import re

from django.template import Context, loader
from django import newforms as forms
from django.newforms.forms import DeclarativeFieldsMetaclass

replace_res = [re.compile('(<[^>]+) (%s=\\\\"[a-zA-Z0-9-_]+\.)#(\\\\")([^<]*>)' % s) for s in ('id', 'for', 'name')]

# This differs a bit from django.template.defaultfilters.addslashes,
# see http://code.djangoproject.com/ticket/2986
def addslashes(value):
    "Adds slashes - useful for passing strings to JavaScript, for example."
    return value.replace('\\', '\\\\').replace('"', '\\"').replace("'", "\\'").replace('\n', '\\n').replace('\r', '\\r')

class FormCollection(list):
    def are_valid(self):
        for form in self:
            if not form.is_valid():
                return False
        return True

class BaseForm(forms.BaseForm):
    def __init__(self, *args, **kwargs):
        self.postfix = kwargs.pop('postfix', '#')
        kwargs['prefix'] = kwargs.get('prefix', '') or getattr(self, 'PREFIX', '')
        self.template = kwargs.pop('template', '') or getattr(self, 'TEMPLATE', '')
        self.core = kwargs.pop('core', '') or getattr(self, 'CORE', [])
        self.id = kwargs.pop('id', '')
        super(BaseForm, self).__init__(*args, **kwargs)
    def add_prefix(self, field_name):
        prefixed = super(BaseForm, self).add_prefix(field_name)
        return self.postfix and ('%s.%s' % (prefixed, self.postfix)) or prefixed
    def header(self):
        return u'<input type="hidden" name="%s" value="%s" />' % (self.add_prefix('id'), self.id)
    def render(self, how):
        return u'%s%s' % (self.header(), getattr(self, how)())
    def render_js(self, how):
        data = addslashes(self.render(how))
        for replace_re in replace_res:
            data = re.sub(replace_re, '\\1 \\2\', FormId, \'\\3\\4', data)
        return u"['%s']" % data
    def from_template(self, extra_context={}):
        template = loader.get_template(self.template)
        context = Context(dict([('form', self)]+extra_context.items()))
        return template.render(context)

    @classmethod
    def get_forms(cls, request, kwargs={}):
        form = cls(request.POST, **kwargs)
        id_name = form.add_prefix('id')

        form_ids = [key[len(id_name)-1:] for key in request.POST.keys() if key.startswith(id_name[:-1])]

        forms = FormCollection()

        for form_id in form_ids:
            new_kwargs = dict(kwargs.items() + 
                    [('postfix', form_id), ('id', request.POST[id_name[:-1]+form_id])])
            form = cls(request.POST, **new_kwargs)
            if not form.id:
                # Ignore empty forms where no core field is specified
                core_available = False
                for core in form.core:
                    if request.POST.get(form.add_prefix(core), ''):
                        core_available = True
                        break
            if form.id or core_available:
                forms.append(form)

        return forms

class Form(BaseForm):
    __metaclass__ = DeclarativeFieldsMetaclass