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/*
 * 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.compression;

import com.ning.compress.BufferRecycler;
import com.ning.compress.lzf.ChunkDecoder;
import com.ning.compress.lzf.LZFChunk;
import com.ning.compress.lzf.util.ChunkDecoderFactory;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;

import java.util.List;

import static com.ning.compress.lzf.LZFChunk.BLOCK_TYPE_COMPRESSED;
import static com.ning.compress.lzf.LZFChunk.BLOCK_TYPE_NON_COMPRESSED;
import static com.ning.compress.lzf.LZFChunk.BYTE_V;
import static com.ning.compress.lzf.LZFChunk.BYTE_Z;
import static com.ning.compress.lzf.LZFChunk.HEADER_LEN_NOT_COMPRESSED;

/**
 * Uncompresses a {@link ByteBuf} encoded with the LZF format.
 *
 * See original LZF package
 * and LZF format for full description.
 */
public class LzfDecoder extends ByteToMessageDecoder {
    /**
     * Current state of decompression.
     */
    private enum State {
        INIT_BLOCK,
        INIT_ORIGINAL_LENGTH,
        DECOMPRESS_DATA,
        CORRUPTED
    }

    private State currentState = State.INIT_BLOCK;

    /**
     * Magic number of LZF chunk.
     */
    private static final short MAGIC_NUMBER = BYTE_Z << 8 | BYTE_V;

    /**
     * Underlying decoder in use.
     */
    private ChunkDecoder decoder;

    /**
     * Object that handles details of buffer recycling.
     */
    private BufferRecycler recycler;

    /**
     * Length of current received chunk of data.
     */
    private int chunkLength;

    /**
     * Original length of current received chunk of data.
     * It is equal to {@link #chunkLength} for non compressed chunks.
     */
    private int originalLength;

    /**
     * Indicates is this chunk compressed or not.
     */
    private boolean isCompressed;

    /**
     * Creates a new LZF decoder with the most optimal available methods for underlying data access.
     * It will "unsafe" instance if one can be used on current JVM.
     * It should be safe to call this constructor as implementations are dynamically loaded; however, on some
     * non-standard platforms it may be necessary to use {@link #LzfDecoder(boolean)} with {@code true} param.
     */
    public LzfDecoder() {
        this(false);
    }

    /**
     * Creates a new LZF decoder with specified decoding instance.
     *
     * @param safeInstance
     *        If {@code true} decoder will use {@link ChunkDecoder} that only uses standard JDK access methods,
     *        and should work on all Java platforms and JVMs.
     *        Otherwise decoder will try to use highly optimized {@link ChunkDecoder} implementation that uses
     *        Sun JDK's {@link sun.misc.Unsafe} class (which may be included by other JDK's as well).
     */
    public LzfDecoder(boolean safeInstance) {
        decoder = safeInstance ?
                ChunkDecoderFactory.safeInstance()
              : ChunkDecoderFactory.optimalInstance();

        recycler = BufferRecycler.instance();
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List