/*
 * Licensed 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 com.facebook.presto.orc.reader;

import com.facebook.presto.orc.OrcCorruptionException;
import com.facebook.presto.orc.StreamDescriptor;
import com.facebook.presto.orc.metadata.ColumnEncoding;
import com.facebook.presto.orc.stream.BooleanInputStream;
import com.facebook.presto.orc.stream.DecimalInputStream;
import com.facebook.presto.orc.stream.InputStreamSource;
import com.facebook.presto.orc.stream.InputStreamSources;
import com.facebook.presto.orc.stream.LongInputStream;
import com.facebook.presto.spi.block.Block;
import com.facebook.presto.spi.block.BlockBuilder;
import com.facebook.presto.spi.block.BlockBuilderStatus;
import com.facebook.presto.spi.type.DecimalType;
import com.facebook.presto.spi.type.Type;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import java.io.IOException;
import java.util.Arrays;
import java.util.List;

import static com.facebook.presto.orc.metadata.Stream.StreamKind.DATA;
import static com.facebook.presto.orc.metadata.Stream.StreamKind.PRESENT;
import static com.facebook.presto.orc.metadata.Stream.StreamKind.SECONDARY;
import static com.facebook.presto.orc.stream.MissingInputStreamSource.missingStreamSource;
import static com.google.common.base.MoreObjects.toStringHelper;
import static java.util.Objects.requireNonNull;

public class DecimalStreamReader
        implements StreamReader
{
    private final StreamDescriptor streamDescriptor;

    private int readOffset;
    private int nextBatchSize;

    private boolean[] nullVector = new boolean[0];
    private long[] scaleVector = new long[0];

    @Nonnull
    private InputStreamSource<BooleanInputStream> presentStreamSource = missingStreamSource(BooleanInputStream.class);
    @Nullable
    private BooleanInputStream presentStream;

    @Nonnull
    private InputStreamSource<DecimalInputStream> decimalStreamSource = missingStreamSource(DecimalInputStream.class);
    @Nullable
    private DecimalInputStream decimalStream;

    @Nonnull
    private InputStreamSource<LongInputStream> scaleStreamSource = missingStreamSource(LongInputStream.class);
    @Nullable
    private LongInputStream scaleStream;

    private boolean rowGroupOpen;

    public DecimalStreamReader(StreamDescriptor streamDescriptor)
    {
        this.streamDescriptor = requireNonNull(streamDescriptor, "stream is null");
    }

    @Override
    public void prepareNextRead(int batchSize)
    {
        readOffset += nextBatchSize;
        nextBatchSize = batchSize;
    }

    @Override
    public Block readBlock(Type type)
            throws IOException
    {
        DecimalType decimalType = (DecimalType) type;

        if (!rowGroupOpen) {
            openRowGroup();
        }

        seekToOffset();
        allocateVectors();

        BlockBuilder builder = decimalType.createBlockBuilder(new BlockBuilderStatus(), nextBatchSize);
        if (presentStream == null) {
            if (decimalStream == null) {
                throw new OrcCorruptionException(streamDescriptor.getOrcDataSourceId(), "Value is not null but decimal stream is not present");
            }
            if (scaleStream == null) {
                throw new OrcCorruptionException(streamDescriptor.getOrcDataSourceId(), "Value is not null but scale stream is not present");
            }

            Arrays.fill(nullVector, false);
            scaleStream.nextLongVector(nextBatchSize, scaleVector);

            if (decimalType.isShort()) {
                decimalStream.nextShortDecimalVector(nextBatchSize, builder, decimalType, scaleVector);
            }
            else {
                decimalStream.nextLongDecimalVector(nextBatchSize, builder, decimalType, scaleVector);
            }
        }
        else {
            int nullValues = presentStream.getUnsetBits(nextBatchSize, nullVector);
            if (nullValues != nextBatchSize) {
                if (decimalStream == null) {
                    throw new OrcCorruptionException(streamDescriptor.getOrcDataSourceId(), "Value is not null but decimal stream is not present");
                }
                if (scaleStream == null) {
                    throw new OrcCorruptionException(streamDescriptor.getOrcDataSourceId(), "Value is not null but scale stream is not present");
                }

                scaleStream.nextLongVector(nextBatchSize, scaleVector, nullVector);

                if (decimalType.isShort()) {
                    decimalStream.nextShortDecimalVector(nextBatchSize, builder, decimalType, scaleVector, nullVector);
                }
                else {
                    decimalStream.nextLongDecimalVector(nextBatchSize, builder, decimalType, scaleVector, nullVector);
                }
            }
            else {
                for (int i = 0; i < nextBatchSize; i++) {
                    builder.appendNull();
                }
            }
        }

        readOffset = 0;
        nextBatchSize = 0;

        return builder.build();
    }

    private void openRowGroup()
            throws IOException
    {
        presentStream = presentStreamSource.openStream();
        decimalStream = decimalStreamSource.openStream();
        scaleStream = scaleStreamSource.openStream();
        rowGroupOpen = true;
    }

    private void seekToOffset()
            throws IOException
    {
        if (readOffset > 0) {
            if (presentStream != null) {
                // skip ahead the present bit reader, but count the set bits
                // and use this as the skip size for the data reader
                readOffset = presentStream.countBitsSet(readOffset);
            }
            if (readOffset > 0) {
                if (decimalStream == null) {
                    throw new OrcCorruptionException(streamDescriptor.getOrcDataSourceId(), "Value is not null but decimal stream is not present");
                }
                if (scaleStream == null) {
                    throw new OrcCorruptionException(streamDescriptor.getOrcDataSourceId(), "Value is not null but scale stream is not present");
                }

                decimalStream.skip(readOffset);
                scaleStream.skip(readOffset);
            }
        }
    }

    private void allocateVectors()
    {
        if (nullVector.length < nextBatchSize) {
            nullVector = new boolean[nextBatchSize];
            scaleVector = new long[nextBatchSize];
        }
    }

    @Override
    public void startStripe(InputStreamSources dictionaryStreamSources, List<ColumnEncoding> encoding)
            throws IOException
    {
        presentStreamSource = missingStreamSource(BooleanInputStream.class);
        decimalStreamSource = missingStreamSource(DecimalInputStream.class);
        scaleStreamSource = missingStreamSource(LongInputStream.class);

        readOffset = 0;
        nextBatchSize = 0;

        presentStream = null;
        decimalStream = null;
        scaleStream = null;

        rowGroupOpen = false;
    }

    @Override
    public void startRowGroup(InputStreamSources dataStreamSources)
            throws IOException
    {
        presentStreamSource = dataStreamSources.getInputStreamSource(streamDescriptor, PRESENT, BooleanInputStream.class);
        decimalStreamSource = dataStreamSources.getInputStreamSource(streamDescriptor, DATA, DecimalInputStream.class);
        scaleStreamSource = dataStreamSources.getInputStreamSource(streamDescriptor, SECONDARY, LongInputStream.class);

        readOffset = 0;
        nextBatchSize = 0;

        presentStream = null;
        decimalStream = null;
        scaleStream = null;

        rowGroupOpen = false;
    }

    @Override
    public String toString()
    {
        return toStringHelper(this)
                .addValue(streamDescriptor)
                .toString();
    }
}