/**
 * A simple mechanism for printing binary trees in "outline form".  In
 * this form, the tree
 * <pre>
 *     A
 *   /   \
 *  B     E
 *   \   / \
 *    Q  T  S
 * <pre>
 * would be printed as
 * <pre>
 *    A
 *      B
 *        -
 *        Q
 *      E
 *        T
 *        S
 * </pre>
 */
public class BinaryTreePrinter {

  // +---------+-------------------------------------------------
  // | Methods |
  // +---------+

  /**
   * Print a tree to a particular output object.
   */
  public void printTree(SimpleOutput out, BinaryTree tree) {
    printTree(out, tree.rootCursor());
  } // printTree(SimpleOutput, BinaryTree)

  /**
   * Print the portion of a tree given by a cursor to a particular
   * output object.
   */
  public void printTree(SimpleOutput out, BinaryTreeCursor subRoot) {
    printTree(out, subRoot, "");
  } // printTree(SimpleOutput, BinaryTreeCursor)

  // +---------+-------------------------------------------------
  // | Helpers |
  // +---------+

  /**
   * Print the portion of a tree given by a cusror to a particular
   * output object, indended a specified amount.
   */
  protected void printTree(
    SimpleOutput out, 
    BinaryTreeCursor subRoot, 
    String indent) 
  {
     // Sanity check.  Make sure the cursor is on the tree. 
     if (!subRoot.onTree()) {
       out.println(indent + "?");
       return;
     }
     // Print the value in the current node.
     out.println(indent + subRoot.getValue().toString());
     // If we're not at a leaf, print the left and right subtrees,
     // indented slightly more.
     if (!subRoot.onLeaf()) {
       // If it has a left subtree, print it.
       if (subRoot.hasLeftChild())
         printTree(out, subRoot.getLeftChild(), indent + "  ");
       // If it doens't have a left subtree, print a dash.
       else
         out.println(indent + "  -");
       // If it has a right subtree, print it.
       if (subRoot.hasRightChild())
         printTree(out, subRoot.getRightChild(), indent + "  ");
       // If it doens't have a right subtree, print a dash.
       else
         out.println(indent + "  -");
    } // If we're not at a leaf.
  } // printTree(SimpleOutput, BinaryTreeCursor, String)
} // class BinaryTreePrinter