#! /usr/bin/env python3
#
def graph_tools_test ( ):

#*****************************************************************************80
#
## graph_tools_test() tests graph_tools().
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license. 
#
#  Modified:
#
#    04 April 2023
#
#  Author:
#
#    Original code by Bernd Klein,
#    Modifications by John Burkardt
#
#  Reference:
#
#    Bernd Klein,
#    Graph Theory and Graphs in Python,
#    https://python-course.eu/applications-python/graphs-python.php
#
  print ( '' )
  print ( 'graph_tools_test():' )
  print ( '  Some simple functions for a directed graph ("digraph")' )
  print ( '  defined using a Python dictionary:' )
  print ( '  G = { from0: [ to0, to1, ... tok], from1:[], ...}' )

  G = digraph_example1 ( )
  print ( '' )
  print ( '  The digraph:' )
  print ( G )

  nodes = digraph_nodes_all ( G )
  print ( '' )
  print ( '  The nodes:' )
  print ( nodes )

  edges = digraph_edges_all ( G )
  print ( '' )
  print ( '  The edges:' )
  print ( edges )

  digraph_plot ( G )

  isolated = digraph_find_isolated_nodes ( G )
  print ( '' )
  print ( '  The isolated nodes:' )
  print ( isolated )

  print ( '' )
  print ( '  Add node "Denver":' )
  G = digraph_add_node ( G, 'Denver' )
  print ( '  Add node "h":' )
  G = digraph_add_node ( G, 'Pittsburgh' )
  print ( '  Updated node list:' )
  nodes = digraph_nodes_all ( G )
  print ( nodes )

  print ( '' )
  print ( '  Add edge "Boston->Pittsburgh":' )
  G = digraph_add_edge ( G, [ 'Boston', 'Pittsburgh' ] )
  edges = digraph_edges_all ( G )
  print ( '  Updated edge list.' )
  print ( edges )

  print ( '' )
  print ( '  List all edges from node "Boston":' )
  edges = digraph_edges_node_from ( G, 'Boston' )
  print ( edges )

  print ( '' )
  print ( '  List all edges to node "New York":' )
  edges = digraph_edges_node_to ( G, 'New York' )
  print ( edges )
#
#  "reach"
#
  print ( '' )
  print ( '  What nodes can we reach from "Boston"?' )
  reach = digraph_reach_node ( G, 'Boston' )
  print ( reach )
  print ( '' )
  print ( '  What nodes can we reach from "Chicago"?' )
  reach = digraph_reach_node ( G, 'Chicago' )
  print ( reach )
#
#  Find a path from one node to another.
#
  print ( '' )
  print ( '  Seek path from "Boston" to "Phoenix"' )
  path = digraph_path_find ( G, "Boston", "Phoenix" )
  print ( path )

  print ( '' )
  print ( '  Seek path from "New York" to "Boston"' )
  path = digraph_path_find ( G, "New York", "Boston" )
  print ( path )
#
#  Shortest path.
#
  print ( '' )
  print ( '  Seek shortest path from "Boston" to "Phoenix"' )
  path = digraph_shortest_path ( G, "Boston", "Phoenix" )
  print ( path )
#
#  Terminate.
#
  print ( '' )
  print ( 'graph_tools_test():' )
  print ( '  Normal end of execution.' )

  return

def digraph_add_edge ( G, e ):
  n0 = e[0]
  n1 = e[1]
  if ( n0 in G ):
    G[n0].append ( n1 )
  else:
    G[n0] = [ n1 ]
  return G

def digraph_add_node ( G, n ):
  if ( n not in G ):
    G[n] = []
  else:
    print ( 'Node', n, 'is already in the digraph.' )
  return G

def digraph_edges_all ( G ):
  edges = []
  for node in G.keys ( ):
    for dest in G[node]:
      edges.append ( [ node, dest ] )
  return edges

def digraph_edges_node_from ( G, node ):
  edges = []
  if ( node in G.keys ( ) ):
    for dest in G[node]:
      edges.append ( [ node, dest ] )
  else:
    print ( node, 'is not a node of this digraph!' )
  return edges

def digraph_edges_node_to ( G, node ):
  edges = []
  for src in G.keys ( ):
    if ( node in G[src] ):
      edges.append ( [ src, node ] )
  return edges

def digraph_example1 ( ):
  G = { 
    'Boston'      : [ 'Providence', 'New York' ],
    'Providence'  : [ 'Boston', 'New York' ],
    'New York'    : [ 'Chicago' ],
    'Chicago'     : [ 'Denver', 'Phoenix' ],
    'Denver'      : [ 'Phoenix', 'New York' ],
    'Phoenix'     : [],
    'Los Angeles' : [ 'Boston' ]
   }
  return G

def digraph_find_isolated_nodes ( G ):
  isolated = list()
  for node in G:
    if ( not G[node] ):
      isolated.append ( node )
  return isolated

def digraph_nodes_all ( G ):
  nodes = list ( G.keys ( ) )
  return nodes

def digraph_path_find ( G, start_node, end_node, path = None ):
  if ( path == None ):
    path = []
  path = path + [ start_node ]
  if ( start_node == end_node ):
    return path
  if ( start_node not in G ):
    return None
  for node in G[start_node]:
    if ( node not in path ):
      extended_path = digraph_path_find ( G, node, end_node, path )
      if ( extended_path ):
        return extended_path
  return None

def digraph_plot ( G ):
  from graphviz import Digraph
  edges = digraph_edges_all ( G )
  nodes = digraph_nodes_all ( G )
  dot = Digraph ( format = 'png' )
  for n in nodes:
    dot.node ( n )
  for e in edges:
    dot.edge ( e[0], e[1] )
  dot.render ( 'digraph.dot', view = False )
  filename = 'digraph.dot.png'
  print ( '  Graphics saved as "%s"' % ( filename ) )
  return

def digraph_reach_node ( G, node ):
#
## digraph_reach_node() returns the nodes reachable from a given node.
#
  reach = [ node ]
  more = True
  while ( more ):
    more = False
    for n in reach:
      for dest in G[n]:
        if ( not dest in reach ):
          reach = reach + [ dest ]
          more = True
  return reach

def digraph_shortest_path ( graph, node1, node2 ):
  path_list = [[node1]]
  path_index = 0
  # This set keeps track of previously visited nodes
  previous_nodes = {node1}
  if node1 == node2:
    return path_list[0]
  while path_index < len(path_list):
    current_path = path_list[path_index]
    last_node = current_path[-1]
    next_nodes = graph[last_node]
    # Search goal node
    if node2 in next_nodes:
      current_path.append(node2)
      return current_path
    # Add new paths
    for next_node in next_nodes:
      if not next_node in previous_nodes:
        new_path = current_path[:]
        new_path.append(next_node)
        path_list.append(new_path)
        # To avoid backtracking
        previous_nodes.add(next_node)
    # Continue to next path in list
    path_index += 1
  # No path was found
  return []

def timestamp ( ):

#*****************************************************************************80
#
## timestamp() prints the date as a timestamp.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license. 
#
#  Modified:
#
#    21 August 2019
#
#  Author:
#
#    John Burkardt
#
  import time

  t = time.time ( )
  print ( time.ctime ( t ) )

  return

if ( __name__ == "__main__" ):
  timestamp ( )
  graph_tools_test ( )
  timestamp ( )