@code null}) associated with {@code streamId}.
         */
        private boolean shouldIgnoreHeadersOrDataFrame(ChannelHandlerContext ctx, int streamId, Http2Stream stream,
                String frameName) throws Http2Exception {
            if (stream == null) {
                if (streamCreatedAfterGoAwaySent(streamId)) {
                    logger.info("{} ignoring {} frame for stream {}. Stream sent after GOAWAY sent",
                            ctx.channel(), frameName, streamId);
                    return true;
                }

                // Make sure it's not an out-of-order frame, like a rogue DATA frame, for a stream that could
                // never have existed.
                verifyStreamMayHaveExisted(streamId);

                // Its possible that this frame would result in stream ID out of order creation (PROTOCOL ERROR) and its
                // also possible that this frame is received on a CLOSED stream (STREAM_CLOSED after a RST_STREAM is
                // sent). We don't have enough information to know for sure, so we choose the lesser of the two errors.
                throw streamError(streamId, STREAM_CLOSED, "Received %s frame for an unknown stream %d",
                                  frameName, streamId);
            } else if (stream.isResetSent() || streamCreatedAfterGoAwaySent(streamId)) {
                // If we have sent a reset stream it is assumed the stream will be closed after the write completes.
                // If we have not sent a reset, but the stream was created after a GoAway this is not supported by
                // DefaultHttp2Connection and if a custom Http2Connection is used it is assumed the lifetime is managed
                // elsewhere so we don't close the stream or otherwise modify the stream's state.

                if (logger.isInfoEnabled()) {
                    logger.info("{} ignoring {} frame for stream {}", ctx.channel(), frameName,
                            stream.isResetSent() ? "RST_STREAM sent." :
                                ("Stream created after GOAWAY sent. Last known stream by peer " +
                                 connection.remote().lastStreamKnownByPeer()));
                }

                return true;
            }
            return false;
        }

        /**
         * Helper method for determining whether or not to ignore inbound frames. A stream is considered to be created
         * after a {@code GOAWAY} is sent if the following conditions hold:
         * <p/>
         * <ul>
         *     <li>A {@code GOAWAY} must have been sent by the local endpoint</li>
         *     <li>The {@code streamId} must identify a legitimate stream id for the remote endpoint to be creating</li>
         *     <li>{@code streamId} is greater than the Last Known Stream ID which was sent by the local endpoint
         *     in the last {@code GOAWAY} frame</li>
         * </ul>
         * <p/>
         */
        private boolean streamCreatedAfterGoAwaySent(int streamId) {
            Endpoint<?> remote = connection.remote();
            return connection.goAwaySent() && remote.isValidStreamId(streamId) &&
                    streamId > remote.lastStreamKnownByPeer();
        }

        private void verifyStreamMayHaveExisted(int streamId) throws Http2Exception {
            if (!connection.streamMayHaveExisted(streamId)) {
                throw connectionError(PROTOCOL_ERROR, "Stream %d does not exist", streamId);
            }
        }
    }

    private final class PrefaceFrameListener implements Http2FrameListener {
        /**
         * Verifies that the HTTP/2 connection preface has been received from the remote endpoint.
         * It is possible that the current call to
         * {@link Http2FrameReader#readFrame(ChannelHandlerContext, ByteBuf, Http2FrameListener)} will have multiple
         * frames to dispatch. So it may be OK for this class to get legitimate frames for the first readFrame.
         */
        private void verifyPrefaceReceived() throws Http2Exception {
            if (!prefaceReceived()) {
                throw connectionError(PROTOCOL_ERROR, "Received non-SETTINGS as first frame.");
            }
        }

        @Override
        public int onDataRead(ChannelHandlerContext ctx, int streamId, ByteBuf data, int padding, boolean endOfStream)
                throws Http2Exception {
            verifyPrefaceReceived();
            return internalFrameListener.onDataRead(ctx, streamId, data, padding, endOfStream);
        }

        @Override
        public void onHeadersRead(ChannelHandlerContext ctx, int streamId, Http2Headers headers, int padding,
                boolean endOfStream) throws Http2Exception {
            verifyPrefaceReceived();
            internalFrameListener.onHeadersRead(ctx, streamId, headers, padding, endOfStream);
        }

        @Override
        public void onHeadersRead(ChannelHandlerContext ctx, int streamId, Http2Headers headers, int streamDependency,
                short weight, boolean exclusive, int padding, boolean endOfStream) throws Http2Exception {
            verifyPrefaceReceived();
            internalFrameListener.onHeadersRead(ctx, streamId, headers, streamDependency, weight,
                    exclusive, padding, endOfStream);
        }

        @Override
        public void onPriorityRead(ChannelHandlerContext ctx, int streamId, int streamDependency, short weight,
                boolean exclusive) throws Http2Exception {
            verifyPrefaceReceived();
            internalFrameListener.onPriorityRead(ctx, streamId, streamDependency, weight, exclusive);
        }

        @Override
        public void onRstStreamRead(ChannelHandlerContext ctx, int streamId, long errorCode) throws Http2Exception {
            verifyPrefaceReceived();
            internalFrameListener.onRstStreamRead(ctx, streamId, errorCode);
        }

        @Override
        public void onSettingsAckRead(ChannelHandlerContext ctx) throws Http2Exception {
            verifyPrefaceReceived();
            internalFrameListener.onSettingsAckRead(ctx);
        }

        @Override
        public void onSettingsRead(ChannelHandlerContext ctx, Http2Settings settings) throws Http2Exception {
            // The first settings should change the internalFrameListener to the "real" listener
            // that expects the preface to be verified.
            if (!prefaceReceived()) {
                internalFrameListener = new FrameReadListener();
            }
            internalFrameListener.onSettingsRead(ctx, settings);
        }

        @Override
        public void onPingRead(ChannelHandlerContext ctx, long data) throws Http2Exception {
            verifyPrefaceReceived();
            internalFrameListener.onPingRead(ctx, data);
        }

        @Override
        public void onPingAckRead(ChannelHandlerContext ctx, long data) throws Http2Exception {
            verifyPrefaceReceived();
            internalFrameListener.onPingAckRead(ctx, data);
        }

        @Override
        public void onPushPromiseRead(ChannelHandlerContext ctx, int streamId, int promisedStreamId,
                Http2Headers headers, int padding) throws Http2Exception {
            verifyPrefaceReceived();
            internalFrameListener.onPushPromiseRead(ctx, streamId, promisedStreamId, headers, padding);
        }

        @Override
        public void onGoAwayRead(ChannelHandlerContext ctx, int lastStreamId, long errorCode, ByteBuf debugData)
                throws Http2Exception {
            onGoAwayRead0(ctx, lastStreamId, errorCode, debugData);
        }

        @Override
        public void onWindowUpdateRead(ChannelHandlerContext ctx, int streamId, int windowSizeIncrement)
                throws Http2Exception {
            verifyPrefaceReceived();
            internalFrameListener.onWindowUpdateRead(ctx, streamId, windowSizeIncrement);
        }

        @Override
        public void onUnknownFrame(ChannelHandlerContext ctx, byte frameType, int streamId, Http2Flags flags,
                ByteBuf payload) throws Http2Exception {
            onUnknownFrame0(ctx, frameType, streamId, flags, payload);
        }
    }
}
