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/*
 * Copyright (c) 2009, James Leigh All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * - Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution. 
 * - Neither the name of the openrdf.org nor the names of its contributors may
 *   be used to endorse or promote products derived from this software without
 *   specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 */
package org.openrdf.repository.object.compiler;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.openrdf.model.Model;
import org.openrdf.model.Resource;
import org.openrdf.model.Statement;
import org.openrdf.model.URI;
import org.openrdf.model.Value;
import org.openrdf.model.ValueFactory;
import org.openrdf.model.impl.ContextStatementImpl;
import org.openrdf.model.impl.ValueFactoryImpl;
import org.openrdf.model.vocabulary.OWL;
import org.openrdf.model.vocabulary.RDF;
import org.openrdf.rio.RDFFormat;
import org.openrdf.rio.RDFHandlerException;
import org.openrdf.rio.RDFParseException;
import org.openrdf.rio.RDFParser;
import org.openrdf.rio.RDFParserRegistry;
import org.openrdf.rio.helpers.StatementCollector;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Reads ontologies and schemas into memory from remote sources.
 * 
 * @author James Leigh
 *
 */
public class OntologyLoader {

    private Logger logger = LoggerFactory.getLogger(OntologyLoader.class);
    private Model model;
    /** context -> prefix -> namespace */
    private Map<URI, Map<String, String>> namespaces = new HashMap<URI, Map<String,String>>();
    private List<URL> imported = new ArrayList<URL>();
    private ValueFactory vf = ValueFactoryImpl.getInstance();

    public OntologyLoader(Model model) {
        this.model = model;
    }

    public List<URL> getImported() {
        return imported;
    }

    public Model getModel() {
        return model;
    }

    /** context -&gt; prefix -&gt; namespace */
    public Map<URI, Map<String, String>> getNamespaces() {
        return namespaces;
    }

    public void loadOntologies(List<URL> urls) throws RDFParseException,
            IOException {
        for (URL url : urls) {
            loadOntology(url, null, vf.createURI(url.toExternalForm()));
        }
    }

    public void followImports() throws RDFParseException, IOException {
        List<URL> urls = new ArrayList<URL>();
        for (Value obj : model.filter(null, OWL.IMPORTS, null).objects()) {
            if (obj instanceof URI) {
                URI uri = (URI) obj;
                if (!model.contains(null, null, null, uri)
                        && !model.contains(uri, RDF.TYPE, OWL.ONTOLOGY)) {
                    URL url = new URL(uri.stringValue());
                    if (!imported.contains(url)) {
                        urls.add(url);
                    }
                }
            }
        }
        if (!urls.isEmpty()) {
            imported.addAll(urls);
            for (URL url : urls) {
                String uri = url.toExternalForm();
                loadOntology(url, null, vf.createURI(uri));
            }
            followImports();
        }
    }

    private void loadOntology(URL url, RDFFormat override, final URI uri)
            throws IOException, RDFParseException {
        try {
            URLConnection conn = url.openConnection();
            if (override == null) {
                conn.setRequestProperty("Accept", getAcceptHeader());
            } else {
                conn
                        .setRequestProperty("Accept", override
                                .getDefaultMIMEType());
            }
            RDFFormat format = override;
            if (override == null) {
                format = RDFFormat.RDFXML;
                format = RDFFormat.forFileName(url.toString(), format);
                format = RDFFormat.forMIMEType(conn.getContentType(), format);
            }
            RDFParserRegistry registry = RDFParserRegistry.getInstance();
            RDFParser parser = registry.get(format).getParser();
            parser.setRDFHandler(new StatementCollector(model, model
                    .getNamespaces()) {
                @Override
                public void handleStatement(Statement st) {
                    Resource s = st.getSubject();
                    URI p = st.getPredicate();
                    Value o = st.getObject();
                    super
                            .handleStatement(new ContextStatementImpl(s, p, o,
                                    uri));
                }

                @Override
                public void handleNamespace(String prefix, String ns)
                        throws RDFHandlerException {
                    Map<String, String> map = namespaces.get(uri);
                    if (map == null) {
                        namespaces
                                .put(uri, map = new HashMap<String, String>());
                    }
                    map.put(prefix, ns);
                    super.handleNamespace(prefix, ns);
                }
            });
            InputStream in = conn.getInputStream();
            try {
                parser.parse(in, url.toExternalForm());
            } catch (RDFHandlerException e) {
                throw new AssertionError(e);
            } catch (RDFParseException e) {
                if (override == null && format.equals(RDFFormat.NTRIPLES)) {
                    // sometimes text/plain is used for rdf+xml
                    loadOntology(url, RDFFormat.RDFXML, uri);
                } else {
                    throw e;
                }
            } finally {
                in.close();
            }
        } catch (RDFParseException e) {
            logger.warn("Could not load {} {}", url, e.getMessage());
            String msg = e.getMessage() + " in " + url;
            throw new RDFParseException(msg, e.getLineNumber(), e.getColumnNumber());
        } catch (IOException e) {
            logger.warn("Could not load {} {}", url, e.getMessage());
        } catch (SecurityException e) {
            logger.warn("Could not load {} {}", url, e.getMessage());
        }
    }

    private String getAcceptHeader() {
        StringBuilder sb = new StringBuilder();
        String preferred = RDFFormat.RDFXML.getDefaultMIMEType();
        sb.append(preferred).append(";q=0.2");
        Set<RDFFormat> rdfFormats = RDFParserRegistry.getInstance().getKeys();
        for (RDFFormat format : rdfFormats) {
            for (String type : format.getMIMETypes()) {
                if (!preferred.equals(type)) {
                    sb.append(", ").append(type);
                }
            }
        }
        return sb.toString();
    }
}