"""
Tagging components for Django's ``newforms`` form library.
"""
from django import forms
from django.utils.translation import ugettext as _

from tagging import settings
from tagging.utils import parse_tag_input

class TagField(forms.CharField):
    """
    A ``CharField`` which validates that its input is a valid list of
    tag names.
    """
    def clean(self, value):
        value = super(TagField, self).clean(value)
        if value == u'':
            return value
        for tag_name in parse_tag_input(value):
            if len(tag_name) > settings.MAX_TAG_LENGTH:
                raise forms.ValidationError(
                    _('Each tag may be no more than %s characters long.') % settings.MAX_TAG_LENGTH)
        return value