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DSpace core data model and service APIs.
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/**
 * The contents of this file are subject to the license and copyright
 * detailed in the LICENSE and NOTICE files at the root of the source
 * tree and available online at
 *
 * http://www.dspace.org/license/
 */

package org.dspace.rdf.storage;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import com.hp.hpl.jena.graph.Graph;
import com.hp.hpl.jena.graph.Node;
import com.hp.hpl.jena.graph.NodeFactory;
import com.hp.hpl.jena.query.Dataset;
import com.hp.hpl.jena.query.DatasetFactory;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.QuerySolution;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.sparql.core.DatasetGraph;
import com.hp.hpl.jena.update.GraphStore;
import com.hp.hpl.jena.update.GraphStoreFactory;
import org.apache.commons.lang3.StringUtils;
import org.apache.jena.atlas.web.auth.HttpAuthenticator;
import org.apache.jena.atlas.web.auth.SimpleAuthenticator;
import org.apache.jena.web.DatasetGraphAccessor;
import org.apache.jena.web.DatasetGraphAccessorHTTP;
import org.apache.logging.log4j.Logger;
import org.dspace.rdf.RDFUtil;
import org.dspace.services.ConfigurationService;
import org.springframework.beans.factory.annotation.Autowired;

/**
 * @author Pascal-Nicolas Becker (dspace -at- pascal -hyphen- becker -dot- de)
 */
public class RDFStorageImpl
    implements RDFStorage {
    private static final Logger log = org.apache.logging.log4j.LogManager.getLogger(RDFStorageImpl.class);

    @Autowired(required = true)
    protected ConfigurationService configurationService;

    @Override
    public void store(String uri, Model model) {
        Node graphNode = NodeFactory.createURI(uri);
        DatasetGraphAccessor accessor = this.getAccessor();
        Dataset ds = DatasetFactory.create(model);
        DatasetGraph dsg = ds.asDatasetGraph();
        Graph g = dsg.getDefaultGraph();
        accessor.httpPut(graphNode, g);
    }

    @Override
    public Model load(String uri) {
        Node graphNode = NodeFactory.createURI(uri);
        DatasetGraphAccessor accessor = this.getAccessor();
        Graph g = accessor.httpGet(graphNode);
        if (g == null || g.isEmpty()) {
            return null;
        }
        GraphStore gs = GraphStoreFactory.create(g);
        Dataset ds = gs.toDataset();
        Model m = ds.getDefaultModel();
        return m;
    }

    protected DatasetGraphAccessor getAccessor() {
        DatasetGraphAccessor accessor;
        if (configurationService.hasProperty(RDFUtil.STORAGE_GRAPHSTORE_LOGIN_KEY)
            && configurationService.hasProperty(RDFUtil.STORAGE_GRAPHSTORE_PASSWORD_KEY)) {
            HttpAuthenticator httpAuthenticator = new SimpleAuthenticator(
                configurationService.getProperty(RDFUtil.STORAGE_GRAPHSTORE_LOGIN_KEY),
                configurationService.getProperty(RDFUtil.STORAGE_GRAPHSTORE_PASSWORD_KEY).toCharArray());
            accessor = new DatasetGraphAccessorHTTP(getGraphStoreEndpoint(),
                                                    httpAuthenticator);
        } else {
            log.debug("Did not found credential to use for our connection to the "
                          + "Graph Store HTTP endpoint, trying to connect unauthenticated.");
            accessor = new DatasetGraphAccessorHTTP(getGraphStoreEndpoint());
        }
        return accessor;
    }

    @Override
    public void delete(String uri) {
        this.getAccessor().httpDelete(NodeFactory.createURI(uri));
    }

    @Override
    public void deleteAll() {
        for (String graph : this.getAllStoredGraphs()) {
            this.delete(graph);
        }
        // clean default graph:
        this.getAccessor().httpDelete();
    }

    @Override
    public List getAllStoredGraphs() {
        String queryString = "SELECT DISTINCT ?g WHERE { GRAPH ?g { ?s ?p ?o } }";
        QueryExecution qexec;
        if (configurationService.hasProperty(RDFUtil.STORAGE_SPARQL_LOGIN_KEY)
            && configurationService.hasProperty(RDFUtil.STORAGE_SPARQL_PASSWORD_KEY)) {
            HttpAuthenticator httpAuthenticator = new SimpleAuthenticator(
                configurationService.getProperty(RDFUtil.STORAGE_SPARQL_LOGIN_KEY),
                configurationService.getProperty(RDFUtil.STORAGE_GRAPHSTORE_PASSWORD_KEY).toCharArray());
            qexec = QueryExecutionFactory.sparqlService(getSparqlEndpoint(),
                                                        queryString, httpAuthenticator);
        } else {
            qexec = QueryExecutionFactory.sparqlService(getSparqlEndpoint(),
                                                        queryString);
        }

        ResultSet rs = qexec.execSelect();
        List graphs = Collections.synchronizedList(new ArrayList());
        while (rs.hasNext()) {
            QuerySolution solution = rs.next();
            if (solution.contains("g")) {
                graphs.add(solution.get("g").asResource().getURI());
            }
        }
        qexec.close();
        return graphs;
    }

    protected String getGraphStoreEndpoint() {
        String endpoint = configurationService.getProperty(RDFUtil.STORAGE_GRAPHSTORE_ENDPOINT_KEY);
        if (StringUtils.isEmpty(endpoint)) {
            log.warn("Cannot load Graph Store HTTP Protocol endpoint! Property "
                         + RDFUtil.STORAGE_GRAPHSTORE_ENDPOINT_KEY + " does not "
                         + "exist or is empty.");
            throw new RuntimeException("Cannot load Graph Store HTTP Protocol "
                                           + "endpoint! Property "
                                           + RDFUtil.STORAGE_GRAPHSTORE_ENDPOINT_KEY + " does not "
                                           + "exist or is empty.");
        }
        return endpoint;
    }

    protected String getSparqlEndpoint() {
        // Lets see if a SPARQL endpoint is defined to be used by RDFStorageImpl
        String endpoint = configurationService.getProperty(RDFUtil.STORAGE_SPARQL_ENDPOINT_KEY);
        if (StringUtils.isEmpty(endpoint)) {
            // try to load the public sparql endpoint
            endpoint = configurationService.getProperty(RDFUtil.SPARQL_ENDPOINT_KEY);
        }
        // check if we found an endpoint
        if (StringUtils.isEmpty(endpoint)) {
            log.warn("Cannot load internal or public SPARQL endpoint!");
            throw new RuntimeException("Cannot load internal or public SPARQL "
                                           + "endpoint!");
        }
        return endpoint;
    }
}