from django.db import models
from django.utils.text import capfirst
from django.core import exceptions

from multiselectfield import MultiSelectFormField


class MultiSelectField(models.Field):
    """ Choice values can not contain commas. """
    __metaclass__ = models.SubfieldBase

    def get_internal_type(self):
        return "CharField"

    def get_choices_default(self):
        return self.get_choices(include_blank=False)

    def get_choices_selected(self, arr_choices=''):
        if not arr_choices:
            return False
        list = []
        for choice_selected in arr_choices:
            list.append(choice_selected[0])
        return list

    def _get_FIELD_display(self, field):
        value = getattr(self, field.attname)
        choicedict = dict(field.choices)

    def value_to_string(self, obj):
        value = self._get_val_from_obj(obj)
        return self.get_db_prep_value(value)

    def validate(self, value, model_instance):
        arr_choices = self.get_choices_selected(self.get_choices_default())
        for opt_select in value:
            if (opt_select not in arr_choices):
                raise exceptions.ValidationError(self.error_messages['invalid_choice'] % value)
        return

    def formfield(self, **kwargs):
        defaults = {'required': not self.blank, 'label': capfirst(self.verbose_name),
                    'help_text': self.help_text, 'choices': self.choices}
        if self.has_default():
            defaults['initial'] = self.get_default()
        defaults.update(kwargs)
        return MultiSelectFormField(**defaults)

    def get_db_prep_value(self, value, connection, prepared=False):
        if isinstance(value, basestring):
            return value
        elif isinstance(value, list):
            return ",".join(value)

    def to_python(self, value):
        if value is not None:
            return value if isinstance(value, list) else value.split(',')
        return ''

    def contribute_to_class(self, cls, name):
        super(MultiSelectField, self).contribute_to_class(cls, name)
        if self.choices:
            func = lambda self, fieldname = name, choicedict = dict(self.choices): ",".join([choicedict.get(value, value) for value in getattr(self, fieldname)])
            setattr(cls, 'get_%s_display' % self.name, func)