# automaton.py
# Andrew Davison, ad@coe.psu.ac.th, May 2025

import graphviz

TEMP_FNM = 'temp_graph'

dg = graphviz.Digraph(format='png')
dg.attr(rankdir='LR')
dg.attr(label='An Automaton')
dg.attr('edge', fontcolor='blue')

# Initial state arrow with no node
dg.node('', shape='none')
dg.edge('', 's0', label='Start')

# nodes
dg.node('s0', shape='doublecircle')
dg.node('s3', shape='doublecircle')

with dg.subgraph(name='cluster1') as c1:
  c1.attr(label='Internal', style='rounded,dashed')
  c1.node('s1')   # nodes inside a cluster
  c1.node('s2')

# transitions
dg.edge('s0', 's0', label='0')
dg.edge('s0', 's1', label='1')
dg.edge('s1', 's2', label='1')
dg.edge('s2', 's3', label='0')
dg.edge('s3', 's3', label='0, 1')
dg.edge('s2', 's2', label='1')
dg.edge('s1', 's3', label='0')

dg.render(filename=TEMP_FNM, view=True, cleanup=True)