# 
#    Copyright 2009 - Cigital, Inc. - www.cigital.com
#    Romain Gaucher <rgaucher@cigital.com>
#    http://rgaucher.info - @rgaucher
#
import inspect, math

class DDFactory(object):
	"""
	Factory that returns the object constructor based on a given list of arguments.
	The returned class ctor has the best matching number of common args with the given list.

	example:
		class Shape(object):
			pass

		class Circle(Shape):
			def __init__(self, center, radius=RAD_MAX):
				....

		class DiskHole(Shape):
			def __init__(self, center, radius, small_radius=RAD_SMALL):
				....



		factory = DDFactory()
		factory.register(Shape)
		factory.register(Circle)
		factory.register(DiskHole)

		print factory.get(['center', 'radius'])                   #> return 'Circle' ctor
		print factory.get(['center', 'radius', 'small_radius'])   #> return 'DiskHole' ctor
	"""
	def __init__(self):
		self.registrar = {}

	@staticmethod
	def defaults_values(cls):
		args, vargs, vkw, defaults = inspect.getargspec(cls.__init__)
		if inspect.ismethod(cls.__init__):
			args = args[1:]
		ret_dict = dict(zip(args, [None] * len(args)))
		if defaults:
			ret_dict.update(dict(zip(args[-len(defaults):], defaults)))
		return args, ret_dict

	@staticmethod
	def descent(d, level_return=3):
		if level_return < 1:
			return d
		ld = d.keys(); ld.sort()
		for i in ld:
			if not len(d[i]):
				continue
			return DDFactory.descent(d[i], level_return - 1)
		return None

	def register(self, cls, has_attr='__tablename__'):
		if hasattr(cls, has_attr) and hasattr(cls, '__init__'):
			args, defaults_dict = DDFactory.defaults_values(cls)
			if cls.__tablename__ not in self.registrar:
				self.registrar[cls.__tablename__] = {'class' : cls, 'args' : args, 'defaults' : defaults_dict}

	# from given 'args' return matching dict
	def get(self, args):
		set_args, len_args = set(args), len(args)
		best_matches = {}
		for cls_name in self.registrar:
			s = set(self.registrar[cls_name]['args'])
			len_s = len(s)

			c1 = len_s - len(set_args.intersection(s)) # found minus number args
			c2 = int(math.fabs(len_s - len_args))

			if c1 not in best_matches:
				best_matches[c1] = {}
			if c2 >= 0 and c2 not in best_matches[c1]:
				best_matches[c1][c2] = []
			if c2 >= 0 and self.registrar[cls_name] not in best_matches[c1][c2]:
				best_matches[c1][c2].append((cls_name, self.registrar[cls_name]))

		return DDFactory.descent(best_matches, 2)[0][1]