/*
 * Copyright 2006 - 2013
 *     Stefan Balev     <stefan.balev@graphstream-project.org>
 *     Julien Baudry    <julien.baudry@graphstream-project.org>
 *     Antoine Dutot    <antoine.dutot@graphstream-project.org>
 *     Yoann Pigné      <yoann.pigne@graphstream-project.org>
 *     Guilhelm Savin   <guilhelm.savin@graphstream-project.org>
 * 
 * This file is part of GraphStream <http://graphstream-project.org>.
 * 
 * GraphStream is a library whose purpose is to handle static or dynamic
 * graph, create them from scratch, file or any source and display them.
 * 
 * This program is free software distributed under the terms of two licenses, the
 * CeCILL-C license that fits European law, and the GNU Lesser General Public
 * License. You can  use, modify and/ or redistribute the software under the terms
 * of the CeCILL-C license as circulated by CEA, CNRS and INRIA at the following
 * URL <http://www.cecill.info> or under the terms of the GNU LGPL as published by
 * the Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * 
 * The fact that you are presently reading this means that you have had
 * knowledge of the CeCILL-C and LGPL licenses and that you accept their terms.
 */
package org.graphstream.stream.file;

import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.RandomAccessFile;

import javax.xml.stream.FactoryConfigurationError;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.XMLEvent;

/**
 * File source factory.
 * 
 * <p>
 * A graph reader factory allow to create readers according to a given file. It
 * both tries to read the start of the file to infer its type (works well for
 * file formats with a magic cookie or header), and if it fails it tries to look
 * at the file name extension.
 * </p>
 */
public class FileSourceFactory {
        /**
         * Create a file input for the given file name.
         * 
         * <p>
         * This method first tests if the file is a regular file and is readable. If
         * so, it opens it and reads the magic cookie to test the known file formats
         * that can be inferred from their header. If it works, it returns a file
         * input for the format. Else it looks at the file name extension, and
         * returns a file input for the extension. Finally if all fail, it throws a
         * NotFoundException.
         * </p>
         * 
         * <p>
         * Notice that this method only creates the file input and does not connect
         * it to a graph.
         * </p>
         * 
         * @param fileName
         *            Name of the graph file.
         * @return A graph reader suitable for the fileName graph format.
         * @throws IOException
         *             If the file is not readable or accessible.
         */
        public static FileSource sourceFor(String fileName) throws IOException {
                File file = new File(fileName);

                if (!file.isFile())
                        throw new IOException("not a regular file '" + fileName + "'");

                if (!file.canRead())
                        throw new IOException("not a readable file '" + fileName + "'");

                // Try to read the beginning of the file.

                RandomAccessFile in = new RandomAccessFile(fileName, "r");

                byte b[] = new byte[10];
                int n = in.read(b, 0, 10);

                // System.err.printf( "[" );
                // for( int i=0; i<n; ++i )
                // {
                // System.err.printf( "%c", (char)b[i] );
                // }
                // System.err.printf( "]%n" );

                in.close();

                // Surely match a DGS file, as DGS files are well done and have a
                // signature.

                if (n >= 3 && b[0] == 'D' && b[1] == 'G' && b[2] == 'S') {
                        if (n >= 6 && b[3] == '0' && b[4] == '0') {
                                if (b[5] == '1' || b[5] == '2') {
                                        return new FileSourceDGS1And2();
                                } else if (b[5] == '3' || b[5] == '4') {
                                        return new FileSourceDGS();
                                }
                        }
                }

                // Maybe match a GML file as most GML files begin by the line "graph [",
                // but not sure, you may create a GML file that starts by a comment, an
                // empty line, with any kind of spaces, etc.

                if (n >= 7 && b[0] == 'g' && b[1] == 'r' && b[2] == 'a' && b[3] == 'p'
                                && b[4] == 'h' && b[5] == ' ' && b[6] == '[') {
                        return new org.graphstream.stream.file.FileSourceGML();
                }

                if (n >= 4 && b[0] == '(' && b[1] == 't' && b[2] == 'l' && b[3] == 'p')
                        return new FileSourceTLP();

                // The web reader.

                String flc = fileName.toLowerCase();

                // If we did not found anything, we try with the filename extension ...

                if (flc.endsWith(".dgs")) {
                        return new FileSourceDGS();
                }

                if (flc.endsWith(".gml") || flc.endsWith(".dgml")) {
                        return new org.graphstream.stream.file.FileSourceGML();
                }

                if (flc.endsWith(".net")) {
                        return new FileSourcePajek();
                }

                if (flc.endsWith(".chaco") || flc.endsWith(".graph")) {
                        // return new GraphReaderChaco();
                }

                if (flc.endsWith(".dot")) {
                        return new org.graphstream.stream.file.FileSourceDOT();
                }

                if (flc.endsWith(".edge")) {
                        return new FileSourceEdge();
                }

                if (flc.endsWith(".lgl")) {
                        return new FileSourceLGL();
                }

                if (flc.endsWith(".ncol")) {
                        return new FileSourceNCol();
                }

                if (flc.endsWith(".tlp")) {
                        return new FileSourceTLP();
                }

                if (flc.endsWith(".xml")) {
                        String root = getXMLRootElement(fileName);

                        if (root.equalsIgnoreCase("gexf"))
                                return new FileSourceGEXF();
                        
                        return new FileSourceGraphML();
                }

                if (flc.endsWith(".gexf")) {
                        return new FileSourceGEXF();
                }

                return null;
        }

        public static String getXMLRootElement(String fileName) throws IOException {
                FileReader stream = new FileReader(fileName);
                XMLEventReader reader;
                XMLEvent e;
                String root;

                try {
                        reader = XMLInputFactory.newInstance().createXMLEventReader(stream);

                        do {
                                e = reader.nextEvent();
                        } while (!e.isStartElement() && !e.isEndDocument());

                        if (e.isEndDocument())
                                throw new IOException(
                                                "document ended before catching root element");

                        root = e.asStartElement().getName().getLocalPart();
                        reader.close();
                        stream.close();

                        return root;
                } catch (XMLStreamException ex) {
                        throw new IOException(ex);
                } catch (FactoryConfigurationError ex) {
                        throw new IOException(ex);
                }
        }
}