/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.hc.core5.http.config;
  
  import org.apache.hc.core5.util.Args;
  
  /**
   * Chain of doubly linked elements.
   * <p>
   * This implementation makes no attempts to ensure uniqueness of element names.
   *
   * @param <E>
   */
  public class NamedElementChain<E> {
  
      private final Node master;
      private int size;
  
      public NamedElementChain() {
          this.master = new Node("master", null);
          this.master.previous = this.master;
          this.master.next = this.master;
          this.size = 0;
      }
  
      public Node getFirst() {
          return master.next != master ? master.next : null;
      }
  
      public Node getLast() {
          return master.previous != master ? master.previous : null;
      }
  
      public Node addFirst(final E value, final String name) {
          Args.notBlank(name, "Name");
          Args.notNull(value, "Value");
          final Node newNode = new Node(name, value);
          final Node oldNode = master.next;
          master.next = newNode;
          newNode.previous = master;
          newNode.next = oldNode;
          oldNode.previous = newNode;
          size++;
          return newNode;
      }
  
      public Node addLast(final E value, final String name) {
          Args.notBlank(name, "Name");
          Args.notNull(value, "Value");
          final Node newNode = new Node(name, value);
          final Node oldNode = master.previous;
          master.previous = newNode;
          newNode.previous = oldNode;
          newNode.next = master;
          oldNode.next = newNode;
          size++;
          return newNode;
      }
  
      public Node find(final String name) {
          Args.notBlank(name, "Name");
          return doFind(name);
      }
  
      private Node doFind(final String name) {
          Node current = master.next;
          while (current != master) {
              if (name.equals(current.name)) {
                  return current;
              }
              current = current.next;
          }
          return null;
      }
 
     public Node addBefore(final String existing, final E value, final String name) {
         Args.notBlank(name, "Name");
         Args.notNull(value, "Value");
         final Node current = doFind(existing);
         if (current == null) {
             return null;
         }
         final Node newNode = new Node(name, value);
         final Node previousNode = current.previous;
         previousNode.next = newNode;
         newNode.previous = previousNode;
         newNode.next = current;
         current.previous = newNode;
         size++;
         return newNode;
     }
 
     public Node addAfter(final String existing, final E value, final String name) {
         Args.notBlank(name, "Name");
         Args.notNull(value, "Value");
         final Node current = doFind(existing);
         if (current == null) {
             return null;
         }
         final Node newNode = new Node(name, value);
         final Node nextNode = current.next;
         current.next = newNode;
         newNode.previous = current;
         newNode.next = nextNode;
         nextNode.previous = newNode;
         size++;
         return newNode;
     }
 
     public boolean remove(final String name) {
         final Node node = doFind(name);
         if (node == null) {
             return false;
         }
         node.previous.next = node.next;
         node.next.previous = node.previous;
         node.previous = null;
         node.next = null;
         size--;
         return true;
     }
 
     public boolean replace(final String existing, final E value) {
         final Node node = doFind(existing);
         if (node == null) {
             return false;
         }
         node.value = value;
         return true;
     }
 
     public int getSize() {
         return size;
     }
 
     public class Node {
 
         private final String name;
         private E value;
         private Node previous;
         private Node next;
 
         Node(final String name, final E value) {
             this.name = name;
             this.value = value;
         }
 
         public String getName() {
             return name;
         }
 
         public E getValue() {
             return value;
         }
 
         public Node getPrevious() {
             return previous != master ? previous : null;
         }
 
         public Node getNext() {
             return next != master ? next: null;
         }
 
         @Override
         public String toString() {
             return name + ": " + value;
         }
 
     }
 
 }