package org.lsst.ccs.utilities.structs;
   
   import javax.swing.tree.TreeNode;
   import java.beans.ConstructorProperties;
   import java.io.Serializable;
   import java.util.*;
   
   /**
    * Immutable simple tree that can be used by swing Trees.
   *
   * @author bamade
   */
  // Date: 07/01/2014
  
  public class TreeBranch<T extends Serializable> implements Serializable, TreeNode, Iterable<T> {
  
      private static final long serialVersionUID = -8299651867210784530L;
      /**
       * the parent node. null if node is root.
       */
      private TreeBranch<T> parent;
      /**
       * list of children
       */
      private ArrayList<TreeBranch<T>> children;
      /**
       * the value attached to this node
       */
      private T content;
      /**
       * @ImplNote : there is a problem here: what is the currentIndex of the rootNode?
       * if 0 this could lead to bugs, if -1 other problems arise
       */
      private int currentIndex = -1;
  
      /**
       * to be used initially to build the root (avoid otherwise)
       *
       * @param content
       */
      public TreeBranch(T content) {
          this.content = content;
      }
  
      /**
       * Avoid using this constructor: for beans purposes use
       * the constructor annotated with <TT>ConstructorProperties</TT>
       */
      protected TreeBranch() {
      }
  
      /**
       * prefer the use of this constructor when building a tree
       * (instead of using sequence one-arg constructor + addChild)
       *
       * @param parent  may be null if node is intended as a root Node.
       * @param content
       */
      @ConstructorProperties({"realParent", "content"})
      public TreeBranch(TreeBranch<T> parent, T content) {
          //this.parent = parent;
          this.content = content;
          if (parent != null) {
              parent.addChild(this);
          }
      }
  
      /**
       * adds a child to the current node.
       * Prefer the use of the 2-args constructor if possible;
       *
       * @param child
       */
      public synchronized void addChild(TreeBranch<T> child) {
          if (child == null) {
              throw new IllegalArgumentException("null child");
          }
          if (child.parent != null) {
              throw new IllegalArgumentException(this + " node " + child + " already part of another tree " + child.parent);
          }
          if (children == null) {
              children = new ArrayList<>();
          }
          int index = children.size();
          children.add(child);
          child.currentIndex = index;
          child.parent = this;
      }
  
      /**
       * @return the data stored in this node
       */
      public T getContent() {
          return content;
      }
  
      /**
       * @return the current index of this node in the parent's
       * child list. For the rootNode the index is -1 ;
      */
     public int getCurrentIndex() {
         return currentIndex;
     }
 
     /**
      * @return an iterator of contents where tree is explored in preOrder.
      */
     @Override
     public Iterator<T> iterator() {
         return new PreOrderIterator<T>(this);
     }
 
     /**
      * @return an iterator of nodes where tree is explored in preOrder.
      */
     public Iterator<TreeBranch<T>> nodeIterator() {
         return new PreOrderNodeIterator<T>(this);
     }
 
     /**
      * @return the list of immediate children of this node or an empty list if none
      */
     public List<TreeBranch<T>> getChildren() {
         if (children != null) {
             return children;
         }
         return Collections.emptyList();
     }
 
     /**
      * @return an iterator over immediate children or an empty Iterator if none
      */
     public Iterator<TreeBranch<T>> getChildIterator() {
         if (children != null) {
             return children.iterator();
         }
         return Collections.emptyIterator();
     }
 
 
     /**
      * @return the list of parent nodes starting from the rootNode
      */
     public List<TreeBranch<T>> getPath() {
         ArrayList<TreeBranch<T>> res = new ArrayList<>();
         TreeBranch<T> curNode = this;
         while (null != (curNode = curNode.getRealParent())) {
             res.add(curNode);
         }
         Collections.reverse(res);
         return res;
     }
 
     /**
      * @param childIndex
      * @return the child at the requested index or <TT>null</TT>
      * if out of range.
      * @ImplNote TODO: specify what happens if childIndex out of range
      */
     @Override
     public TreeNode getChildAt(int childIndex) {
         if (children != null) {
             if (childIndex >= children.size() || childIndex < 0) {
                 return null;
             }
             TreeBranch<T> res = children.get(childIndex);
             assert childIndex == res.currentIndex;
             return res;
         }
         return null;
     }
 
     /**
      * @return the number of children of this node
      */
     @Override
     public int getChildCount() {
         if (children == null) return 0;
         return children.size();
     }
 
     /**
      * @return the parent of this node with type
      * <TT>TreeNode</TT> (TreeNode interface contract)
      */
     @Override
     public TreeNode getParent() {
         return parent;
     }
 
     /**
      * same as <TT>getParent</TT> but with proper return type
      *
      * @return a <TT>TreeBranch</TT> node or null when at the top
      * of the tree.
      */
     public TreeBranch<T> getRealParent() {
         return parent;
     }
 
     /**
      * @param node should be a child node of the current node
      * @return the index in the child list or -1 if the argument
      * is not found in this list
      */
     @Override
     public int getIndex(TreeNode node) {
         if (node.getParent() != this) {
             return -1;
         }
         if (children != null) {
             TreeBranch<T> branch = (TreeBranch<T>) node;
             return branch.currentIndex;
         }
         return -1;
     }
 
     /**
      * since the tree is immutable this method is not intended to be called during building operations.
      * It is here for the <TT>TreeNode</TT> contract.
      *
      * @return
      */
     @Override
     public boolean getAllowsChildren() {
         return children != null;
     }
 
     /**
      * @return true if this node has no children
      */
     @Override
     public boolean isLeaf() {
         return children == null;
     }
 
     /**
      * @return true of this node is the top of the tree.
      */
     public boolean isRootNode() {
         return parent == null;
     }
 
     /**
      * @return an enumeration over children of this node
      * (TreeNode interface contract)
      */
     @Override
     public Enumeration children() {
         //was return children.elements(); when Vector was used
         return new Enumeration() {
             final Iterator iter = children.iterator();
 
             @Override
             public boolean hasMoreElements() {
                 return iter.hasNext();
             }
 
             @Override
             public Object nextElement() {
                 return iter.next();
             }
         };
     }
     //utilities
 
     /**
      * @return a String representing the value attached to this node.
      */
     @Override
     public String toString() {
         return String.valueOf(content);
     }
 
     /**
      * inner class that delegates to <TT>PreOrderNodeIterator</TT>
      * to fetch content in pre-order.
      *
      * @param <X>
      */
     protected static class PreOrderIterator<X extends Serializable> implements Iterator<X> {
         private final PreOrderNodeIterator<X> preOrderNodeIterator;
 
         public PreOrderIterator(TreeBranch<X> rootNode) {
             preOrderNodeIterator = new PreOrderNodeIterator<>(rootNode);
         }
 
 
         @Override
         public X next() {
             TreeBranch<X> node = preOrderNodeIterator.next();
             return node.getContent();
         }
 
 
         @Override
         public boolean hasNext() {
             return preOrderNodeIterator.hasNext();
         }
 
 
         @Override
         public void remove() {
             throw new UnsupportedOperationException("remove");
         }
     }
 
     /**
      * Inner class to fetch nodes in pre-order.
      *
      * @param <X>
      */
     protected static class PreOrderNodeIterator<X extends Serializable> implements Iterator<TreeBranch<X>> {
         private final Stack<Iterator<TreeBranch<X>>> stack = new Stack<>();
 
         public PreOrderNodeIterator(TreeBranch<X> rootNode) {
             //hack to generalize the algorithm: the rootNode is seen as a virtual member of a child list
             ArrayList<TreeBranch<X>> edenChildList = new ArrayList<>(1);
             edenChildList.add(rootNode);
             stack.push(edenChildList.iterator());
         }
 
 
         @Override
         public TreeBranch<X> next() {
             // get two aspirins before reading code! this is an idiom
             // gets Iterator on the stack
             Iterator<TreeBranch<X>> iter = stack.peek();
             // gets the next element
             TreeBranch<X> node = iter.next();
             // gets an Iterator over children
             Iterator<TreeBranch<X>> itChildren = node.getChildIterator();
             // if nothing else to read at next iteration -> pop
             if (!iter.hasNext()) {
                 stack.pop();
             }
             // if child Iterator not empty push child Iterator
             if (itChildren.hasNext()) {
                 stack.push(itChildren);
             }
             return node;
         }
 
 
         /**
          * is there an iterator on the stack and
          * is there something to read ?
          *
          * @return
          */
         @Override
         public boolean hasNext() {
             return (!stack.empty() && stack.peek().hasNext());
         }
 
 
         @Override
         public void remove() {
             throw new UnsupportedOperationException("remove");
         }
     }
 }