__init__.py

import copy
import datetime
import os
import time
try:
    import decimal
except ImportError:
    from django.utils import _decimal as decimal    # for Python 2.3

from django.db import connection, get_creation_module
from django.db.models import signals
from django.db.models.query_utils import QueryWrapper
from django.dispatch import dispatcher
from django.conf import settings
from django.core import validators
from django import oldforms
from django import newforms as forms
from django.core.exceptions import ObjectDoesNotExist
from django.utils.functional import curry
from django.utils.itercompat import tee
from django.utils.text import capfirst
from django.utils.translation import ugettext_lazy, ugettext as _
from django.utils.encoding import smart_unicode, force_unicode, smart_str
from django.utils.maxlength import LegacyMaxlength

class NOT_PROVIDED:
    pass

# Values for filter_interface.
HORIZONTAL, VERTICAL = 1, 2

# The values to use for "blank" in SelectFields. Will be appended to the start of most "choices" lists.
BLANK_CHOICE_DASH = [("", "---------")]
BLANK_CHOICE_NONE = [("", "None")]

# returns the <ul> class for a given radio_admin value
get_ul_class = lambda x: 'radiolist%s' % ((x == HORIZONTAL) and ' inline' or '')

class FieldDoesNotExist(Exception):
    pass

def manipulator_validator_unique(f, opts, self, field_data, all_data):
    "Validates that the value is unique for this field."
    lookup_type = f.get_validator_unique_lookup_type()
    try:
        old_obj = self.manager.get(**{lookup_type: field_data})
    except ObjectDoesNotExist:
        return
    if getattr(self, 'original_object', None) and self.original_object._get_pk_val() == old_obj._get_pk_val():
        return
    raise validators.ValidationError, _("%(optname)s with this %(fieldname)s already exists.") % {'optname': capfirst(opts.verbose_name), 'fieldname': f.verbose_name}

# A guide to Field parameters:
#
#   * name:      The name of the field specifed in the model.
#   * attname:   The attribute to use on the model object. This is the same as
#                "name", except in the case of ForeignKeys, where "_id" is
#                appended.
#   * db_column: The db_column specified in the model (or None).
#   * column:    The database column for this field. This is the same as
#                "attname", except if db_column is specified.
#
# Code that introspects values, or does other dynamic things, should use
# attname. For example, this gets the primary key value of object "obj":
#
#     getattr(obj, opts.pk.attname)

class Field(object):
    # Provide backwards compatibility for the maxlength attribute and
    # argument for this class and all subclasses.
    __metaclass__ = LegacyMaxlength

    # Designates whether empty strings fundamentally are allowed at the
    # database level.
    empty_strings_allowed = True

    # These track each time a Field instance is created. Used to retain order.
    # The auto_creation_counter is used for fields that Django implicitly
    # creates, creation_counter is used for all user-specified fields.
    creation_counter = 0
    auto_creation_counter = -1

    def __init__(self, verbose_name=None, name=None, primary_key=False,
            max_length=None, unique=False, blank=False, null=False,
            db_index=False, core=False, rel=None, default=NOT_PROVIDED,
            editable=True, serialize=True, prepopulate_from=None,
            unique_for_date=None, unique_for_month=None, unique_for_year=None,
            validator_list=None, choices=None, radio_admin=None, help_text='',
            db_column=None, db_tablespace=None, auto_created=False):
        self.name = name
        self.verbose_name = verbose_name
        self.primary_key = primary_key
        self.max_length, self.unique = max_length, unique
        self.blank, self.null = blank, null
        # Oracle treats the empty string ('') as null, so coerce the null
        # option whenever '' is a possible value.
        if self.empty_strings_allowed and connection.features.interprets_empty_strings_as_nulls:
            self.null = True
        self.core, self.rel, self.default = core, rel, default
        self.editable = editable
        self.serialize = serialize
        self.validator_list = validator_list or []
        self.prepopulate_from = prepopulate_from
        self.unique_for_date, self.unique_for_month = unique_for_date, unique_for_month
        self.unique_for_year = unique_for_year
        self._choices = choices or []
        self.radio_admin = radio_admin
        self.help_text = help_text
        self.db_column = db_column
        self.db_tablespace = db_tablespace or settings.DEFAULT_INDEX_TABLESPACE

        # Set db_index to True if the field has a relationship and doesn't explicitly set db_index.
        self.db_index = db_index

        # Adjust the appropriate creation counter, and save our local copy.
        if auto_created:
            self.creation_counter = Field.auto_creation_counter
            Field.auto_creation_counter -= 1
        else:
            self.creation_counter = Field.creation_counter
            Field.creation_counter += 1

    def __cmp__(self, other):
        # This is needed because bisect does not take a comparison function.
        return cmp(self.creation_counter, other.creation_counter)

    def __deepcopy__(self, memodict):
        # We don't have to deepcopy very much here, since most things are not
        # intended to be altered after initial creation.
        obj = copy.copy(self)
        if self.rel:
            obj.rel = copy.copy(self.rel)
        memodict[id(self)] = obj
        return obj

    def to_python(self, value):
        """
        Converts the input value into the expected Python data type, raising
        validators.ValidationError if the data can't be converted. Returns the
        converted value. Subclasses should override this.
        """
        return value

    def db_type(self):
        """
        Returns the database column data type for this field, taking into
        account the DATABASE_ENGINE setting.
        """
        # The default implementation of this method looks at the
        # backend-specific DATA_TYPES dictionary, looking up the field by its
        # "internal type".
        #
        # A Field class can implement the get_internal_type() method to specify
        # which *preexisting* Django Field class it's most similar to -- i.e.,
        # an XMLField is represented by a TEXT column type, which is the same
        # as the TextField Django field type, which means XMLField's
        # get_internal_type() returns 'TextField'.
        #
        # But the limitation of the get_internal_type() / DATA_TYPES approach
        # is that it cannot handle database column types that aren't already
        # mapped to one of the built-in Django field types. In this case, you
        # can implement db_type() instead of get_internal_type() to specify
        # exactly which wacky database column type you want to use.
        try:
            return get_creation_module().DATA_TYPES[self.get_internal_type()] % self.__dict__
        except KeyError:
            return None

    def validate_full(self, field_data, all_data):
        """
        Returns a list of errors for this field. This is the main interface,
        as it encapsulates some basic validation logic used by all fields.
        Subclasses should implement validate(), not validate_full().
        """
        if not self.blank and not field_data:
            return [_('This field is required.')]
        try:
            self.validate(field_data, all_data)
        except validators.ValidationError, e:
            return e.messages
        return []

    def validate(self, field_data, all_data):
        """
        Raises validators.ValidationError if field_data has any errors.
        Subclasses should override this to specify field-specific validation
        logic. This method should assume field_data has already been converted
        into the appropriate data type by Field.to_python().
        """
        pass

    def set_attributes_from_name(self, name):
        self.name = name
        self.attname, self.column = self.get_attname_column()
        self.verbose_name = self.verbose_name or (name and name.replace('_', ' '))

    def contribute_to_class(self, cls, name):
        self.set_attributes_from_name(name)
        cls._meta.add_field(self)
        if self.choices:
            setattr(cls, 'get_%s_display' % self.name, curry(cls._get_FIELD_display, field=self))

    def get_attname(self):
        return self.name

    def get_attname_column(self):
        attname = self.get_attname()
        column = self.db_column or attname
        return attname, column

    def get_cache_name(self):
        return '_%s_cache' % self.name

    def get_internal_type(self):
        return self.__class__.__name__

    def pre_save(self, model_instance, add):
        "Returns field's value just before saving."
        return getattr(model_instance, self.attname)

    def get_db_prep_save(self, value):
        "Returns field's value prepared for saving into a database."
        return value

    def get_db_prep_lookup(self, lookup_type, value):
        "Returns field's value prepared for database lookup."
        if hasattr(value, 'as_sql'):
            sql, params = value.as_sql()
            return QueryWrapper(('(%s)' % sql), params)
        if lookup_type in ('exact', 'regex', 'iregex', 'gt', 'gte', 'lt', 'lte', 'month', 'day', 'search'):
            return [value]
        elif lookup_type in ('range', 'in'):
            return value
        elif lookup_type in ('contains', 'icontains'):
            return ["%%%s%%" % connection.ops.prep_for_like_query(value)]
        elif lookup_type == 'iexact':
            return [connection.ops.prep_for_like_query(value)]
        elif lookup_type in ('startswith', 'istartswith'):
            return ["%s%%" % connection.ops.prep_for_like_query(value)]
        elif lookup_type in ('endswith', 'iendswith'):
            return ["%%%s" % connection.ops.prep_for_like_query(value)]
        elif lookup_type == 'isnull':
            return []
        elif lookup_type == 'year':
            try:
                value = int(value)
            except ValueError:
                raise ValueError("The __year lookup type requires an integer argument")
            if settings.DATABASE_ENGINE == 'sqlite3':
                first = '%s-01-01'
                second = '%s-12-31 23:59:59.999999'
            elif not connection.features.date_field_supports_time_value and self.get_internal_type() == 'DateField':
                first = '%s-01-01'
                second = '%s-12-31'
            elif not connection.features.supports_usecs:
                first = '%s-01-01 00:00:00'
                second = '%s-12-31 23:59:59.99'
            else:
                first = '%s-01-01 00:00:00'
                second = '%s-12-31 23:59:59.999999'
            return [first % value, second % value]
        raise TypeError("Field has invalid lookup: %s" % lookup_type)

    def has_default(self):
        "Returns a boolean of whether this field has a default value."
        return self.default is not NOT_PROVIDED

    def get_default(self):
        "Returns the default value for this field."
        if self.default is not NOT_PROVIDED:
            if callable(self.default):
                return self.default()
            return force_unicode(self.default, strings_only=True)
        if not self.empty_strings_allowed or (self.null and not connection.features.interprets_empty_strings_as_nulls):
            return None
        return ""

    def get_manipulator_field_names(self, name_prefix):
        """
        Returns a list of field names that this object adds to the manipulator.
        """
        return [name_prefix + self.name]

    def prepare_field_objs_and_params(self, manipulator, name_prefix):
        params = {'validator_list': self.validator_list[:]}
        if self.max_length and not self.choices: # Don't give SelectFields a max_length parameter.
            params['max_length'] = self.max_length

        if self.choices:
            if self.radio_admin:
                field_objs = [oldforms.RadioSelectField]
                params['ul_class'] = get_ul_class(self.radio_admin)
            else:
                field_objs = [oldforms.SelectField]

            params['choices'] = self.get_choices_default()
        else:
            field_objs = self.get_manipulator_field_objs()
        return (field_objs, params)

    def get_manipulator_fields(self, opts, manipulator, change, name_prefix='', rel=False, follow=True):
        """
        Returns a list of oldforms.FormField instances for this field. It
        calculates the choices at runtime, not at compile time.

        name_prefix is a prefix to prepend to the "field_name" argument.
        rel is a boolean specifying whether this field is in a related context.
        """
        field_objs, params = self.prepare_field_objs_and_params(manipulator, name_prefix)

        # Add the "unique" validator(s).
        for field_name_list in opts.unique_together:
            if field_name_list[0] == self.name:
                params['validator_list'].append(getattr(manipulator, 'isUnique%s' % '_'.join(field_name_list)))

        # Add the "unique for..." validator(s).
        if self.unique_for_date:
            params['validator_list'].append(getattr(manipulator, 'isUnique%sFor%s' % (self.name, self.unique_for_date)))
        if self.unique_for_month:
            params['validator_list'].append(getattr(manipulator, 'isUnique%sFor%s' % (self.name, self.unique_for_month)))
        if self.unique_for_year:
            params['validator_list'].append(getattr(manipulator, 'isUnique%sFor%s' % (self.name, self.unique_for_year)))
        if self.unique or (self.primary_key and not rel):
            params['validator_list'].append(curry(manipulator_validator_unique, self, opts, manipulator))

        # Only add is_required=True if the field cannot be blank. Primary keys
        # are a special case, and fields in a related context should set this
        # as False, because they'll be caught by a separate validator --
        # RequiredIfOtherFieldGiven.
        params['is_required'] = not self.blank and not self.primary_key and not rel

        # BooleanFields (CheckboxFields) are a special case. They don't take
        # is_required.
        if isinstance(self, BooleanField):
            del params['is_required']

        # If this field is in a related context, check whether any other fields
        # in the related object have core=True. If so, add a validator --
        # RequiredIfOtherFieldsGiven -- to this FormField.
        if rel and not self.blank and not isinstance(self, AutoField) and not isinstance(self, FileField):
            # First, get the core fields, if any.
            core_field_names = []
            for f in opts.fields:
                if f.core and f != self:
                    core_field_names.extend(f.get_manipulator_field_names(name_prefix))
            # Now, if there are any, add the validator to this FormField.
            if core_field_names:
                params['validator_list'].append(validators.RequiredIfOtherFieldsGiven(core_field_names, ugettext_lazy("This field is required.")))

        # Finally, add the field_names.
        field_names = self.get_manipulator_field_names(name_prefix)
        return [man(field_name=field_names[i], **params) for i, man in enumerate(field_objs)]

    def get_validator_unique_lookup_type(self):
        return '%s__exact' % self.name

    def get_manipulator_new_data(self, new_data, rel=False):
        """
        Given the full new_data dictionary (from the manipulator), returns this
        field's data.
        """
        if rel:
            return new_data.get(self.name, [self.get_default()])[0]
        val = new_data.get(self.name, self.get_default())
        if not self.empty_strings_allowed and val == '' and self.null:
            val = None
        return val

    def get_choices(self, include_blank=True, blank_choice=BLANK_CHOICE_DASH):
        "Returns a list of tuples used as SelectField choices for this field."
        first_choice = include_blank and blank_choice or []
        if self.choices:
            return first_choice + list(self.choices)
        rel_model = self.rel.to
        if hasattr(self.rel, 'get_related_field'):
            lst = [(getattr(x, self.rel.get_related_field().attname), smart_unicode(x)) for x in rel_model._default_manager.complex_filter(self.rel.limit_choices_to)]
        else:
            lst = [(x._get_pk_val(), smart_unicode(x)) for x in rel_model._default_manager.complex_filter(self.rel.limit_choices_to)]
        return first_choice + lst

    def get_choices_default(self):
        if self.radio_admin:
            return self.get_choices(include_blank=self.blank, blank_choice=BLANK_CHOICE_NONE)
        else:
            return self.get_choices()

    def _get_val_from_obj(self, obj):
        if obj:
            return getattr(obj, self.attname)
        else:
            return self.get_default()

    def flatten_data(self, follow, obj=None):
        """
        Returns a dictionary mapping the field's manipulator field names to its
        "flattened" string values for the admin view. obj is the instance to
        extract the values from.
        """
        return {self.attname: self._get_val_from_obj(obj)}

    def get_follow(self, override=None):
        if override != None:
            return override
        else:
            return self.editable

    def bind(self, fieldmapping, original, bound_field_class):
        return bound_field_class(self, fieldmapping, original)

    def _get_choices(self):
        if hasattr(self._choices, 'next'):
            choices, self._choices = tee(self._choices)
            return choices
        else:
            return self._choices
    choices = property(_get_choices)

    def save_form_data(self, instance, data):
        setattr(instance, self.name, data)

    def formfield(self, form_class=forms.CharField, **kwargs):
        "Returns a django.newforms.Field instance for this database Field."
        defaults = {'required': not self.blank, 'label': capfirst(self.verbose_name), 'help_text': self.help_text}
        if self.choices:
            defaults['widget'] = forms.Select(choices=self.get_choices(include_blank=self.blank or not (self.has_default() or 'initial' in kwargs)))
        if self.has_default():
            defaults['initial'] = self.get_default()
        defaults.update(kwargs)
        return form_class(**defaults)

    def value_from_object(self, obj):
        "Returns the value of this field in the given model instance."
        return getattr(obj, self.attname)

class AutoField(Field):
    empty_strings_allowed = False
    def __init__(self, *args, **kwargs):
        assert kwargs.get('primary_key', False) is True, "%ss must have primary_key=True." % self.__class__.__name__
        kwargs['blank'] = True
        Field.__init__(self, *args, **kwargs)

    def to_python(self, value):
        if value is None:
            return value
        try:
            return int(value)
        except (TypeError, ValueError):
            raise validators.ValidationError, _("This value must be an integer.")

    def get_manipulator_fields(self, opts, manipulator, change, name_prefix='', rel=False, follow=True):
        if not rel:
            return [] # Don't add a FormField unless it's in a related context.
        return Field.get_manipulator_fields(self, opts, manipulator, change, name_prefix, rel, follow)

    def get_manipulator_field_objs(self):
        return [oldforms.HiddenField]

    def get_manipulator_new_data(self, new_data, rel=False):
        # Never going to be called
        # Not in main change pages
        # ignored in related context
        if not rel:
            return None
        return Field.get_manipulator_new_data(self, new_data, rel)

    def contribute_to_class(self, cls, name):
        assert not cls._meta.has_auto_field, "A model can't have more than one AutoField."
        super(AutoField, self).contribute_to_class(cls, name)
        cls._meta.has_auto_field = True
        cls._meta.auto_field = self

    def formfield(self, **kwargs):
        return None

class BooleanField(Field):
    def __init__(self, *args, **kwargs):
        kwargs['blank'] = True
        Field.__init__(self, *args, **kwargs)

    def get_internal_type(self):
        return "BooleanField"

    def to_python(self, value):
        if value in (True, False): return value
        if value in ('t', 'True', '1'): return True
        if value in ('f', 'False', '0'): return False
        raise validators.ValidationError, _("This value must be either True or False.")

    def get_manipulator_field_objs(self):
        return [oldforms.CheckboxField]

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.BooleanField}
        defaults.update(kwargs)
        return super(BooleanField, self).formfield(**defaults)

class CharField(Field):
    def get_manipulator_field_objs(self):
        return [oldforms.TextField]

    def get_internal_type(self):
        return "CharField"

    def to_python(self, value):
        if isinstance(value, basestring):
            return value
        if value is None:
            if self.null:
                return value
            else:
                raise validators.ValidationError, ugettext_lazy("This field cannot be null.")
        return smart_unicode(value)

    def formfield(self, **kwargs):
        defaults = {'max_length': self.max_length}
        defaults.update(kwargs)
        return super(CharField, self).formfield(**defaults)

# TODO: Maybe move this into contrib, because it's specialized.
class CommaSeparatedIntegerField(CharField):
    def get_manipulator_field_objs(self):
        return [oldforms.CommaSeparatedIntegerField]

class DateField(Field):
    empty_strings_allowed = False
    def __init__(self, verbose_name=None, name=None, auto_now=False, auto_now_add=False, **kwargs):
        self.auto_now, self.auto_now_add = auto_now, auto_now_add
        #HACKs : auto_now_add/auto_now should be done as a default or a pre_save.
        if auto_now or auto_now_add:
            kwargs['editable'] = False
            kwargs['blank'] = True
        Field.__init__(self, verbose_name, name, **kwargs)

    def get_internal_type(self):
        return "DateField"

    def to_python(self, value):
        if value is None:
            return value
        if isinstance(value, datetime.datetime):
            return value.date()
        if isinstance(value, datetime.date):
            return value
        validators.isValidANSIDate(value, None)
        try:
            return datetime.date(*time.strptime(value, '%Y-%m-%d')[:3])
        except ValueError:
            raise validators.ValidationError, _('Enter a valid date in YYYY-MM-DD format.')

    def get_db_prep_lookup(self, lookup_type, value):
        if lookup_type == 'range':
            value = [smart_unicode(v) for v in value]
        elif lookup_type in ('exact', 'gt', 'gte', 'lt', 'lte') and hasattr(value, 'strftime'):
            value = value.strftime('%Y-%m-%d')
        else:
            value = smart_unicode(value)
        return Field.get_db_prep_lookup(self, lookup_type, value)

    def pre_save(self, model_instance, add):
        if self.auto_now or (self.auto_now_add and add):
            value = datetime.datetime.now()
            setattr(model_instance, self.attname, value)
            return value
        else:
            return super(DateField, self).pre_save(model_instance, add)

    def contribute_to_class(self, cls, name):
        super(DateField,self).contribute_to_class(cls, name)
        if not self.null:
            setattr(cls, 'get_next_by_%s' % self.name,
                curry(cls._get_next_or_previous_by_FIELD, field=self, is_next=True))
            setattr(cls, 'get_previous_by_%s' % self.name,
                curry(cls._get_next_or_previous_by_FIELD, field=self, is_next=False))

    # Needed because of horrible auto_now[_add] behaviour wrt. editable
    def get_follow(self, override=None):
        if override != None:
            return override
        else:
            return self.editable or self.auto_now or self.auto_now_add

    def get_db_prep_save(self, value):
        # Casts dates into string format for entry into database.
        if value is not None:
            try:
                value = value.strftime('%Y-%m-%d')
            except AttributeError:
                # If value is already a string it won't have a strftime method,
                # so we'll just let it pass through.
                pass
        return Field.get_db_prep_save(self, value)

    def get_manipulator_field_objs(self):
        return [oldforms.DateField]

    def flatten_data(self, follow, obj=None):
        val = self._get_val_from_obj(obj)
        return {self.attname: (val is not None and val.strftime("%Y-%m-%d") or '')}

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.DateField}
        defaults.update(kwargs)
        return super(DateField, self).formfield(**defaults)

class DateTimeField(DateField):
    def get_internal_type(self):
        return "DateTimeField"

    def to_python(self, value):
        if value is None:
            return value
        if isinstance(value, datetime.datetime):
            return value
        if isinstance(value, datetime.date):
            return datetime.datetime(value.year, value.month, value.day)
        try: # Seconds are optional, so try converting seconds first.
            return datetime.datetime(*time.strptime(value, '%Y-%m-%d %H:%M:%S')[:6])
        except ValueError:
            try: # Try without seconds.
                return datetime.datetime(*time.strptime(value, '%Y-%m-%d %H:%M')[:5])
            except ValueError: # Try without hour/minutes/seconds.
                try:
                    return datetime.datetime(*time.strptime(value, '%Y-%m-%d')[:3])
                except ValueError:
                    raise validators.ValidationError, _('Enter a valid date/time in YYYY-MM-DD HH:MM format.')

    def get_db_prep_save(self, value):
        # Casts dates into string format for entry into database.
        if value is not None:
            # MySQL will throw a warning if microseconds are given, because it
            # doesn't support microseconds.
            if not connection.features.supports_usecs and hasattr(value, 'microsecond'):
                value = value.replace(microsecond=0)
            value = smart_unicode(value)
        return Field.get_db_prep_save(self, value)

    def get_db_prep_lookup(self, lookup_type, value):
        if lookup_type == 'range':
            value = [smart_unicode(v) for v in value]
        else:
            value = smart_unicode(value)
        return Field.get_db_prep_lookup(self, lookup_type, value)

    def get_manipulator_field_objs(self):
        return [oldforms.DateField, oldforms.TimeField]

    def get_manipulator_field_names(self, name_prefix):
        return [name_prefix + self.name + '_date', name_prefix + self.name + '_time']

    def get_manipulator_new_data(self, new_data, rel=False):
        date_field, time_field = self.get_manipulator_field_names('')
        if rel:
            d = new_data.get(date_field, [None])[0]
            t = new_data.get(time_field, [None])[0]
        else:
            d = new_data.get(date_field, None)
            t = new_data.get(time_field, None)
        if d is not None and t is not None:
            return datetime.datetime.combine(d, t)
        return self.get_default()

    def flatten_data(self,follow, obj = None):
        val = self._get_val_from_obj(obj)
        date_field, time_field = self.get_manipulator_field_names('')
        return {date_field: (val is not None and val.strftime("%Y-%m-%d") or ''),
                time_field: (val is not None and val.strftime("%H:%M:%S") or '')}

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.DateTimeField}
        defaults.update(kwargs)
        return super(DateTimeField, self).formfield(**defaults)

class DecimalField(Field):
    empty_strings_allowed = False
    def __init__(self, verbose_name=None, name=None, max_digits=None, decimal_places=None, **kwargs):
        self.max_digits, self.decimal_places = max_digits, decimal_places
        Field.__init__(self, verbose_name, name, **kwargs)

    def get_internal_type(self):
        return "DecimalField"

    def to_python(self, value):
        if value is None:
            return value
        try:
            return decimal.Decimal(value)
        except decimal.InvalidOperation:
            raise validators.ValidationError(
                _("This value must be a decimal number."))

    def _format(self, value):
        if isinstance(value, basestring):
            return value
        else:
            return self.format_number(value)

    def format_number(self, value):
        """
        Formats a number into a string with the requisite number of digits and
        decimal places.
        """
        num_chars = self.max_digits
        # Allow for a decimal point
        if self.decimal_places > 0:
            num_chars += 1
        # Allow for a minus sign
        if value < 0:
            num_chars += 1

        return u"%.*f" % (self.decimal_places, value)

    def get_db_prep_save(self, value):
        if value is not None:
            value = self._format(value)
        return super(DecimalField, self).get_db_prep_save(value)

    def get_db_prep_lookup(self, lookup_type, value):
        if lookup_type == 'range':
            value = [self._format(v) for v in value]
        else:
            value = self._format(value)
        return super(DecimalField, self).get_db_prep_lookup(lookup_type, value)

    def get_manipulator_field_objs(self):
        return [curry(oldforms.DecimalField, max_digits=self.max_digits, decimal_places=self.decimal_places)]

    def formfield(self, **kwargs):
        defaults = {
            'max_digits': self.max_digits,
            'decimal_places': self.decimal_places,
            'form_class': forms.DecimalField,
        }
        defaults.update(kwargs)
        return super(DecimalField, self).formfield(**defaults)

class EmailField(CharField):
    def __init__(self, *args, **kwargs):
        kwargs['max_length'] = kwargs.get('max_length', 75)
        CharField.__init__(self, *args, **kwargs)

    def get_manipulator_field_objs(self):
        return [oldforms.EmailField]

    def validate(self, field_data, all_data):
        validators.isValidEmail(field_data, all_data)

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.EmailField}
        defaults.update(kwargs)
        return super(EmailField, self).formfield(**defaults)

class FileField(Field):
    def __init__(self, verbose_name=None, name=None, upload_to='', **kwargs):
        self.upload_to = upload_to
        kwargs['max_length'] = kwargs.get('max_length', 100)
        Field.__init__(self, verbose_name, name, **kwargs)

    def get_internal_type(self):
        return "FileField"

    def get_db_prep_save(self, value):
        "Returns field's value prepared for saving into a database."
        # Need to convert UploadedFile objects provided via a form to unicode for database insertion
        if value is None:
            return None
        return unicode(value)

    def get_manipulator_fields(self, opts, manipulator, change, name_prefix='', rel=False, follow=True):
        field_list = Field.get_manipulator_fields(self, opts, manipulator, change, name_prefix, rel, follow)
        if not self.blank:
            if rel:
                # This validator makes sure FileFields work in a related context.
                class RequiredFileField(object):
                    def __init__(self, other_field_names, other_file_field_name):
                        self.other_field_names = other_field_names
                        self.other_file_field_name = other_file_field_name
                        self.always_test = True
                    def __call__(self, field_data, all_data):
                        if not all_data.get(self.other_file_field_name, False):
                            c = validators.RequiredIfOtherFieldsGiven(self.other_field_names, ugettext_lazy("This field is required."))
                            c(field_data, all_data)
                # First, get the core fields, if any.
                core_field_names = []
                for f in opts.fields:
                    if f.core and f != self:
                        core_field_names.extend(f.get_manipulator_field_names(name_prefix))
                # Now, if there are any, add the validator to this FormField.
                if core_field_names:
                    field_list[0].validator_list.append(RequiredFileField(core_field_names, field_list[1].field_name))
            else:
                v = validators.RequiredIfOtherFieldNotGiven(field_list[1].field_name, ugettext_lazy("This field is required."))
                v.always_test = True
                field_list[0].validator_list.append(v)
                field_list[0].is_required = field_list[1].is_required = False

        # If the raw path is passed in, validate it's under the MEDIA_ROOT.
        def isWithinMediaRoot(field_data, all_data):
            f = os.path.abspath(os.path.join(settings.MEDIA_ROOT, field_data))
            if not f.startswith(os.path.abspath(os.path.normpath(settings.MEDIA_ROOT))):
                raise validators.ValidationError, _("Enter a valid filename.")
        field_list[1].validator_list.append(isWithinMediaRoot)
        return field_list

    def contribute_to_class(self, cls, name):
        super(FileField, self).contribute_to_class(cls, name)
        setattr(cls, 'get_%s_filename' % self.name, curry(cls._get_FIELD_filename, field=self))
        setattr(cls, 'get_%s_url' % self.name, curry(cls._get_FIELD_url, field=self))
        setattr(cls, 'get_%s_size' % self.name, curry(cls._get_FIELD_size, field=self))
        setattr(cls, 'save_%s_file' % self.name, lambda instance, filename, raw_contents, save=True: instance._save_FIELD_file(self, filename, raw_contents, save))
        dispatcher.connect(self.delete_file, signal=signals.post_delete, sender=cls)

    def delete_file(self, instance):
        if getattr(instance, self.attname):
            file_name = getattr(instance, 'get_%s_filename' % self.name)()
            # If the file exists and no other object of this type references it,
            # delete it from the filesystem.
            if os.path.exists(file_name) and \
                not instance.__class__._default_manager.filter(**{'%s__exact' % self.name: getattr(instance, self.attname)}):
                os.remove(file_name)

    def get_manipulator_field_objs(self):
        return [oldforms.FileUploadField, oldforms.HiddenField]

    def get_manipulator_field_names(self, name_prefix):
        return [name_prefix + self.name + '_file', name_prefix + self.name]

    def save_file(self, new_data, new_object, original_object, change, rel, save=True):
        upload_field_name = self.get_manipulator_field_names('')[0]
        if new_data.get(upload_field_name, False):
            func = getattr(new_object, 'save_%s_file' % self.name)
            if rel:
                func(new_data[upload_field_name][0]["filename"], new_data[upload_field_name][0]["content"], save)
            else:
                func(new_data[upload_field_name]["filename"], new_data[upload_field_name]["content"], save)

    def get_directory_name(self):
        return os.path.normpath(force_unicode(datetime.datetime.now().strftime(smart_str(self.upload_to))))

    def get_filename(self, filename):
        from django.utils.text import get_valid_filename
        f = os.path.join(self.get_directory_name(), get_valid_filename(os.path.basename(filename)))
        return os.path.normpath(f)

    def save_form_data(self, instance, data):
        from django.newforms.fields import UploadedFile
        if data and isinstance(data, UploadedFile):
            getattr(instance, "save_%s_file" % self.name)(data.filename, data.content, save=False)

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.FileField}
        # If a file has been provided previously, then the form doesn't require
        # that a new file is provided this time.
        # The code to mark the form field as not required is used by
        # form_for_instance, but can probably be removed once form_for_instance
        # is gone. ModelForm uses a different method to check for an existing file.
        if 'initial' in kwargs:
            defaults['required'] = False
        defaults.update(kwargs)
        return super(FileField, self).formfield(**defaults)

class FilePathField(Field):
    def __init__(self, verbose_name=None, name=None, path='', match=None, recursive=False, **kwargs):
        self.path, self.match, self.recursive = path, match, recursive
        kwargs['max_length'] = kwargs.get('max_length', 100)
        Field.__init__(self, verbose_name, name, **kwargs)

    def formfield(self, **kwargs):
        defaults = {
            'path': self.path,
            'match': self.match,
            'recursive': self.recursive,
            'form_class': forms.FilePathField,
        }
        defaults.update(kwargs)
        return super(FilePathField, self).formfield(**defaults)

    def get_manipulator_field_objs(self):
        return [curry(oldforms.FilePathField, path=self.path, match=self.match, recursive=self.recursive)]

    def get_internal_type(self):
        return "FilePathField"

class FloatField(Field):
    empty_strings_allowed = False

    def get_manipulator_field_objs(self):
        return [oldforms.FloatField]

    def get_internal_type(self):
        return "FloatField"

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.FloatField}
        defaults.update(kwargs)
        return super(FloatField, self).formfield(**defaults)

class ImageField(FileField):
    def __init__(self, verbose_name=None, name=None, width_field=None, height_field=None, **kwargs):
        self.width_field, self.height_field = width_field, height_field
        FileField.__init__(self, verbose_name, name, **kwargs)

    def get_manipulator_field_objs(self):
        return [oldforms.ImageUploadField, oldforms.HiddenField]

    def contribute_to_class(self, cls, name):
        super(ImageField, self).contribute_to_class(cls, name)
        # Add get_BLAH_width and get_BLAH_height methods, but only if the
        # image field doesn't have width and height cache fields.
        if not self.width_field:
            setattr(cls, 'get_%s_width' % self.name, curry(cls._get_FIELD_width, field=self))
        if not self.height_field:
            setattr(cls, 'get_%s_height' % self.name, curry(cls._get_FIELD_height, field=self))

    def get_internal_type(self):
        return "ImageField"

    def save_file(self, new_data, new_object, original_object, change, rel, save=True):
        FileField.save_file(self, new_data, new_object, original_object, change, rel, save)
        # If the image has height and/or width field(s) and they haven't
        # changed, set the width and/or height field(s) back to their original
        # values.
        if change and (self.width_field or self.height_field) and save:
            if self.width_field:
                setattr(new_object, self.width_field, getattr(original_object, self.width_field))
            if self.height_field:
                setattr(new_object, self.height_field, getattr(original_object, self.height_field))
            new_object.save()

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.ImageField}
        defaults.update(kwargs)
        return super(ImageField, self).formfield(**defaults)

class IntegerField(Field):
    empty_strings_allowed = False
    def get_manipulator_field_objs(self):
        return [oldforms.IntegerField]

    def get_internal_type(self):
        return "IntegerField"

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.IntegerField}
        defaults.update(kwargs)
        return super(IntegerField, self).formfield(**defaults)

class IPAddressField(Field):
    empty_strings_allowed = False
    def __init__(self, *args, **kwargs):
        kwargs['max_length'] = 15
        Field.__init__(self, *args, **kwargs)

    def get_manipulator_field_objs(self):
        return [oldforms.IPAddressField]

    def get_internal_type(self):
        return "IPAddressField"

    def validate(self, field_data, all_data):
        validators.isValidIPAddress4(field_data, None)

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.IPAddressField}
        defaults.update(kwargs)
        return super(IPAddressField, self).formfield(**defaults)

class NullBooleanField(Field):
    empty_strings_allowed = False
    def __init__(self, *args, **kwargs):
        kwargs['null'] = True
        Field.__init__(self, *args, **kwargs)

    def get_internal_type(self):
        return "NullBooleanField"

    def to_python(self, value):
        if value in (None, True, False): return value
        if value in ('None'): return None
        if value in ('t', 'True', '1'): return True
        if value in ('f', 'False', '0'): return False
        raise validators.ValidationError, _("This value must be either None, True or False.")

    def get_manipulator_field_objs(self):
        return [oldforms.NullBooleanField]

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.NullBooleanField}
        defaults.update(kwargs)
        return super(NullBooleanField, self).formfield(**defaults)

class PhoneNumberField(IntegerField):
    def get_manipulator_field_objs(self):
        return [oldforms.PhoneNumberField]

    def get_internal_type(self):
        return "PhoneNumberField"

    def validate(self, field_data, all_data):
        validators.isValidPhone(field_data, all_data)

    def formfield(self, **kwargs):
        from django.contrib.localflavor.us.forms import USPhoneNumberField
        defaults = {'form_class': USPhoneNumberField}
        defaults.update(kwargs)
        return super(PhoneNumberField, self).formfield(**defaults)

class PositiveIntegerField(IntegerField):
    def get_manipulator_field_objs(self):
        return [oldforms.PositiveIntegerField]

    def get_internal_type(self):
        return "PositiveIntegerField"

    def formfield(self, **kwargs):
        defaults = {'min_value': 0}
        defaults.update(kwargs)
        return super(PositiveIntegerField, self).formfield(**defaults)

class PositiveSmallIntegerField(IntegerField):
    def get_manipulator_field_objs(self):
        return [oldforms.PositiveSmallIntegerField]

    def get_internal_type(self):
        return "PositiveSmallIntegerField"

    def formfield(self, **kwargs):
        defaults = {'min_value': 0}
        defaults.update(kwargs)
        return super(PositiveSmallIntegerField, self).formfield(**defaults)

class SlugField(CharField):
    def __init__(self, *args, **kwargs):
        kwargs['max_length'] = kwargs.get('max_length', 50)
        kwargs.setdefault('validator_list', []).append(validators.isSlug)
        # Set db_index=True unless it's been set manually.
        if 'db_index' not in kwargs:
            kwargs['db_index'] = True
        super(SlugField, self).__init__(*args, **kwargs)

    def get_internal_type(self):
        return "SlugField"

class SmallIntegerField(IntegerField):
    def get_manipulator_field_objs(self):
        return [oldforms.SmallIntegerField]

    def get_internal_type(self):
        return "SmallIntegerField"

class TextField(Field):
    def get_manipulator_field_objs(self):
        return [oldforms.LargeTextField]

    def get_internal_type(self):
        return "TextField"

    def formfield(self, **kwargs):
        defaults = {'widget': forms.Textarea}
        defaults.update(kwargs)
        return super(TextField, self).formfield(**defaults)

class TimeField(Field):
    empty_strings_allowed = False
    def __init__(self, verbose_name=None, name=None, auto_now=False, auto_now_add=False, **kwargs):
        self.auto_now, self.auto_now_add = auto_now, auto_now_add
        if auto_now or auto_now_add:
            kwargs['editable'] = False
        Field.__init__(self, verbose_name, name, **kwargs)

    def get_internal_type(self):
        return "TimeField"

    def get_db_prep_lookup(self, lookup_type, value):
        if connection.features.time_field_needs_date:
            # Oracle requires a date in order to parse.
            def prep(value):
                if isinstance(value, datetime.time):
                    value = datetime.datetime.combine(datetime.date(1900, 1, 1), value)
                return smart_unicode(value)
        else:
            prep = smart_unicode
        if lookup_type == 'range':
            value = [prep(v) for v in value]
        else:
            value = prep(value)
        return Field.get_db_prep_lookup(self, lookup_type, value)

    def pre_save(self, model_instance, add):
        if self.auto_now or (self.auto_now_add and add):
            value = datetime.datetime.now().time()
            setattr(model_instance, self.attname, value)
            return value
        else:
            return super(TimeField, self).pre_save(model_instance, add)

    def get_db_prep_save(self, value):
        # Casts dates into string format for entry into database.
        if value is not None:
            # MySQL will throw a warning if microseconds are given, because it
            # doesn't support microseconds.
            if not connection.features.supports_usecs and hasattr(value, 'microsecond'):
                value = value.replace(microsecond=0)
            if connection.features.time_field_needs_date:
                # cx_Oracle expects a datetime.datetime to persist into TIMESTAMP field.
                if isinstance(value, datetime.time):
                    value = datetime.datetime(1900, 1, 1, value.hour, value.minute,
                                              value.second, value.microsecond)
                elif isinstance(value, basestring):
                    value = datetime.datetime(*(time.strptime(value, '%H:%M:%S')[:6]))
            else:
                value = smart_unicode(value)
        return Field.get_db_prep_save(self, value)

    def get_manipulator_field_objs(self):
        return [oldforms.TimeField]

    def flatten_data(self,follow, obj = None):
        val = self._get_val_from_obj(obj)
        return {self.attname: (val is not None and val.strftime("%H:%M:%S") or '')}

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.TimeField}
        defaults.update(kwargs)
        return super(TimeField, self).formfield(**defaults)

class URLField(CharField):
    def __init__(self, verbose_name=None, name=None, verify_exists=True, **kwargs):
        kwargs['max_length'] = kwargs.get('max_length', 200)
        if verify_exists:
            kwargs.setdefault('validator_list', []).append(validators.isExistingURL)
        self.verify_exists = verify_exists
        CharField.__init__(self, verbose_name, name, **kwargs)

    def get_manipulator_field_objs(self):
        return [oldforms.URLField]

    def formfield(self, **kwargs):
        defaults = {'form_class': forms.URLField, 'verify_exists': self.verify_exists}
        defaults.update(kwargs)
        return super(URLField, self).formfield(**defaults)

class USStateField(Field):
    def get_manipulator_field_objs(self):
        return [oldforms.USStateField]

    def get_internal_type(self):
        return "USStateField"

    def formfield(self, **kwargs):
        from django.contrib.localflavor.us.forms import USStateSelect
        defaults = {'widget': USStateSelect}
        defaults.update(kwargs)
        return super(USStateField, self).formfield(**defaults)

class XMLField(TextField):
    def __init__(self, verbose_name=None, name=None, schema_path=None, **kwargs):
        self.schema_path = schema_path
        Field.__init__(self, verbose_name, name, **kwargs)

    def get_manipulator_field_objs(self):
        return [curry(oldforms.XMLLargeTextField, schema_path=self.schema_path)]

class OrderingField(IntegerField):
    empty_strings_allowed=False
    def __init__(self, with_respect_to, **kwargs):
        self.wrt = with_respect_to
        kwargs['null'] = True
        IntegerField.__init__(self, **kwargs )

    def get_manipulator_fields(self, opts, manipulator, change, name_prefix='', rel=False, follow=True):
        return [oldforms.HiddenField(name_prefix + self.name)]