#!/usr/bin/env python

# generates a graphviz file for visualizing syndetic 
# links between subjects when skos rdf/xml fed on stdin 

from rdflib.Graph import Graph
from rdflib import Namespace
from sys import stdin
from lcsh.namespaces import SKOS

g = Graph()
g.parse(stdin)

print 'digraph G {'
print '  rankdir = "BT"'
for s, o in g.subject_objects(SKOS["broader"]):
    s_label = g.value(subject=s, predicate=SKOS["prefLabel"])
    o_label = g.value(subject=o, predicate=SKOS["prefLabel"])
    if o_label is not None:
        print ('  "%s" -> "%s";' % (s_label, o_label)).encode('utf8')
print "}"