FormEncode validation

# -*- coding: utf-8 -*-
# Copyright (C) <2009>  Gabriel Falcão <gabriel@nacaolivre.org>
#
# 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 3 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, see <http://www.gnu.org/licenses/>.
import re
import formencode
from formencode import validators

class UsernameValidator(formencode.FancyValidator):
    def _to_python(self, value, state):
        if not re.match(r"^[a-zA-Z][\w._-]+$", value):
            raise formencode.Invalid(
                'Invalid username, it must start with a letter, and'
                'contain only alpha-numeric, dot, underscore or dash',
                value, state)

        return value

class Registration(formencode.Schema):
    name = validators.String(not_empty=True)
    email = validators.Email(not_empty=True)
    username = UsernameValidator(not_empty=True)
    password = validators.String(not_empty=True)
    password_confirm = validators.String()
    chained_validators = [validators.FieldsMatch(
        'password', 'password_confirm')]