Jenkins plugin download

PluginDownloader.java

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.jar.JarFile;


class PluginDownloader {
    private static final String REPO = "https://updates.jenkins-ci.org/latest/";

    public static void main(String[] args) throws Exception {
        final Set<String> needed = new HashSet<>(Set.of(args));
        final Set<String> onHand = new HashSet<>();

        while (!needed.isEmpty()) {
            final String plugin = needed.stream().sorted().findFirst().get();

            needed.addAll(fetch(plugin));

            // Mark the plugin as downloaded
            onHand.add(plugin);

            // Remove the stuff we already have
            needed.removeAll(onHand);
        }
    }

    private static Set<String> fetch(String plugin) throws IOException, MalformedURLException {
        final Path path = Paths.get(plugin + ".hpi");

        if (!Files.exists(path)) {
            final URL url = new URL(REPO + path);
            System.out.println("\033[33mfetch:\033[0m " + url);
            Files.copy(url.openStream(), path);
        }
        else {
            System.out.println("\033[32mpresent:\033[0m " + path);
        }

        // Parse dependencies
        final String dependencies = new JarFile(path.toFile())
            .getManifest()
            .getMainAttributes()
            .getValue("Plugin-Dependencies");

        if (dependencies == null) {
            return Collections.emptySet();
        }

        // Return list of dependencies
        return Arrays.stream(dependencies.split(","))
            .map(s -> s.replaceAll(":.*$", ""))
            .sorted()
            .collect(Collectors.toSet());
    }

    private static void print(String message, Object... args) {
        System.out.printf(message + "\n", args);
    }
}