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/*******************************************************************************
 * * Copyright 2012 Impetus Infotech.
 *  *
 *  * Licensed 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.impetus.kundera.classreading;

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import javassist.bytecode.AnnotationsAttribute;
import javassist.bytecode.ClassFile;
import javassist.bytecode.annotation.Annotation;

import com.impetus.kundera.loader.PersistenceXMLLoader.AllowedProtocol;

/**
 * Base class-reader.
 * 
 * @author animesh.kumar
 */
public abstract class Reader
{

    /** The valid annotations. */
    private List validAnnotations = new ArrayList();

    /** The annotation discovery listeners. */
    private List annotationDiscoveryListeners = new ArrayList();

    /**
     * Instantiates a new reader.
     */
    public Reader()
    {
    }

    /**
     * Scan class.
     * 
     * @param bits
     *            the bits
     * 
     * @throws IOException
     *             Signals that an I/O exception has occurred.
     */
    public void scanClass(InputStream bits) throws IOException
    {
        DataInputStream dstream = new DataInputStream(new BufferedInputStream(bits));
        ClassFile cf = null;
        try
        {
            cf = new ClassFile(dstream);

            String className = cf.getName();
            List annotations = new ArrayList();

            accumulateAnnotations(annotations, (AnnotationsAttribute) cf.getAttribute(AnnotationsAttribute.visibleTag));
            accumulateAnnotations(annotations,
                    (AnnotationsAttribute) cf.getAttribute(AnnotationsAttribute.invisibleTag));

            // iterate through all valid annotations
            for (String validAnn : getValidAnnotations())
            {
                // check if the current class has one?
                if (annotations.contains(validAnn))
                {
                    // fire all listeners
                    for (AnnotationDiscoveryListener listener : getAnnotationDiscoveryListeners())
                    {
                        listener.discovered(className);
                    }
                }
            }

        }
        finally
        {
            dstream.close();
            bits.close();
        }
    }

    // helper method to accumulate annotations.
    /**
     * Accumulate annotations.
     * 
     * @param annotations
     *            the annotations
     * @param annatt
     *            the annatt
     */
    public void accumulateAnnotations(List annotations, AnnotationsAttribute annatt)
    {
        if (null == annatt)
        {
            return;
        }
        for (Annotation ann : annatt.getAnnotations())
        {
            annotations.add(ann.getTypeName());
        }
    }

    /**
     * Gets the resource iterator.
     * 
     * @param url
     *            the url
     * @param filter
     *            the filter
     * 
     * @return the resource iterator
     * 
     * @throws IOException
     *             Signals that an I/O exception has occurred.
     */
    public ResourceIterator getResourceIterator(URL url, Filter filter)
    {
        String urlString = url.toString();
        try
        {
            if (urlString.endsWith("!/"))
            {
                urlString = urlString.substring(4);
                urlString = urlString.substring(0, urlString.length() - 2);
                url = new URL(urlString);
            }

            if (urlString.endsWith(".class"))
            {
                File f = new File(url.getPath());
                return new ClassFileIterator(f);
            }
            else if (!urlString.endsWith("/"))
            {
                return new JarFileIterator(url.openStream(), filter);
            }
            else
            {
                if (!url.getProtocol().equals("file"))
                {
                    throw new ResourceReadingException("Unable to understand protocol: " + url.getProtocol());
                }

                File f = new File(url.getPath());
                if (f.isDirectory() || url.getProtocol().toUpperCase().equals(AllowedProtocol.VFS.name()))
                {
                    return new ClassFileIterator(f, filter);
                }
                else
                {
                    return new JarFileIterator(url.openStream(), filter);
                }
            }
        }
        catch (MalformedURLException e)
        {
            throw new ResourceReadingException(e);
        }
        catch (IOException e)
        {
            throw new ResourceReadingException(e);
        }
    }

    /**
     * Gets the valid annotations.
     * 
     * @return the valid annotations
     */
    public List getValidAnnotations()
    {
        return validAnnotations;
    }

    /**
     * Adds the valid annotations.
     * 
     * @param annotation
     *            the annotation
     */
    public void addValidAnnotations(String annotation)
    {
        this.validAnnotations.add(annotation);
    }

    /**
     * Gets the annotation discovery listeners.
     * 
     * @return the annotation discovery listeners
     */
    public List getAnnotationDiscoveryListeners()
    {
        return annotationDiscoveryListeners;
    }

    /**
     * Adds the annotation discovery listeners.
     * 
     * @param annotationDiscoveryListener
     *            the annotation discovery listener
     */
    public void addAnnotationDiscoveryListeners(AnnotationDiscoveryListener annotationDiscoveryListener)
    {
        this.annotationDiscoveryListeners.add(annotationDiscoveryListener);
    }

    /**
     * Read.
     */
    public abstract void read();

    /**
     * Gets the filter.
     * 
     * @return the filter
     */
    public abstract Filter getFilter();

    /**
     * Find resources.
     * 
     * @return the uR l[]
     */
    public abstract URL[] findResources();


    /**
     * Find resources.
     * 
     * @return the uR l[]
     */
    public abstract InputStream[] findResourcesAsStream();


    /**
     * Find resources by classpath.
     * 
     * @return the uR l[]
     */
    public abstract URL[] findResourcesByClasspath();

}