/*
 * Copyright 2010-2011 Ning, Inc.
 *
 * Ning 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 com.ning.billing.util.config;

import com.ning.billing.catalog.api.InvalidConfigException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xml.sax.SAXException;

import javax.xml.XMLConstants;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
import javax.xml.transform.TransformerException;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;

public class XMLLoader {
	public static Logger log = LoggerFactory.getLogger(XMLLoader.class);

	public static <T extends ValidatingConfig<T>> T getObjectFromString(String uri, Class<T> objectType) throws Exception {
		if (uri == null) {
			return null;
		}
		log.info("Initializing an object of class " + objectType.getName() + " from xml file at: " + uri);
					
		return getObjectFromStream(new URI(uri), UriAccessor.accessUri(uri), objectType);
	}
	
	public static <T extends ValidatingConfig<T>> T getObjectFromUri(URI uri, Class<T> objectType) throws Exception {
		if (uri == null) {
			return null;
		}
		log.info("Initializing an object of class " + objectType.getName() + " from xml file at: " + uri);
					
		return getObjectFromStream(uri, UriAccessor.accessUri(uri), objectType);
	}
	
	public static <T extends ValidatingConfig<T>> T getObjectFromStream(URI uri, InputStream stream, Class<T> clazz) throws SAXException, InvalidConfigException, JAXBException, IOException, TransformerException, ValidationException {
	    if(stream == null) {
	        return null;
	    }
	    
	    Object o = unmarshaller(clazz).unmarshal(stream);
        if (clazz.isInstance(o)) {
        	@SuppressWarnings("unchecked")
			T castObject = (T)o;
        	try {
        		validate(uri,castObject);
        	} catch (ValidationException e) {
        		e.getErrors().log(log);
        		System.err.println(e.getErrors().toString());
        		throw e;
        	}
            return castObject;
        } else {
            return null;
        }
    } 
	
	public static <T> T getObjectFromStreamNoValidation(InputStream stream, Class<T> clazz) throws SAXException, InvalidConfigException, JAXBException, IOException, TransformerException {
        Object o = unmarshaller(clazz).unmarshal(stream);
        if (clazz.isInstance(o)) {
        	@SuppressWarnings("unchecked")
			T castObject = (T)o;
        	return castObject;
        } else {
            return null;
        }
    } 


	public static <T extends ValidatingConfig<T>> void validate(URI uri, T c) throws ValidationException {
            c.initialize(c, uri);
            ValidationErrors errs = c.validate(c, new ValidationErrors());
            log.info("Errors: " + errs.size() + " for " + uri);  
            if(errs.size() > 0) {
            	throw new ValidationException(errs);
            }
    }
    
    public static Unmarshaller unmarshaller(Class<?> clazz) throws JAXBException, SAXException, IOException, TransformerException {
    	 JAXBContext context =JAXBContext.newInstance(clazz);

         SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI );
         Unmarshaller um = context.createUnmarshaller();

         Schema schema = factory.newSchema(new StreamSource(XMLSchemaGenerator.xmlSchema(clazz)));
         um.setSchema(schema);
         
         return um;
    }
	
}
