/*
 * 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:
 *
 * https://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.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;
import io.netty.channel.CoalescingBufferQueue;
import io.netty.handler.codec.http.HttpStatusClass;
import io.netty.handler.codec.http2.Http2CodecUtil.SimpleChannelPromiseAggregator;

import java.util.ArrayDeque;
import java.util.Queue;

import static io.netty.handler.codec.http.HttpStatusClass.INFORMATIONAL;
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.Http2Exception.connectionError;
import static io.netty.util.internal.ObjectUtil.checkNotNull;
import static io.netty.util.internal.ObjectUtil.checkPositiveOrZero;
import static java.lang.Integer.MAX_VALUE;
import static java.lang.Math.min;

/**
 * Default implementation of {@link Http2ConnectionEncoder}.
 */
public class DefaultHttp2ConnectionEncoder implements Http2ConnectionEncoder, Http2SettingsReceivedConsumer {
    private final Http2FrameWriter frameWriter;
    private final Http2Connection connection;
    private Http2LifecycleManager lifecycleManager;
    // We prefer ArrayDeque to LinkedList because later will produce more GC.
    // This initial capacity is plenty for SETTINGS traffic.
    private final Queue<Http2Settings> outstandingLocalSettingsQueue = new ArrayDeque<Http2Settings>(4);
    private Queue<Http2Settings> outstandingRemoteSettingsQueue;

    public DefaultHttp2ConnectionEncoder(Http2Connection connection, Http2FrameWriter frameWriter) {
        this.connection = checkNotNull(connection, "connection");
        this.frameWriter = checkNotNull(frameWriter, "frameWriter");
        if (connection.remote().flowController() == null) {
            connection.remote().flowController(new DefaultHttp2RemoteFlowController(connection));
        }
    }

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

    @Override
    public Http2FrameWriter frameWriter() {
        return frameWriter;
    }

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

    @Override
    public final Http2RemoteFlowController flowController() {
        return connection().remote().flowController();
    }

    @Override
    public void remoteSettings(Http2Settings settings) throws Http2Exception {
        Boolean pushEnabled = settings.pushEnabled();
        Http2FrameWriter.Configuration config = configuration();
        Http2HeadersEncoder.Configuration outboundHeaderConfig = config.headersConfiguration();
        Http2FrameSizePolicy outboundFrameSizePolicy = config.frameSizePolicy();
        if (pushEnabled != null) {
            if (!connection.isServer() && pushEnabled) {
                throw connectionError(PROTOCOL_ERROR,
                    "Client received a value of ENABLE_PUSH specified to other than 0");
            }
            connection.remote().allowPushTo(pushEnabled);
        }

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

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

        Long maxHeaderListSize = settings.maxHeaderListSize();
        if (maxHeaderListSize != null) {
            outboundHeaderConfig.maxHeaderListSize(maxHeaderListSize);
        }

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

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

    @Override
    public ChannelFuture writeData(final ChannelHandlerContext ctx, final int streamId, ByteBuf data, int padding,
            final boolean endOfStream, ChannelPromise promise) {
        promise = promise.unvoid();
        final Http2Stream stream;
        try {
            stream = requireStream(streamId);

            // Verify that the stream is in the appropriate state for sending DATA frames.
            switch (stream.state()) {
                case OPEN:
                case HALF_CLOSED_REMOTE:
                    // Allowed sending DATA frames in these states.
                    break;
                default:
                    throw new IllegalStateException("Stream " + stream.id() + " in unexpected state " + stream.state());
            }
        } catch (Throwable e) {
            data.release();
            return promise.setFailure(e);
        }

        // Hand control of the frame to the flow controller.
        flowController().addFlowControlled(stream,
                new FlowControlledData(stream, data, padding, endOfStream, promise));
        return promise;
    }

    @Override
    public ChannelFuture writeHeaders(ChannelHandlerContext ctx, int streamId, Http2Headers headers, int padding,
            boolean endStream, ChannelPromise promise) {
        return writeHeaders0(ctx, streamId, headers, false, 0, (short) 0, false, padding, endStream, promise);
    }

    private static boolean validateHeadersSentState(Http2Stream stream, Http2Headers headers, boolean isServer,
                                                    boolean endOfStream) {
        boolean isInformational = isServer && HttpStatusClass.valueOf(headers.status()) == INFORMATIONAL;
        if ((isInformational || !endOfStream) && stream.isHeadersSent() || stream.isTrailersSent()) {
            throw new IllegalStateException("Stream " + stream.id() + " sent too many headers EOS: " + endOfStream);
        }
        return isInformational;
    }

    @Override
    public ChannelFuture writeHeaders(final ChannelHandlerContext ctx, final int streamId,
            final Http2Headers headers, final int streamDependency, final short weight,
            final boolean exclusive, final int padding, final boolean endOfStream, ChannelPromise promise) {
        return writeHeaders0(ctx, streamId, headers, true, streamDependency,
                weight, exclusive, padding, endOfStream, promise);
    }

    /**
     * Write headers via {@link Http2FrameWriter}. If {@code hasPriority} is {@code false} it will ignore the
     * {@code streamDependency}, {@code weight} and {@code exclusive} parameters.
     */
    private static ChannelFuture sendHeaders(Http2FrameWriter frameWriter, ChannelHandlerContext ctx, int streamId,
                                       Http2Headers headers, final boolean hasPriority,
                                       int streamDependency, final short weight,
                                       boolean exclusive, final int padding,
                                       boolean endOfStream, ChannelPromise promise) {
        if (hasPriority) {
            return frameWriter.writeHeaders(ctx, streamId, headers, streamDependency,
                    weight, exclusive, padding, endOfStream, promise);
        }
        return frameWriter.writeHeaders(ctx, streamId, headers, padding, endOfStream, promise);
    }

    private ChannelFuture writeHeaders0(final ChannelHandlerContext ctx, final int streamId,
                                        final Http2Headers headers, final boolean hasPriority,
                                        final int streamDependency, final short weight,
                                        final boolean exclusive, final int padding,
                                        final boolean endOfStream, ChannelPromise promise) {
        try {
            Http2Stream stream = connection.stream(streamId);
            if (stream == null) {
                try {
                    // We don't create the stream in a `halfClosed` state because if this is an initial
                    // HEADERS frame we don't want the connection state to signify that the HEADERS have
                    // been sent until after they have been encoded and placed in the outbound buffer.
                    // Therefore, we let the `LifeCycleManager` will take care of transitioning the state
                    // as appropriate.
                    stream = connection.local().createStream(streamId, /*endOfStream*/ false);
                } catch (Http2Exception cause) {
                    if (connection.remote().mayHaveCreatedStream(streamId)) {
                        promise.tryFailure(new IllegalStateException("Stream no longer exists: " + streamId, cause));
                        return promise;
                    }
                    throw cause;
                }
            } else {
                switch (stream.state()) {
                    case RESERVED_LOCAL:
                        stream.open(endOfStream);
                        break;
                    case OPEN:
                    case HALF_CLOSED_REMOTE:
                        // Allowed sending headers in these states.
                        break;
                    default:
                        throw new IllegalStateException("Stream " + stream.id() + " in unexpected state " +
                                                        stream.state());
                }
            }

            // Trailing headers must go through flow control if there are other frames queued in flow control
            // for this stream.
            Http2RemoteFlowController flowController = flowController();
            if (!endOfStream || !flowController.hasFlowControlled(stream)) {
                // The behavior here should mirror that in FlowControlledHeaders

                promise = promise.unvoid();
                boolean isInformational = validateHeadersSentState(stream, headers, connection.isServer(), endOfStream);

                ChannelFuture future = sendHeaders(frameWriter, ctx, streamId, headers, hasPriority, streamDependency,
                        weight, exclusive, padding, endOfStream, promise);

                // Writing headers may fail during the encode state if they violate HPACK limits.
                Throwable failureCause = future.cause();
                if (failureCause == null) {
                    // Synchronously set the headersSent flag to ensure that we do not subsequently write
                    // other headers containing pseudo-header fields.
                    //
                    // This just sets internal stream state which is used elsewhere in the codec and doesn't
                    // necessarily mean the write will complete successfully.
                    stream.headersSent(isInformational);

                    if (!future.isSuccess()) {
                        // Either the future is not done or failed in the meantime.
                        notifyLifecycleManagerOnError(future, ctx);
                    }
                } else {
                    lifecycleManager.onError(ctx, true, failureCause);
                }

                if (endOfStream) {
                    // Must handle calling onError before calling closeStreamLocal, otherwise the error handler will
                    // incorrectly think the stream no longer exists and so may not send RST_STREAM or perform similar
                    // appropriate action.
                    lifecycleManager.closeStreamLocal(stream, future);
                }

                return future;
            } else {
                // Pass headers to the flow-controller so it can maintain their sequence relative to DATA frames.
                flowController.addFlowControlled(stream,
                        new FlowControlledHeaders(stream, headers, hasPriority, streamDependency,
                                weight, exclusive, padding, true, promise));
                return promise;
            }
        } catch (Throwable t) {
            lifecycleManager.onError(ctx, true, t);
            promise.tryFailure(t);
            return promise;
        }
    }

    @Override
    public ChannelFuture writePriority(ChannelHandlerContext ctx, int streamId, int streamDependency, short weight,
            boolean exclusive, ChannelPromise promise) {
        return frameWriter.writePriority(ctx, streamId, streamDependency, weight, exclusive, promise);
    }

    @Override
    public ChannelFuture writeRstStream(ChannelHandlerContext ctx, int streamId, long errorCode,
            ChannelPromise promise) {
        // Delegate to the lifecycle manager for proper updating of connection state.
        return lifecycleManager.resetStream(ctx, streamId, errorCode, promise);
    }

    @Override
    public ChannelFuture writeSettings(ChannelHandlerContext ctx, Http2Settings settings,
            ChannelPromise promise) {
        outstandingLocalSettingsQueue.add(settings);
        try {
            Boolean pushEnabled = settings.pushEnabled();
            if (pushEnabled != null && connection.isServer()) {
                throw connectionError(PROTOCOL_ERROR, "Server sending SETTINGS frame with ENABLE_PUSH specified");
            }
        } catch (Throwable e) {
            return promise.setFailure(e);
        }

        return frameWriter.writeSettings(ctx, settings, promise);
    }

    @Override
    public ChannelFuture writeSettingsAck(ChannelHandlerContext ctx, ChannelPromise promise) {
        if (outstandingRemoteSettingsQueue == null) {
            return frameWriter.writeSettingsAck(ctx, promise);
        }
        Http2Settings settings = outstandingRemoteSettingsQueue.poll();
        if (settings == null) {
            return promise.setFailure(new Http2Exception(INTERNAL_ERROR, "attempted to write a SETTINGS ACK with no " +
                    " pending SETTINGS"));
        }
        SimpleChannelPromiseAggregator aggregator = new SimpleChannelPromiseAggregator(promise, ctx.channel(),
                ctx.executor());
        // 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.
        frameWriter.writeSettingsAck(ctx, aggregator.newPromise());

        // We create a "new promise" to make sure that status from both the write and the application are taken into
        // account independently.
        ChannelPromise applySettingsPromise = aggregator.newPromise();
        try {
            remoteSettings(settings);
            applySettingsPromise.setSuccess();
        } catch (Throwable e) {
            applySettingsPromise.setFailure(e);
            lifecycleManager.onError(ctx, true, e);
        }
        return aggregator.doneAllocatingPromises();
    }

    @Override
    public ChannelFuture writePing(ChannelHandlerContext ctx, boolean ack, long data, ChannelPromise promise) {
        return frameWriter.writePing(ctx, ack, data, promise);
    }

    @Override
    public ChannelFuture writePushPromise(ChannelHandlerContext ctx, int streamId, int promisedStreamId,
            Http2Headers headers, int padding, ChannelPromise promise) {
        try {
            if (connection.goAwayReceived()) {
                throw connectionError(PROTOCOL_ERROR, "Sending PUSH_PROMISE after GO_AWAY received.");
            }

            Http2Stream stream = requireStream(streamId);
            // Reserve the promised stream.
            connection.local().reservePushStream(promisedStreamId, stream);

            promise = promise.unvoid();
            ChannelFuture future = frameWriter.writePushPromise(ctx, streamId, promisedStreamId, headers, padding,
                                                                promise);
            // Writing headers may fail during the encode state if they violate HPACK limits.
            Throwable failureCause = future.cause();
            if (failureCause == null) {
                // This just sets internal stream state which is used elsewhere in the codec and doesn't
                // necessarily mean the write will complete successfully.
                stream.pushPromiseSent();

                if (!future.isSuccess()) {
                    // Either the future is not done or failed in the meantime.
                    notifyLifecycleManagerOnError(future, ctx);
                }
            } else {
                lifecycleManager.onError(ctx, true, failureCause);
            }
            return future;
        } catch (Throwable t) {
            lifecycleManager.onError(ctx, true, t);
            promise.tryFailure(t);
            return promise;
        }
    }

    @Override
    public ChannelFuture writeGoAway(ChannelHandlerContext ctx, int lastStreamId, long errorCode, ByteBuf debugData,
            ChannelPromise promise) {
        return lifecycleManager.goAway(ctx, lastStreamId, errorCode, debugData, promise);
    }

    @Override
    public ChannelFuture writeWindowUpdate(ChannelHandlerContext ctx, int streamId, int windowSizeIncrement,
            ChannelPromise promise) {
        return promise.setFailure(new UnsupportedOperationException("Use the Http2[Inbound|Outbound]FlowController" +
                " objects to control window sizes"));
    }

    @Override
    public ChannelFuture writeFrame(ChannelHandlerContext ctx, byte frameType, int streamId, Http2Flags flags,
            ByteBuf payload, ChannelPromise promise) {
        return frameWriter.writeFrame(ctx, frameType, streamId, flags, payload, promise);
    }

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

    @Override
    public Http2Settings pollSentSettings() {
        return outstandingLocalSettingsQueue.poll();
    }

    @Override
    public Configuration configuration() {
        return frameWriter.configuration();
    }

    private Http2Stream requireStream(int streamId) {
        Http2Stream stream = connection.stream(streamId);
        if (stream == null) {
            final String message;
            if (connection.streamMayHaveExisted(streamId)) {
                message = "Stream no longer exists: " + streamId;
            } else {
                message = "Stream does not exist: " + streamId;
            }
            throw new IllegalArgumentException(message);
        }
        return stream;
    }

    @Override
    public void consumeReceivedSettings(Http2Settings settings) {
        if (outstandingRemoteSettingsQueue == null) {
            outstandingRemoteSettingsQueue = new ArrayDeque<Http2Settings>(2);
        }
        outstandingRemoteSettingsQueue.add(settings);
    }

    /**
     * Wrap a DATA frame so it can be written subject to flow-control. Note that this implementation assumes it
     * only writes padding once for the entire payload as opposed to writing it once per-frame. This makes the
     * {@link #size} calculation deterministic thereby greatly simplifying the implementation.
     * <p>
     * If frame-splitting is required to fit within max-frame-size and flow-control constraints we ensure that
     * the passed promise is not completed until last frame write.
     * </p>
     */
    private final class FlowControlledData extends FlowControlledBase {
        private final CoalescingBufferQueue queue;
        private int dataSize;

        FlowControlledData(Http2Stream stream, ByteBuf buf, int padding, boolean endOfStream,
                                   ChannelPromise promise) {
            super(stream, padding, endOfStream, promise);
            queue = new CoalescingBufferQueue(promise.channel());
            queue.add(buf, promise);
            dataSize = queue.readableBytes();
        }

        @Override
        public int size() {
            return dataSize + padding;
        }

        @Override
        public void error(ChannelHandlerContext ctx, Throwable cause) {
            queue.releaseAndFailAll(cause);
            // Don't update dataSize because we need to ensure the size() method returns a consistent size even after
            // error so we don't invalidate flow control when returning bytes to flow control.
            //
            // That said we will set dataSize and padding to 0 in the write(...) method if we cleared the queue
            // because of an error.
            lifecycleManager.onError(ctx, true, cause);
        }

        @Override
        public void write(ChannelHandlerContext ctx, int allowedBytes) {
            int queuedData = queue.readableBytes();
            if (!endOfStream) {
                if (queuedData == 0) {
                    if (queue.isEmpty()) {
                        // When the queue is empty it means we did clear it because of an error(...) call
                        // (as otherwise we will have at least 1 entry in there), which will happen either when called
                        // explicit or when the write itself fails. In this case just set dataSize and padding to 0
                        // which will signal back that the whole frame was consumed.
                        //
                        // See https://github.com/netty/netty/issues/8707.
                        padding = dataSize = 0;
                    } else {
                        // There's no need to write any data frames because there are only empty data frames in the
                        // queue and it is not end of stream yet. Just complete their promises by getting the buffer
                        // corresponding to 0 bytes and writing it to the channel (to preserve notification order).
                        ChannelPromise writePromise = ctx.newPromise().addListener(this);
                        ctx.write(queue.remove(0, writePromise), writePromise);
                    }
                    return;
                }

                if (allowedBytes == 0) {
                    return;
                }
            }

            // Determine how much data to write.
            int writableData = min(queuedData, allowedBytes);
            ChannelPromise writePromise = ctx.newPromise().addListener(this);
            ByteBuf toWrite = queue.remove(writableData, writePromise);
            dataSize = queue.readableBytes();

            // Determine how much padding to write.
            int writablePadding = min(allowedBytes - writableData, padding);
            padding -= writablePadding;

            // Write the frame(s).
            frameWriter().writeData(ctx, stream.id(), toWrite, writablePadding,
                    endOfStream && size() == 0, writePromise);
        }

        @Override
        public boolean merge(ChannelHandlerContext ctx, Http2RemoteFlowController.FlowControlled next) {
            FlowControlledData nextData;
            if (FlowControlledData.class != next.getClass() ||
                MAX_VALUE - (nextData = (FlowControlledData) next).size() < size()) {
                return false;
            }
            nextData.queue.copyTo(queue);
            dataSize = queue.readableBytes();
            // Given that we're merging data into a frame it doesn't really make sense to accumulate padding.
            padding = Math.max(padding, nextData.padding);
            endOfStream = nextData.endOfStream;
            return true;
        }
    }

    private void notifyLifecycleManagerOnError(ChannelFuture future, final ChannelHandlerContext ctx) {
        future.addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future) throws Exception {
                Throwable cause = future.cause();
                if (cause != null) {
                    lifecycleManager.onError(ctx, true, cause);
                }
            }
        });
    }

    /**
     * Wrap headers so they can be written subject to flow-control. While headers do not have cost against the
     * flow-control window their order with respect to other frames must be maintained, hence if a DATA frame is
     * blocked on flow-control a HEADER frame must wait until this frame has been written.
     */
    private final class FlowControlledHeaders extends FlowControlledBase {
        private final Http2Headers headers;
        private final boolean hasPriority;
        private final int streamDependency;
        private final short weight;
        private final boolean exclusive;

        FlowControlledHeaders(Http2Stream stream, Http2Headers headers, boolean hasPriority,
                              int streamDependency, short weight, boolean exclusive,
                              int padding, boolean endOfStream, ChannelPromise promise) {
            super(stream, padding, endOfStream, promise.unvoid());
            this.headers = headers;
            this.hasPriority = hasPriority;
            this.streamDependency = streamDependency;
            this.weight = weight;
            this.exclusive = exclusive;
        }

        @Override
        public int size() {
            return 0;
        }

        @Override
        public void error(ChannelHandlerContext ctx, Throwable cause) {
            if (ctx != null) {
                lifecycleManager.onError(ctx, true, cause);
            }
            promise.tryFailure(cause);
        }

        @Override
        public void write(ChannelHandlerContext ctx, int allowedBytes) {
            boolean isInformational = validateHeadersSentState(stream, headers, connection.isServer(), endOfStream);
            // The code is currently requiring adding this listener before writing, in order to call onError() before
            // closeStreamLocal().
            promise.addListener(this);

            ChannelFuture f = sendHeaders(frameWriter, ctx, stream.id(), headers, hasPriority, streamDependency,
                    weight, exclusive, padding, endOfStream, promise);
            // Writing headers may fail during the encode state if they violate HPACK limits.
            Throwable failureCause = f.cause();
            if (failureCause == null) {
                // This just sets internal stream state which is used elsewhere in the codec and doesn't
                // necessarily mean the write will complete successfully.
                stream.headersSent(isInformational);
            }
        }

        @Override
        public boolean merge(ChannelHandlerContext ctx, Http2RemoteFlowController.FlowControlled next) {
            return false;
        }
    }

    /**
     * Common base type for payloads to deliver via flow-control.
     */
    public abstract class FlowControlledBase implements Http2RemoteFlowController.FlowControlled,
            ChannelFutureListener {
        protected final Http2Stream stream;
        protected ChannelPromise promise;
        protected boolean endOfStream;
        protected int padding;

        FlowControlledBase(final Http2Stream stream, int padding, boolean endOfStream,
                final ChannelPromise promise) {
            checkPositiveOrZero(padding, "padding");
            this.padding = padding;
            this.endOfStream = endOfStream;
            this.stream = stream;
            this.promise = promise;
        }

        @Override
        public void writeComplete() {
            if (endOfStream) {
                lifecycleManager.closeStreamLocal(stream, promise);
            }
        }

        @Override
        public void operationComplete(ChannelFuture future) throws Exception {
            if (!future.isSuccess()) {
                error(flowController().channelHandlerContext(), future.cause());
            }
        }
    }
}
