from django import template, forms

from django.contrib.admin.views.decorators import staff_member_required

from django.template import loader

from django.shortcuts import render_to_response

from django.contrib.sites.models import Site

from django.conf import settings

from django.utils.importlib import import_module

from django.utils.translation import ugettext_lazy as _

from django.contrib import messages

def template_validator(request):

    """

    Displays the template validator form, which finds and displays template

    syntax errors.

    """

    # get a dict of {site_id : settings_module} for the validator

    settings_modules = {}

    for mod in settings.ADMIN_FOR:

        settings_module = import_module(mod)

        settings_modules[settings_module.SITE_ID] = settings_module

    site_list = Site.objects.in_bulk(settings_modules.keys()).values()

    if request.POST:

        form = TemplateValidatorForm(settings_modules, site_list,

                                     data=request.POST)

        if form.is_valid():

            messages.info(request, 'The template is valid.')

    else:

        form = TemplateValidatorForm(settings_modules, site_list)

    return render_to_response('admin/template_validator.html', {

        'title': 'Template validator',

        'form': form,

    }, context_instance=template.RequestContext(request))

template_validator = staff_member_required(template_validator)

class TemplateValidatorForm(forms.Form):

    site = forms.ChoiceField(_('site'))

    template = forms.CharField(

        _('template'), widget=forms.Textarea({'rows': 25, 'cols': 80}))

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

        self.settings_modules = settings_modules

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

        self.fields['site'].choices = [(s.id, s.name) for s in site_list]

    def clean_template(self):

        # Get the settings module. If the site isn't set, we don't raise an

        # error since the site field will.

        try:

            site_id = int(self.cleaned_data.get('site', None))

        except (ValueError, TypeError):

            return

        settings_module = self.settings_modules.get(site_id, None)

        if settings_module is None:

            return

        # So that inheritance works in the site's context, register a new

        # function for "extends" that uses the site's TEMPLATE_DIRS instead.

        def new_do_extends(parser, token):

            node = loader.do_extends(parser, token)

            node.template_dirs = settings_module.TEMPLATE_DIRS

            return node

        register = template.Library()

        register.tag('extends', new_do_extends)

        template.builtins.append(register)

        # Now validate the template using the new TEMPLATE_DIRS, making sure to

        # reset the extends function in any case.

        error = None

        template_string = self.cleaned_data['template']

        try:

            tmpl = loader.get_template_from_string(template_string)

            tmpl.render(template.Context({}))

        except template.TemplateSyntaxError, e:

            error = e

        template.builtins.remove(register)

        if error:

            raise forms.ValidationError(e.args)