# Taken & modified from https://github.com/chapkovski/otree_tools

from django.forms.fields import MultipleChoiceField
from django.core.exceptions import ValidationError
from django.forms import CheckboxSelectMultiple


class MultiSelectFormField(MultipleChoiceField):
    widget = CheckboxSelectMultiple

    def __init__(self, *args, **kwargs):
        self.max_choices = kwargs.pop('max_choices', None)
        self.min_choices = kwargs.pop('min_choices', None)
        super(MultiSelectFormField, self).__init__(*args, **kwargs)

    def clean(self, value):
        if not value and self.required:
            raise ValidationError(self.error_messages['required'])
        if value and self.max_choices and self.min_choices:
            if self.max_choices == self.min_choices:
                if len(value) != self.max_choices:
                    ending = '' if self.max_choices == 1 else 's'
                    raise ValidationError('You must select exactly {} choice{}.'.format(self.max_choices, ending))
        if value and self.max_choices:
            if len(value) > self.max_choices:
                ending = '' if self.max_choices == 1 else 's'
                raise ValidationError('You must select a maximum of {} choice{}.'.format(self.max_choices, ending))
        if value and self.min_choices:
            if len(value) < self.min_choices:
                ending = '' if self.min_choices == 1 else 's'
                raise ValidationError('You must select a minimum of {} choice{}.'.format(self.min_choices, ending))
        return value