import org.eclipse.aether.artifact.Artifact;
import org.eclipse.aether.repository.WorkspaceReader;

/**
 * MavenWorkspaceReader
 */
public interface MavenWorkspaceReader extends WorkspaceReader {

    Model findModel(Artifact artifact);

    }

    @Override
    public Model findModel(Artifact artifact) {
        requireNonNull(artifact, "artifact cannot be null");
        Model model = null;

        for (WorkspaceReader workspaceReader : readers) {
            if (workspaceReader instanceof MavenWorkspaceReader) {
                model = ((MavenWorkspaceReader) workspaceReader).findModel(artifact);
                if (model != null) {

        return null;
    }

    @Override
    public List<String> findVersions(Artifact artifact) {
        return Collections.emptyList();
    }

    @Override
    public Model findModel(Artifact artifact) {
        if (GROUP_ID.equals(artifact.getGroupId())
                && ARTIFACT_ID.equals(artifact.getArtifactId())
                && VERSION.equals(artifact.getVersion())) {

            final WorkspaceReader workspace = session.getWorkspaceReader();
            if (workspace instanceof MavenWorkspaceReader) {
                model = ((MavenWorkspaceReader) workspace).findModel(pomArtifact);
                if (model != null) {
                    return model;
                }
            }

            try {
                InternalSession iSession = InternalSession.from(session);

                .map(MavenProject::getVersion)
                .collect(Collectors.collectingAndThen(Collectors.toList(), Collections::unmodifiableList));
    }

    @Override
    public Model findModel(Artifact artifact) {
        MavenProject project = getProject(artifact);
        return project == null ? null : project.getModel().getDelegate();
    }

    //
    // Implementation
    //

        final WorkspaceReader workspace = repositorySession.getWorkspaceReader();
        Model model;
        if (workspace instanceof MavenWorkspaceReader) {
            model = ((MavenWorkspaceReader) workspace).findModel(RepositoryUtils.toArtifact(artifact));
        } else {
            model = null;
        }

        if (model != null) {
            pomArtifact = artifact;
            dependencies = model.getDependencies();

    }

    public void addNode(MetadataGraphNode node) {
        nodes.add(node);
    }

    /**
     * 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;
            }
        }