/* 
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 parquet.hadoop.codec;

import java.io.IOException;
import java.nio.ByteBuffer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.compress.Compressor;
import org.xerial.snappy.Snappy;

import parquet.Preconditions;

/**
 * This class is a wrapper around the snappy compressor. It always consumes the
 * entire input in setInput and compresses it as one compressed block.
 */
public class SnappyCompressor implements Compressor {
    // Buffer for compressed output. This buffer grows as necessary.
    private ByteBuffer outputBuffer = ByteBuffer.allocateDirect(0);

    // Buffer for uncompressed input. This buffer grows as necessary.
    private ByteBuffer inputBuffer = ByteBuffer.allocateDirect(0);

    private long bytesRead = 0L;
    private long bytesWritten = 0L;
    private boolean finishCalled = false;

    /**
     * Fills specified buffer with compressed data. Returns actual number
     * of bytes of compressed data. A return value of 0 indicates that
     * needsInput() should be called in order to determine if more input
     * data is required.
     *
     * @param buffer Buffer for the compressed data
     * @param off    Start offset of the data
     * @param len    Size of the buffer
     * @return The actual number of bytes of compressed data.
     */
    @Override
    public synchronized int compress(byte[] buffer, int off, int len) throws IOException {
        SnappyUtil.validateBuffer(buffer, off, len);

        if (needsInput()) {
            // No buffered output bytes and no input to consume, need more input
            return 0;
        }

        if (!outputBuffer.hasRemaining()) {
            // There is uncompressed input, compress it now
            int maxOutputSize = Snappy.maxCompressedLength(inputBuffer.position());
            if (maxOutputSize > outputBuffer.capacity()) {
                outputBuffer = ByteBuffer.allocateDirect(maxOutputSize);
            }
            // Reset the previous outputBuffer
            outputBuffer.clear();
            inputBuffer.limit(inputBuffer.position());
            inputBuffer.position(0);

            int size = Snappy.compress(inputBuffer, outputBuffer);
            outputBuffer.limit(size);
            inputBuffer.limit(0);
            inputBuffer.rewind();
        }

        // Return compressed output up to 'len'
        int numBytes = Math.min(len, outputBuffer.remaining());
        outputBuffer.get(buffer, off, numBytes);
        bytesWritten += numBytes;
        return numBytes;
    }

    @Override
    public synchronized void setInput(byte[] buffer, int off, int len) {
        SnappyUtil.validateBuffer(buffer, off, len);

        Preconditions.checkArgument(!outputBuffer.hasRemaining(),
                "Output buffer should be empty. Caller must call compress()");

        if (inputBuffer.capacity() - inputBuffer.position() < len) {
            ByteBuffer tmp = ByteBuffer.allocateDirect(inputBuffer.position() + len);
            inputBuffer.rewind();
            tmp.put(inputBuffer);
            inputBuffer = tmp;
        } else {
            inputBuffer.limit(inputBuffer.position() + len);
        }

        // Append the current bytes to the input buffer
        inputBuffer.put(buffer, off, len);
        bytesRead += len;
    }

    @Override
    public void end() {
        // No-op
    }

    @Override
    public void finish() {
        finishCalled = true;
    }

    @Override
    public synchronized boolean finished() {
        return finishCalled && inputBuffer.position() == 0 && !outputBuffer.hasRemaining();
    }

    @Override
    public long getBytesRead() {
        return bytesRead;
    }

    @Override
    public long getBytesWritten() {
        return bytesWritten;
    }

    @Override
    // We want to compress all the input in one go so we always need input until it is
    // all consumed.
    public synchronized boolean needsInput() {
        return !finishCalled;
    }

    @Override
    public void reinit(Configuration c) {
        reset();
    }

    @Override
    public synchronized void reset() {
        finishCalled = false;
        bytesRead = bytesWritten = 0;
        inputBuffer.rewind();
        outputBuffer.rewind();
        inputBuffer.limit(0);
        outputBuffer.limit(0);
    }

    @Override
    public void setDictionary(byte[] dictionary, int off, int len) {
        // No-op
    }
}