//
//  ========================================================================
//  Copyright (c) 1995-2020 Mort Bay Consulting Pty Ltd and others.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.spdy.parser;

import java.nio.ByteBuffer;

import org.eclipse.jetty.spdy.CompressionFactory;
import org.eclipse.jetty.spdy.api.HeadersInfo;
import org.eclipse.jetty.spdy.api.SPDY;
import org.eclipse.jetty.spdy.frames.ControlFrameType;
import org.eclipse.jetty.spdy.frames.HeadersFrame;
import org.eclipse.jetty.util.Fields;

public class HeadersBodyParser extends ControlFrameBodyParser
{
    private final Fields headers = new Fields();
    private final ControlFrameParser controlFrameParser;
    private final HeadersBlockParser headersBlockParser;
    private State state = State.STREAM_ID;
    private int cursor;
    private int streamId;

    public HeadersBodyParser(CompressionFactory.Decompressor decompressor, ControlFrameParser controlFrameParser)
    {
        this.controlFrameParser = controlFrameParser;
        this.headersBlockParser = new HeadersHeadersBlockParser(decompressor);
    }

    @Override
    public boolean parse(ByteBuffer buffer)
    {
        while (buffer.hasRemaining())
        {
            switch (state)
            {
                case STREAM_ID:
                {
                    if (buffer.remaining() >= 4)
                    {
                        streamId = buffer.getInt() & 0x7F_FF_FF_FF;
                        state = State.ADDITIONAL;
                    }
                    else
                    {
                        state = State.STREAM_ID_BYTES;
                        cursor = 4;
                    }
                    break;
                }
                case STREAM_ID_BYTES:
                {
                    byte currByte = buffer.get();
                    --cursor;
                    streamId += (currByte & 0xFF) << 8 * cursor;
                    if (cursor == 0)
                    {
                        streamId &= 0x7F_FF_FF_FF;
                        state = State.ADDITIONAL;
                    }
                    break;
                }
                case ADDITIONAL:
                {
                    switch (controlFrameParser.getVersion())
                    {
                        case SPDY.V2:
                        {
                            if (buffer.remaining() >= 2)
                            {
                                buffer.getShort();
                                state = State.HEADERS;
                            }
                            else
                            {
                                state = State.ADDITIONAL_BYTES;
                                cursor = 2;
                            }
                            break;
                        }
                        case SPDY.V3:
                        {
                            state = State.HEADERS;
                            break;
                        }
                        default:
                        {
                            throw new IllegalStateException();
                        }
                    }
                    break;
                }
                case ADDITIONAL_BYTES:
                {
                    assert controlFrameParser.getVersion() == SPDY.V2;
                    buffer.get();
                    --cursor;
                    if (cursor == 0)
                        state = State.HEADERS;
                    break;
                }
                case HEADERS:
                {
                    short version = controlFrameParser.getVersion();
                    int length = controlFrameParser.getLength() - 4;
                    if (version == SPDY.V2)
                        length -= 2;
                    if (headersBlockParser.parse(streamId, version, length, buffer))
                    {
                        byte flags = controlFrameParser.getFlags();
                        if (flags != 0 && flags != HeadersInfo.FLAG_CLOSE && flags != HeadersInfo.FLAG_RESET_COMPRESSION)
                            throw new IllegalArgumentException("Invalid flag " + flags + " for frame " + ControlFrameType.HEADERS);

                        HeadersFrame frame = new HeadersFrame(version, flags, streamId, new Fields(headers, true));
                        controlFrameParser.onControlFrame(frame);

                        reset();
                        return true;
                    }
                    break;
                }
                default:
                {
                    throw new IllegalStateException();
                }
            }
        }
        return false;
    }

    private void reset()
    {
        headers.clear();
        state = State.STREAM_ID;
        cursor = 0;
        streamId = 0;
    }

    private enum State
    {
        STREAM_ID, STREAM_ID_BYTES, ADDITIONAL, ADDITIONAL_BYTES, HEADERS
    }

    private class HeadersHeadersBlockParser extends HeadersBlockParser
    {
        public HeadersHeadersBlockParser(CompressionFactory.Decompressor decompressor)
        {
            super(decompressor);
        }

        @Override
        protected void onHeader(String name, String[] values)
        {
            for (String value : values)
                headers.add(name, value);
        }
    }
}
