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/*
 * 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.kafka.snapshot;

import org.apache.kafka.common.record.FileRecords;
import org.apache.kafka.common.record.Records;
import org.apache.kafka.common.record.UnalignedRecords;
import org.apache.kafka.raft.OffsetAndEpoch;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.Path;

public final class FileRawSnapshotReader implements RawSnapshotReader, AutoCloseable {
    private final FileRecords fileRecords;
    private final OffsetAndEpoch snapshotId;

    private FileRawSnapshotReader(FileRecords fileRecords, OffsetAndEpoch snapshotId) {
        this.fileRecords = fileRecords;
        this.snapshotId = snapshotId;
    }

    @Override
    public OffsetAndEpoch snapshotId() {
        return snapshotId;
    }

    @Override
    public long sizeInBytes() {
        return fileRecords.sizeInBytes();
    }

    @Override
    public UnalignedRecords slice(long position, int size) {
        return fileRecords.sliceUnaligned(Math.toIntExact(position), size);
    }

    @Override
    public Records records() {
        return fileRecords;
    }

    @Override
    public void close() {
        try {
            fileRecords.close();
        } catch (IOException e) {
            throw new UncheckedIOException(
                String.format("Unable to close snapshot reader %s at %s", snapshotId, fileRecords),
                e
            );
        }
    }

    /**
     * Opens a snapshot for reading.
     *
     * @param logDir the directory for the topic partition
     * @param snapshotId the end offset and epoch for the snapshotId
     */
    public static FileRawSnapshotReader open(Path logDir, OffsetAndEpoch snapshotId) {
        FileRecords fileRecords;
        Path filePath = Snapshots.snapshotPath(logDir, snapshotId);
        try {
            fileRecords = FileRecords.open(
                filePath.toFile(),
                false, // mutable
                true, // fileAlreadyExists
                0, // initFileSize
                false // preallocate
            );
        } catch (IOException e) {
            throw new UncheckedIOException(
                String.format("Unable to Opens a snapshot file %s", filePath.toAbsolutePath()), e
            );
        }

        return new FileRawSnapshotReader(fileRecords, snapshotId);
    }
}