#!/usr/bin/env python3
"""
binary_heap.py
This demonstration uses a list to build and maintain a minHeap tree.
@author Richard White
@version 2017-04-24
"""

class BinaryHeap():
    """The BinaryHeap class implements the Binary Heap Abstract 
    Data Type as a list of values, where the index p of a parent
    can be calculated from the index c of a child as c // 2.
    """
    def __init__(self):
        self.heap_list = [0]  # not used. Here just to make parent-
                             # child calculations work nicely.
        # Note that current size of heap = len(self.heapList) - 1

    def insert(self,value):
        """Inserts a value into the heap by:
        a. adding it to the end of the list, and then
        b. "percolating" it up to an appropriate position
        """
        pass

    def percolate_up(self, i):
        """Beginning at i, check to see if parent above is greater than
        value at i. If so, percolate i upwards to parent's position.
        """
        pass 

    def del_min(self):
        """This is a bit trickier. It's easy to return the minimum item,
        the first item on the list, but how do we readjust the heap then?
        """
        pass

    def percolate_down(self,i):
        """Moves the item at i down to a correct level in the heap. To
        work correctly, needs to identify the minimum child for parent i.
        """
        pass

    def find_min(self):
        """Returns the minimum item in the heap, without removing it.
        """
        return self.heap_list[1]

    def is_empty(self):
        return len(self.heap_list) - 1 == 0

    def size(self):
        return len(self.heap_list) - 1

    def build_heap(self, list_of_keys):
        """Returns a new heap based on a pre-existing list of key 
        values."""
        pass

    def __repr__(self):
        return "BinaryHeap" + str(self.heap_list)

def main():
    print("Demonstrating minHeap binary tree")
    bh = BinaryHeap()
    bh.insert(5)
    print(bh)
    '''
    bh.insert(7)
    bh.insert(3)
    bh.insert(11)
    bh.insert(1)
    bh.insert(50)
    bh.insert(15)
    print(bh)
    print(bh.find_min())
    print(bh.del_min())
    print(bh)
    '''

if __name__ == "__main__":
    main()