from StringIO import StringIO
from django.utils.translation import ugettext as _
from lxml import etree
import re

# example XmlField:
#class XmlField(forms.CharField):
#	widget = forms.Textarea
#	
#	def __init__(self, schema_path=None, additional_root_element=None, *args, **kwargs):
#		super(XmlField, self).__init__(*args, **kwargs)
#		self.additional_root_element = additional_root_element
#		self.schema_path = schema_path
#	
#	def clean(self, value):
#		from ....validators import RelaxNGValidator
#		super(XmlField, self).clean(value)
#		schema_path = self.schema_path
#		xml_validator = RelaxNGValidator(schema_path, self.additional_root_element)
#		return xml_validator.forms_validate(value)

# copy of django.core.validators.ValidationError, cut most of the code out
# needed to throw different exceptions for new/old-forms
class ValidationError(Exception):
	def __init__(self, messages): # messages must be a list
		self.messages = messages

# for rnc-files see:
# rnc2rng: http://www.gnosis.cx/download/relax/
class RelaxNGValidator(object):
	"Validate against a Relax NG schema"
	def __init__(self, schema_path, additional_root_element=None):
		self.schema_path = schema_path
		self.additional_root_element = additional_root_element
	
	def raiseValidationError(self, xml_data, error_log):
		display_errors = []
		if self.additional_root_element:
			adjust_line = -1
		else:
			adjust_line = 0
		lines = xml_data.split('\n')
		for error in error_log:
			# Scrape the lxml error messages to reword them more nicely.
			m = re.search(r'Opening and ending tag mismatch: (.+?) line (\d+?) and (.+?)$', error.message)
			if m:
				display_errors.append(_(u'Please close the unclosed %(tag)s tag from line %(line)s. (Line starts with "%(start)s".)') % \
					{'tag':m.group(1).replace('/', ''), 'line':int(m.group(2)) + adjust_line, 'start':lines[int(m.group(2)) - 1][:30]})
				continue
			m = re.search(r'Did not expect text in element (.+?) content', error.message)
			if m:
				display_errors.append(_(u'Some text starting on line %(line)s is not allowed in that context. (Line starts with "%(start)s".)') % \
					{'line':error.line + adjust_line, 'start':lines[int(error.line) - 1][:30]})
				continue
			m = re.search(r'Specification mandate value for attribute (.+?)$', error.message)
			if m:
				display_errors.append(_(u'"%(attr)s" on line %(line)s is an invalid attribute. (Line starts with "%(start)s".)') % \
					{'attr':m.group(1), 'line':error.line + adjust_line, 'start':lines[int(error.line) - 1][:30]})
				continue
			m = re.search(r'Invalid attribute (.+?) for element (.+?)$', error.message)
			if m:
				display_errors.append(_(u'"%(attr)s" on line %(line)s is an invalid attribute. (Line starts with "%(start)s".)') % \
					{'attr':m.group(1), 'line':error.line + adjust_line, 'start':lines[int(error.line) - 1][:30]})
				continue
			m = re.search(r'Did not expect element (.+?) there', error.message)
			if m:
				display_errors.append(_(u'"<%(tag)s>" on line %(line)s is an invalid tag. (Line starts with "%(start)s".)') % \
					{'tag':m.group(1), 'line':error.line + adjust_line, 'start':lines[int(error.line) - 1][:30]})
				continue
			m = re.search(r'Element (.+?) failed to validate attributes', error.message)
			if m:
				display_errors.append(_(u'A tag on line %(line)s is missing one or more required attributes. (Line starts with "%(start)s".)') % \
					{'line':error.line + adjust_line, 'start':lines[int(error.line) - 1][:30]})
				continue
			m = re.search(r'Invalid attribute (.+?) for element (.+?)$', error.message)
			if m:
				display_errors.append(_(u'The "%(attr)s" attribute on line %(line)s has an invalid value. (Line starts with "%(start)s".)') % \
					{'attr':m.group(1), 'line':error.line + adjust_line, 'start':lines[int(error.line) - 1][:30]})
				continue
			# Failing all those checks, use the default error message.
			display_errors.append(u'Line %s: %s [%s]' % (error.line + adjust_line, error.message, error.level_name))
		raise ValidationError, display_errors
	
	def validate(self, xml_data):
		self.errors = []
		if self.additional_root_element:
			xml_data = '<%(are)s>\n%(data)s\n</%(are)s>' % {
				'are': self.additional_root_element,
				'data': xml_data
			}
		
		etree.clearErrorLog()
		try:
			doc = etree.parse(StringIO(xml_data))
		except etree.XMLSyntaxError, e:
			self.raiseValidationError(xml_data, e.error_log)
		etree.clearErrorLog()
		
		schema_path = self.schema_path
		if schema_path:
			if not schema_path[0] == '/':
				import os.path
				schema_path = os.path.join(os.path.dirname(__file__), "rng/%s" % schema_path)
			
			try:
				rng_doc = etree.parse(schema_path)
				rng = etree.RelaxNG(rng_doc)
			except (etree.XMLSyntaxError, etree.RelaxNGParseError), e:
				import os.path
				raise ValidationError, [_(u"Could not load %s for validation, please contact the admin") % os.path.basename(self.schema_path)]
			if not rng(doc):
				self.raiseValidationError(xml_data, rng.error_log)
	
	# oldforms-way of using this
	def __call__(self, field_data, all_data):
		from django.core.validators import ValidationError as CoreValidationError
		try:
			self.validate(field_data)
		except ValidationError, e:
			raise CoreValidationError(e.messages)
	
	# newforms-way of using this
	def forms_validate(self, value):
		from django.newforms.util import ValidationError as FormsValidationError
		from django.utils.encoding import smart_unicode
		try:
			self.validate(value)
		except ValidationError, e:
			raise FormsValidationError(e.messages)
		return smart_unicode(value)