from __future__ import unicode_literals

import decimal
import operator

from wtforms import fields, widgets
from wtforms.compat import text_type, string_types


class ReferencePropertyField(fields.SelectFieldBase):
    """
    A field for ``db.ReferenceProperty``. The list items are rendered in a
    select.

    :param reference_class:
        A db.Model class which will be used to generate the default query
        to make the list of items. If this is not specified, The `query`
        property must be overridden before validation.
    :param get_label:
        If a string, use this attribute on the model class as the label
        associated with each option. If a one-argument callable, this callable
        will be passed model instance and expected to return the label text.
        Otherwise, the model object's `__str__` or `__unicode__` will be used.
    :param allow_blank:
        If set to true, a blank choice will be added to the top of the list
        to allow `None` to be chosen.
    :param blank_text:
        Use this to override the default blank option's label.
    """
    widget = widgets.Select()

    def __init__(self, label=None, validators=None, reference_class=None,
                 get_label=None, allow_blank=False,
                 blank_text='', **kwargs):
        super(ReferencePropertyField, self).__init__(label, validators,
                                                     **kwargs)
        if get_label is None:
            self.get_label = lambda x: x
        elif isinstance(get_label, string_types):
            self.get_label = operator.attrgetter(get_label)
        else:
            self.get_label = get_label

        self.allow_blank = allow_blank
        self.blank_text = blank_text
        self._set_data(None)
        if reference_class is not None:
            self.query = reference_class.all()

    def _get_data(self):
        if self._formdata is not None:
            for obj in self.query:
                if str(obj.key()) == self._formdata:
                    self._set_data(obj)
                    break
        return self._data

    def _set_data(self, data):
        self._data = data
        self._formdata = None

    data = property(_get_data, _set_data)

    def iter_choices(self):
        if self.allow_blank:
            yield ('__None', self.blank_text, self.data is None)

        for obj in self.query:
            key = str(obj.key())