#!/usr/bin/env python3
"""
binary_traversal_demo.py
This program demonstrates the three strategies for traversing a binary tree:
1. preorder
2. inorder
3. postorder
@author Richard White
@version 2017-04-18
"""

from binary_tree_class import BinaryTree

def preorder(binary_tree, result):
    """Returns a list of the values in binary_tree,
    ordered according to a preorder traversal:
    1. Begin at root and evaluate
    2. Call preorder on left child (recursively)
    3. Call preorder on right child (recursively)
    """
    if binary_tree is None:
        pass
    else:
        result.append(binary_tree.get_root_val())
        preorder(binary_tree.get_left_child(),result)
        preorder(binary_tree.get_right_child(),result)
    return result

def inorder(binary_tree, result):
    """Returns a list of the values in binary_tree,
    ordered according to an inorder traversal:
    1. Call inorder recursively on left subtree
    2. Visit root node
    3. Call inorder recursively on right subtree
    """
    pass
    

def postorder(binary_tree, result):
    """Returns a list of the values in binary_tree,
    ordered according to an postorder traversal.
    """
    pass

def main():
    bt = BinaryTree("a")
    bt.insert_left("g")
    bt.insert_left("d")
    bt.insert_left("b")
    bt.get_left_child().get_left_child().insert_right("h")
    bt.get_left_child().insert_right("e")
    bt.get_left_child().get_right_child().insert_right("i")
    bt.insert_right("c")
    bt.get_right_child().insert_right("f")
    # print(bt)
    print("""     The Binary Tree
            a
           / \ 
          b   c 
         / \   \ 
        d   e   f 
       / \   \ 
      g   h   i 
    """) 

    result = []
    print("Preorder Traversal")
    print(preorder(bt,result))
    result = []
    print("Inorder Traversal")
    print(inorder(bt,result))
    result = []
    print("Postorder Traversal")
    print(postorder(bt,result))

if __name__ == "__main__":
    main()