"""

Helper functions for creating Form classes from Django models

and database field objects.

"""

from django.utils.encoding import smart_unicode

from django.utils.datastructures import SortedDict

from django.utils.text import get_text_list, capfirst

from django.utils.translation import ugettext_lazy as _

from util import ValidationError, ErrorList

from forms import BaseForm, get_declared_fields

from fields import Field, ChoiceField, IntegerField, EMPTY_VALUES

from widgets import Select, SelectMultiple, HiddenInput, MultipleHiddenInput

from widgets import media_property

from formsets import BaseFormSet, formset_factory, DELETION_FIELD_NAME

try:

    set

except NameError:

    from sets import Set as set     # Python 2.3 fallback

__all__ = (

    'ModelForm', 'BaseModelForm', 'model_to_dict', 'fields_for_model',

    'save_instance', 'form_for_fields', 'ModelChoiceField',

    'ModelMultipleChoiceField',

)

def save_instance(form, instance, fields=None, fail_message='saved',

                  commit=True, exclude=None):

    """

    Saves bound Form ``form``'s cleaned_data into model instance ``instance``.

    If commit=True, then the changes to ``instance`` will be saved to the

    database. Returns ``instance``.

    """

    from django.db import models

    opts = instance._meta

    if form.errors:

        raise ValueError("The %s could not be %s because the data didn't"

                         " validate." % (opts.object_name, fail_message))

    cleaned_data = form.cleaned_data

    for f in opts.fields:

        if not f.editable or isinstance(f, models.AutoField) \

                or not f.name in cleaned_data:

            continue

        if fields and f.name not in fields:

            continue

        if exclude and f.name in exclude:

            continue

        f.save_form_data(instance, cleaned_data[f.name])

    # Wrap up the saving of m2m data as a function.

    def save_m2m():

        opts = instance._meta

        cleaned_data = form.cleaned_data

        for f in opts.many_to_many:

            if fields and f.name not in fields:

                continue

            if f.name in cleaned_data:

                f.save_form_data(instance, cleaned_data[f.name])

    if commit:

        # If we are committing, save the instance and the m2m data immediately.

        instance.save()

        save_m2m()

    else:

        # We're not committing. Add a method to the form to allow deferred

        # saving of m2m data.

        form.save_m2m = save_m2m

    return instance

def make_model_save(model, fields, fail_message):

    """Returns the save() method for a Form."""

    def save(self, commit=True):

        return save_instance(self, model(), fields, fail_message, commit)

    return save

def make_instance_save(instance, fields, fail_message):

    """Returns the save() method for a Form."""

    def save(self, commit=True):

        return save_instance(self, instance, fields, fail_message, commit)

    return save

def form_for_fields(field_list):

    """

    Returns a Form class for the given list of Django database field instances.

    """

    fields = SortedDict([(f.name, f.formfield())

                         for f in field_list if f.editable])

    return type('FormForFields', (BaseForm,), {'base_fields': fields})

# ModelForms #################################################################

def model_to_dict(instance, fields=None, exclude=None):

    """

    Returns a dict containing the data in ``instance`` suitable for passing as

    a Form's ``initial`` keyword argument.

    ``fields`` is an optional list of field names. If provided, only the named

    fields will be included in the returned dict.

    ``exclude`` is an optional list of field names. If provided, the named

    fields will be excluded from the returned dict, even if they are listed in

    the ``fields`` argument.

    """

    # avoid a circular import

    from django.db.models.fields.related import ManyToManyField, OneToOneField

    opts = instance._meta

    data = {}

    for f in opts.fields + opts.many_to_many:

        if not f.editable:

            continue

        if fields and not f.name in fields:

            continue

        if exclude and f.name in exclude:

            continue

        if isinstance(f, ManyToManyField):

            # If the object doesn't have a primry key yet, just use an empty

            # list for its m2m fields. Calling f.value_from_object will raise

            # an exception.

            if instance.pk is None:

                data[f.name] = []

            else:

                # MultipleChoiceWidget needs a list of pks, not object instances.

                data[f.name] = [obj.pk for obj in f.value_from_object(instance)]

        else:

            data[f.name] = f.value_from_object(instance)

    return data

def fields_for_model(model, fields=None, exclude=None, formfield_callback=lambda f: f.formfield()):

    """

    Returns a ``SortedDict`` containing form fields for the given model.

    ``fields`` is an optional list of field names. If provided, only the named

    fields will be included in the returned fields.

    ``exclude`` is an optional list of field names. If provided, the named

    fields will be excluded from the returned fields, even if they are listed

    in the ``fields`` argument.

    """

    # TODO: if fields is provided, it would be nice to return fields in that order

    field_list = []

    opts = model._meta

    for f in opts.fields + opts.many_to_many:

        if not f.editable:

            continue

        if fields and not f.name in fields:

            continue

        if exclude and f.name in exclude:

            continue

        formfield = formfield_callback(f)

        if formfield:

            field_list.append((f.name, formfield))

    return SortedDict(field_list)

class ModelFormOptions(object):

    def __init__(self, options=None):

        self.model = getattr(options, 'model', None)

        self.fields = getattr(options, 'fields', None)

        self.exclude = getattr(options, 'exclude', None)

class ModelFormMetaclass(type):

    def __new__(cls, name, bases, attrs):

        formfield_callback = attrs.pop('formfield_callback',

                lambda f: f.formfield())

        try:

            parents = [b for b in bases if issubclass(b, ModelForm)]

        except NameError:

            # We are defining ModelForm itself.

            parents = None

        declared_fields = get_declared_fields(bases, attrs, False)

        new_class = super(ModelFormMetaclass, cls).__new__(cls, name, bases,

                attrs)

        if not parents:

            return new_class

        if 'media' not in attrs:

            new_class.media = media_property(new_class)

        opts = new_class._meta = ModelFormOptions(getattr(new_class, 'Meta', None))

        if opts.model:

            # If a model is defined, extract form fields from it.

            fields = fields_for_model(opts.model, opts.fields,

                                      opts.exclude, formfield_callback)

            # Override default model fields with any custom declared ones

            # (plus, include all the other declared fields).

            fields.update(declared_fields)

        else:

            fields = declared_fields

        new_class.declared_fields = declared_fields

        new_class.base_fields = fields

        return new_class

class BaseModelForm(BaseForm):

    def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,

                 initial=None, error_class=ErrorList, label_suffix=':',

                 empty_permitted=False, instance=None):

        opts = self._meta

        if instance is None:

            # if we didn't get an instance, instantiate a new one

            self.instance = opts.model()

            object_data = {}

        else:

            self.instance = instance

            object_data = model_to_dict(instance, opts.fields, opts.exclude)

        # if initial was provided, it should override the values from instance

        if initial is not None:

            object_data.update(initial)

        super(BaseModelForm, self).__init__(data, files, auto_id, prefix, object_data,

                                            error_class, label_suffix, empty_permitted)

    def clean(self):

        self.validate_unique()

        return self.cleaned_data

    def validate_unique(self):

        from django.db.models.fields import FieldDoesNotExist

        # Gather a list of checks to perform. Since this is a ModelForm, some

        # fields may have been excluded; we can't perform a unique check on a

        # form that is missing fields involved in that check.

        unique_checks = []

        for check in self.instance._meta.unique_together[:]:

            fields_on_form = [field for field in check if field in self.fields]

            if len(fields_on_form) == len(check):

                unique_checks.append(check)

        form_errors = []

        # Gather a list of checks for fields declared as unique and add them to

        # the list of checks. Again, skip fields not on the form.

        for name, field in self.fields.items():

            try:

                f = self.instance._meta.get_field_by_name(name)[0]

            except FieldDoesNotExist:

                # This is an extra field that's not on the ModelForm, ignore it

                continue

            # MySQL can't handle ... WHERE pk IS NULL, so make sure we

            # don't generate queries of that form.

            is_null_pk = f.primary_key and self.cleaned_data[name] is None

            if name in self.cleaned_data and f.unique and not is_null_pk:

                unique_checks.append((name,))

        # Don't run unique checks on fields that already have an error.

        unique_checks = [check for check in unique_checks if not [x in self._errors for x in check if x in self._errors]]

        bad_fields = set()

        for unique_check in unique_checks:

            # Try to look up an existing object with the same values as this

            # object's values for all the unique field.

            lookup_kwargs = {}

            for field_name in unique_check:

                lookup_kwargs[field_name] = self.cleaned_data[field_name]

            qs = self.instance.__class__._default_manager.filter(**lookup_kwargs)

            # Exclude the current object from the query if we are editing an

            # instance (as opposed to creating a new one)

            if self.instance.pk is not None:

                qs = qs.exclude(pk=self.instance.pk)

            # This cute trick with extra/values is the most efficient way to

            # tell if a particular query returns any results.

            if qs.extra(select={'a': 1}).values('a').order_by():

                model_name = capfirst(self.instance._meta.verbose_name)

                # A unique field

                if len(unique_check) == 1:

                    field_name = unique_check[0]

                    field_label = self.fields[field_name].label

                    # Insert the error into the error dict, very sneaky

                    self._errors[field_name] = ErrorList([

                        _(u"%(model_name)s with this %(field_label)s already exists.") % \

                        {'model_name': unicode(model_name),

                         'field_label': unicode(field_label)}

                    ])

                # unique_together

                else:

                    field_labels = [self.fields[field_name].label for field_name in unique_check]

                    field_labels = get_text_list(field_labels, _('and'))

                    form_errors.append(

                        _(u"%(model_name)s with this %(field_label)s already exists.") % \

                        {'model_name': unicode(model_name),

                         'field_label': unicode(field_labels)}

                    )

                # Mark these fields as needing to be removed from cleaned data

                # later.

                for field_name in unique_check:

                    bad_fields.add(field_name)

        for field_name in bad_fields:

            del self.cleaned_data[field_name]

        if form_errors:

            # Raise the unique together errors since they are considered

            # form-wide.

            raise ValidationError(form_errors)

    def save(self, commit=True):

        """

        Saves this ``form``'s cleaned_data into model instance

        ``self.instance``.

        If commit=True, then the changes to ``instance`` will be saved to the

        database. Returns ``instance``.

        """

        if self.instance.pk is None:

            fail_message = 'created'

        else:

            fail_message = 'changed'

        return save_instance(self, self.instance, self._meta.fields, fail_message, commit)

class ModelForm(BaseModelForm):

    __metaclass__ = ModelFormMetaclass

def modelform_factory(model, form=ModelForm, fields=None, exclude=None,

                       formfield_callback=lambda f: f.formfield()):

    # HACK: we should be able to construct a ModelForm without creating

    # and passing in a temporary inner class

    class Meta:

        pass

    setattr(Meta, 'model', model)

    setattr(Meta, 'fields', fields)

    setattr(Meta, 'exclude', exclude)

    class_name = model.__name__ + 'Form'

    return ModelFormMetaclass(class_name, (form,), {'Meta': Meta,

                              'formfield_callback': formfield_callback})

# ModelFormSets ##############################################################

class BaseModelFormSet(BaseFormSet):

    """

    A ``FormSet`` for editing a queryset and/or adding new objects to it.

    """

    model = None

    def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,

                 queryset=None, **kwargs):

        self.queryset = queryset

        defaults = {'data': data, 'files': files, 'auto_id': auto_id, 'prefix': prefix}

        defaults['initial'] = [model_to_dict(obj) for obj in self.get_queryset()]

        defaults.update(kwargs)

        super(BaseModelFormSet, self).__init__(**defaults)

    def _construct_form(self, i, **kwargs):

        if i < self._initial_form_count:

            kwargs['instance'] = self.get_queryset()[i]

        return super(BaseModelFormSet, self)._construct_form(i, **kwargs)

    def get_queryset(self):

        if not hasattr(self, '_queryset'):

            if self.queryset is not None:

                qs = self.queryset

            else:

                qs = self.model._default_manager.get_query_set()

            if self.max_num > 0:

                self._queryset = qs[:self.max_num]

            else:

                self._queryset = qs

        return self._queryset

    def save_new(self, form, commit=True):

        """Saves and returns a new model instance for the given form."""

        return save_instance(form, self.model(), exclude=[self._pk_field.name], commit=commit)

    def save_existing(self, form, instance, commit=True):

        """Saves and returns an existing model instance for the given form."""

        return save_instance(form, instance, exclude=[self._pk_field.name], commit=commit)

    def save(self, commit=True):

        """Saves model instances for every form, adding and changing instances

        as necessary, and returns the list of instances.

        """

        if not commit:

            self.saved_forms = []

            def save_m2m():

                for form in self.saved_forms:

                    form.save_m2m()

            self.save_m2m = save_m2m

        return self.save_existing_objects(commit) + self.save_new_objects(commit)

    def save_existing_objects(self, commit=True):

        self.changed_objects = []

        self.deleted_objects = []

        if not self.get_queryset():

            return []

        # Put the objects from self.get_queryset into a dict so they are easy to lookup by pk

        existing_objects = {}

        for obj in self.get_queryset():

            existing_objects[obj.pk] = obj

        saved_instances = []

        for form in self.initial_forms:

            obj = existing_objects[form.cleaned_data[self._pk_field.name]]

            if self.can_delete and form.cleaned_data[DELETION_FIELD_NAME]:

                self.deleted_objects.append(obj)

                obj.delete()

            else:

                if form.changed_data:

                    self.changed_objects.append((obj, form.changed_data))

                    saved_instances.append(self.save_existing(form, obj, commit=commit))

                    if not commit:

                        self.saved_forms.append(form)

        return saved_instances

    def save_new_objects(self, commit=True):

        self.new_objects = []

        for form in self.extra_forms:

            if not form.has_changed():

                continue

            # If someone has marked an add form for deletion, don't save the

            # object.

            if self.can_delete and form.cleaned_data[DELETION_FIELD_NAME]:

                continue

            self.new_objects.append(self.save_new(form, commit=commit))

            if not commit:

                self.saved_forms.append(form)

        return self.new_objects

    def add_fields(self, form, index):

        """Add a hidden field for the object's primary key."""

        from django.db.models import AutoField

        self._pk_field = pk = self.model._meta.pk

        if pk.auto_created or isinstance(pk, AutoField):

            form.fields[self._pk_field.name] = IntegerField(required=False, widget=HiddenInput)

        super(BaseModelFormSet, self).add_fields(form, index)

def modelformset_factory(model, form=ModelForm, formfield_callback=lambda f: f.formfield(),

                         formset=BaseModelFormSet,

                         extra=1, can_delete=False, can_order=False,

                         max_num=0, fields=None, exclude=None):

    """

    Returns a FormSet class for the given Django model class.

    """

    form = modelform_factory(model, form=form, fields=fields, exclude=exclude,

                             formfield_callback=formfield_callback)

    FormSet = formset_factory(form, formset, extra=extra, max_num=max_num,

                              can_order=can_order, can_delete=can_delete)

    FormSet.model = model

    return FormSet

# InlineFormSets #############################################################

class BaseInlineFormSet(BaseModelFormSet):

    """A formset for child objects related to a parent."""

    def __init__(self, data=None, files=None, instance=None,

                 save_as_new=False, prefix=None):

        from django.db.models.fields.related import RelatedObject

        self.instance = instance

        self.save_as_new = save_as_new

        # is there a better way to get the object descriptor?

        self.rel_name = RelatedObject(self.fk.rel.to, self.model, self.fk).get_accessor_name()

        super(BaseInlineFormSet, self).__init__(data, files, prefix=prefix or self.rel_name)

    def _construct_forms(self):

        if self.save_as_new:

            self._total_form_count = self._initial_form_count

            self._initial_form_count = 0

        super(BaseInlineFormSet, self)._construct_forms()

    def _construct_form(self, i, **kwargs):

        form = super(BaseInlineFormSet, self)._construct_form(i, **kwargs)

        if self.save_as_new:

            # Remove the primary key from the form's data, we are only

            # creating new instances

            form.data[form.add_prefix(self._pk_field.name)] = None

        return form

    def get_queryset(self):

        """

        Returns this FormSet's queryset, but restricted to children of

        self.instance

        """

        kwargs = {self.fk.name: self.instance}

        return self.model._default_manager.filter(**kwargs)

    def save_new(self, form, commit=True):

        kwargs = {self.fk.get_attname(): self.instance.pk}

        new_obj = self.model(**kwargs)

        return save_instance(form, new_obj, exclude=[self._pk_field.name], commit=commit)

    def add_fields(self, form, index):

        super(BaseInlineFormSet, self).add_fields(form, index)

        if self._pk_field == self.fk:

            form.fields[self._pk_field.name] = IntegerField(required=False, widget=HiddenInput)

def _get_foreign_key(parent_model, model, fk_name=None):

    """

    Finds and returns the ForeignKey from model to parent if there is one.

    If fk_name is provided, assume it is the name of the ForeignKey field.

    """

    # avoid circular import

    from django.db.models import ForeignKey

    opts = model._meta

    if fk_name:

        fks_to_parent = [f for f in opts.fields if f.name == fk_name]

        if len(fks_to_parent) == 1:

            fk = fks_to_parent[0]

            if not isinstance(fk, ForeignKey) or \

                    (fk.rel.to != parent_model and

                     fk.rel.to not in parent_model._meta.get_parent_list()):

                raise Exception("fk_name '%s' is not a ForeignKey to %s" % (fk_name, parent_model))

        elif len(fks_to_parent) == 0:

            raise Exception("%s has no field named '%s'" % (model, fk_name))

    else:

        # Try to discover what the ForeignKey from model to parent_model is

        fks_to_parent = [

            f for f in opts.fields

            if isinstance(f, ForeignKey)

            and (f.rel.to == parent_model

                or f.rel.to in parent_model._meta.get_parent_list())

        ]

        if len(fks_to_parent) == 1:

            fk = fks_to_parent[0]

        elif len(fks_to_parent) == 0:

            raise Exception("%s has no ForeignKey to %s" % (model, parent_model))

        else:

            raise Exception("%s has more than 1 ForeignKey to %s" % (model, parent_model))

    return fk

def inlineformset_factory(parent_model, model, form=ModelForm,

                          formset=BaseInlineFormSet, fk_name=None,

                          fields=None, exclude=None,

                          extra=3, can_order=False, can_delete=True, max_num=0,

                          formfield_callback=lambda f: f.formfield()):