#!/usr/bin/python3
# A simple script to convert an LDIF file to DOT format for drawing graphs.
# Copyright 2022 Marcin Owsiany <marcin@owsiany.pl>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

"""A simple script to convert an LDIF file to DOT format for drawing graphs.

So far it only supports the most basic form of entry records: "attrdesc: value".
In particular line continuations, BASE64 or other encodings, change records,
include statements, etc...  are not supported.

Example usage, assuming your DIT's base is dc=nodomain:

ldapsearch -x -b 'dc=nodomain' | \\
  ldif2dot | \\
  dot -o nodomain.png -Nshape=box -Tpng /dev/stdin

"""


import sys


class Element(object):
	"""Represents an LDIF entry."""

	def __init__(self):
		"""Initializes an object."""
		self.attributes = []

	def __repr__(self):
		"""Returns a basic state dump."""
		return 'Element' + str(self.index) + str(self.attributes)

	def add(self, line):
		"""Adds a line of input to the object.

		Args:
		 - line: a string with trailing newline stripped

		Returns: True if this object is ready for processing (i.e. a separator
		line was passed). Otherwise returns False. Behaviour is undefined if
		this method is called after a previous invocation has returned True.
		"""

		def _valid(line):
			return line and not line.startswith('#')

		def _interesting(line):
			return line != 'objectClass: top'

		if self.is_valid() and not _valid(line):
			return True
		if _valid(line) and _interesting(line):
			self.attributes.append(line)
		return False

	def is_valid(self):
		"""Indicates whether a valid entry has been read."""
		return len(self.attributes) != 0 and self.attributes[0].startswith('dn: ')

	def dn(self):
		"""Returns the DN for this entry."""
		if self.attributes[0].startswith('dn: '):
			return self.attributes[0][4:]
		else:
			return None

	def edge(self, dnmap):
		"""Returns a text represenation of a grapsh edge.

		Finds its parent in provided dnmap (dictionary mapping dn names to
		Element objects) and returns a string which declares a DOT edge, or an
		empty string, if no parent was found.
		"""
		dn_components = self.dn().split(',')
		for i in range(1, len(dn_components) + 1):
			parent = ','.join(dn_components[i:])
			if parent in dnmap:
				return '  n%d->n%d\n' % (dnmap[parent].index, self.index)
		return ''

	def dot(self, dnmap):
		"""Returns a text representation of the node and perhaps its parent edge.

		Args:
		 - dnmap: dictionary mapping dn names to Element objects
		"""
		return '  n%d [label="%s\\l"]\n%s' % (self.index, '\\l'.join(self.attributes), self.edge(dnmap))


class Converter(object):
	"""An LDIF to DOT converter."""

	def __init__(self):
		"""Initializes the object."""
		self.elements = []
		self.dnmap = {}

	def _append(self, e):
		"""Adds an element to internal list and map.
		
		First sets it up with an index in the list, for node naming.
		"""
		index = len(self.elements)
		e.index = index
		self.elements.append(e)
		self.dnmap[e.dn()] = e

	def parse(self, file, name):
		"""Reads the given file into memory.

		Args:
		 - file: an object which yields text lines on iteration.
		 - name: a name for the graph

		Returns a string containing the graph in DOT format.
		"""
		e = Element()
		for line in file:
			line = line.rstrip()
			if e.add(line):
				self._append(e)
				e = Element()
		if e.is_valid():
			self._append(e)
		return ('strict digraph "%s" {\n  rankdir=LR\n%s}\n'
		        % (name, ''.join([e.dot(self.dnmap) for e in self.elements])))


if __name__ == '__main__':
	if len(sys.argv) > 2:
		raise Exception('Expected at most one argument.')
	elif len(sys.argv) == 2:
		name = sys.argv[1]
		file = open(sys.argv[1], 'r')
	else:
		name = '<stdin>'
		file = sys.stdin
	print(Converter().parse(file, name))