package eu.openaire.urls_controller.util;

import org.apache.commons.compress.archivers.tar.TarArchiveEntry;
import org.apache.commons.compress.archivers.tar.TarArchiveInputStream;
import org.apache.commons.compress.compressors.zstandard.ZstdCompressorInputStream;
import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

@Component
public class FileDecompressor {

    private static final Logger logger = LoggerFactory.getLogger(FileDecompressor.class);


    public void decompressFiles(String zstdSource, Path targetDir) throws Exception
    {
        // Decompress the zstd file.
        Path tarPath = Paths.get(StringUtils.replace(zstdSource, ".zstd", "", 1)); // Remove the ".zstd" extension.
        int readByte = -1;

        try ( ZstdCompressorInputStream zsIn = new ZstdCompressorInputStream(new BufferedInputStream(Files.newInputStream(Paths.get(zstdSource)), FileUtils.tenMb));
              BufferedOutputStream out = new BufferedOutputStream(Files.newOutputStream(tarPath), FileUtils.tenMb) )
        {
            while ( (readByte = zsIn.read()) != -1 )
                out.write(readByte);
        }

        // Now we have a decompressed tar-file, which we will Un-tar, in order to extract the full-text files.
        try ( TarArchiveInputStream tarInput = new TarArchiveInputStream(new BufferedInputStream(Files.newInputStream(tarPath)), FileUtils.tenMb) )
        {
            TarArchiveEntry entry;
            while ( ((entry = (TarArchiveEntry) tarInput.getNextEntry()) != null) )
            {
                // Copy an individual entry.
                try ( BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(Files.newOutputStream(targetDir.resolve(entry.getName())), FileUtils.tenMb) ) {
                    while ( (readByte = tarInput.read()) != -1 )
                        bufferedOutputStream.write(readByte);
                }   // The exception will be given to the caller method.
                // No need to close the tarEntry (no "close()" method is provided).
            }
        }

        // Now we have a batch-directory which contains the tar-file along with the extracted full-text files.
        // After uploading the full-texts, the batch-directories will be deleted.
    }

}