/*
    *  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.mina.core.filterchain;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.ListIterator;
  import java.util.Map;
  import java.util.Random;
  import java.util.concurrent.CopyOnWriteArrayList;
  
  import org.apache.mina.core.filterchain.IoFilter.NextFilter;
  import org.apache.mina.core.filterchain.IoFilterChain.Entry;
  import org.apache.mina.core.session.IoSession;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * The default implementation of {@link IoFilterChainBuilder} which is useful
   * in most cases.  {@link DefaultIoFilterChainBuilder} has an identical interface
   * with {@link IoFilter}; it contains a list of {@link IoFilter}s that you can
   * modify. The {@link IoFilter}s which are added to this builder will be appended
   * to the {@link IoFilterChain} when {@link #buildFilterChain(IoFilterChain)} is
   * invoked.
   * <p>
   * However, the identical interface doesn't mean that it behaves in an exactly
   * same way with {@link IoFilterChain}.  {@link DefaultIoFilterChainBuilder}
   * doesn't manage the life cycle of the {@link IoFilter}s at all, and the
   * existing {@link IoSession}s won't get affected by the changes in this builder.
   * {@link IoFilterChainBuilder}s affect only newly created {@link IoSession}s.
   *
   * <pre>
   * IoAcceptor acceptor = ...;
   * DefaultIoFilterChainBuilder builder = acceptor.getFilterChain();
   * builder.addLast( "myFilter", new MyFilter() );
   * ...
   * </pre>
   *
   * @author The Apache MINA Project (dev@mina.apache.org)
   * @version $Rev: 594846 $, $Date: 2007-11-14 13:03:07 +0100 (Wed, 14 Nov 2007) $
   */
  public class DefaultIoFilterChainBuilder implements IoFilterChainBuilder {
      
      private final Logger logger = LoggerFactory.getLogger(getClass());
      private final List<Entry> entries;
  
      /**
       * Creates a new instance with an empty filter list.
       */
      public DefaultIoFilterChainBuilder() {
          entries = new CopyOnWriteArrayList<Entry>();
      }
  
      /**
       * Creates a new copy of the specified {@link DefaultIoFilterChainBuilder}.
       */
      public DefaultIoFilterChainBuilder(DefaultIoFilterChainBuilder filterChain) {
          if (filterChain == null) {
              throw new NullPointerException("filterChain");
          }
          entries = new CopyOnWriteArrayList<Entry>(filterChain.entries);
      }
  
      /**
       * @see IoFilterChain#getEntry(String)
       */
      public Entry getEntry(String name) {
          for (Entry e: entries) {
              if (e.getName().equals(name)) {
                  return e;
              }
          }
  
          return null;
      }
  
      /**
       * @see IoFilterChain#getEntry(IoFilter)
       */
     public Entry getEntry(IoFilter filter) {
         for (Entry e: entries) {
             if (e.getFilter() == filter) {
                 return e;
             }
         }
 
         return null;
     }
 
     /**
      * @see IoFilterChain#getEntry(Class)
      */
     public Entry getEntry(Class<? extends IoFilter> filterType) {
         for (Entry e: entries) {
             if (filterType.isAssignableFrom(e.getFilter().getClass())) {
                 return e;
             }
         }
 
         return null;
     }
 
     /**
      * @see IoFilterChain#get(String)
      */
     public IoFilter get(String name) {
         Entry e = getEntry(name);
         if (e == null) {
             return null;
         }
 
         return e.getFilter();
     }
 
     /**
      * @see IoFilterChain#get(Class)
      */
     public IoFilter get(Class<? extends IoFilter> filterType) {
         Entry e = getEntry(filterType);
         if (e == null) {
             return null;
         }
 
         return e.getFilter();
     }
 
     /**
      * @see IoFilterChain#getAll()
      */
     public List<Entry> getAll() {
         return new ArrayList<Entry>(entries);
     }
 
     /**
      * @see IoFilterChain#getAllReversed()
      */
     public List<Entry> getAllReversed() {
         List<Entry> result = getAll();
         Collections.reverse(result);
         return result;
     }
 
     /**
      * @see IoFilterChain#contains(String)
      */
     public boolean contains(String name) {
         return getEntry(name) != null;
     }
 
     /**
      * @see IoFilterChain#contains(IoFilter)
      */
     public boolean contains(IoFilter filter) {
         return getEntry(filter) != null;
     }
 
     /**
      * @see IoFilterChain#contains(Class)
      */
     public boolean contains(Class<? extends IoFilter> filterType) {
         return getEntry(filterType) != null;
     }
 
     /**
      * @see IoFilterChain#addFirst(String, IoFilter)
      */
     public synchronized void addFirst(String name, IoFilter filter) {
         register(0, new EntryImpl(name, filter));
     }
 
     /**
      * @see IoFilterChain#addLast(String, IoFilter)
      */
     public synchronized void addLast(String name, IoFilter filter) {
         register(entries.size(), new EntryImpl(name, filter));
     }
 
     /**
      * @see IoFilterChain#addBefore(String, String, IoFilter)
      */
     public synchronized void addBefore(String baseName, String name,
             IoFilter filter) {
         checkBaseName(baseName);
 
         for (ListIterator<Entry> i = entries.listIterator(); i.hasNext();) {
             Entry base = i.next();
             if (base.getName().equals(baseName)) {
                 register(i.previousIndex(), new EntryImpl(name, filter));
                 break;
             }
         }
     }
 
     /**
      * @see IoFilterChain#addAfter(String, String, IoFilter)
      */
     public synchronized void addAfter(String baseName, String name,
             IoFilter filter) {
         checkBaseName(baseName);
 
         for (ListIterator<Entry> i = entries.listIterator(); i.hasNext();) {
             Entry base = i.next();
             if (base.getName().equals(baseName)) {
                 register(i.nextIndex(), new EntryImpl(name, filter));
                 break;
             }
         }
     }
 
     /**
      * @see IoFilterChain#remove(String)
      */
     public synchronized IoFilter remove(String name) {
         if (name == null) {
             throw new NullPointerException("name");
         }
 
         for (ListIterator<Entry> i = entries.listIterator(); i.hasNext();) {
             Entry e = i.next();
             if (e.getName().equals(name)) {
                 entries.remove(i.previousIndex());
                 return e.getFilter();
             }
         }
 
         throw new IllegalArgumentException("Unknown filter name: " + name);
     }
 
     /**
      * @see IoFilterChain#remove(IoFilter)
      */
     public synchronized IoFilter remove(IoFilter filter) {
         if (filter == null) {
             throw new NullPointerException("filter");
         }
 
         for (ListIterator<Entry> i = entries.listIterator(); i.hasNext();) {
             Entry e = i.next();
             if (e.getFilter() == filter) {
                 entries.remove(i.previousIndex());
                 return e.getFilter();
             }
         }
 
         throw new IllegalArgumentException("Filter not found: " + filter.getClass().getName());
     }
 
     /**
      * @see IoFilterChain#remove(Class)
      */
     public synchronized IoFilter remove(Class<? extends IoFilter> filterType) {
         if (filterType == null) {
             throw new NullPointerException("filterType");
         }
 
         for (ListIterator<Entry> i = entries.listIterator(); i.hasNext();) {
             Entry e = i.next();
             if (filterType.isAssignableFrom(e.getFilter().getClass())) {
                 entries.remove(i.previousIndex());
                 return e.getFilter();
             }
         }
 
         throw new IllegalArgumentException("Filter not found: " + filterType.getName());
     }
 
     public synchronized IoFilter replace(String name, IoFilter newFilter) {
         checkBaseName(name);
         EntryImpl e = (EntryImpl) get(name);
         IoFilter oldFilter = e.getFilter();
         e.setFilter(newFilter);
         return oldFilter;
     }
 
     public synchronized void replace(IoFilter oldFilter, IoFilter newFilter) {
         for (Entry e : entries) {
             if (e.getFilter() == oldFilter) {
                 ((EntryImpl) e).setFilter(newFilter);
                 return;
             }
         }
         throw new IllegalArgumentException("Filter not found: "
                 + oldFilter.getClass().getName());
     }
 
     public synchronized void replace(Class<? extends IoFilter> oldFilterType,
             IoFilter newFilter) {
         for (Entry e : entries) {
             if (oldFilterType.isAssignableFrom(e.getFilter().getClass())) {
                 ((EntryImpl) e).setFilter(newFilter);
                 return;
             }
         }
         throw new IllegalArgumentException("Filter not found: "
                 + oldFilterType.getName());
     }
 
     /**
      * @see IoFilterChain#clear()
      */
     public synchronized void clear() {
         entries.clear();
     }
     
     /**
      * Clears the current list of filters and adds the specified
      * filter mapping to this builder.  Please note that you must specify
      * a {@link Map} implementation that iterates the filter mapping in the
      * order of insertion such as {@link LinkedHashMap}.  Otherwise, it will
      * throw an {@link IllegalArgumentException}.
      */
     public void setFilters(Map<String, ? extends IoFilter> filters) {
         if (filters == null) {
             throw new NullPointerException("filters");
         }
         
         if (!isOrderedMap(filters)) {
             throw new IllegalArgumentException(
                     "filters is not an ordered map. Please try " + 
                     LinkedHashMap.class.getName() + ".");
         }
 
         filters = new LinkedHashMap<String, IoFilter>(filters);
         for (Map.Entry<String, ? extends IoFilter> e: filters.entrySet()) {
             if (e.getKey() == null) {
                 throw new NullPointerException("filters contains a null key.");
             }
             if (e.getValue() == null) {
                 throw new NullPointerException("filters contains a null value.");
             }
         }
         
         synchronized (this) {
             clear();
             for (Map.Entry<String, ? extends IoFilter> e: filters.entrySet()) {
                 addLast(e.getKey(), e.getValue());
             }
         }
     }
     
     @SuppressWarnings("unchecked")
     private boolean isOrderedMap(Map map) {
         Class<?> mapType = map.getClass();
         if (LinkedHashMap.class.isAssignableFrom(mapType)) {
             if (logger.isDebugEnabled()) {
                 logger.debug(mapType.getSimpleName() + " is an ordered map.");
             }
             return true;
         }
         
         if (logger.isDebugEnabled()) {
             logger.debug(mapType.getName() + " is not a " + LinkedHashMap.class.getSimpleName());
         }
 
         // Detect Jakarta Commons Collections OrderedMap implementations.
         Class<?> type = mapType;
         while (type != null) {
             for (Class<?> i: type.getInterfaces()) {
                 if (i.getName().endsWith("OrderedMap")) {
                     if (logger.isDebugEnabled()) {
                         logger.debug(
                                 mapType.getSimpleName() +
                                 " is an ordered map (guessed from that it " +
                                 " implements OrderedMap interface.)");
                     }
                     return true;
                 }
             }
             type = type.getSuperclass();
         }
         
         if (logger.isDebugEnabled()) {
             logger.debug(
                     mapType.getName() +
                     " doesn't implement OrderedMap interface.");
         }
         
         // Last resort: try to create a new instance and test if it maintains
         // the insertion order.
         logger.debug(
                 "Last resort; trying to create a new map instance with a " +
                 "default constructor and test if insertion order is " +
                 "maintained.");
         
         Map newMap;
         try {
             newMap = (Map) mapType.newInstance();
         } catch (Exception e) {
             if (logger.isDebugEnabled()) {
                 logger.debug(
                         "Failed to create a new map instance of '" + 
                         mapType.getName() +"'.", e);
             }
             return false;
         }
         
         Random rand = new Random();
         List<String> expectedNames = new ArrayList<String>();
         IoFilter dummyFilter = new IoFilterAdapter();
         for (int i = 0; i < 65536; i ++) {
             String filterName;
             do {
                 filterName = String.valueOf(rand.nextInt());
             } while (newMap.containsKey(filterName));
             
             newMap.put(filterName, dummyFilter);
             expectedNames.add(filterName);
 
             Iterator<String> it = expectedNames.iterator();
             for (Object key: newMap.keySet()) {
                 if (!it.next().equals(key)) {
                     if (logger.isDebugEnabled()) {
                         logger.debug(
                                 "The specified map didn't pass the insertion " +
                                 "order test after " + (i + 1) + " tries.");
                     }
                     return false;
                 }
             }
         }
         
         if (logger.isDebugEnabled()) {
             logger.debug(
                     "The specified map passed the insertion order test.");
         }
         return true;
     }
 
     public void buildFilterChain(IoFilterChain chain) throws Exception {
         for (Entry e : entries) {
             chain.addLast(e.getName(), e.getFilter());
         }
     }
 
     @Override
     public String toString() {
         StringBuffer buf = new StringBuffer();
         buf.append("{ ");
 
         boolean empty = true;
 
         for (Entry e : entries) {
             if (!empty) {
                 buf.append(", ");
             } else {
                 empty = false;
             }
 
             buf.append('(');
             buf.append(e.getName());
             buf.append(':');
             buf.append(e.getFilter());
             buf.append(')');
         }
 
         if (empty) {
             buf.append("empty");
         }
 
         buf.append(" }");
 
         return buf.toString();
     }
 
     private void checkBaseName(String baseName) {
         if (baseName == null) {
             throw new NullPointerException("baseName");
         }
 
         if (!contains(baseName)) {
             throw new IllegalArgumentException("Unknown filter name: "
                     + baseName);
         }
     }
 
     private void register(int index, Entry e) {
         if (contains(e.getName())) {
             throw new IllegalArgumentException(
                     "Other filter is using the same name: " + e.getName());
         }
 
         entries.add(index, e);
     }
 
     private class EntryImpl implements Entry {
         private final String name;
         private volatile IoFilter filter;
 
         private EntryImpl(String name, IoFilter filter) {
             if (name == null) {
                 throw new NullPointerException("name");
             }
             if (filter == null) {
                 throw new NullPointerException("filter");
             }
 
             this.name = name;
             this.filter = filter;
         }
 
         public String getName() {
             return name;
         }
 
         public IoFilter getFilter() {
             return filter;
         }
 
         private void setFilter(IoFilter filter) {
             this.filter = filter;
         }
 
         public NextFilter getNextFilter() {
             throw new IllegalStateException();
         }
 
         @Override
         public String toString() {
             return "(" + getName() + ':' + filter + ')';
         }
 
         public void addAfter(String name, IoFilter filter) {
             DefaultIoFilterChainBuilder.this.addAfter(getName(), name, filter);
         }
 
         public void addBefore(String name, IoFilter filter) {
             DefaultIoFilterChainBuilder.this.addBefore(getName(), name, filter);
         }
 
         public void remove() {
             DefaultIoFilterChainBuilder.this.remove(getName());
         }
 
         public void replace(IoFilter newFilter) {
             DefaultIoFilterChainBuilder.this.replace(getName(), newFilter);
         }
     }
 }