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.OutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;

@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.

        try ( ZstdCompressorInputStream zsIn = new ZstdCompressorInputStream(new BufferedInputStream(Files.newInputStream(Paths.get(zstdSource))));
              OutputStream out = Files.newOutputStream(tarPath) )
        {
            final byte[] buffer = new byte[1048576];    // 1 Mb
            int n = 0;
            while ( (n = zsIn.read(buffer)) != -1 ) {
                out.write(buffer, 0, n);
            }
        }

        // 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))) )
        {
            TarArchiveEntry entry;
            while ( ((entry = (TarArchiveEntry) tarInput.getNextEntry()) != null) )
            {
                String entryName = entry.getName();
                Path targetFilePath = targetDir.resolve(entryName);
                Files.copy(tarInput, targetFilePath, StandardCopyOption.REPLACE_EXISTING);   // Copy an individual entry.
                // No need to close the tarEntry.
            }
        }

        // 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.
    }

}