from forms import Form

from django.utils.encoding import StrAndUnicode

from django.utils.safestring import mark_safe

from django.utils.translation import ugettext as _

from fields import IntegerField, BooleanField

from widgets import Media, HiddenInput

from util import ErrorList, ValidationError

__all__ = ('BaseFormSet', 'all_valid')

# special field names

TOTAL_FORM_COUNT = 'TOTAL_FORMS'

INITIAL_FORM_COUNT = 'INITIAL_FORMS'

ORDERING_FIELD_NAME = 'ORDER'

DELETION_FIELD_NAME = 'DELETE'

class ManagementForm(Form):

    """

    ``ManagementForm`` is used to keep track of how many form instances

    are displayed on the page. If adding new forms via javascript, you should

    increment the count field of this form as well.

    """

    def __init__(self, *args, **kwargs):

        self.base_fields[TOTAL_FORM_COUNT] = IntegerField(widget=HiddenInput)

        self.base_fields[INITIAL_FORM_COUNT] = IntegerField(widget=HiddenInput)

        super(ManagementForm, self).__init__(*args, **kwargs)

class BaseFormSet(StrAndUnicode):

    """

    A collection of instances of the same Form class.

    """

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

                 initial=None, error_class=ErrorList):

        self.is_bound = data is not None or files is not None

        self.prefix = prefix or 'form'

        self.auto_id = auto_id

        self.data = data

        self.files = files

        self.initial = initial

        self.error_class = error_class

        self._errors = None

        self._non_form_errors = None

        # initialization is different depending on whether we recieved data, initial, or nothing

        if data or files:

            self.management_form = ManagementForm(data, auto_id=self.auto_id, prefix=self.prefix)

            if self.management_form.is_valid():

                self._total_form_count = self.management_form.cleaned_data[TOTAL_FORM_COUNT]

                self._initial_form_count = self.management_form.cleaned_data[INITIAL_FORM_COUNT]

            else:

                raise ValidationError('ManagementForm data is missing or has been tampered with')

        else:

            if initial:

                self._initial_form_count = len(initial)

                if self._initial_form_count > self.max_num and self.max_num > 0:

                    self._initial_form_count = self.max_num

                self._total_form_count = self._initial_form_count + self.extra

            else:

                self._initial_form_count = 0

                self._total_form_count = self.extra

            if self._total_form_count > self.max_num and self.max_num > 0:

                self._total_form_count = self.max_num

            initial = {TOTAL_FORM_COUNT: self._total_form_count,

                       INITIAL_FORM_COUNT: self._initial_form_count}

            self.management_form = ManagementForm(initial=initial, auto_id=self.auto_id, prefix=self.prefix)

        # construct the forms in the formset

        self._construct_forms()

    def __unicode__(self):

        return self.as_table()

    def _construct_forms(self):

        # instantiate all the forms and put them in self.forms

        self.forms = []

        for i in xrange(self._total_form_count):

            self.forms.append(self._construct_form(i))

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

        """

        Instantiates and returns the i-th form instance in a formset.

        """

        defaults = {'auto_id': self.auto_id, 'prefix': self.add_prefix(i)}

        if self.data or self.files:

            defaults['data'] = self.data

            defaults['files'] = self.files

        if self.initial:

            try:

                defaults['initial'] = self.initial[i]

            except IndexError:

                pass

        # Allow extra forms to be empty.

        if i >= self._initial_form_count:

            defaults['empty_permitted'] = True

        defaults.update(kwargs)

        form = self.form(**defaults)

        self.add_fields(form, i)

        return form

    def _get_initial_forms(self):

        """Return a list of all the intial forms in this formset."""

        return self.forms[:self._initial_form_count]

    initial_forms = property(_get_initial_forms)

    def _get_extra_forms(self):

        """Return a list of all the extra forms in this formset."""

        return self.forms[self._initial_form_count:]

    extra_forms = property(_get_extra_forms)

    # Maybe this should just go away?

    def _get_cleaned_data(self):

        """

        Returns a list of form.cleaned_data dicts for every form in self.forms.

        """

        if not self.is_valid():

            raise AttributeError("'%s' object has no attribute 'cleaned_data'" % self.__class__.__name__)

        return [form.cleaned_data for form in self.forms]

    cleaned_data = property(_get_cleaned_data)

    def _get_deleted_forms(self):

        """

        Returns a list of forms that have been marked for deletion. Raises an 

        AttributeError if deletion is not allowed.

        """

        if not self.is_valid() or not self.can_delete:

            raise AttributeError("'%s' object has no attribute 'deleted_forms'" % self.__class__.__name__)

        # construct _deleted_form_indexes which is just a list of form indexes

        # that have had their deletion widget set to True

        if not hasattr(self, '_deleted_form_indexes'):

            self._deleted_form_indexes = []

            for i in range(0, self._total_form_count):

                form = self.forms[i]

                # if this is an extra form and hasn't changed, don't consider it

                if i >= self._initial_form_count and not form.has_changed():

                    continue

                if form.cleaned_data[DELETION_FIELD_NAME]:

                    self._deleted_form_indexes.append(i)

        return [self.forms[i] for i in self._deleted_form_indexes]

    deleted_forms = property(_get_deleted_forms)

    def _get_ordered_forms(self):

        """

        Returns a list of form in the order specified by the incoming data.

        Raises an AttributeError if deletion is not allowed.

        """

        if not self.is_valid() or not self.can_order:

            raise AttributeError("'%s' object has no attribute 'ordered_forms'" % self.__class__.__name__)

        # Construct _ordering, which is a list of (form_index, order_field_value)

        # tuples. After constructing this list, we'll sort it by order_field_value

        # so we have a way to get to the form indexes in the order specified

        # by the form data.

        if not hasattr(self, '_ordering'):

            self._ordering = []

            for i in range(0, self._total_form_count):

                form = self.forms[i]

                # if this is an extra form and hasn't changed, don't consider it

                if i >= self._initial_form_count and not form.has_changed():

                    continue

                # don't add data marked for deletion to self.ordered_data

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

                    continue

                # A sort function to order things numerically ascending, but

                # None should be sorted below anything else. Allowing None as

                # a comparison value makes it so we can leave ordering fields

                # blamk.

                def compare_ordering_values(x, y):

                    if x[1] is None:

                        return 1

                    if y[1] is None:

                        return -1

                    return x[1] - y[1]

                self._ordering.append((i, form.cleaned_data[ORDERING_FIELD_NAME]))

            # After we're done populating self._ordering, sort it.

            self._ordering.sort(compare_ordering_values)

        # Return a list of form.cleaned_data dicts in the order spcified by

        # the form data.

        return [self.forms[i[0]] for i in self._ordering]

    ordered_forms = property(_get_ordered_forms)

    def non_form_errors(self):

        """

        Returns an ErrorList of errors that aren't associated with a particular

        form -- i.e., from formset.clean(). Returns an empty ErrorList if there

        are none.

        """

        if self._non_form_errors is not None:

            return self._non_form_errors

        return self.error_class()

    def _get_errors(self):

        """

        Returns a list of form.errors for every form in self.forms.

        """

        if self._errors is None:

            self.full_clean()

        return self._errors

    errors = property(_get_errors)

    def is_valid(self):

        """

        Returns True if form.errors is empty for every form in self.forms.

        """

        if not self.is_bound:

            return False

        # We loop over every form.errors here rather than short circuiting on the

        # first failure to make sure validation gets triggered for every form.

        forms_valid = True

        for errors in self.errors:

            if bool(errors):

                forms_valid = False

        return forms_valid and not bool(self.non_form_errors())

    def full_clean(self):

        """

        Cleans all of self.data and populates self._errors.

        """

        self._errors = []

        if not self.is_bound: # Stop further processing.

            return

        for i in range(0, self._total_form_count):

            form = self.forms[i]

            self._errors.append(form.errors)

        # Give self.clean() a chance to do cross-form validation.

        try:

            self.clean()

        except ValidationError, e:

            self._non_form_errors = e.messages

    def clean(self):

        """

        Hook for doing any extra formset-wide cleaning after Form.clean() has

        been called on every form. Any ValidationError raised by this method

        will not be associated with a particular form; it will be accesible

        via formset.non_form_errors()

        """

        pass

    def add_fields(self, form, index):

        """A hook for adding extra fields on to each form instance."""

        if self.can_order:

            # Only pre-fill the ordering field for initial forms.

            if index < self._initial_form_count:

                form.fields[ORDERING_FIELD_NAME] = IntegerField(label=_(u'Order'), initial=index+1, required=False)

            else:

                form.fields[ORDERING_FIELD_NAME] = IntegerField(label=_(u'Order'), required=False)

        if self.can_delete:

            form.fields[DELETION_FIELD_NAME] = BooleanField(label=_(u'Delete'), required=False)

    def add_prefix(self, index):

        return '%s-%s' % (self.prefix, index)

    def is_multipart(self):

        """

        Returns True if the formset needs to be multipart-encrypted, i.e. it

        has FileInput. Otherwise, False.

        """

        return self.forms[0].is_multipart()

    def _get_media(self):

        # All the forms on a FormSet are the same, so you only need to

        # interrogate the first form for media.

        if self.forms:

            return self.forms[0].media

        else:

            return Media()

    media = property(_get_media)

    def as_table(self):

        "Returns this formset rendered as HTML <tr>s -- excluding the <table></table>."

        # XXX: there is no semantic division between forms here, there

        # probably should be. It might make sense to render each form as a

        # table row with each field as a td.

        forms = u' '.join([form.as_table() for form in self.forms])

        return mark_safe(u'\n'.join([unicode(self.management_form), forms]))

def formset_factory(form, formset=BaseFormSet, extra=1, can_order=False,

                    can_delete=False, max_num=0):

    """Return a FormSet for the given form class."""

    attrs = {'form': form, 'extra': extra,

             'can_order': can_order, 'can_delete': can_delete,

             'max_num': max_num}

    return type(form.__name__ + 'FormSet', (formset,), attrs)

def all_valid(formsets):

    """Returns true if every formset in formsets is valid."""

    valid = True

    for formset in formsets:

        if not formset.is_valid():

            valid = False

    return valid