from xml.dom.minidom import parse
import sys

def walk_nodes(root, type_filter=(), bad_names=('#text',)):
  """Return all nodes in the tree as a list"""

  traversed = [] #Traversed nodes
  to_traverse = [root] #Nodes we have not yet visited

  while len(to_traverse) > 0: #Depth first traversal
    current = to_traverse.pop()

    if (current.nodeType in type_filter or len(type_filter) == 0) and current.nodeName not in bad_names:
      to_traverse.extend(current.childNodes)

    #Compensate for weird #text nodes
    if current.nodeName not in bad_names:
      traversed.append(current)

  return traversed

def find_nodes(root, node_name):
  """Finds all nodes with the given name under root"""
  return [node for node in walk_nodes(root) if node.nodeName == node_name]

def compare_nodes(root1, root2, element_name='Signal', attr='Name'):
  """Given two root nodes, find the elements with the given name and do a set difference based on the attribute name"""
  attr1 = set([element.getAttribute(attr) for element in root1.getElementsByTagName(element_name)])
  attr2 = set([element.getAttribute(attr) for element in root2.getElementsByTagName(element_name)])

  return attr2 - attr1

def choice_nodes(root):
  """Find all possible element names in the tree"""

  return set([node.nodeName for node in walk_nodes(root, (1,))])

if __name__ == '__main__':
  assert len(sys.argv) >= 3, 'You must provide valid xml file!'

  #Move past the Document tag
  dom1 = parse(sys.argv[1]).firstChild
  dom2 = parse(sys.argv[2]).firstChild

  for name in compare_nodes(dom1, dom2):
    print name