return null;
        }

        MetadataTreeNode tree = null;
        MetadataTreeNode parent = null;

        for (ArtifactMetadata md : classpath) {
            MetadataTreeNode node = new MetadataTreeNode(md, parent, md.isResolved(), md.getArtifactScope());
            if (tree == null) {
                tree = node;
            }

            if (parent != null) {

        if (!vertices.contains(vertex)) {
            vertices.add(vertex);
        }

        if (parentVertex != null) // then create the edge
        {
            ArtifactMetadata md = node.getMd();
            MetadataGraphEdge e =
                    new MetadataGraphEdge(md.version, md.resolved, md.artifactScope, md.artifactUri, depth, pomOrder);

        MessageDigest md = MessageDigest.getInstance("MD5");
        mac.init(key);
        byte[] dk = mac.doFinal(MD5_CONSTANT);
        try {
            // little endian
            md.update((byte) ( ms_usage & 0xFF ));
            md.update((byte) ( ( ms_usage >> 8 ) & 0xFF ));
            md.update((byte) ( ( ms_usage >> 16 ) & 0xFF ));
            md.update((byte) ( ( ms_usage >> 24 ) & 0xFF ));

    private boolean asGraph = false;

    public MetadataResolutionRequest() {}

    public MetadataResolutionRequest(
            MavenArtifactMetadata md, ArtifactRepository localRepository, List<ArtifactRepository> remoteRepositories) {
        this.mad = md;
        this.localRepository = localRepository;
        this.remoteRepositories = remoteRepositories;
    }

    public MavenArtifactMetadata getArtifactMetadata() {

    @Override
    public String toString() {
        return "[ " + "FROM:("
                + (source == null ? "no source" : (source.md == null ? "no source MD" : source.md.toString())) + ") "
                + "TO:(" + (target == null ? "no target" : (target.md == null ? "no target MD" : target.md.toString()))
                + ") " + "version=" + version + ", scope=" + (scope == null ? "null" : scope.getScope()) + ", depth="

    /**
     * find a node by the GAV (metadata)
     *
     * @param md
     */
    public MetadataGraphNode findNode(MavenArtifactMetadata md) {
        for (MetadataGraphNode mgn : nodes) {
            if (mgn.metadata.equals(md)) {
                return mgn;
            }
        }

        MetadataGraphNode node = new MetadataGraphNode(md);
        addNode(node);
        return node;
    }

    /**

  private enum HashMethod {
    MESSAGE_DIGEST_API() {
      @Override
      public byte[] hash(Algorithm algorithm, byte[] input) {
        MessageDigest md = algorithm.getMessageDigest();
        md.update(input);
        return md.digest();
      }
    },
    HASH_FUNCTION_DIRECT() {
      @Override
      public byte[] hash(Algorithm algorithm, byte[] input) {

    static String sha1(Path path) throws NoSuchAlgorithmException, IOException {
        MessageDigest md = MessageDigest.getInstance("SHA-1");
        try (InputStream fis = Files.newInputStream(path)) {
            byte[] buffer = new byte[SHA1_BUFFER_SIZE];
            int read;
            while ((read = fis.read(buffer)) != -1) {
                md.update(buffer, 0, read);
            }
        }

        return new PluginsMetadataGenerator(session, request);
    }

    @SuppressWarnings("checkstyle:magicnumber")
    @Override
    public float getPriority() {
        return 10; // G level MD should be deployed as 3rd MD
    }

        pd.setArtifactId("my-plugin");
        pd.setGroupId("org.myco.plugins");
        pd.setVersion("1");

        MojoDescriptor md = new MojoDescriptor();
        md.setPluginDescriptor(pd);

        pd.addComponentDescriptor(md);

        return new MojoExecution(md);
    }

    private MavenSession newMavenSession() throws Exception {
        return createMavenSession(null);
    }