/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 org.apache.naming.resources;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Hashtable;

import javax.naming.Context;
import javax.naming.Name;
import javax.naming.NameNotFoundException;
import javax.naming.NameParser;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.ModificationItem;
import javax.naming.directory.SearchControls;

import org.apache.naming.StringManager;

/**
 * Proxy Directory Context implementation.
 *
 * @author Remy Maucherat
 * @version $Revision$ $Date$
 */

public class ProxyDirContext implements DirContext {


    // -------------------------------------------------------------- Constants


    public static final String CONTEXT = "context";
    public static final String HOST = "host";


    // ----------------------------------------------------------- Constructors


    /**
     * Builds a proxy directory context using the given environment.
     */
    public ProxyDirContext(Hashtable env, DirContext dirContext) {
        this.env = env;
        this.dirContext = dirContext;
        if (dirContext instanceof BaseDirContext) {
            // Initialize parameters based on the associated dir context, like
            // the caching policy.
            BaseDirContext baseDirContext = (BaseDirContext) dirContext;
            if (baseDirContext.isCached()) {
                try {
                    cache = (ResourceCache) 
                        Class.forName(cacheClassName).newInstance();
                } catch (Exception e) {
                    //FIXME
                    e.printStackTrace();
                }
                cache.setCacheMaxSize(baseDirContext.getCacheMaxSize());
                cacheTTL = baseDirContext.getCacheTTL();
                cacheObjectMaxSize = baseDirContext.getCacheMaxSize() / 20;
            }
        }
        hostName = (String) env.get(HOST);
        contextName = (String) env.get(CONTEXT);
    }


    /**
     * Builds a clone of this proxy dir context, wrapping the given directory
     * context, and sharing the same cache.
     */
    // TODO: Refactor using the proxy field
    /*
    protected ProxyDirContext(ProxyDirContext proxyDirContext, 
                              DirContext dirContext, String vPath) {
        this.env = proxyDirContext.env;
        this.dirContext = dirContext;
        this.vPath = vPath;
        this.cache = proxyDirContext.cache;
        this.cacheMaxSize = proxyDirContext.cacheMaxSize;
        this.cacheSize = proxyDirContext.cacheSize;
        this.cacheTTL = proxyDirContext.cacheTTL;
        this.cacheObjectMaxSize = proxyDirContext.cacheObjectMaxSize;
        this.notFoundCache = proxyDirContext.notFoundCache;
        this.hostName = proxyDirContext.hostName;
        this.contextName = proxyDirContext.contextName;
    }
    */


    // ----------------------------------------------------- Instance Variables


    /**
     * Proxy DirContext (either this or the real proxy).
     */
    protected ProxyDirContext proxy = this;


    /**
     * Environment.
     */
    protected Hashtable env;


    /**
     * The string manager for this package.
     */
    protected StringManager sm = StringManager.getManager(Constants.Package);


    /**
     * Associated DirContext.
     */
    protected DirContext dirContext;


    /**
     * Virtual path.
     */
    protected String vPath = null;


    /**
     * Host name.
     */
    protected String hostName;


    /**
     * Context name.
     */
    protected String contextName;


    /**
     * Cache class.
     */
    protected String cacheClassName = 
        "org.apache.naming.resources.ResourceCache";


    /**
     * Cache.
     */
    protected ResourceCache cache = null;


    /**
     * Cache TTL.
     */
    protected int cacheTTL = 5000; // 5s


    /**
     * Max size of resources which will have their content cached.
     */
    protected int cacheObjectMaxSize = 512; // 512 KB


    /**
     * Immutable name not found exception.
     */
    protected NameNotFoundException notFoundException =
        new ImmutableNameNotFoundException();


    /**
     * Non cacheable resources.
     */
    protected String[] nonCacheable = { "/WEB-INF/lib/", "/WEB-INF/classes/" };


    // --------------------------------------------------------- Public Methods


    /**
     * Get the cache used for this context.
     */
    public ResourceCache getCache() {
        return cache;
    }


    /**
     * Return the actual directory context we are wrapping.
     */
    public DirContext getDirContext() {
        return this.dirContext;
    }


    /**
     * Return the document root for this component.
     */
    public String getDocBase() {
        if (dirContext instanceof BaseDirContext)
            return ((BaseDirContext) dirContext).getDocBase();
        else
            return "";
    }


    /**
     * Return the host name.
     */
    public String getHostName() {
        return this.hostName;
    }


    /**
     * Return the context name.
     */
    public String getContextName() {
        return this.contextName;
    }


    // -------------------------------------------------------- Context Methods


    /**
     * Retrieves the named object. If name is empty, returns a new instance 
     * of this context (which represents the same naming context as this 
     * context, but its environment may be modified independently and it may 
     * be accessed concurrently).
     * 
     * @param name the name of the object to look up
     * @return the object bound to name
     * @exception NamingException if a naming exception is encountered
     */
    public Object lookup(Name name)
        throws NamingException {
        CacheEntry entry = cacheLookup(name.toString());
        if (entry != null) {
            if (!entry.exists) {
                throw notFoundException;
            }
            if (entry.resource != null) {
                // Check content caching.
                return entry.resource;
            } else {
                return entry.context;
            }
        }
        Object object = dirContext.lookup(parseName(name));
        if (object instanceof InputStream)
            return new Resource((InputStream) object);
        else
            return object;
    }


    /**
     * Retrieves the named object.
     * 
     * @param name the name of the object to look up
     * @return the object bound to name
     * @exception NamingException if a naming exception is encountered
     */
    public Object lookup(String name)
        throws NamingException {
        CacheEntry entry = cacheLookup(name);
        if (entry != null) {
            if (!entry.exists) {
                throw notFoundException;
            }
            if (entry.resource != null) {
                return entry.resource;
            } else {
                return entry.context;
            }
        }
        Object object = dirContext.lookup(parseName(name));
        if (object instanceof InputStream) {
            return new Resource((InputStream) object);
        } else if (object instanceof DirContext) {
            return object;
        } else if (object instanceof Resource) {
            return object;
        } else {
            return new Resource(new ByteArrayInputStream
                (object.toString().getBytes()));
        }
    }


    /**
     * Binds a name to an object. All intermediate contexts and the target 
     * context (that named by all but terminal atomic component of the name) 
     * must already exist.
     * 
     * @param name the name to bind; may not be empty
     * @param obj the object to bind; possibly null
     * @exception NameAlreadyBoundException if name is already bound
     * @exception InvalidAttributesException if object did not supply all 
     * mandatory attributes
     * @exception NamingException if a naming exception is encountered
     */
    public void bind(Name name, Object obj)
        throws NamingException {
        dirContext.bind(parseName(name), obj);
        cacheUnload(name.toString());
    }


    /**
     * Binds a name to an object.
     * 
     * @param name the name to bind; may not be empty
     * @param obj the object to bind; possibly null
     * @exception NameAlreadyBoundException if name is already bound
     * @exception InvalidAttributesException if object did not supply all 
     * mandatory attributes
     * @exception NamingException if a naming exception is encountered
     */
    public void bind(String name, Object obj)
        throws NamingException {
        dirContext.bind(parseName(name), obj);
        cacheUnload(name);
    }


    /**
     * Binds a name to an object, overwriting any existing binding. All 
     * intermediate contexts and the target context (that named by all but 
     * terminal atomic component of the name) must already exist.
     * <p>
     * If the object is a DirContext, any existing attributes associated with 
     * the name are replaced with those of the object. Otherwise, any 
     * existing attributes associated with the name remain unchanged.
     * 
     * @param name the name to bind; may not be empty
     * @param obj the object to bind; possibly null
     * @exception InvalidAttributesException if object did not supply all 
     * mandatory attributes
     * @exception NamingException if a naming exception is encountered
     */
    public void rebind(Name name, Object obj)
        throws NamingException {
        dirContext.rebind(parseName(name), obj);
        cacheUnload(name.toString());
    }


    /**
     * Binds a name to an object, overwriting any existing binding.
     * 
     * @param name the name to bind; may not be empty
     * @param obj the object to bind; possibly null
     * @exception InvalidAttributesException if object did not supply all 
     * mandatory attributes
     * @exception NamingException if a naming exception is encountered
     */
    public void rebind(String name, Object obj)
        throws NamingException {
        dirContext.rebind(parseName(name), obj);
        cacheUnload(name);
    }


    /**
     * Unbinds the named object. Removes the terminal atomic name in name 
     * from the target context--that named by all but the terminal atomic 
     * part of name.
     * <p>
     * This method is idempotent. It succeeds even if the terminal atomic 
     * name is not bound in the target context, but throws 
     * NameNotFoundException if any of the intermediate contexts do not exist. 
     * 
     * @param name the name to bind; may not be empty
     * @exception NameNotFoundException if an intermediate context does not 
     * exist
     * @exception NamingException if a naming exception is encountered
     */
    public void unbind(Name name)
        throws NamingException {
        dirContext.unbind(parseName(name));
        cacheUnload(name.toString());
    }


    /**
     * Unbinds the named object.
     * 
     * @param name the name to bind; may not be empty
     * @exception NameNotFoundException if an intermediate context does not 
     * exist
     * @exception NamingException if a naming exception is encountered
     */
    public void unbind(String name)
        throws NamingException {
        dirContext.unbind(parseName(name));
        cacheUnload(name);
    }


    /**
     * Binds a new name to the object bound to an old name, and unbinds the 
     * old name. Both names are relative to this context. Any attributes 
     * associated with the old name become associated with the new name. 
     * Intermediate contexts of the old name are not changed.
     * 
     * @param oldName the name of the existing binding; may not be empty
     * @param newName the name of the new binding; may not be empty
     * @exception NameAlreadyBoundException if newName is already bound
     * @exception NamingException if a naming exception is encountered
     */
    public void rename(Name oldName, Name newName)
        throws NamingException {
        dirContext.rename(parseName(oldName), parseName(newName));
        cacheUnload(oldName.toString());
    }


    /**
     * Binds a new name to the object bound to an old name, and unbinds the 
     * old name.
     * 
     * @param oldName the name of the existing binding; may not be empty
     * @param newName the name of the new binding; may not be empty
     * @exception NameAlreadyBoundException if newName is already bound
     * @exception NamingException if a naming exception is encountered
     */
    public void rename(String oldName, String newName)
        throws NamingException {
        dirContext.rename(parseName(oldName), parseName(newName));
        cacheUnload(oldName);
    }


    /**
     * Enumerates the names bound in the named context, along with the class 
     * names of objects bound to them. The contents of any subcontexts are 
     * not included.
     * <p>
     * If a binding is added to or removed from this context, its effect on 
     * an enumeration previously returned is undefined.
     * 
     * @param name the name of the context to list
     * @return an enumeration of the names and class names of the bindings in 
     * this context. Each element of the enumeration is of type NameClassPair.
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration list(Name name)
        throws NamingException {
        return dirContext.list(parseName(name));
    }


    /**
     * Enumerates the names bound in the named context, along with the class 
     * names of objects bound to them.
     * 
     * @param name the name of the context to list
     * @return an enumeration of the names and class names of the bindings in 
     * this context. Each element of the enumeration is of type NameClassPair.
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration list(String name)
        throws NamingException {
        return dirContext.list(parseName(name));
    }


    /**
     * Enumerates the names bound in the named context, along with the 
     * objects bound to them. The contents of any subcontexts are not 
     * included.
     * <p>
     * If a binding is added to or removed from this context, its effect on 
     * an enumeration previously returned is undefined.
     * 
     * @param name the name of the context to list
     * @return an enumeration of the bindings in this context. 
     * Each element of the enumeration is of type Binding.
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration listBindings(Name name)
        throws NamingException {
        return dirContext.listBindings(parseName(name));
    }


    /**
     * Enumerates the names bound in the named context, along with the 
     * objects bound to them.
     * 
     * @param name the name of the context to list
     * @return an enumeration of the bindings in this context. 
     * Each element of the enumeration is of type Binding.
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration listBindings(String name)
        throws NamingException {
        return dirContext.listBindings(parseName(name));
    }


    /**
     * Destroys the named context and removes it from the namespace. Any 
     * attributes associated with the name are also removed. Intermediate 
     * contexts are not destroyed.
     * <p>
     * This method is idempotent. It succeeds even if the terminal atomic 
     * name is not bound in the target context, but throws 
     * NameNotFoundException if any of the intermediate contexts do not exist. 
     * 
     * In a federated naming system, a context from one naming system may be 
     * bound to a name in another. One can subsequently look up and perform 
     * operations on the foreign context using a composite name. However, an 
     * attempt destroy the context using this composite name will fail with 
     * NotContextException, because the foreign context is not a "subcontext" 
     * of the context in which it is bound. Instead, use unbind() to remove 
     * the binding of the foreign context. Destroying the foreign context 
     * requires that the destroySubcontext() be performed on a context from 
     * the foreign context's "native" naming system.
     * 
     * @param name the name of the context to be destroyed; may not be empty
     * @exception NameNotFoundException if an intermediate context does not 
     * exist
     * @exception NotContextException if the name is bound but does not name 
     * a context, or does not name a context of the appropriate type
     */
    public void destroySubcontext(Name name)
        throws NamingException {
        dirContext.destroySubcontext(parseName(name));
        cacheUnload(name.toString());
    }


    /**
     * Destroys the named context and removes it from the namespace.
     * 
     * @param name the name of the context to be destroyed; may not be empty
     * @exception NameNotFoundException if an intermediate context does not 
     * exist
     * @exception NotContextException if the name is bound but does not name 
     * a context, or does not name a context of the appropriate type
     */
    public void destroySubcontext(String name)
        throws NamingException {
        dirContext.destroySubcontext(parseName(name));
        cacheUnload(name);
    }


    /**
     * Creates and binds a new context. Creates a new context with the given 
     * name and binds it in the target context (that named by all but 
     * terminal atomic component of the name). All intermediate contexts and 
     * the target context must already exist.
     * 
     * @param name the name of the context to create; may not be empty
     * @return the newly created context
     * @exception NameAlreadyBoundException if name is already bound
     * @exception InvalidAttributesException if creation of the subcontext 
     * requires specification of mandatory attributes
     * @exception NamingException if a naming exception is encountered
     */
    public Context createSubcontext(Name name)
        throws NamingException {
        Context context = dirContext.createSubcontext(parseName(name));
        cacheUnload(name.toString());
        return context;
    }


    /**
     * Creates and binds a new context.
     * 
     * @param name the name of the context to create; may not be empty
     * @return the newly created context
     * @exception NameAlreadyBoundException if name is already bound
     * @exception InvalidAttributesException if creation of the subcontext 
     * requires specification of mandatory attributes
     * @exception NamingException if a naming exception is encountered
     */
    public Context createSubcontext(String name)
        throws NamingException {
        Context context = dirContext.createSubcontext(parseName(name));
        cacheUnload(name);
        return context;
    }


    /**
     * Retrieves the named object, following links except for the terminal 
     * atomic component of the name. If the object bound to name is not a 
     * link, returns the object itself.
     * 
     * @param name the name of the object to look up
     * @return the object bound to name, not following the terminal link 
     * (if any).
     * @exception NamingException if a naming exception is encountered
     */
    public Object lookupLink(Name name)
        throws NamingException {
        return dirContext.lookupLink(parseName(name));
    }


    /**
     * Retrieves the named object, following links except for the terminal 
     * atomic component of the name.
     * 
     * @param name the name of the object to look up
     * @return the object bound to name, not following the terminal link 
     * (if any).
     * @exception NamingException if a naming exception is encountered
     */
    public Object lookupLink(String name)
        throws NamingException {
        return dirContext.lookupLink(parseName(name));
    }


    /**
     * Retrieves the parser associated with the named context. In a 
     * federation of namespaces, different naming systems will parse names 
     * differently. This method allows an application to get a parser for 
     * parsing names into their atomic components using the naming convention 
     * of a particular naming system. Within any single naming system, 
     * NameParser objects returned by this method must be equal (using the 
     * equals() test).
     * 
     * @param name the name of the context from which to get the parser
     * @return a name parser that can parse compound names into their atomic 
     * components
     * @exception NamingException if a naming exception is encountered
     */
    public NameParser getNameParser(Name name)
        throws NamingException {
        return dirContext.getNameParser(parseName(name));
    }


    /**
     * Retrieves the parser associated with the named context.
     * 
     * @param name the name of the context from which to get the parser
     * @return a name parser that can parse compound names into their atomic 
     * components
     * @exception NamingException if a naming exception is encountered
     */
    public NameParser getNameParser(String name)
        throws NamingException {
        return dirContext.getNameParser(parseName(name));
    }


    /**
     * Composes the name of this context with a name relative to this context.
     * <p>
     * Given a name (name) relative to this context, and the name (prefix) 
     * of this context relative to one of its ancestors, this method returns 
     * the composition of the two names using the syntax appropriate for the 
     * naming system(s) involved. That is, if name names an object relative 
     * to this context, the result is the name of the same object, but 
     * relative to the ancestor context. None of the names may be null.
     * 
     * @param name a name relative to this context
     * @param prefix the name of this context relative to one of its ancestors
     * @return the composition of prefix and name
     * @exception NamingException if a naming exception is encountered
     */
    public Name composeName(Name name, Name prefix)
        throws NamingException {
        prefix = (Name) prefix.clone();
        return prefix.addAll(name);
    }


    /**
     * Composes the name of this context with a name relative to this context.
     * 
     * @param name a name relative to this context
     * @param prefix the name of this context relative to one of its ancestors
     * @return the composition of prefix and name
     * @exception NamingException if a naming exception is encountered
     */
    public String composeName(String name, String prefix)
        throws NamingException {
        return prefix + "/" + name;
    }


    /**
     * Adds a new environment property to the environment of this context. If 
     * the property already exists, its value is overwritten.
     * 
     * @param propName the name of the environment property to add; may not 
     * be null
     * @param propVal the value of the property to add; may not be null
     * @exception NamingException if a naming exception is encountered
     */
    public Object addToEnvironment(String propName, Object propVal)
        throws NamingException {
        return dirContext.addToEnvironment(propName, propVal);
    }


    /**
     * Removes an environment property from the environment of this context. 
     * 
     * @param propName the name of the environment property to remove; 
     * may not be null
     * @exception NamingException if a naming exception is encountered
     */
    public Object removeFromEnvironment(String propName)
        throws NamingException {
        return dirContext.removeFromEnvironment(propName);
    }


    /**
     * Retrieves the environment in effect for this context. See class 
     * description for more details on environment properties. 
     * The caller should not make any changes to the object returned: their 
     * effect on the context is undefined. The environment of this context 
     * may be changed using addToEnvironment() and removeFromEnvironment().
     * 
     * @return the environment of this context; never null
     * @exception NamingException if a naming exception is encountered
     */
    public Hashtable getEnvironment()
        throws NamingException {
        return dirContext.getEnvironment();
    }


    /**
     * Closes this context. This method releases this context's resources 
     * immediately, instead of waiting for them to be released automatically 
     * by the garbage collector.
     * This method is idempotent: invoking it on a context that has already 
     * been closed has no effect. Invoking any other method on a closed 
     * context is not allowed, and results in undefined behaviour.
     * 
     * @exception NamingException if a naming exception is encountered
     */
    public void close()
        throws NamingException {
        dirContext.close();
    }


    /**
     * Retrieves the full name of this context within its own namespace.
     * <p>
     * Many naming services have a notion of a "full name" for objects in 
     * their respective namespaces. For example, an LDAP entry has a 
     * distinguished name, and a DNS record has a fully qualified name. This 
     * method allows the client application to retrieve this name. The string 
     * returned by this method is not a JNDI composite name and should not be 
     * passed directly to context methods. In naming systems for which the 
     * notion of full name does not make sense, 
     * OperationNotSupportedException is thrown.
     * 
     * @return this context's name in its own namespace; never null
     * @exception OperationNotSupportedException if the naming system does 
     * not have the notion of a full name
     * @exception NamingException if a naming exception is encountered
     */
    public String getNameInNamespace()
        throws NamingException {
        return dirContext.getNameInNamespace();
    }


    // ----------------------------------------------------- DirContext Methods


    /**
     * Retrieves all of the attributes associated with a named object. 
     * 
     * @return the set of attributes associated with name. 
     * Returns an empty attribute set if name has no attributes; never null.
     * @param name the name of the object from which to retrieve attributes
     * @exception NamingException if a naming exception is encountered
     */
    public Attributes getAttributes(Name name)
        throws NamingException {
        CacheEntry entry = cacheLookup(name.toString());
        if (entry != null) {
            if (!entry.exists) {
                throw notFoundException;
            }
            return entry.attributes;
        }
        Attributes attributes = dirContext.getAttributes(parseName(name));
        if (!(attributes instanceof ResourceAttributes)) {
            attributes = new ResourceAttributes(attributes);
        }
        return attributes;
    }


    /**
     * Retrieves all of the attributes associated with a named object.
     * 
     * @return the set of attributes associated with name
     * @param name the name of the object from which to retrieve attributes
     * @exception NamingException if a naming exception is encountered
     */
    public Attributes getAttributes(String name)
        throws NamingException {
        CacheEntry entry = cacheLookup(name);
        if (entry != null) {
            if (!entry.exists) {
                throw notFoundException;
            }
            return entry.attributes;
        }
        Attributes attributes = dirContext.getAttributes(parseName(name));
        if (!(attributes instanceof ResourceAttributes)) {
            attributes = new ResourceAttributes(attributes);
        }
        return attributes;
    }


    /**
     * Retrieves selected attributes associated with a named object. 
     * See the class description regarding attribute models, attribute type 
     * names, and operational attributes.
     * 
     * @return the requested attributes; never null
     * @param name the name of the object from which to retrieve attributes
     * @param attrIds the identifiers of the attributes to retrieve. null 
     * indicates that all attributes should be retrieved; an empty array 
     * indicates that none should be retrieved
     * @exception NamingException if a naming exception is encountered
     */
    public Attributes getAttributes(Name name, String[] attrIds)
        throws NamingException {
        Attributes attributes = 
            dirContext.getAttributes(parseName(name), attrIds);
        if (!(attributes instanceof ResourceAttributes)) {
            attributes = new ResourceAttributes(attributes);
        }
        return attributes;
    }


    /**
     * Retrieves selected attributes associated with a named object.
     * 
     * @return the requested attributes; never null
     * @param name the name of the object from which to retrieve attributes
     * @param attrIds the identifiers of the attributes to retrieve. null 
     * indicates that all attributes should be retrieved; an empty array 
     * indicates that none should be retrieved
     * @exception NamingException if a naming exception is encountered
     */
     public Attributes getAttributes(String name, String[] attrIds)
         throws NamingException {
        Attributes attributes = 
            dirContext.getAttributes(parseName(name), attrIds);
        if (!(attributes instanceof ResourceAttributes)) {
            attributes = new ResourceAttributes(attributes);
        }
        return attributes;
     }


    /**
     * Modifies the attributes associated with a named object. The order of 
     * the modifications is not specified. Where possible, the modifications 
     * are performed atomically.
     * 
     * @param name the name of the object whose attributes will be updated
     * @param mod_op the modification operation, one of: ADD_ATTRIBUTE, 
     * REPLACE_ATTRIBUTE, REMOVE_ATTRIBUTE
     * @param attrs the attributes to be used for the modification; may not 
     * be null
     * @exception AttributeModificationException if the modification cannot be
     * completed successfully
     * @exception NamingException if a naming exception is encountered
     */
    public void modifyAttributes(Name name, int mod_op, Attributes attrs)
        throws NamingException {
        dirContext.modifyAttributes(parseName(name), mod_op, attrs);
        cacheUnload(name.toString());
    }


    /**
     * Modifies the attributes associated with a named object.
     * 
     * @param name the name of the object whose attributes will be updated
     * @param mod_op the modification operation, one of: ADD_ATTRIBUTE, 
     * REPLACE_ATTRIBUTE, REMOVE_ATTRIBUTE
     * @param attrs the attributes to be used for the modification; may not 
     * be null
     * @exception AttributeModificationException if the modification cannot be
     * completed successfully
     * @exception NamingException if a naming exception is encountered
     */
    public void modifyAttributes(String name, int mod_op, Attributes attrs)
        throws NamingException {
        dirContext.modifyAttributes(parseName(name), mod_op, attrs);
        cacheUnload(name);
    }


    /**
     * Modifies the attributes associated with a named object using an an 
     * ordered list of modifications. The modifications are performed in the 
     * order specified. Each modification specifies a modification operation 
     * code and an attribute on which to operate. Where possible, the 
     * modifications are performed atomically.
     * 
     * @param name the name of the object whose attributes will be updated
     * @param mods an ordered sequence of modifications to be performed; may 
     * not be null
     * @exception AttributeModificationException if the modification cannot be
     * completed successfully
     * @exception NamingException if a naming exception is encountered
     */
    public void modifyAttributes(Name name, ModificationItem[] mods)
        throws NamingException {
        dirContext.modifyAttributes(parseName(name), mods);
        cacheUnload(name.toString());
    }


    /**
     * Modifies the attributes associated with a named object using an an 
     * ordered list of modifications.
     * 
     * @param name the name of the object whose attributes will be updated
     * @param mods an ordered sequence of modifications to be performed; may 
     * not be null
     * @exception AttributeModificationException if the modification cannot be
     * completed successfully
     * @exception NamingException if a naming exception is encountered
     */
    public void modifyAttributes(String name, ModificationItem[] mods)
        throws NamingException {
        dirContext.modifyAttributes(parseName(name), mods);
        cacheUnload(name);
    }


    /**
     * Binds a name to an object, along with associated attributes. If attrs 
     * is null, the resulting binding will have the attributes associated 
     * with obj if obj is a DirContext, and no attributes otherwise. If attrs 
     * is non-null, the resulting binding will have attrs as its attributes; 
     * any attributes associated with obj are ignored.
     * 
     * @param name the name to bind; may not be empty
     * @param obj the object to bind; possibly null
     * @param attrs the attributes to associate with the binding
     * @exception NameAlreadyBoundException if name is already bound
     * @exception InvalidAttributesException if some "mandatory" attributes 
     * of the binding are not supplied
     * @exception NamingException if a naming exception is encountered
     */
    public void bind(Name name, Object obj, Attributes attrs)
        throws NamingException {
        dirContext.bind(parseName(name), obj, attrs);
        cacheUnload(name.toString());
    }


    /**
     * Binds a name to an object, along with associated attributes.
     * 
     * @param name the name to bind; may not be empty
     * @param obj the object to bind; possibly null
     * @param attrs the attributes to associate with the binding
     * @exception NameAlreadyBoundException if name is already bound
     * @exception InvalidAttributesException if some "mandatory" attributes 
     * of the binding are not supplied
     * @exception NamingException if a naming exception is encountered
     */
    public void bind(String name, Object obj, Attributes attrs)
        throws NamingException {
        dirContext.bind(parseName(name), obj, attrs);
        cacheUnload(name);
    }


    /**
     * Binds a name to an object, along with associated attributes, 
     * overwriting any existing binding. If attrs is null and obj is a 
     * DirContext, the attributes from obj are used. If attrs is null and obj 
     * is not a DirContext, any existing attributes associated with the object
     * already bound in the directory remain unchanged. If attrs is non-null, 
     * any existing attributes associated with the object already bound in 
     * the directory are removed and attrs is associated with the named 
     * object. If obj is a DirContext and attrs is non-null, the attributes 
     * of obj are ignored.
     * 
     * @param name the name to bind; may not be empty
     * @param obj the object to bind; possibly null
     * @param attrs the attributes to associate with the binding
     * @exception InvalidAttributesException if some "mandatory" attributes 
     * of the binding are not supplied
     * @exception NamingException if a naming exception is encountered
     */
    public void rebind(Name name, Object obj, Attributes attrs)
        throws NamingException {
        dirContext.rebind(parseName(name), obj, attrs);
        cacheUnload(name.toString());
    }


    /**
     * Binds a name to an object, along with associated attributes, 
     * overwriting any existing binding.
     * 
     * @param name the name to bind; may not be empty
     * @param obj the object to bind; possibly null
     * @param attrs the attributes to associate with the binding
     * @exception InvalidAttributesException if some "mandatory" attributes 
     * of the binding are not supplied
     * @exception NamingException if a naming exception is encountered
     */
    public void rebind(String name, Object obj, Attributes attrs)
        throws NamingException {
        dirContext.rebind(parseName(name), obj, attrs);
        cacheUnload(name);
    }


    /**
     * Creates and binds a new context, along with associated attributes. 
     * This method creates a new subcontext with the given name, binds it in 
     * the target context (that named by all but terminal atomic component of 
     * the name), and associates the supplied attributes with the newly 
     * created object. All intermediate and target contexts must already 
     * exist. If attrs is null, this method is equivalent to 
     * Context.createSubcontext().
     * 
     * @param name the name of the context to create; may not be empty
     * @param attrs the attributes to associate with the newly created context
     * @return the newly created context
     * @exception NameAlreadyBoundException if the name is already bound
     * @exception InvalidAttributesException if attrs does not contain all 
     * the mandatory attributes required for creation
     * @exception NamingException if a naming exception is encountered
     */
    public DirContext createSubcontext(Name name, Attributes attrs)
        throws NamingException {
        DirContext context = 
            dirContext.createSubcontext(parseName(name), attrs);
        cacheUnload(name.toString());
        return context;
    }


    /**
     * Creates and binds a new context, along with associated attributes.
     * 
     * @param name the name of the context to create; may not be empty
     * @param attrs the attributes to associate with the newly created context
     * @return the newly created context
     * @exception NameAlreadyBoundException if the name is already bound
     * @exception InvalidAttributesException if attrs does not contain all 
     * the mandatory attributes required for creation
     * @exception NamingException if a naming exception is encountered
     */
    public DirContext createSubcontext(String name, Attributes attrs)
        throws NamingException {
        DirContext context = 
            dirContext.createSubcontext(parseName(name), attrs);
        cacheUnload(name);
        return context;
    }


    /**
     * Retrieves the schema associated with the named object. The schema 
     * describes rules regarding the structure of the namespace and the 
     * attributes stored within it. The schema specifies what types of 
     * objects can be added to the directory and where they can be added; 
     * what mandatory and optional attributes an object can have. The range 
     * of support for schemas is directory-specific.
     * 
     * @param name the name of the object whose schema is to be retrieved
     * @return the schema associated with the context; never null
     * @exception OperationNotSupportedException if schema not supported
     * @exception NamingException if a naming exception is encountered
     */
    public DirContext getSchema(Name name)
        throws NamingException {
        return dirContext.getSchema(parseName(name));
    }


    /**
     * Retrieves the schema associated with the named object.
     * 
     * @param name the name of the object whose schema is to be retrieved
     * @return the schema associated with the context; never null
     * @exception OperationNotSupportedException if schema not supported
     * @exception NamingException if a naming exception is encountered
     */
    public DirContext getSchema(String name)
        throws NamingException {
        return dirContext.getSchema(parseName(name));
    }


    /**
     * Retrieves a context containing the schema objects of the named 
     * object's class definitions.
     * 
     * @param name the name of the object whose object class definition is to 
     * be retrieved
     * @return the DirContext containing the named object's class 
     * definitions; never null
     * @exception OperationNotSupportedException if schema not supported
     * @exception NamingException if a naming exception is encountered
     */
    public DirContext getSchemaClassDefinition(Name name)
        throws NamingException {
        return dirContext.getSchemaClassDefinition(parseName(name));
    }


    /**
     * Retrieves a context containing the schema objects of the named 
     * object's class definitions.
     * 
     * @param name the name of the object whose object class definition is to 
     * be retrieved
     * @return the DirContext containing the named object's class 
     * definitions; never null
     * @exception OperationNotSupportedException if schema not supported
     * @exception NamingException if a naming exception is encountered
     */
    public DirContext getSchemaClassDefinition(String name)
        throws NamingException {
        return dirContext.getSchemaClassDefinition(parseName(name));
    }


    /**
     * Searches in a single context for objects that contain a specified set 
     * of attributes, and retrieves selected attributes. The search is 
     * performed using the default SearchControls settings.
     * 
     * @param name the name of the context to search
     * @param matchingAttributes the attributes to search for. If empty or 
     * null, all objects in the target context are returned.
     * @param attributesToReturn the attributes to return. null indicates 
     * that all attributes are to be returned; an empty array indicates that 
     * none are to be returned.
     * @return a non-null enumeration of SearchResult objects. Each 
     * SearchResult contains the attributes identified by attributesToReturn 
     * and the name of the corresponding object, named relative to the 
     * context named by name.
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration search(Name name, Attributes matchingAttributes,
                                    String[] attributesToReturn)
        throws NamingException {
        return dirContext.search(parseName(name), matchingAttributes, 
                                 attributesToReturn);
    }


    /**
     * Searches in a single context for objects that contain a specified set 
     * of attributes, and retrieves selected attributes.
     * 
     * @param name the name of the context to search
     * @param matchingAttributes the attributes to search for. If empty or 
     * null, all objects in the target context are returned.
     * @param attributesToReturn the attributes to return. null indicates 
     * that all attributes are to be returned; an empty array indicates that 
     * none are to be returned.
     * @return a non-null enumeration of SearchResult objects. Each 
     * SearchResult contains the attributes identified by attributesToReturn 
     * and the name of the corresponding object, named relative to the 
     * context named by name.
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration search(String name, Attributes matchingAttributes,
                                    String[] attributesToReturn)
        throws NamingException {
        return dirContext.search(parseName(name), matchingAttributes, 
                                 attributesToReturn);
    }


    /**
     * Searches in a single context for objects that contain a specified set 
     * of attributes. This method returns all the attributes of such objects. 
     * It is equivalent to supplying null as the atributesToReturn parameter 
     * to the method search(Name, Attributes, String[]).
     * 
     * @param name the name of the context to search
     * @param matchingAttributes the attributes to search for. If empty or 
     * null, all objects in the target context are returned.
     * @return a non-null enumeration of SearchResult objects. Each 
     * SearchResult contains the attributes identified by attributesToReturn 
     * and the name of the corresponding object, named relative to the 
     * context named by name.
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration search(Name name, Attributes matchingAttributes)
        throws NamingException {
        return dirContext.search(parseName(name), matchingAttributes);
    }


    /**
     * Searches in a single context for objects that contain a specified set 
     * of attributes.
     * 
     * @param name the name of the context to search
     * @param matchingAttributes the attributes to search for. If empty or 
     * null, all objects in the target context are returned.
     * @return a non-null enumeration of SearchResult objects. Each 
     * SearchResult contains the attributes identified by attributesToReturn 
     * and the name of the corresponding object, named relative to the 
     * context named by name.
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration search(String name, Attributes matchingAttributes)
        throws NamingException {
        return dirContext.search(parseName(name), matchingAttributes);
    }


    /**
     * Searches in the named context or object for entries that satisfy the 
     * given search filter. Performs the search as specified by the search 
     * controls.
     * 
     * @param name the name of the context or object to search
     * @param filter the filter expression to use for the search; may not be 
     * null
     * @param cons the search controls that control the search. If null, 
     * the default search controls are used (equivalent to 
     * (new SearchControls())).
     * @return an enumeration of SearchResults of the objects that satisfy 
     * the filter; never null
     * @exception InvalidSearchFilterException if the search filter specified 
     * is not supported or understood by the underlying directory
     * @exception InvalidSearchControlsException if the search controls 
     * contain invalid settings
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration search(Name name, String filter, 
                                    SearchControls cons)
        throws NamingException {
        return dirContext.search(parseName(name), filter, cons);
    }


    /**
     * Searches in the named context or object for entries that satisfy the 
     * given search filter. Performs the search as specified by the search 
     * controls.
     * 
     * @param name the name of the context or object to search
     * @param filter the filter expression to use for the search; may not be 
     * null
     * @param cons the search controls that control the search. If null, 
     * the default search controls are used (equivalent to 
     * (new SearchControls())).
     * @return an enumeration of SearchResults of the objects that satisfy 
     * the filter; never null
     * @exception InvalidSearchFilterException if the search filter 
     * specified is not supported or understood by the underlying directory
     * @exception InvalidSearchControlsException if the search controls 
     * contain invalid settings
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration search(String name, String filter, 
                                    SearchControls cons)
        throws NamingException {
        return dirContext.search(parseName(name), filter, cons);
    }


    /**
     * Searches in the named context or object for entries that satisfy the 
     * given search filter. Performs the search as specified by the search 
     * controls.
     * 
     * @param name the name of the context or object to search
     * @param filterExpr the filter expression to use for the search. 
     * The expression may contain variables of the form "{i}" where i is a 
     * nonnegative integer. May not be null.
     * @param filterArgs the array of arguments to substitute for the 
     * variables in filterExpr. The value of filterArgs[i] will replace each 
     * occurrence of "{i}". If null, equivalent to an empty array.
     * @param cons the search controls that control the search. If null, the 
     * default search controls are used (equivalent to (new SearchControls())).
     * @return an enumeration of SearchResults of the objects that satisy the 
     * filter; never null
     * @exception ArrayIndexOutOfBoundsException if filterExpr contains {i} 
     * expressions where i is outside the bounds of the array filterArgs
     * @exception InvalidSearchControlsException if cons contains invalid 
     * settings
     * @exception InvalidSearchFilterException if filterExpr with filterArgs 
     * represents an invalid search filter
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration search(Name name, String filterExpr,
                                    Object[] filterArgs, SearchControls cons)
        throws NamingException {
        return dirContext.search(parseName(name), filterExpr, filterArgs, 
                                 cons);
    }


    /**
     * Searches in the named context or object for entries that satisfy the 
     * given search filter. Performs the search as specified by the search 
     * controls.
     * 
     * @param name the name of the context or object to search
     * @param filterExpr the filter expression to use for the search. 
     * The expression may contain variables of the form "{i}" where i is a 
     * nonnegative integer. May not be null.
     * @param filterArgs the array of arguments to substitute for the 
     * variables in filterExpr. The value of filterArgs[i] will replace each 
     * occurrence of "{i}". If null, equivalent to an empty array.
     * @param cons the search controls that control the search. If null, the 
     * default search controls are used (equivalent to (new SearchControls())).
     * @return an enumeration of SearchResults of the objects that satisy the 
     * filter; never null
     * @exception ArrayIndexOutOfBoundsException if filterExpr contains {i} 
     * expressions where i is outside the bounds of the array filterArgs
     * @exception InvalidSearchControlsException if cons contains invalid 
     * settings
     * @exception InvalidSearchFilterException if filterExpr with filterArgs 
     * represents an invalid search filter
     * @exception NamingException if a naming exception is encountered
     */
    public NamingEnumeration search(String name, String filterExpr,
                                    Object[] filterArgs, SearchControls cons)
        throws NamingException {
        return dirContext.search(parseName(name), filterExpr, filterArgs, 
                                 cons);
    }


    // --------------------------------------------------------- Public Methods


    /**
     * Retrieves the named object as a cache entry, without any exception.
     * 
     * @param name the name of the object to look up
     * @return the cache entry bound to name
     */
    public CacheEntry lookupCache(String name) {
        CacheEntry entry = cacheLookup(name);
        if (entry == null) {
            entry = new CacheEntry();
            entry.name = name;
            try {
                Object object = dirContext.lookup(parseName(name));
                if (object instanceof InputStream) {
                    entry.resource = new Resource((InputStream) object);
                } else if (object instanceof DirContext) {
                    entry.context = (DirContext) object;
                } else if (object instanceof Resource) {
                    entry.resource = (Resource) object;
                } else {
                    entry.resource = new Resource(new ByteArrayInputStream
                        (object.toString().getBytes()));
                }
                Attributes attributes = dirContext.getAttributes(parseName(name));
                if (!(attributes instanceof ResourceAttributes)) {
                    attributes = new ResourceAttributes(attributes);
                }
                entry.attributes = (ResourceAttributes) attributes;
            } catch (NamingException e) {
                entry.exists = false;
            }
        }
        return entry;
    }


    // ------------------------------------------------------ Protected Methods


    /**
     * Parses a name.
     * 
     * @return the parsed name
     */
    protected String parseName(String name) 
        throws NamingException {
        return name;
    }


    /**
     * Parses a name.
     * 
     * @return the parsed name
     */
    protected Name parseName(Name name) 
        throws NamingException {
        return name;
    }


    /**
     * Lookup in cache.
     */
    protected CacheEntry cacheLookup(String name) {
        if (cache == null)
            return (null);
        if (name == null)
            name = "";
        for (int i = 0; i < nonCacheable.length; i++) {
            if (name.startsWith(nonCacheable[i])) {
                return (null);
            }
        }
        CacheEntry cacheEntry = cache.lookup(name);
        if (cacheEntry == null) {
            cacheEntry = new CacheEntry();
            cacheEntry.name = name;
            // Load entry
            cacheLoad(cacheEntry);
        } else {
            if (!validate(cacheEntry)) {
                if (!revalidate(cacheEntry)) {
                    cacheUnload(cacheEntry.name);
                    return (null);
                } else {
                    cacheEntry.timestamp = 
                        System.currentTimeMillis() + cacheTTL;
                }
            }
            cacheEntry.accessCount++;
        }
        return (cacheEntry);
    }


    /**
     * Validate entry.
     */
    protected boolean validate(CacheEntry entry) {
        if (((!entry.exists)
             || (entry.context != null)
             || ((entry.resource != null) 
                 && (entry.resource.getContent() != null)))
            && (System.currentTimeMillis() < entry.timestamp)) {
            return true;
        }
        return false;
    }


    /**
     * Revalidate entry.
     */
    protected boolean revalidate(CacheEntry entry) {
        // Get the attributes at the given path, and check the last 
        // modification date
        if (!entry.exists)
            return false;
        if (entry.attributes == null)
            return false;
        long lastModified = entry.attributes.getLastModified();
        long contentLength = entry.attributes.getContentLength();
        if (lastModified <= 0)
            return false;
        try {
            Attributes tempAttributes = dirContext.getAttributes(entry.name);
            ResourceAttributes attributes = null;
            if (!(tempAttributes instanceof ResourceAttributes)) {
                attributes = new ResourceAttributes(tempAttributes);
            } else {
                attributes = (ResourceAttributes) tempAttributes;
            }
            long lastModified2 = attributes.getLastModified();
            long contentLength2 = attributes.getContentLength();
            return (lastModified == lastModified2) 
                && (contentLength == contentLength2);
        } catch (NamingException e) {
            return false;
        }
    }


    /**
     * Load entry into cache.
     */
    protected void cacheLoad(CacheEntry entry) {

        String name = entry.name;

        // Retrieve missing info
        boolean exists = true;

        // Retrieving attributes
        if (entry.attributes == null) {
            try {
                Attributes attributes = dirContext.getAttributes(entry.name);
                if (!(attributes instanceof ResourceAttributes)) {
                    entry.attributes = 
                        new ResourceAttributes(attributes);
                } else {
                    entry.attributes = (ResourceAttributes) attributes;
                }
            } catch (NamingException e) {
                exists = false;
            }
        }

        // Retriving object
        if ((exists) && (entry.resource == null) && (entry.context == null)) {
            try {
                Object object = dirContext.lookup(name);
                if (object instanceof InputStream) {
                    entry.resource = new Resource((InputStream) object);
                } else if (object instanceof DirContext) {
                    entry.context = (DirContext) object;
                } else if (object instanceof Resource) {
                    entry.resource = (Resource) object;
                } else {
                    entry.resource = new Resource(new ByteArrayInputStream
                        (object.toString().getBytes()));
                }
            } catch (NamingException e) {
                exists = false;
            }
        }

        // Load object content
        if ((exists) && (entry.resource != null) 
            && (entry.resource.getContent() == null) 
            && (entry.attributes.getContentLength() >= 0)
            && (entry.attributes.getContentLength() < 
                (cacheObjectMaxSize * 1024))) {
            int length = (int) entry.attributes.getContentLength();
            // The entry size is 1 + the resource size in KB, if it will be 
            // cached
            entry.size += (entry.attributes.getContentLength() / 1024);
            InputStream is = null;
            try {
                is = entry.resource.streamContent();
                int pos = 0;
                byte[] b = new byte[length];
                while (pos < length) {
                    int n = is.read(b, pos, length - pos);
                    if (n < 0)
                        break;
                    pos = pos + n;
                }
                entry.resource.setContent(b);
            } catch (IOException e) {
                ; // Ignore
            } finally {
                try {
                    if (is != null)
                        is.close();
                } catch (IOException e) {
                    ; // Ignore
                }
            }
        }

        // Set existence flag
        entry.exists = exists;

        // Set timestamp
        entry.timestamp = System.currentTimeMillis() + cacheTTL;

        // Add new entry to cache
        synchronized (cache) {
            // Check cache size, and remove elements if too big
            if ((cache.lookup(name) == null) && cache.allocate(entry.size)) {
                cache.load(entry);
            }
        }

    }


    /**
     * Remove entry from cache.
     */
    protected boolean cacheUnload(String name) {
        if (cache == null)
            return false;
        synchronized (cache) {
            return cache.unload(name);
        }
    }


}