/*
    * 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.ChannelHandlerContext;
  
  /**
   * An listener of HTTP/2 frames.
   */
  public interface Http2FrameListener {
      /**
       * Handles an inbound {@code DATA} frame.
       *
       * @param ctx the context from the handler where the frame was read.
       * @param streamId the subject stream for the frame.
       * @param data payload buffer for the frame. This buffer will be released by the codec.
       * @param padding additional bytes that should be added to obscure the true content size. Must be between 0 and
       *                256 (inclusive).
       * @param endOfStream Indicates whether this is the last frame to be sent from the remote endpoint for this stream.
       * @return the number of bytes that have been processed by the application. The returned bytes are used by the
       * inbound flow controller to determine the appropriate time to expand the inbound flow control window (i.e. send
       * {@code WINDOW_UPDATE}). Returning a value equal to the length of {@code data} + {@code padding} will effectively
       * opt-out of application-level flow control for this frame. Returning a value less than the length of {@code data}
       * + {@code padding} will defer the returning of the processed bytes, which the application must later return via
       * {@link Http2LocalFlowController#consumeBytes(Http2Stream, int)}. The returned value must
       * be >= {@code 0} and <= {@code data.readableBytes()} + {@code padding}.
       */
      int onDataRead(ChannelHandlerContext ctx, int streamId, ByteBuf data, int padding,
                     boolean endOfStream) throws Http2Exception;
  
      /**
       * Handles an inbound {@code HEADERS} frame.
       * <p>
       * Only one of the following methods will be called for each {@code HEADERS} frame sequence.
       * One will be called when the {@code END_HEADERS} flag has been received.
       * <ul>
       * <li>{@link #onHeadersRead(ChannelHandlerContext, int, Http2Headers, int, boolean)}</li>
       * <li>{@link #onHeadersRead(ChannelHandlerContext, int, Http2Headers, int, short, boolean, int, boolean)}</li>
       * <li>{@link #onPushPromiseRead(ChannelHandlerContext, int, int, Http2Headers, int)}</li>
       * </ul>
       * <p>
       * To say it another way; the {@link Http2Headers} will contain all of the headers
       * for the current message exchange step (additional queuing is not necessary).
       *
       * @param ctx the context from the handler where the frame was read.
       * @param streamId the subject stream for the frame.
       * @param headers the received headers.
       * @param padding additional bytes that should be added to obscure the true content size. Must be between 0 and
       *                256 (inclusive).
       * @param endOfStream Indicates whether this is the last frame to be sent from the remote endpoint
       *            for this stream.
       */
      void onHeadersRead(ChannelHandlerContext ctx, int streamId, Http2Headers headers, int padding,
              boolean endOfStream) throws Http2Exception;
  
      /**
       * Handles an inbound {@code HEADERS} frame with priority information specified.
       * Only called if {@code END_HEADERS} encountered.
       * <p>
       * Only one of the following methods will be called for each {@code HEADERS} frame sequence.
       * One will be called when the {@code END_HEADERS} flag has been received.
       * <ul>
       * <li>{@link #onHeadersRead(ChannelHandlerContext, int, Http2Headers, int, boolean)}</li>
       * <li>{@link #onHeadersRead(ChannelHandlerContext, int, Http2Headers, int, short, boolean, int, boolean)}</li>
       * <li>{@link #onPushPromiseRead(ChannelHandlerContext, int, int, Http2Headers, int)}</li>
       * </ul>
       * <p>
       * To say it another way; the {@link Http2Headers} will contain all of the headers
       * for the current message exchange step (additional queuing is not necessary).
       *
       * @param ctx the context from the handler where the frame was read.
       * @param streamId the subject stream for the frame.
       * @param headers the received headers.
       * @param streamDependency the stream on which this stream depends, or 0 if dependent on the
       *            connection.
       * @param weight the new weight for the stream.
       * @param exclusive whether or not the stream should be the exclusive dependent of its parent.
       * @param padding additional bytes that should be added to obscure the true content size. Must be between 0 and
       *                256 (inclusive).
       * @param endOfStream Indicates whether this is the last frame to be sent from the remote endpoint
       *            for this stream.
       */
      void onHeadersRead(ChannelHandlerContext ctx, int streamId, Http2Headers headers,
              int streamDependency, short weight, boolean exclusive, int padding, boolean endOfStream)
              throws Http2Exception;
 
     /**
      * Handles an inbound {@code PRIORITY} frame.
      * <p>
      * Note that is it possible to have this method called and no stream object exist for either
      * {@code streamId}, {@code streamDependency}, or both. This is because the {@code PRIORITY} frame can be
      * sent/received when streams are in the {@code CLOSED} state.
      *
      * @param ctx the context from the handler where the frame was read.
      * @param streamId the subject stream for the frame.
      * @param streamDependency the stream on which this stream depends, or 0 if dependent on the
      *            connection.
      * @param weight the new weight for the stream.
      * @param exclusive whether or not the stream should be the exclusive dependent of its parent.
      */
     void onPriorityRead(ChannelHandlerContext ctx, int streamId, int streamDependency,
             short weight, boolean exclusive) throws Http2Exception;
 
     /**
      * Handles an inbound {@code RST_STREAM} frame.
      *
      * @param ctx the context from the handler where the frame was read.
      * @param streamId the stream that is terminating.
      * @param errorCode the error code identifying the type of failure.
      */
     void onRstStreamRead(ChannelHandlerContext ctx, int streamId, long errorCode) throws Http2Exception;
 
     /**
      * Handles an inbound {@code SETTINGS} acknowledgment frame.
      * @param ctx the context from the handler where the frame was read.
      */
     void onSettingsAckRead(ChannelHandlerContext ctx) throws Http2Exception;
 
     /**
      * Handles an inbound {@code SETTINGS} frame.
      *
      * @param ctx the context from the handler where the frame was read.
      * @param settings the settings received from the remote endpoint.
      */
     void onSettingsRead(ChannelHandlerContext ctx, Http2Settings settings) throws Http2Exception;
 
     /**
      * Handles an inbound {@code PING} frame.
      *
      * @param ctx the context from the handler where the frame was read.
      * @param data the payload of the frame.
      */
     void onPingRead(ChannelHandlerContext ctx, long data) throws Http2Exception;
 
     /**
      * Handles an inbound {@code PING} acknowledgment.
      *
      * @param ctx the context from the handler where the frame was read.
      * @param data the payload of the frame.
      */
     void onPingAckRead(ChannelHandlerContext ctx, long data) throws Http2Exception;
 
     /**
      * Handles an inbound {@code PUSH_PROMISE} frame. Only called if {@code END_HEADERS} encountered.
      * <p>
      * Promised requests MUST be authoritative, cacheable, and safe.
      * See <a href="https://tools.ietf.org/html/rfc7540#section-8.2">[RFC 7540], Section 8.2</a>.
      * <p>
      * Only one of the following methods will be called for each {@code HEADERS} frame sequence.
      * One will be called when the {@code END_HEADERS} flag has been received.
      * <ul>
      * <li>{@link #onHeadersRead(ChannelHandlerContext, int, Http2Headers, int, boolean)}</li>
      * <li>{@link #onHeadersRead(ChannelHandlerContext, int, Http2Headers, int, short, boolean, int, boolean)}</li>
      * <li>{@link #onPushPromiseRead(ChannelHandlerContext, int, int, Http2Headers, int)}</li>
      * </ul>
      * <p>
      * To say it another way; the {@link Http2Headers} will contain all of the headers
      * for the current message exchange step (additional queuing is not necessary).
      *
      * @param ctx the context from the handler where the frame was read.
      * @param streamId the stream the frame was sent on.
      * @param promisedStreamId the ID of the promised stream.
      * @param headers the received headers.
      * @param padding additional bytes that should be added to obscure the true content size. Must be between 0 and
      *                256 (inclusive).
      */
     void onPushPromiseRead(ChannelHandlerContext ctx, int streamId, int promisedStreamId,
             Http2Headers headers, int padding) throws Http2Exception;
 
     /**
      * Handles an inbound {@code GO_AWAY} frame.
      *
      * @param ctx the context from the handler where the frame was read.
      * @param lastStreamId the last known stream of the remote endpoint.
      * @param errorCode the error code, if abnormal closure.
      * @param debugData application-defined debug data. If this buffer needs to be retained by the
      *            listener they must make a copy.
      */
     void onGoAwayRead(ChannelHandlerContext ctx, int lastStreamId, long errorCode, ByteBuf debugData)
             throws Http2Exception;
 
     /**
      * Handles an inbound {@code WINDOW_UPDATE} frame.
      *
      * @param ctx the context from the handler where the frame was read.
      * @param streamId the stream the frame was sent on.
      * @param windowSizeIncrement the increased number of bytes of the remote endpoint's flow
      *            control window.
      */
     void onWindowUpdateRead(ChannelHandlerContext ctx, int streamId, int windowSizeIncrement)
             throws Http2Exception;
 
     /**
      * Handler for a frame not defined by the HTTP/2 spec.
      *
      * @param ctx the context from the handler where the frame was read.
      * @param frameType the frame type from the HTTP/2 header.
      * @param streamId the stream the frame was sent on.
      * @param flags the flags in the frame header.
      * @param payload the payload of the frame.
      */
     void onUnknownFrame(ChannelHandlerContext ctx, byte frameType, int streamId, Http2Flags flags, ByteBuf payload)
             throws Http2Exception;
 }