/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2014 Mike Becker. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. 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.
 *
 * 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 HOLDER 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 de.uapcore.sigred.doc.base;

import de.uapcore.sigred.doc.Resources;
import de.uapcore.sigrapi.impl.Digraph;
import de.uapcore.sigrapi.impl.Graph;
import de.uapcore.sigrapi.IGraph;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.xerces.impl.Constants;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.Namespace;
import org.dom4j.QName;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;

public abstract class AbstractGraphDocument<T extends IGraph>
        extends FileBackedDocument {
    
    protected static final Namespace NAMESPACE = Namespace.get("sigred",
        "http://develop.uap-core.de/sigred/");
    
    private static final
        QName TAG_GRAPHDOC = QName.get("graph-document", NAMESPACE);
    private static final
        QName TAG_GRAPH = QName.get("graph", NAMESPACE);
    private static final
        QName TAG_DIGRAPH = QName.get("digraph", NAMESPACE);
    private static final
        QName TAG_METADATA = QName.get("metadata", NAMESPACE);
    
    protected final T graph;
    
    private final GraphDocumentMetadata metadata;
    
    public AbstractGraphDocument(Class<T> graphType) {
        T g;
        try {
            g = graphType.newInstance();
        } catch (ReflectiveOperationException e) {
            assert false;
            g = null; // for the compiler
        }
        graph = g;
        metadata = new GraphDocumentMetadata();
    }

    public T getGraph() {
        return graph;
    }
    
    public GraphDocumentMetadata getMetadata() {
        return metadata;
    }

    protected abstract void writeGraph(Element rootNode) throws IOException;
    protected abstract void readGraph(Element rootNode) throws IOException;

    @Override
    public void writeTo(OutputStream out) throws IOException {
        Document doc = DocumentHelper.createDocument();

        Element rootNode = doc.addElement(TAG_GRAPHDOC);

        Element metadataNode = rootNode.addElement(TAG_METADATA);

        metadata.write(metadataNode);

        if (graph instanceof Graph) {
            writeGraph(rootNode.addElement(TAG_GRAPH));
        } else if (graph instanceof Digraph) {
            writeGraph(rootNode.addElement(TAG_DIGRAPH));
        } else {
            throw new IOException("unsupported graph type");
        }

        XMLWriter writer = new XMLWriter(out, OutputFormat.createPrettyPrint());
        writer.write(doc);
        writer.flush();
    }

    @Override
    public void readFrom(InputStream in) throws IOException {
        try {
            SAXReader reader = new SAXReader(true);
            reader.setStripWhitespaceText(true);
            
            reader.setFeature(Constants.XERCES_FEATURE_PREFIX+
                Constants.SCHEMA_VALIDATION_FEATURE, true);
            reader.setProperty(Constants.XERCES_PROPERTY_PREFIX +
                Constants.SCHEMA_LOCATION, String.format("%s %s",
                    NAMESPACE.getURI(), Resources.class.getResource(
                        "graph-document.xsd").toExternalForm()));
            
            final AtomicBoolean passed = new AtomicBoolean(true);
            final AtomicReference<SAXParseException> xmlerror = new AtomicReference<>();
            // TODO: we should do more detailed error handling here
            reader.setErrorHandler(new ErrorHandler() {
                @Override
                public void warning(SAXParseException exception) throws SAXException {
                }

                @Override
                public void error(SAXParseException exception) throws SAXException {
                    xmlerror.set(exception);
                    passed.set(false);
                }

                @Override
                public void fatalError(SAXParseException exception) throws SAXException {
                    xmlerror.set(exception);
                    passed.set(false);
                }
                
            });
            Document doc = reader.read(in);
            if (!passed.get()) {
                // TODO: provide details (maybe via separate error object?)
                throw xmlerror.get();
            }
            
            doc.normalize();
            
            Element root = doc.getRootElement();
            metadata.read(root.element(TAG_METADATA));
            
            if (graph instanceof Graph) {
                readGraph(root.element(TAG_GRAPH));
            } else if (graph instanceof Digraph) {
                readGraph(root.element(TAG_DIGRAPH));
            } else {
                throw new IOException("unsupported graph type");
            }
        } catch (DocumentException | SAXException ex) {
            throw new IOException(ex);
        }
    }
}