import com.github.luben.zstd.ZstdDecompressCtx;
import com.github.luben.zstd.ZstdInputStream;
import org.apache.commons.io.IOUtils;
import sun.nio.ch.DirectBuffer;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.Paths;

import static java.nio.file.StandardOpenOption.*;

public class DirectBufExample {
    public static void main(String[] args) throws IOException {
        long uncompressedSize = 209715200;
        long compressedSize = 126745877;
        int loops = 10;

        var compressedFile = Paths.get("c:/temp/foo.zstd");

        var uncompressedFile = Paths.get("c:/temp/foo");


        long time = System.currentTimeMillis();
        for (var i = 0; i < loops; i++) {
            extractUsingDirect(compressedSize, uncompressedSize, compressedFile, uncompressedFile);
        }
        System.out.printf("Direct: %s\n", System.currentTimeMillis() - time);


        time = System.currentTimeMillis();
        for (var i = 0; i < loops; i++) {
            extractUsingStreams(compressedFile, uncompressedFile);
        }
        System.out.printf("Streams: %s\n", System.currentTimeMillis() - time);


        time = System.currentTimeMillis();
        for (var i = 0; i < loops; i++) {
            extractUsingByteArray(uncompressedSize, compressedFile, uncompressedFile);
        }
        System.out.printf("Byte arrays: %s\n", System.currentTimeMillis() - time);
    }


    private static void extractUsingByteArray(long uncompressedSize, Path compressedFile, Path uncompressedFile) throws IOException {
        try (
                var inputStream = new FileInputStream(compressedFile.toFile());
                var outFile = new FileOutputStream(uncompressedFile.toFile());
                var zstd = new ZstdDecompressCtx();
        ) {
            zstd.setFinalize(false);
            byte[] data = zstd.decompress(inputStream.readAllBytes(), (int) uncompressedSize);
            outFile.write(data);

        }
    }

    private static void extractUsingStreams(Path compressedFile, Path uncompressedFile) throws IOException {
        try (
                var inputStream = new FileInputStream(compressedFile.toFile());
                var outFile = new FileOutputStream(uncompressedFile.toFile());
                var zstd = new ZstdInputStream(inputStream)
        ) {
            zstd.setFinalize(false);
            IOUtils.copy(zstd, outFile);
        }
    }

    private static void extractUsingDirect(long compressedSize, long uncompressedSize, Path compressedFile, Path uncompressedFile) throws IOException {
        try (
                var from = FileChannel.open(compressedFile, READ);
                var to = FileChannel.open(uncompressedFile, TRUNCATE_EXISTING, WRITE, READ);
                var zstd = new ZstdDecompressCtx()
        ) {
            var directBufferFrom = from.map(FileChannel.MapMode.READ_ONLY, 0, compressedSize);
            var directBufferTo = to.map(FileChannel.MapMode.READ_WRITE, 0, uncompressedSize);

            zstd.setFinalize(false);
            zstd.decompressDirectByteBuffer(directBufferTo, 0, (int) uncompressedSize, directBufferFrom, 0, (int) compressedSize);

            ((DirectBuffer) directBufferFrom).cleaner().clean();
            ((DirectBuffer) directBufferTo).cleaner().clean();

        }
    }
}