# -*- coding: Latin-1 -*-
"""Graphviz's dot language Python interface.

This module provides with a full interface to create handle modify
and process graphs in Graphviz's dot language.

References:

pydot Homepage:	http://www.dkbza.org/pydot.html
Graphviz:	http://www.research.att.com/sw/tools/graphviz/
DOT Language:	http://www.research.att.com/~erg/graphviz/info/lang.html

Programmed and tested with Graphviz 1.12 and Python 2.3.3 on GNU/Linux
by Ero Carrera (c) 2004	[ero@dkbza.org]

Distributed under MIT license [http://opensource.org/licenses/mit-license.html].
"""

__author__ = 'Ero Carrera'
__version__ = '0.9.9'
__license__ = 'MIT'

import os
import tempfile
import copy
import dot_parser


def graph_from_dot_data(data):
	"""Load graph as defined by data in DOT format.
	
	The data is assumed to be in DOT format. It will
	be parsed and a Dot class will be returned, 
	representing the graph.
	"""
	
	graph = dot_parser.parse_dot_data(data)
	if graph is not None:
		dot = Dot()
		dot.__dict__.update(graph.__dict__)
		return dot
		
	return None

def graph_from_dot_file(path):
	"""Load graph as defined by a DOT file.
	
	The file is assumed to be in DOT format. It will
	be loaded, parsed and a Dot class will be returned, 
	representing the graph.
	"""
	
	fd = file(path, 'rb')
	data = fd.read()
	fd.close()
	
	return graph_from_dot_data(data)


def graph_from_edges(edge_list, node_prefix='', directed=False):
	"""Creates a basic graph out of an edge list.
	
	The edge list has to be a list of tuples representing
	the nodes connected by the edge.
	The values can be anything: bool, int, float, str.
	
	If the graph is undirected by default, it is only
	calculated from one of the symmetric halves of the matrix.
	"""
	if directed:
		graph = Dot(graph_type='digraph')
	else:
		graph = Dot(graph_type='graph')
	for edge in edge_list:
		e = Edge(node_prefix+str(edge[0]), node_prefix+str(edge[1]))
		graph.add_edge(e)
	return graph


def graph_from_adjacency_matrix(matrix, node_prefix='', directed=False):
	"""Creates a basic graph out of an adjacency matrix.
	
	The matrix has to be a list of rows of values
	representing an adjacency matrix.
	The values can be anything: bool, int, float, as long
	as they can evaluate to True or False.
	"""
	node_orig = 1
	if directed:
		graph = Dot(graph_type='digraph')
	else:
		graph = Dot(graph_type='graph')
	for row in matrix:
		if not directed:
			skip = matrix.index(row)
			r = row[skip:]
		else:
			skip = 0
			r = row
		node_dest = skip+1
		for e in r:
			if e:
				graph.add_edge(	\
					Edge(	node_prefix+str(node_orig), \
						node_prefix+str(node_dest)))
			node_dest += 1
		node_orig += 1
	return graph

def graph_from_incidence_matrix(matrix, node_prefix='', directed=False):
	"""Creates a basic graph out of an incidence matrix.
	
	The matrix has to be a list of rows of values
	representing an incidence matrix.
	The values can be anything: bool, int, float, as long
	as they can evaluate to True or False.
	"""
	node_orig = 1
	if directed:
		graph = Dot(graph_type='digraph')
	else:
		graph = Dot(graph_type='graph')
	for row in matrix:
		nodes = []
		c = 1
		for node in row:
			if node:
				nodes.append(c*node)
			c += 1
			nodes.sort()
		if len(nodes) == 2:
			graph.add_edge(	\
				Edge(node_prefix+str(abs(nodes[0])),	\
					node_prefix+str(nodes[1]) ))
	if not directed:
		graph.set_simplify(True)
	return graph

			
def find_graphviz():
	"""Locate Graphviz's executables in the system.

	Attempts  to locate  graphviz's  executables in a Unix system.
	It will look for 'dot', 'twopi' and 'neato' in all the directories
	specified in the PATH environment variable.
	It will return a dictionary containing the program names as keys
	and their paths as values.
	"""
	progs = {'dot': '', 'twopi': '', 'neato': '', 'circo': '', 'fdp': ''}
	if not os.environ.has_key('PATH'):
		return None
	for path in os.environ['PATH'].split(os.pathsep):
		for prg in progs.keys():
			if os.path.exists(path+os.path.sep+prg):
				progs[prg] = path+os.path.sep+prg
			elif os.path.exists(path+os.path.sep+prg + '.exe'):
				progs[prg] = path+os.path.sep+prg + '.exe'
	return progs

class Common:
	"""Common information to several classes.
	
	Should not be directly used, several classes are derived from
	this one.
	"""
	chars_ID = None
	parent_graph = None
	
	def char_range(self, a,b):
		"""Generate a list containing a range of characters.
		
		Returns a list of characters starting from 'a' up to 'b'
		both inclusive.
		"""
		return map(chr, range(ord(a), ord(b)+1))
	
	def is_ID(self, s):
		"""Checks whether a string is an dot language ID.
		
		It will check whether the string is solely composed
		by the characters allowed in an ID or not.
		"""
		if not self.chars_ID:
			self.chars_ID = self.char_range('a','z')+self.char_range('A','Z')+ \
					self.char_range('0','9')+['_']
		for c in s:
			if c not in self.chars_ID:
				return False
		return True

class Error(Exception):
	"""General error handling class.
	"""
	def __init__(self, value):
		self.value = value
	def __str__(self):
		return self.value


class Node(object, Common):
	"""A graph node.
	
	This class represents a graph's node with all its attributes.
	
	node(name, attribute=value, ...)
	
	name: node's name
	
	All the attributes defined in the Graphviz dot language should
	be supported.
	"""
	attributes = ['showboxes', 'URL', 'fontcolor', 'fontsize', 'label', 'fontname',	\
		'comment', 'root', 'toplabel', 'vertices', 'width', 'z', 'bottomlabel',	\
		'distortion', 'fixedsize', 'group', 'height', 'orientation', 'pin',	\
		'rects', 'regular', 'shape', 'shapefile', 'sides', 'skew', 'pos',	\
		'layer', 'tooltip', 'style', 'target', 'color', 'peripheries',
		'fillcolor']

	def __init__(self, name, **attrs):
	
		if isinstance(name, str) and not name.startswith('"'):
			idx = name.find(':')
			if idx>0:
				name = name[:idx]
		
		self.name = str(name)
		for attr in self.attributes:
			# Set all the attributes to None.
			self.__setattr__(attr, None)
			# Generate all the Setter methods.
			self.__setattr__('set_'+attr, lambda x, a=attr : self.__setattr__(a, x))
			# Generate all the Getter methods.
			self.__setattr__('get_'+attr, lambda a=attr : self.__getattribute__(a))
		for attr, val in attrs.items():
			self.__setattr__(attr, val)

	def set_name(self, node_name):
		"""Set the node's name."""
		
		self.name = str(node_name)
		
	def get_name(self):
		"""Get the node's name."""
		
		return self.name

	def set(self, name, value):
		"""Set an attribute value by name.
		
		Given an attribute 'name' it will set its value to 'value'.
		There's always the possibility of using the methods:
			set_'name'(value)
		which are defined for all the existing attributes.
		"""
		if name in self.attributes:
			self.__dict__[name] = value
			return True
		# Attribute is not known
		return False

	def to_string(self):
		"""Returns a string representation of the node in dot language.
		"""
		
		if not isinstance(self.name, str):
			self.name = str(self.name)
		
		# RMF: special case defaults for node, edge and graph properties.
		if self.name in ['node', 'edge', 'graph']:
			node = self.name
		else:
			node = '"'+self.name+'"'

		node_attr = None
		all_attrs = [a for a in self.attributes]
		all_attrs += [a for a  in Graph.attributes if a not in all_attrs]
		all_attrs += [a for a  in Edge.attributes if a not in all_attrs]
		for attr in all_attrs:
			if self.__dict__.has_key(attr)	\
			and self.__getattribute__(attr) is not None:
				if not node_attr:
					node_attr = ''
				else:
					node_attr += ', '
				node_attr += attr+'='
				val = self.__dict__[attr]
				
				if val.startswith('<') and val.endswith('>'):
					node_attr += val
				elif (isinstance(val, str) or isinstance(val, unicode)) and not self.is_ID(val):
					node_attr += '"'+val+'"'
				else:
					node_attr += str(val)

		if node_attr:
			node += ' ['+node_attr+']'
		node += ';'

		return node


class Edge(object, Common):
	"""A graph edge.
	
	This class represents a graph's edge with all its attributes.
	
	edge(src, dst, attribute=value, ...)
	
	src: source node's name
	dst: destination node's name
	
	All the attributes defined in the Graphviz dot language should
	be supported.
	
 	Attributes can be set through the dynamically generated methods:
	
	 set_[attribute name], i.e. set_label, set_fontname
	 
	or using the instance's attributes:
	
	 Edge.[attribute name], i.e. edge_instance.label, edge_instance.fontname
	"""
	attributes = ['style', 'target', 'pos', 'layer', 'tooltip', 'color', 'showboxes',\
		'URL', 'fontcolor', 'fontsize', 'label', 'fontname', 'comment', 'lp',	\
		'arrowhead', 'arrowsize', 'arrowtail', 'constraint', 'decorate', 'dir',	\
		'headURL', 'headclip', 'headhref', 'headlabel', 'headport',		\
		'headtarget', 'headtooltip', 'href', 'labelangle', 'labeldistance',	\
		'labelfloat', 'labelfontcolor', 'labelfontname', 'labelfontsize', 'len',\
		'lhead', 'ltail', 'minlen', 'samehead', 'sametail', 'weight', 'tailURL',\
		'tailclip', 'tailhref', 'taillabel', 'tailport', 'tailtarget',		\
		'tailtooltip']

	def __init__(self, src, dst, **attrs):
		self.src = src
		self.dst = dst
		for attr in self.attributes:
			# Set all the attributes to None.
			self.__setattr__(attr, None)
			# Generate all the Setter methods.
			self.__setattr__('set_'+attr, lambda x, a=attr : self.__setattr__(a, x))
			# Generate all the Getter methods.
			self.__setattr__('get_'+attr, lambda a=attr : self.__getattribute__(a))
		for attr, val in attrs.items():
			self.__setattr__(attr, val)

	def get_source(self):
		"""Get the edges source node name."""
	
		return self.src
		
	def get_destination(self):
		"""Get the edge's destination node name."""
		
		return self.dst
			
	def __eq__(self, edge):
		"""Compare two edges.
		
		If the parent graph is directed, arcs linking
		node A to B are considered equal and A->B != B->A
		
		If the parent graph is undirected, any edge
		connecting two nodes is equal to any other
		edge connecting the same nodes, A->B == B->A
		"""
		
		if not isinstance(edge, Edge):
			raise Error, 'Can\'t compare and edge to a non-edge object.'
		if self.parent_graph.graph_type=='graph':
			# If the graph is undirected, the edge has neither
			# source nor destination.
			if	(self.src==edge.src and self.dst==edge.dst) or	\
				(self.src==edge.dst and self.dst==edge.src):
				return True
		else:
			if	self.src==edge.src and self.dst==edge.dst:
				return True
		return False

		
	def set(self, name, value):
		"""Set an attribute value by name.
		
		Given an attribute 'name' it will set its value to 'value'.
		There's always the possibility of using the methods:
			set_'name'(value)
		which are defined for all the existing attributes.
		"""
		if name in self.attributes:
			self.__dict__[name] = value
			return True
		# Attribute is not known
		return False

	
	def parse_node_ref(self, node_str):
	
		if not isinstance(node_str, str):
			node_str = str(node_str)
	
		if node_str[0]=='"' and node_str[-1]=='"' and node_str[0].count('"')%2!=0:
			return node_str
		
		node_port_idx = node_str.rfind(':')
		
		if node_port_idx>0 and node_str[0]=='"' and node_str[node_port_idx-1]=='"':
			return node_str
				
		node_str = node_str.replace('"', '')
		
		if node_port_idx>0:
			a = node_str[:node_port_idx]
			b = node_str[node_port_idx+1:]
			if self.is_ID(a):
				node = a
			else:
				node = '"'+a+'"'
			if self.is_ID(b):
				node += ':'+b
			else:
				node+=':"'+b+'"'	
			return node
			
		return '"'+node_str+'"'
		
	
	def to_string(self):
		"""Returns a string representation of the edge in dot language.
		"""

		src = self.parse_node_ref(self.src)
		dst = self.parse_node_ref(self.dst)
		
		edge = src	
		if	self.parent_graph and		\
			self.parent_graph.graph_type and	\
			self.parent_graph.graph_type=='digraph':
			edge+=' -> '
		else:
			edge+=' -- '
		edge+=dst

		edge_attr = None
		for attr in self.attributes:
			if self.__dict__.has_key(attr)	\
			and self.__getattribute__(attr) is not None:
				if not edge_attr:
					edge_attr = ''
				else:
					edge_attr+=', '
				edge_attr+=attr+'='
				val = self.__dict__[attr]
				if (isinstance(val, str) or isinstance(val, unicode)) and not self.is_ID(val):
					edge_attr+='"'+val+'"'
				else:
					edge_attr+=str(val)

		if edge_attr:
			edge+=' ['+edge_attr+']'
		edge+=';'

		return edge
	
class Graph(object, Common):

	"""Class representing a graph in Graphviz's dot language.

	This class implements the methods to work on a representation
	of a graph in Graphviz's dot language.
	
	graph(graph_name='G', type='digraph', strict=False, suppress_disconnected=False, attribute=value, ...)
	
	graph_name:
		the graph's name
	type:
		can be 'graph' or 'digraph'
	suppress_disconnected:
		defaults to False, which will remove from the
		graph any disconnected nodes.
	simplify:
		if True it will avoid displaying equal edges, i.e.
		only one edge between two nodes. removing the
		duplicated ones.
		
	All the attributes defined in the Graphviz dot language should
	be supported.
	
	Attributes can be set through the dynamically generated methods:
	
	 set_[attribute name], i.e. set_size, set_fontname
	 
	or using the instance's attributes:
	
	 Graph.[attribute name], i.e. graph_instance.label, graph_instance.fontname
	"""
	
	attributes = ['Damping', 'bb', 'center', 'clusterrank', 'compound', 'concentrate',\
		'defaultdist', 'dim', 'fontpath', 'epsilon', 'layers', 'layersep',	\
		'margin', 'maxiter', 'mclimit', 'mindist', 'pack', 'packmode', 'model',	\
		'page', 'pagedir', 'nodesep', 'normalize', 'nslimit1', 'ordering',	\
		'orientation', 'outputorder', 'overlap', 'remincross', 'resolution',	\
		'rankdir', 'ranksep', 'ratio', 'rotate', 'samplepoints', 'searchsize',	\
		'sep', 'size', 'splines', 'start', 'stylesheet', 'truecolor',		\
		'viewport', 'voro_margin', 'quantum', 'bgcolor', 'labeljust',		\
		'labelloc', 'root', 'showboxes', 'URL', 'fontcolor', 'fontsize',	\
		'label' ,'fontname', 'comment', 'lp', 'target', 'color', 'style',	\
		'concentrators']

	def __init__(self, graph_name='G', graph_type='digraph', strict=False,	\
		suppress_disconnected=False, simplify=False, **attrs):
		
		if graph_type not in ['graph', 'digraph']:
			raise Error, 'Invalid type. Accepted graph types are: graph, digraph, subgraph'
		self.graph_type = graph_type
		self.graph_name = graph_name
		self.strict = strict
		self.suppress_disconnected = suppress_disconnected
		self.simplify = simplify
		self.node_list = []
		self.edge_list = []
		self.edge_src_list = []
		self.edge_dst_list = []
		self.subgraph_list = []
		self.parent_graph = self
		for attr in self.attributes:
			# Set all the attributes to None.
			self.__setattr__(attr, None)
			# Generate all the Setter methods.
			self.__setattr__('set_'+attr, lambda x, a=attr : self.__setattr__(a, x))
			# Generate all the Getter methods.
			self.__setattr__('get_'+attr, lambda a=attr : self.__getattribute__(a))
		for attr, val in attrs.items():
			self.__setattr__(attr, val)
	
	def set_simplify(self, simplify):
		"""Set whether to simplify or not.
		
		If True it will avoid displaying equal edges, i.e.
		only one edge between two nodes. removing the
		duplicated ones.
		"""
		
		self.simplify = simplify

	def get_simplify(self):
		"""Get whether to simplify or not.
		
		Refer to set_simplify for more information.
		"""
		
		return self.simplify

			
	def set_type(self, graph_type):
		"""Set the graph's type, 'graph' or 'digraph'."""
		self.graph_type = graph_type
		
	def get_type(self):
		"""Get the graph's type, 'graph' or 'digraph'."""
		return self.graph_type

	def set_name(self, graph_name):
		"""Set the graph's name."""
		
		self.graph_name = graph_name

	def get_name(self):
		"""Get the graph's name."""
		
		return self.graph_name
					
	def set_strict(self, val):
		"""Set graph to 'strict' mode.
		
		This option is only valid for top level graphs.
		"""
		
		self.strict = val

	def get_strict(self, val):
		"""Get graph's 'strict' mode (True, False).
		
		This option is only valid for top level graphs.
		"""
		
		return self.strict
		
	def set_suppress_disconnected(self, val):
		"""Suppress disconnected nodes in the output graph.
		
		This option will skip nodes in the graph with no  incoming or outgoing
		edges. This option works also for subgraphs and has effect only in the
		current graph/subgraph.
		"""
		
		self.suppress_disconnected = val
			
	def get_suppress_disconnected(self, val):
		"""Get if suppress disconnected is set.
		
		Refer to set_suppress_disconnected for more information.
		"""
		
		self.suppress_disconnected = val
			
	def set(self, name, value):
		"""Set an attribute value by name.
		
		Given an attribute 'name' it will set its value to 'value'.
		There's always the possibility of using the methods:
		
			set_'name'(value)
			
		which are defined for all the existing attributes.
		"""
		if name in self.attributes:
			self.__dict__[name] = value
			return True
		# Attribute is not known
		return False

	def get(self, name):
		"""Get an attribute value by name.
		
		Given an attribute 'name' it will get its value.
		There's always the possibility of using the methods:
		
			get_'name'()
			
		which are defined for all the existing attributes.
		"""
		return self.__dict__[name]
		
	def add_node(self, graph_node):
		"""Adds a node object to the graph.

		It takes a node object as its only argument and returns
		None.
		"""
		
		if not isinstance(graph_node, Node):
			raise Error, 'add_node received a non node class object'
			
		if self.get_node(graph_node.get_name()) is None:
			self.node_list.append(graph_node)
			graph_node.parent_graph = self.parent_graph

	def get_node(self, name):
		"""Retrieved a node from the graph.
		
		Given a node's name the corresponding Node
		instance will be returned.
		
		If multiple nodes exist with that name, a list of
		Node instances is returned.
		If only one node exists, the instance is returned.
		None is returned otherwise.
		"""
		
		match = [node for node in self.node_list if node.get_name() == str(name)]
		
		l = len(match)
		if l==1:
			return match[0]
		elif l>1:
			return match
		else:
			return None
	
	def get_node_list(self):
		"""Get the list of Node instances.
		
		This method returns the list of Node instances
		composing the graph.
		"""
		
		return self.node_list
			
	def add_edge(self, graph_edge):
		"""Adds an edge object to the graph.
		
		It takes a edge object as its only argument and returns
		None.
		"""
		
		if not isinstance(graph_edge, Edge):
			raise Error, 'add_edge received a non edge class object'
			
		self.edge_list.append(graph_edge)
		
		src = self.get_node(graph_edge.get_source())
		if src is None:
			self.add_node(Node(graph_edge.get_source()))
		
		dst = self.get_node(graph_edge.get_destination())
		if dst is None:
			self.add_node(Node(graph_edge.get_destination()))
		
		graph_edge.parent_graph = self.parent_graph
		
		if graph_edge.src not in self.edge_src_list:
			self.edge_src_list.append(graph_edge.src)
			
		if graph_edge.dst not in self.edge_dst_list:
			self.edge_dst_list.append(graph_edge.dst)

	def get_edge(self, src, dst):
		"""Retrieved an edge from the graph.
		
		Given an edge's source and destination the corresponding
		Edge instance will be returned.
		
		If multiple edges exist with that source and destination,
		a list of Edge instances is returned.
		If only one edge exists, the instance is returned.
		None is returned otherwise.
		"""
		
		match = [edge for edge in self.edge_list if edge.src == src and edge.dst == dst]
		
		l = len(match)
		if l==1:
			return match[0]
		elif l>1:
			return match
		else:
			return None
	
	def get_edge_list(self):
		"""Get the list of Edge instances.
		
		This method returns the list of Edge instances
		composing the graph.
		"""
		
		return self.edge_list
			
	def add_subgraph(self, sgraph):
		"""Adds an edge object to the graph.
		
		It takes a subgraph object as its only argument and returns
		None.
		"""
		if not isinstance(sgraph, Subgraph) and not isinstance(sgraph, Cluster):
			raise Error, 'add_subgraph received a non subgraph class object'
			
		self.subgraph_list.append(sgraph)
		
		sgraph.set_graph_parent(self.parent_graph)
		return None
	
	def get_subgraph(self, name):
		"""Retrieved a subgraph from the graph.
		
		Given a subgraph's name the corresponding
		Subgraph instance will be returned.
		
		If multiple subgraphs exist with the same name,	a list of
		Subgraph instances is returned.
		If only one Subgraph exists, the instance is returned.
		None is returned otherwise.
		"""
		
		match = [sgraph for sgraph in self.subgraph_list if sgraph.graph_name == name]
		
		l = len(match)
		if l==1:
			return match[0]
		elif l>1:
			return match
		else:
			return None
		
	def get_subgraph_list(self):
		"""Get the list of Subgraph instances.
		
		This method returns the list of Subgraph instances
		in the graph.
		"""
		
		return self.subgraph_list
			
	def set_graph_parent(self, parent):
		"""Sets a graph and its elements to point the the parent.
		
		Any subgraph added to a parent graph receives a reference
		to the parent to access some common data.
		"""
		self.parent_graph = parent
		
		for elm in self.edge_list:
			elm.parent_graph = parent
			
		for elm in self.node_list:
			elm.parent_graph = parent
			
		for elm in self.subgraph_list:
			elm.parent_graph = parent
			elm.set_graph_parent(parent)
		
	def to_string(self, indent=''):
		"""Returns a string representation of the graph in dot language.
		
		It will return the graph and all its subelements in string from.
		"""
		graph = indent+''
		if self.__dict__.has_key('strict'):
			if self==self.parent_graph and self.strict:
				graph+='strict '
		
		graph+=self.graph_type+' '+self.graph_name+' {\n'

		for attr in self.attributes:
			if self.__dict__.has_key(attr)	\
			and self.__getattribute__(attr) is not None:
				graph += indent+'\t'+attr+'='
				val = self.__dict__[attr]
				if isinstance(val, str) and not self.is_ID(val):
					graph += '"'+val+'"'
				else:
					graph += str(val)
				graph+=';\n'

		# RMF: for graphviz to handle edge/node defaults correctly,
		# it seems they must appear before the rest of the nodes/edges
		# so if they exist, dump them out first.
		for elm in self.node_list:
			if elm.name in ['node', 'edge', 'graph']:
				graph += indent+'\t'+elm.to_string()+'\n'
		
		for elm in self.subgraph_list:
			graph += elm.to_string(indent+'\t')+'\n'
				
		for elm in self.node_list:
			# RMF: don't repeat the node/edge defaults
			if elm.name in ['node', 'edge', 'graph']:
				continue
			if self.suppress_disconnected:
				if elm.name not in self.edge_src_list+self.edge_dst_list:
					continue
			graph+=indent+'\t'+elm.to_string()+'\n'

		edges_done = []
		for elm in self.edge_list:
			if self.simplify and elm in edges_done:
				continue
			graph+=indent+'\t'+elm.to_string()+'\n'
			edges_done.append(elm)

		graph+=indent+'}\n'
		
		return graph


class Subgraph(Graph):

	"""Class representing a subgraph in Graphviz's dot language.

	This class implements the methods to work on a representation
	of a subgraph in Graphviz's dot language.
	
	subgraph(graph_name='subG', suppress_disconnected=False, attribute=value, ...)
	
	graph_name:
		the subgraph's name
	suppress_disconnected:
		defaults to false, which will remove from the
		subgraph any disconnected nodes.
	All the attributes defined in the Graphviz dot language should
	be supported.
	
	Attributes can be set through the dynamically generated methods:
	
	 set_[attribute name], i.e. set_size, set_fontname
	 
	or using the instance's attributes:
	
	 Subgraph.[attribute name], i.e.
	 	subgraph_instance.label, subgraph_instance.fontname
	"""
	
	attributes = Graph.attributes+['rank']
	
	# RMF: subgraph should have all the attributes of graph so it can be passed
	# as a graph to all methods
	def __init__(self, graph_name='subG', suppress_disconnected=False,	\
		simplify=False, **attrs):
		
		self.graph_type = 'subgraph'
		self.graph_name = graph_name
		self.suppress_disconnected = suppress_disconnected
		self.simplify = simplify
		self.node_list = []
		self.edge_list = []
		self.edge_src_list = []
		self.edge_dst_list = []
		self.subgraph_list = []
		for attr in self.attributes:
			# Set all the attributes to None.
			self.__setattr__(attr, None)
			# Generate all the Setter methods.
			self.__setattr__('set_'+attr, lambda x, a=attr : self.__setattr__(a, x))
			# Generate all the Getter methods.
			self.__setattr__('get_'+attr, lambda a=attr : self.__getattribute__(a))
		for attr, val in attrs.items():
			self.__setattr__(attr, val)
			

class Cluster(Graph):

	"""Class representing a cluster in Graphviz's dot language.

	This class implements the methods to work on a representation
	of a cluster in Graphviz's dot language.
	
	cluster(graph_name='subG', suppress_disconnected=False, attribute=value, ...)
	
	graph_name:
		the cluster's name (the string 'cluster' will be always prepended)
	suppress_disconnected:
		defaults to false, which will remove from the
		cluster any disconnected nodes.
	All the attributes defined in the Graphviz dot language should
	be supported.
	
	Attributes can be set through the dynamically generated methods:
	
	 set_[attribute name], i.e. set_color, set_fontname
	 
	or using the instance's attributes:
	
	 Cluster.[attribute name], i.e.
	 	cluster_instance.color, cluster_instance.fontname
	"""
	
	attributes = ['pencolor', 'bgcolor', 'labeljust', 'labelloc', 'URL', 'fontcolor',	\
		'fontsize', 'label', 'fontname', 'lp', 'style', 'target', 'color',	\
		'peripheries', 'fillcolor']

	def __init__(self, graph_name='subG', suppress_disconnected=False,	\
		simplify=False, **attrs):
		
		#if type not in ['subgraph']:
		#	raise Error, 'Invalid type. Accepted graph types are: subgraph'
		self.graph_type = 'subgraph'
		self.graph_name = 'cluster_'+graph_name
		self.suppress_disconnected = suppress_disconnected
		self.simplify = simplify
		self.node_list = []
		self.edge_list = []
		self.edge_src_list = []
		self.edge_dst_list = []
		self.subgraph_list = []
		for attr in self.attributes:
			# Set all the attributes to None.
			self.__setattr__(attr, None)
			# Generate all the Setter methods.
			self.__setattr__('set_'+attr, lambda x, a=attr : self.__setattr__(a, x))
			# Generate all the Getter methods.
			self.__setattr__('get_'+attr, lambda a=attr : self.__getattribute__(a))
		for attr, val in attrs.items():
			self.__setattr__(attr, val)


class Dot(Graph):
	"""A container for handling a dot language file.

	This class implements methods to write and process
	a dot language file. It is a derived class of
	the base class 'Graph'.
	"""
	
	progs = None
	
	formats = ['ps', 'ps2', 'hpgl', 'pcl', 'mif', 'pic', 'gd', 'gd2', 'gif', 'jpg',	\
		'jpeg', 'png', 'wbmp', 'ismap', 'imap', 'cmap', 'vrml', 'vtx', 'mp',	\
		'fig', 'svg', 'svgz', 'dia', 'dot', 'canon', 'plain', 'plain-ext', 'xdot']

	def __init__(self, prog='dot', **args):
		Graph.__init__(self, **args)
		
		self.prog = prog
		
		# Automatically creates all the methods enabling the creation
		# of output in any of the supported formats.
		for frmt in self.formats:
			self.__setattr__('create_'+frmt, lambda f=frmt, prog=self.prog : self.create(format=f, prog=prog))
			f = self.__dict__['create_'+frmt]
			f.__doc__ = '''Refer to docstring from 'create' for more information.'''
			
		for frmt in self.formats+['raw']:
			self.__setattr__('write_'+frmt, lambda path, f=frmt, prog=self.prog : self.write(path, format=f, prog=prog))
			f = self.__dict__['write_'+frmt]
			f.__doc__ = '''Refer to docstring from 'write' for more information.'''
	
	def set_prog(self, prog):
		"""Sets the default program.
		
		Sets the default program in charge of processing
		the dot file into a graph.
		"""
		self.prog = prog

	def write(self, path, prog=None, format='raw'):
		"""Writes a graph to a file.

		Given a filename 'path' it will open/create and truncate
		such file and write on it a representation of the graph
		defined by the dot object and in the format specified by
		'format'.
		The format 'raw' is used to dump the string representation
		of the Dot object, without further processing.
		The output can be processed by any of graphviz tools, defined
		in 'prog', which defaults to 'dot'
		Returns True or False according to the success of the write
		operation.
		
		There's also the preferred possibility of using:
		
			write_'format'(path, prog='program')
			
		which are automatically defined for all the supported formats.
		[write_ps(), write_gif(), write_dia(), ...]
		"""

		if prog is None:
			prog = self.prog
		
		dot_fd = file(path, "w+b")
		if format == 'raw':
			dot_fd.write(self.to_string())
		else:
			dot_fd.write(self.create(prog, format))
		dot_fd.close()

		return True

	def create(self, prog=None, format='ps'):
		"""Creates and returns a Postscript representation of the graph.

		create will write the graph to a temporary dot file and process
		it with the program given by 'prog' (which defaults to 'twopi'),
		reading the Postscript output and returning it as a string is the
		operation is successful.
		On failure None is returned.
		
		There's also the preferred possibility of using:
		
			create_'format'(prog='program')
			
		which are automatically defined for all the supported formats.
		[create_ps(), create_gif(), create_dia(), ...]
		"""
		if prog is None:
			prog = self.prog
			
		if self.progs is None:
			self.progs = find_graphviz()
			if self.progs is None:
				return None
		if not self.progs.has_key(prog):
			# Program not found ?!?!
			return None
			
		tmp_fd, tmp_name = tempfile.mkstemp()
		os.close(tmp_fd)
		self.write(tmp_name)
		stdin, stdout, stderr = os.popen3(self.progs[prog]+' -T'+format+' '+tmp_name, 'b')
		stdin.close()
		stderr.close()
		data = stdout.read()
		stdout.close()
		os.unlink(tmp_name)
		return data