from django import forms
from django.utils.translation import gettext as _

from taggit.utils import edit_string_for_tags, parse_tags


class TagWidgetMixin:
    def format_value(self, value):
        if value is not None and not isinstance(value, str):
            value = edit_string_for_tags(value)
        return super().format_value(value)


class TagWidget(TagWidgetMixin, forms.TextInput):
    pass


class TextareaTagWidget(TagWidgetMixin, forms.Textarea):
    pass


class TagField(forms.CharField):
    widget = TagWidget

    def clean(self, value):
        value = super().clean(value)
        try:
            return parse_tags(value)
        except ValueError:
            raise forms.ValidationError(
                _("Please provide a comma-separated list of tags.")
            )

    def has_changed(self, initial_value, data_value):
        # Always return False if the field is disabled since self.bound_data
        # always uses the initial value in this case.
        if self.disabled:
            return False

        try:
            data_value = self.clean(data_value)
        except forms.ValidationError:
            pass

        # normalize "empty values"
        if not data_value:
            data_value = []
        if not initial_value:
            initial_value = []

        initial_value = [tag.name for tag in initial_value]
        initial_value.sort()

        return initial_value != data_value