/**
 *
 * 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.qpid.jndi;

import javax.naming.*;
import javax.naming.spi.NamingManager;
import java.io.Serializable;
import java.util.Collections;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;

/**
 * Based on class from ActiveMQ.
 * A read-only Context
 * <p/>
 * This version assumes it and all its subcontext are read-only and any attempt
 * to modify (e.g. through bind) will result in an OperationNotSupportedException.
 * Each Context in the tree builds a cache of the entries in all sub-contexts
 * to optimise the performance of lookup.
 * </p>
 * <p>This implementation is intended to optimise the performance of lookup(String)
 * to about the level of a HashMap get. It has been observed that the scheme
 * resolution phase performed by the JVM takes considerably longer, so for
 * optimum performance lookups should be coded like:</p>
 * <code>
 * Context componentContext = (Context)new InitialContext().lookup("java:comp");
 * String envEntry = (String) componentContext.lookup("env/myEntry");
 * String envEntry2 = (String) componentContext.lookup("env/myEntry2");
 * </code>
 *
 * @version $Revision$ $Date$
 */
public class ReadOnlyContext implements Context, Serializable
{
    private static final long serialVersionUID = -5754338187296859149L;
    protected static final NameParser nameParser = new NameParserImpl();

    protected final Hashtable environment;        // environment for this context
    protected final Map bindings;         // bindings at my level
    protected final Map treeBindings;     // all bindings under me

    private boolean frozen = false;
    private String nameInNamespace = "";
    public static final String SEPARATOR = "/";

    public ReadOnlyContext()
    {
        environment = new Hashtable();
        bindings = new HashMap();
        treeBindings = new HashMap();
    }

    public ReadOnlyContext(Hashtable env)
    {
        if (env == null)
        {
            this.environment = new Hashtable();
        }
        else
        {
            this.environment = new Hashtable(env);
        }
        this.bindings = Collections.EMPTY_MAP;
        this.treeBindings = Collections.EMPTY_MAP;
    }

    public ReadOnlyContext(Hashtable environment, Map bindings)
    {
        if (environment == null)
        {
            this.environment = new Hashtable();
        }
        else
        {
            this.environment = new Hashtable(environment);
        }
        this.bindings = bindings;
        treeBindings = new HashMap();
        frozen = true;
    }

    public ReadOnlyContext(Hashtable environment, Map bindings, String nameInNamespace)
    {
        this(environment, bindings);
        this.nameInNamespace = nameInNamespace;
    }

    protected ReadOnlyContext(ReadOnlyContext clone, Hashtable env)
    {
        this.bindings = clone.bindings;
        this.treeBindings = clone.treeBindings;
        this.environment = new Hashtable(env);
    }

    protected ReadOnlyContext(ReadOnlyContext clone, Hashtable env, String nameInNamespace)
    {
        this(clone, env);
        this.nameInNamespace = nameInNamespace;
    }

    public void freeze()
    {
        frozen = true;
    }

    boolean isFrozen()
    {
        return frozen;
    }

    /**
     * internalBind is intended for use only during setup or possibly by suitably synchronized superclasses.
     * It binds every possible lookup into a map in each context.  To do this, each context
     * strips off one name segment and if necessary creates a new context for it. Then it asks that context
     * to bind the remaining name.  It returns a map containing all the bindings from the next context, plus
     * the context it just created (if it in fact created it). (the names are suitably extended by the segment
     * originally lopped off).
     *
     * @param name
     * @param value
     * @return
     * @throws javax.naming.NamingException
     */
    protected Map internalBind(String name, Object value) throws NamingException
    {
        assert name != null && name.length() > 0;
        assert!frozen;

        Map newBindings = new HashMap();
        int pos = name.indexOf('/');
        if (pos == -1)
        {
            if (treeBindings.put(name, value) != null)
            {
                throw new NamingException("Something already bound at " + name);
            }
            bindings.put(name, value);
            newBindings.put(name, value);
        }
        else
        {
            String segment = name.substring(0, pos);
            assert segment != null;
            assert!segment.equals("");
            Object o = treeBindings.get(segment);
            if (o == null)
            {
                o = newContext();
                treeBindings.put(segment, o);
                bindings.put(segment, o);
                newBindings.put(segment, o);
            }
            else if (!(o instanceof ReadOnlyContext))
            {
                throw new NamingException("Something already bound where a subcontext should go");
            }
            ReadOnlyContext readOnlyContext = (ReadOnlyContext) o;
            String remainder = name.substring(pos + 1);
            Map subBindings = readOnlyContext.internalBind(remainder, value);
            for (Iterator iterator = subBindings.entrySet().iterator(); iterator.hasNext();)
            {
                Map.Entry entry = (Map.Entry) iterator.next();
                String subName = segment + "/" + (String) entry.getKey();
                Object bound = entry.getValue();
                treeBindings.put(subName, bound);
                newBindings.put(subName, bound);
            }
        }
        return newBindings;
    }

    protected ReadOnlyContext newContext()
    {
        return new ReadOnlyContext();
    }

    public Object addToEnvironment(String propName, Object propVal) throws NamingException
    {
        return environment.put(propName, propVal);
    }

    public Hashtable getEnvironment() throws NamingException
    {
        return (Hashtable) environment.clone();
    }

    public Object removeFromEnvironment(String propName) throws NamingException
    {
        return environment.remove(propName);
    }

    public Object lookup(String name) throws NamingException
    {
        if (name.length() == 0)
        {
            return this;
        }
        Object result = treeBindings.get(name);
        if (result == null)
        {
            result = bindings.get(name);
        }
        if (result == null)
        {
            int pos = name.indexOf(':');
            if (pos > 0)
            {
                String scheme = name.substring(0, pos);
                Context ctx = NamingManager.getURLContext(scheme, environment);
                if (ctx == null)
                {
                    throw new NamingException("scheme " + scheme + " not recognized");
                }
                return ctx.lookup(name);
            }
            else
            {
                // Split out the first name of the path
                // and look for it in the bindings map.
                CompositeName path = new CompositeName(name);

                if (path.size() == 0)
                {
                    return this;
                }
                else
                {
                    String first = path.get(0);
                    Object obj = bindings.get(first);
                    if (obj == null)
                    {
                        throw new NameNotFoundException(name);
                    }
                    else if (obj instanceof Context && path.size() > 1)
                    {
                        Context subContext = (Context) obj;
                        obj = subContext.lookup(path.getSuffix(1));
                    }
                    return obj;
                }
            }
        }
        if (result instanceof LinkRef)
        {
            LinkRef ref = (LinkRef) result;
            result = lookup(ref.getLinkName());
        }
        if (result instanceof Reference)
        {
            try
            {
                result = NamingManager.getObjectInstance(result, null, null, this.environment);
            }
            catch (NamingException e)
            {
                throw e;
            }
            catch (Exception e)
            {
                throw(NamingException) new NamingException("could not look up : " + name).initCause(e);
            }
        }
        if (result instanceof ReadOnlyContext)
        {
            String prefix = getNameInNamespace();
            if (prefix.length() > 0)
            {
                prefix = prefix + SEPARATOR;
            }
            result = new ReadOnlyContext((ReadOnlyContext) result, environment, prefix + name);
        }
        return result;
    }

    public Object lookup(Name name) throws NamingException
    {
        return lookup(name.toString());
    }

    public Object lookupLink(String name) throws NamingException
    {
        return lookup(name);
    }

    public Name composeName(Name name, Name prefix) throws NamingException
    {
        Name result = (Name) prefix.clone();
        result.addAll(name);
        return result;
    }

    public String composeName(String name, String prefix) throws NamingException
    {
        CompositeName result = new CompositeName(prefix);
        result.addAll(new CompositeName(name));
        return result.toString();
    }

    public NamingEnumeration list(String name) throws NamingException
    {
        Object o = lookup(name);
        if (o == this)
        {
            return new ListEnumeration();
        }
        else if (o instanceof Context)
        {
            return ((Context) o).list("");
        }
        else
        {
            throw new NotContextException();
        }
    }

    public NamingEnumeration listBindings(String name) throws NamingException
    {
        Object o = lookup(name);
        if (o == this)
        {
            return new ListBindingEnumeration();
        }
        else if (o instanceof Context)
        {
            return ((Context) o).listBindings("");
        }
        else
        {
            throw new NotContextException();
        }
    }

    public Object lookupLink(Name name) throws NamingException
    {
        return lookupLink(name.toString());
    }

    public NamingEnumeration list(Name name) throws NamingException
    {
        return list(name.toString());
    }

    public NamingEnumeration listBindings(Name name) throws NamingException
    {
        return listBindings(name.toString());
    }

    public void bind(Name name, Object obj) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public void bind(String name, Object obj) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public void close() throws NamingException
    {
        // ignore
    }

    public Context createSubcontext(Name name) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public Context createSubcontext(String name) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public void destroySubcontext(Name name) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public void destroySubcontext(String name) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public String getNameInNamespace() throws NamingException
    {
        return nameInNamespace;
    }

    public NameParser getNameParser(Name name) throws NamingException
    {
        return nameParser;
    }

    public NameParser getNameParser(String name) throws NamingException
    {
        return nameParser;
    }

    public void rebind(Name name, Object obj) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public void rebind(String name, Object obj) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public void rename(Name oldName, Name newName) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public void rename(String oldName, String newName) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public void unbind(Name name) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public void unbind(String name) throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    private abstract class LocalNamingEnumeration implements NamingEnumeration
    {
        private Iterator i = bindings.entrySet().iterator();

        public boolean hasMore() throws NamingException
        {
            return i.hasNext();
        }

        public boolean hasMoreElements()
        {
            return i.hasNext();
        }

        protected Map.Entry getNext()
        {
            return (Map.Entry) i.next();
        }

        public void close() throws NamingException
        {
        }
    }

    private class ListEnumeration extends LocalNamingEnumeration
    {
        public Object next() throws NamingException
        {
            return nextElement();
        }

        public Object nextElement()
        {
            Map.Entry entry = getNext();
            return new NameClassPair((String) entry.getKey(), entry.getValue().getClass().getName());
        }
    }

    private class ListBindingEnumeration extends LocalNamingEnumeration
    {
        public Object next() throws NamingException
        {
            return nextElement();
        }

        public Object nextElement()
        {
            Map.Entry entry = getNext();
            return new Binding((String) entry.getKey(), entry.getValue());
        }
    }
}
