/*
 *  eXist Open Source Native XML Database
 *  Copyright (C) 2001-2015 The eXist Project
 *  http://exist-db.org
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public License
 *  as published by the Free Software Foundation; either version 2
 *  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 library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
package org.exist.config.mapper;

import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Stack;

import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.events.XMLEvent;

import org.exist.config.Configurable;
import org.exist.config.Configuration;
import org.exist.config.Configurator;
import org.exist.config.annotation.NewClass;

/**
 * @author <a href="mailto:shabanovd@gmail.com">Dmitriy Shabanov</a>
 */
public class Constructor {

    private static Map<Object, Configuration> configurations = new HashMap<Object, Configuration>();

    public static Configuration getConfiguration(Object obj) {
        return configurations.get(obj);
    }

    /**
     * Create new java object by mapping instructions.
     */
    public static Object load(NewClass newClazz, Configurable instance, Configuration conf) {

        final String url = newClazz.mapper();
        if (url == null) {
            Configurator.LOG.error("Field must have 'ConfigurationFieldClassMask' annotation or " +
                "registered mapping instruction for class '" + newClazz.name() + "' [" + conf.getName() + "], " +
                "skip instance creation.");
            return null;
        }

        final InputStream is = instance.getClass().getClassLoader().getResourceAsStream(url);
        if (is == null) {
            Configurator.LOG.error("Registered mapping instruction for class '" + newClazz.name() + "' " +
                "missing resource '" + url + "', skip instance creation.");
            return null;
        }

        final XMLInputFactory inputFactory = XMLInputFactory.newInstance();
        try {
            final XMLStreamReader reader = inputFactory.createXMLStreamReader(is);

            Object obj = null;
            final Stack<Object> objs = new Stack<>();
            final Stack<CallMethod> instructions = new Stack<>();

            int eventType;
            while (reader.hasNext()) {
                eventType = reader.next();

                switch (eventType) {
                    case XMLEvent.START_ELEMENT:
                        String localName = reader.getLocalName();

                        if ("class".equals(localName)) {
                            if (!"name".equals(reader.getAttributeLocalName(0))) {
                                Configurator.LOG.error("class element first attribute must be 'name', skip instance creation.");
                                return null;
                            }

                            final String clazzName = reader.getAttributeValue(0);
                            final Class<?> clazz = Class.forName(clazzName);
                            final java.lang.reflect.Constructor<?> constructor = clazz.getConstructor();

                            Object newInstance = constructor.newInstance();
                            if (obj == null) {
                                obj = newInstance;
                            }
                            objs.add(newInstance);

                            if (!instructions.empty()) {
                                instructions.peek().setValue(newInstance);
                            }

                        } else if ("callMethod".equals(localName)) {

                            Configuration _conf_ = conf;
                            if (!instructions.empty()) {
                                _conf_ = instructions.peek().getConfiguration();
                            }

                            final CallMethod call = new CallMethod(objs.peek(), _conf_);

                            for (int i = 0; i < reader.getAttributeCount(); i++) {
                                call.set(reader.getAttributeLocalName(i), reader.getAttributeValue(i));
                            }

                            instructions.add(call);
                        }
                        break;
                    case XMLEvent.END_ELEMENT:
                        localName = reader.getLocalName();
                        //System.out.println("END_ELEMENT "+localName);

                        if ("class".equals(localName)) {
                            objs.pop();
                        } else if ("callMethod".equals(localName)) {
                            final CallMethod call = instructions.pop();
                            call.eval();
                        }

                        break;
                }
            }

            configurations.put(obj, conf);
            return obj;

        } catch (final Exception e) {
            Configurator.LOG.error(e);
        }
        return null;
    }
}