rdf.file.storage/src/main/java/org/apache/clerezza/rdf/file/storage/FileMGraph.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.clerezza.rdf.file.storage;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URI;
import java.util.Collection;

import java.util.Iterator;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.clerezza.rdf.core.Graph;
import org.apache.clerezza.rdf.core.NonLiteral;
import org.apache.clerezza.rdf.core.Resource;
import org.apache.clerezza.rdf.core.Triple;
import org.apache.clerezza.rdf.core.UriRef;
import org.apache.clerezza.rdf.core.impl.SimpleMGraph;
import org.apache.clerezza.rdf.core.serializedform.Parser;
import org.apache.clerezza.rdf.core.serializedform.Serializer;
import org.apache.clerezza.rdf.core.serializedform.SupportedFormat;

/**
 *
 * @author mir
 */
public class FileMGraph extends SimpleMGraph {

    private Serializer serializer;
    private File file;
    private String fileType;

    FileMGraph(UriRef uri, Parser parser,
            Serializer serializer) {
        this(new File(URI.create(uri.getUnicodeString())), parser, serializer);    
    }

    public FileMGraph(File file, Parser parser, Serializer serializer) {
        this.file = file;
        String fileEnding = extractFileEnding(file.getPath());
        fileType = getMediaTypeForFileEnding(fileEnding);
        this.serializer = serializer;
        try {
            if (file.exists() && file.length() != 0) {
                InputStream fio = new FileInputStream(file);
                Graph graph = parser.parse(fio, fileType);
                addAllNoFileAccess(graph);
            } else {
                file.createNewFile();
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
    
    @Override
    public boolean add(Triple e) {
        boolean result = super.add(e);
        writeToFile();
        return result;
    }
    
    @Override
    public boolean addAll(Collection<? extends Triple> c) {
        boolean modified = addAllNoFileAccess(c);
        writeToFile();
        return modified;
    }

    @Override
    public boolean remove(Object o) {
        Iterator<Triple> e = super.filter(null, null, null);
        while (e.hasNext()) {
            if (o.equals(e.next())) {
                e.remove();
                writeToFile();
                return true;
            }
        }        
        return false;
    }

    @Override
    public boolean removeAll(Collection<?> c) {
        boolean modified = false;
        Iterator<Triple> e = super.filter(null, null, null);
        while (e.hasNext()) {
            if (c.contains(e.next())) {
                e.remove();
                modified = true;
            }            
        }
        writeToFile();
        return modified;
    }

    @Override
    public boolean retainAll(Collection<?> c) {
        boolean result = super.retainAll(c);
        writeToFile();
        return result;
    }
    
    @Override
    public Iterator<Triple> filter(final NonLiteral subject,
            final UriRef predicate,
            final Resource object) {
        final Iterator<Triple> baseIter = super.filter(subject, predicate, object);
        Iterator<Triple> iterator = new Iterator<Triple>() {

            @Override
            public boolean hasNext() {
                return baseIter.hasNext();
            }

            @Override
            public Triple next() {
                return baseIter.next();
            }

            @Override
            public void remove() {
                baseIter.remove();
                writeToFile();
            }

        };
        return iterator;
    }

    private boolean addAllNoFileAccess(Collection<? extends Triple> c) {
        boolean modified = false;
        Iterator<? extends Triple> e = c.iterator();
        while (e.hasNext()) {
            if (super.add(e.next())) {
                modified = true;
            }
        }
        return modified;
    }

    private String extractFileEnding(String uriString) {
        String fileEnding = uriString.substring(uriString.lastIndexOf(".") + 1, uriString.length());
        return fileEnding;
    }

    private String getMediaTypeForFileEnding(String fileEnding) {
        if (fileEnding.equals("rdf")) {
            return SupportedFormat.RDF_XML;
        }
        if (fileEnding.equals("nt")) {
            return SupportedFormat.N_TRIPLE;
        }
        if (fileEnding.equals("ttl")) {
            return SupportedFormat.TURTLE;
        }
        if (fileEnding.equals("n3")) {
            return SupportedFormat.N3;
        }
        return null;
    }

    private void writeToFile() {
        synchronized(this) {
            OutputStream out;
            try {
                out = new FileOutputStream(file);
            } catch (FileNotFoundException ex) {
                throw new RuntimeException(ex);
            }
            try {
                serializer.serialize(out, this, fileType);
            } finally {
                try {
                    out.close();
                } catch (IOException ex) {
                    throw new RuntimeException(ex);
                }
            }
        }
    }

    public void delete() {
        file.delete();
    }
}