/*
 * 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 org.apache.cassandra.io.compress;

import java.io.BufferedOutputStream;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Collection;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;
import java.util.SortedSet;
import java.util.TreeSet;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Throwables;
import com.google.common.primitives.Longs;

import org.apache.cassandra.db.TypeSizes;
import org.apache.cassandra.exceptions.ConfigurationException;
import org.apache.cassandra.io.FSReadError;
import org.apache.cassandra.io.FSWriteError;
import org.apache.cassandra.io.IVersionedSerializer;
import org.apache.cassandra.io.sstable.Component;
import org.apache.cassandra.io.sstable.CorruptSSTableException;
import org.apache.cassandra.io.sstable.Descriptor;
import org.apache.cassandra.io.util.DataInputPlus;
import org.apache.cassandra.io.util.DataOutputPlus;
import org.apache.cassandra.io.util.Memory;
import org.apache.cassandra.io.util.SafeMemory;
import org.apache.cassandra.schema.CompressionParams;
import org.apache.cassandra.utils.ChecksumType;
import org.apache.cassandra.utils.Pair;
import org.apache.cassandra.utils.concurrent.Transactional;
import org.apache.cassandra.utils.concurrent.Ref;

Holds metadata about compressed file
/**
 * Holds metadata about compressed file
 */
public class CompressionMetadata
{
    // dataLength can represent either the true length of the file
    // or some shorter value, in the case we want to impose a shorter limit on readers
    // (when early opening, we want to ensure readers cannot read past fully written sections)
    public final long dataLength;
    public final long compressedFileLength;
    private final Memory chunkOffsets;
    private final long chunkOffsetsSize;
    public final String indexFilePath;
    public final CompressionParams parameters;
    public final ChecksumType checksumType;

    
Create metadata about given compressed file including uncompressed data length, chunk size
and list of the chunk offsets of the compressed data.
This is an expensive operation! Don't create more than one for each
sstable.
Params:
dataFilePath – Path to the compressed file
Returns:
metadata about given compressed file./**
     * Create metadata about given compressed file including uncompressed data length, chunk size
     * and list of the chunk offsets of the compressed data.
     *
     * This is an expensive operation! Don't create more than one for each
     * sstable.
     *
     * @param dataFilePath Path to the compressed file
     *
     * @return metadata about given compressed file.
     */
    public static CompressionMetadata create(String dataFilePath)
    {
        Descriptor desc = Descriptor.fromFilename(dataFilePath);
        return new CompressionMetadata(desc.filenameFor(Component.COMPRESSION_INFO), new File(dataFilePath).length(), desc.version.compressedChecksumType());
    }

    @VisibleForTesting
    public CompressionMetadata(String indexFilePath, long compressedLength, ChecksumType checksumType)
    {
        this.indexFilePath = indexFilePath;
        this.checksumType = checksumType;

        try (DataInputStream stream = new DataInputStream(new FileInputStream(indexFilePath)))
        {
            String compressorName = stream.readUTF();
            int optionCount = stream.readInt();
            Map<String, String> options = new HashMap<>(optionCount);
            for (int i = 0; i < optionCount; ++i)
            {
                String key = stream.readUTF();
                String value = stream.readUTF();
                options.put(key, value);
            }
            int chunkLength = stream.readInt();
            try
            {
                parameters = new CompressionParams(compressorName, chunkLength, options);
            }
            catch (ConfigurationException e)
            {
                throw new RuntimeException("Cannot create CompressionParams for stored parameters", e);
            }

            dataLength = stream.readLong();
            compressedFileLength = compressedLength;
            chunkOffsets = readChunkOffsets(stream);
        }
        catch (FileNotFoundException e)
        {
            throw new RuntimeException(e);
        }
        catch (IOException e)
        {
            throw new CorruptSSTableException(e, indexFilePath);
        }

        this.chunkOffsetsSize = chunkOffsets.size();
    }

    private CompressionMetadata(String filePath, CompressionParams parameters, SafeMemory offsets, long offsetsSize, long dataLength, long compressedLength, ChecksumType checksumType)
    {
        this.indexFilePath = filePath;
        this.parameters = parameters;
        this.dataLength = dataLength;
        this.compressedFileLength = compressedLength;
        this.chunkOffsets = offsets;
        this.chunkOffsetsSize = offsetsSize;
        this.checksumType = checksumType;
    }

    public ICompressor compressor()
    {
        return parameters.getSstableCompressor();
    }

    public int chunkLength()
    {
        return parameters.chunkLength();
    }

    
Returns the amount of memory in bytes used off heap.
Returns:
the amount of memory in bytes used off heap/**
     * Returns the amount of memory in bytes used off heap.
     * @return the amount of memory in bytes used off heap
     */
    public long offHeapSize()
    {
        return chunkOffsets.size();
    }

    public void addTo(Ref.IdentityCollection identities)
    {
        identities.add(chunkOffsets);
    }

    
Read offsets of the individual chunks from the given input.
Params:
input – Source of the data.
Returns:
collection of the chunk offsets./**
     * Read offsets of the individual chunks from the given input.
     *
     * @param input Source of the data.
     *
     * @return collection of the chunk offsets.
     */
    private Memory readChunkOffsets(DataInput input)
    {
        final int chunkCount;
        try
        {
            chunkCount = input.readInt();
            if (chunkCount <= 0)
                throw new IOException("Compressed file with 0 chunks encountered: " + input);
        }
        catch (IOException e)
        {
            throw new FSReadError(e, indexFilePath);
        }

        @SuppressWarnings("resource")
        Memory offsets = Memory.allocate(chunkCount * 8L);
        int i = 0;
        try
        {

            for (i = 0; i < chunkCount; i++)
            {
                offsets.setLong(i * 8L, input.readLong());
            }

            return offsets;
        }
        catch (IOException e)
        {
            if (offsets != null)
                offsets.close();

            if (e instanceof EOFException)
            {
                String msg = String.format("Corrupted Index File %s: read %d but expected %d chunks.",
                                           indexFilePath, i, chunkCount);
                throw new CorruptSSTableException(new IOException(msg, e), indexFilePath);
            }
            throw new FSReadError(e, indexFilePath);
        }
    }

    
Get a chunk of compressed data (offset, length) corresponding to given position
Params:
position – Position in the file.
Returns:
pair of chunk offset and length./**
     * Get a chunk of compressed data (offset, length) corresponding to given position
     *
     * @param position Position in the file.
     * @return pair of chunk offset and length.
     */
    public Chunk chunkFor(long position)
    {
        // position of the chunk
        int idx = 8 * (int) (position / parameters.chunkLength());

        if (idx >= chunkOffsetsSize)
            throw new CorruptSSTableException(new EOFException(), indexFilePath);

        long chunkOffset = chunkOffsets.getLong(idx);
        long nextChunkOffset = (idx + 8 == chunkOffsetsSize)
                                ? compressedFileLength
                                : chunkOffsets.getLong(idx + 8);

        return new Chunk(chunkOffset, (int) (nextChunkOffset - chunkOffset - 4)); // "4" bytes reserved for checksum
    }

    
Params:
sections – Collection of sections in uncompressed file. Should not contain sections that overlap each other.
Returns:
Total chunk size in bytes for given sections including checksum./**
     * @param sections Collection of sections in uncompressed file. Should not contain sections that overlap each other.
     * @return Total chunk size in bytes for given sections including checksum.
     */
    public long getTotalSizeForSections(Collection<Pair<Long, Long>> sections)
    {
        long size = 0;
        long lastOffset = -1;
        for (Pair<Long, Long> section : sections)
        {
            int startIndex = (int) (section.left / parameters.chunkLength());
            int endIndex = (int) (section.right / parameters.chunkLength());
            endIndex = section.right % parameters.chunkLength() == 0 ? endIndex - 1 : endIndex;
            for (int i = startIndex; i <= endIndex; i++)
            {
                long offset = i * 8L;
                long chunkOffset = chunkOffsets.getLong(offset);
                if (chunkOffset > lastOffset)
                {
                    lastOffset = chunkOffset;
                    long nextChunkOffset = offset + 8 == chunkOffsetsSize
                                                   ? compressedFileLength
                                                   : chunkOffsets.getLong(offset + 8);
                    size += (nextChunkOffset - chunkOffset);
                }
            }
        }
        return size;
    }

    
Params:
sections – Collection of sections in uncompressed file
Returns:
Array of chunks which corresponds to given sections of uncompressed file, sorted by chunk offset/**
     * @param sections Collection of sections in uncompressed file
     * @return Array of chunks which corresponds to given sections of uncompressed file, sorted by chunk offset
     */
    public Chunk[] getChunksForSections(Collection<Pair<Long, Long>> sections)
    {
        // use SortedSet to eliminate duplicates and sort by chunk offset
        SortedSet<Chunk> offsets = new TreeSet<Chunk>(new Comparator<Chunk>()
        {
            public int compare(Chunk o1, Chunk o2)
            {
                return Longs.compare(o1.offset, o2.offset);
            }
        });
        for (Pair<Long, Long> section : sections)
        {
            int startIndex = (int) (section.left / parameters.chunkLength());
            int endIndex = (int) (section.right / parameters.chunkLength());
            endIndex = section.right % parameters.chunkLength() == 0 ? endIndex - 1 : endIndex;
            for (int i = startIndex; i <= endIndex; i++)
            {
                long offset = i * 8L;
                long chunkOffset = chunkOffsets.getLong(offset);
                long nextChunkOffset = offset + 8 == chunkOffsetsSize
                                     ? compressedFileLength
                                     : chunkOffsets.getLong(offset + 8);
                offsets.add(new Chunk(chunkOffset, (int) (nextChunkOffset - chunkOffset - 4))); // "4" bytes reserved for checksum
            }
        }
        return offsets.toArray(new Chunk[offsets.size()]);
    }

    public void close()
    {
        chunkOffsets.close();
    }

    public static class Writer extends Transactional.AbstractTransactional implements Transactional
    {
        // path to the file
        private final CompressionParams parameters;
        private final String filePath;
        private int maxCount = 100;
        private SafeMemory offsets = new SafeMemory(maxCount * 8L);
        private int count = 0;

        // provided by user when setDescriptor
        private long dataLength, chunkCount;

        private Writer(CompressionParams parameters, String path)
        {
            this.parameters = parameters;
            filePath = path;
        }

        public static Writer open(CompressionParams parameters, String path)
        {
            return new Writer(parameters, path);
        }

        public void addOffset(long offset)
        {
            if (count == maxCount)
            {
                SafeMemory newOffsets = offsets.copy((maxCount *= 2L) * 8L);
                offsets.close();
                offsets = newOffsets;
            }
            offsets.setLong(8L * count++, offset);
        }

        private void writeHeader(DataOutput out, long dataLength, int chunks)
        {
            try
            {
                out.writeUTF(parameters.getSstableCompressor().getClass().getSimpleName());
                out.writeInt(parameters.getOtherOptions().size());
                for (Map.Entry<String, String> entry : parameters.getOtherOptions().entrySet())
                {
                    out.writeUTF(entry.getKey());
                    out.writeUTF(entry.getValue());
                }

                // store the length of the chunk
                out.writeInt(parameters.chunkLength());
                // store position and reserve a place for uncompressed data length and chunks count
                out.writeLong(dataLength);
                out.writeInt(chunks);
            }
            catch (IOException e)
            {
                throw new FSWriteError(e, filePath);
            }
        }

        // we've written everything; wire up some final metadata state
        public Writer finalizeLength(long dataLength, int chunkCount)
        {
            this.dataLength = dataLength;
            this.chunkCount = chunkCount;
            return this;
        }

        public void doPrepare()
        {
            assert chunkCount == count;

            // finalize the size of memory used if it won't now change;
            // unnecessary if already correct size
            if (offsets.size() != count * 8L)
            {
                SafeMemory tmp = offsets;
                offsets = offsets.copy(count * 8L);
                tmp.free();
            }

            // flush the data to disk
            try (FileOutputStream fos = new FileOutputStream(filePath);
                 DataOutputStream out = new DataOutputStream(new BufferedOutputStream(fos)))
            {
                writeHeader(out, dataLength, count);
                for (int i = 0; i < count; i++)
                    out.writeLong(offsets.getLong(i * 8L));

                out.flush();
                fos.getFD().sync();
            }
            catch (IOException e)
            {
                throw Throwables.propagate(e);
            }
        }

        @SuppressWarnings("resource")
        public CompressionMetadata open(long dataLength, long compressedLength)
        {
            SafeMemory offsets = this.offsets.sharedCopy();

            // calculate how many entries we need, if our dataLength is truncated
            int count = (int) (dataLength / parameters.chunkLength());
            if (dataLength % parameters.chunkLength() != 0)
                count++;

            assert count > 0;
            // grab our actual compressed length from the next offset from our the position we're opened to
            if (count < this.count)
                compressedLength = offsets.getLong(count * 8L);

            return new CompressionMetadata(filePath, parameters, offsets, count * 8L, dataLength, compressedLength, ChecksumType.CRC32);
        }

        
Get a chunk offset by it's index.
Params:
chunkIndex – Index of the chunk.
Returns:
offset of the chunk in the compressed file./**
         * Get a chunk offset by it's index.
         *
         * @param chunkIndex Index of the chunk.
         *
         * @return offset of the chunk in the compressed file.
         */
        public long chunkOffsetBy(int chunkIndex)
        {
            return offsets.getLong(chunkIndex * 8L);
        }

        
Reset the writer so that the next chunk offset written will be the one of chunkIndex. 
Params:
chunkIndex – the next index to write/**
         * Reset the writer so that the next chunk offset written will be the
         * one of {@code chunkIndex}.
         *
         * @param chunkIndex the next index to write
         */
        public void resetAndTruncate(int chunkIndex)
        {
            count = chunkIndex;
        }

        protected Throwable doPostCleanup(Throwable failed)
        {
            return offsets.close(failed);
        }

        protected Throwable doCommit(Throwable accumulate)
        {
            return accumulate;
        }

        protected Throwable doAbort(Throwable accumulate)
        {
            return accumulate;
        }
    }

    
Holds offset and length of the file chunk
/**
     * Holds offset and length of the file chunk
     */
    public static class Chunk
    {
        public static final IVersionedSerializer<Chunk> serializer = new ChunkSerializer();

        public final long offset;
        public final int length;

        public Chunk(long offset, int length)
        {
            assert(length > 0);

            this.offset = offset;
            this.length = length;
        }

        public boolean equals(Object o)
        {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;

            Chunk chunk = (Chunk) o;
            return length == chunk.length && offset == chunk.offset;
        }

        public int hashCode()
        {
            int result = (int) (offset ^ (offset >>> 32));
            result = 31 * result + length;
            return result;
        }

        public String toString()
        {
            return String.format("Chunk<offset: %d, length: %d>", offset, length);
        }
    }

    static class ChunkSerializer implements IVersionedSerializer<Chunk>
    {
        public void serialize(Chunk chunk, DataOutputPlus out, int version) throws IOException
        {
            out.writeLong(chunk.offset);
            out.writeInt(chunk.length);
        }

        public Chunk deserialize(DataInputPlus in, int version) throws IOException
        {
            return new Chunk(in.readLong(), in.readInt());
        }

        public long serializedSize(Chunk chunk, int version)
        {
            long size = TypeSizes.sizeof(chunk.offset);
            size += TypeSizes.sizeof(chunk.length);
            return size;
        }
    }
}