import re

from ModelObject import ModelObject
from MiscUtils import NoDefault, StringTypes
from MiddleDict import MiddleDict

try: # for Python < 2.3
	True, False
except NameError:
	True, False = 1, 0

nameRE = re.compile('^([A-Za-z_][A-Za-z_0-9]*)$')
reservedRE = re.compile('allattrs|changed|clone|debugstr|dumpattrs|key|klass'
	'|serialnum|store|valueforattr|valueforkey', re.I)


class Attr(MiddleDict, ModelObject):
	"""An Attr represents an attribute of a Klass.

	The Attr objects behave like dictionaries.

	"""

	def __init__(self, dict):
		MiddleDict.__init__(self, {})
		for key, value in dict.items():
			if key == 'Attribute':
				key = 'Name'
			if type(value) in StringTypes and not value.strip():
				value = None
			self[key] = value
		name = self['Name']
		match = nameRE.match(name)
		if match is None or len(match.groups()) != 1:
			raise ValueError, 'Bad name (%r) for attribute: %r.' % (name, dict)
		match = reservedRE.match(name)
		if match is not None:
			raise ValueError, 'Reserved name (%r) for attribute: %r.' % (name, dict)
		self._getPrefix = None
		self._setPrefix = None

	def name(self):
		return self.data['Name']

	def isRequired(self):
		"""Return true if a value is required for this attribute.

		In Python, that means the value cannot be None. In relational theory
		terms, that means the value cannot be NULL.

		"""
		return self.boolForKey('isRequired')

	def setKlass(self, klass):
		"""Set the klass that the attribute belongs to."""
		self._klass = klass

	def klass(self):
		"""Return the klass that this attribute is declared in and, therefore, belongs to."""
		return self._klass

	def pyGetName(self):
		"""Return the name that should be used for the Python "get" accessor method for this attribute."""
		if self._getPrefix is None:
			self._computePrefixes()
		name = self.name()
		if self._getCapped:
			return self._getPrefix + name[0].upper() + name[1:]
		else:
			return self._getPrefix + name

	def pySetName(self):
		"""Return the name that should be used for the Python "set" accessor method for this attribute."""
		if self._setPrefix is None:
			self._computePrefixes()
		name = self.name()
		if self._setCapped:
			return self._setPrefix + name[0].upper() + name[1:]
		else:
			return self._setPrefix + name

	def setting(self, name, default=NoDefault):
		"""Return the value of a particular configuration setting taken from the model.

		Implementation note: Perhaps a future version should ask the klass and so on up the chain.

		"""
		return self.model().setting(name, default)

	def model(self):
		return self._klass.klasses()._model

	def awakeFromRead(self):
		pass


	## Warnings ##

	def printWarnings(self, out):
		pass


	## Self Util ##

	def _computePrefixes(self):
		style = self.setting('AccessorStyle', 'methods').lower()
		assert style in ('properties', 'methods')
		if style == 'properties':
			self._getPrefix = '_get_'
			self._setPrefix = '_set_'
			self._getCapped = False
			self._setCapped = False
		else:
			# methods
			self._getPrefix = ''
			self._setPrefix = 'set'
			self._getCapped = False
			self._setCapped = True
