/*
    * 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.logging.log4j.spi;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.List;
  
  import org.apache.logging.log4j.ThreadContext.ContextStack;
  
  /**
   *
   */
  public class MutableThreadContextStack implements ThreadContextStack {
  
      private static final long serialVersionUID = 50505011L;
  
      /**
       * The underlying list (never null).
       */
      private final List<String> list;
      private boolean frozen;
  
      /**
       * Constructs an empty MutableThreadContextStack.
       */
      public MutableThreadContextStack() {
          this(new ArrayList<String>());
      }
  
      public MutableThreadContextStack(final List<String> list) {
          this.list = new ArrayList<String>(list);
      }
  
      private MutableThreadContextStack(final MutableThreadContextStack stack) {
          this.list = new ArrayList<String>(stack.list);
      }
  
      private void checkInvariants() {
          if (frozen) {
              throw new UnsupportedOperationException("context stack has been frozen");
          }
      }
  
      @Override
      public String pop() {
          checkInvariants();
          if (list.isEmpty()) {
              return null;
          }
          final int last = list.size() - 1;
          final String result = list.remove(last);
          return result;
      }
  
      @Override
      public String peek() {
          if (list.isEmpty()) {
              return null;
          }
          final int last = list.size() - 1;
          return list.get(last);
      }
  
      @Override
      public void push(final String message) {
          checkInvariants();
          list.add(message);
      }
  
      @Override
      public int getDepth() {
          return list.size();
      }
  
      @Override
      public List<String> asList() {
          return list;
      }
  
      @Override
      public void trim(final int depth) {
          checkInvariants();
          if (depth < 0) {
             throw new IllegalArgumentException("Maximum stack depth cannot be negative");
         }
         if (list == null) {
             return;
         }
         final List<String> copy = new ArrayList<String>(list.size());
         final int count = Math.min(depth, list.size());
         for (int i = 0; i < count; i++) {
             copy.add(list.get(i));
         }
         list.clear();
         list.addAll(copy);
     }
 
     @Override
     public ThreadContextStack copy() {
         return new MutableThreadContextStack(this);
     }
 
     @Override
     public void clear() {
         checkInvariants();
         list.clear();
     }
 
     @Override
     public int size() {
         return list.size();
     }
 
     @Override
     public boolean isEmpty() {
         return list.isEmpty();
     }
 
     @Override
     public boolean contains(final Object o) {
         return list.contains(o);
     }
 
     @Override
     public Iterator<String> iterator() {
         return list.iterator();
     }
 
     @Override
     public Object[] toArray() {
         return list.toArray();
     }
 
     @Override
     public <T> T[] toArray(final T[] ts) {
         return list.toArray(ts);
     }
 
     @Override
     public boolean add(final String s) {
         checkInvariants();
         return list.add(s);
     }
 
     @Override
     public boolean remove(final Object o) {
         checkInvariants();
         return list.remove(o);
     }
 
     @Override
     public boolean containsAll(final Collection<?> objects) {
         return list.containsAll(objects);
     }
 
     @Override
     public boolean addAll(final Collection<? extends String> strings) {
         checkInvariants();
         return list.addAll(strings);
     }
 
     @Override
     public boolean removeAll(final Collection<?> objects) {
         checkInvariants();
         return list.removeAll(objects);
     }
 
     @Override
     public boolean retainAll(final Collection<?> objects) {
         checkInvariants();
         return list.retainAll(objects);
     }
 
     @Override
     public String toString() {
         return String.valueOf(list);
     }
 
     @Override
     public int hashCode() {
         final int prime = 31;
         int result = 1;
         result = prime * result + ((this.list == null) ? 0 : this.list.hashCode());
         return result;
     }
 
     @Override
     public boolean equals(final Object obj) {
         if (this == obj) {
             return true;
         }
         if (obj == null) {
             return false;
         }
         if (!(obj instanceof ThreadContextStack)) {
             return false;
         }
         final ThreadContextStack other = (ThreadContextStack) obj;
         final List<String> otherAsList = other.asList();
         if (this.list == null) {
             if (otherAsList != null) {
                 return false;
             }
         } else if (!this.list.equals(otherAsList)) {
             return false;
         }
         return true;
     }
 
     @Override
     public ContextStack getImmutableStackOrNull() {
         return copy();
     }
 
     /**
      * "Freezes" this context stack so it becomes immutable: all mutator methods will throw an exception from now on.
      */
     public void freeze() {
         frozen = true;
     }
     
     public boolean isFrozen() {
         return frozen;
     }
 }