Hacked around the descriptor issues, since there were only three.

[philo.git] / philo / models / nodes.py

from inspect import getargspec

from django.contrib.contenttypes import generic
from django.contrib.contenttypes.models import ContentType
from django.contrib.sites.models import Site, RequestSite
from django.core.exceptions import ValidationError
from django.core.servers.basehttp import FileWrapper
from django.core.urlresolvers import resolve, clear_url_caches, reverse, NoReverseMatch
from django.db import models
from django.http import HttpResponse, HttpResponseServerError, HttpResponseRedirect, Http404
from django.utils.encoding import smart_str

from philo.exceptions import MIDDLEWARE_NOT_CONFIGURED, ViewCanNotProvideSubpath, ViewDoesNotProvideSubpaths
from philo.models.base import TreeEntity, Entity, register_value_model
from philo.models.fields import JSONField
from philo.utils import ContentTypeSubclassLimiter
from philo.utils.entities import LazyPassthroughAttributeMapper
from philo.signals import view_about_to_render, view_finished_rendering


__all__ = ('Node', 'View', 'MultiView', 'Redirect', 'File')


_view_content_type_limiter = ContentTypeSubclassLimiter(None)


class Node(TreeEntity):
        """
        :class:`Node`\ s are the basic building blocks of a website using Philo. They define the URL hierarchy and connect each URL to a :class:`View` subclass instance which is used to generate an HttpResponse.
        
        """
        view_content_type = models.ForeignKey(ContentType, related_name='node_view_set', limit_choices_to=_view_content_type_limiter)
        view_object_id = models.PositiveIntegerField()
        #: :class:`GenericForeignKey` to a non-abstract subclass of :class:`View`
        view = generic.GenericForeignKey('view_content_type', 'view_object_id')
        
        @property
        def accepts_subpath(self):
                """A property shortcut for :attr:`self.view.accepts_subpath <View.accepts_subpath>`"""
                if self.view:
                        return self.view.accepts_subpath
                return False
        
        def handles_subpath(self, subpath):
                return self.view.handles_subpath(subpath)
        
        def render_to_response(self, request, extra_context=None):
                """This is a shortcut method for :meth:`View.render_to_response`"""
                return self.view.render_to_response(request, extra_context)
        
        def get_absolute_url(self, request=None, with_domain=False, secure=False):
                """
                This is essentially a shortcut for calling :meth:`construct_url` without a subpath.
                
                :returns: The absolute url of the node on the current site.
                
                """
                return self.construct_url(request=request, with_domain=with_domain, secure=secure)
        
        def construct_url(self, subpath="/", request=None, with_domain=False, secure=False):
                """
                This method will do its best to construct a URL based on the Node's location. If with_domain is True, that URL will include a domain and a protocol; if secure is True as well, the protocol will be https. The request will be used to construct a domain in cases where a call to :meth:`Site.objects.get_current` fails.
                
                Node urls will not contain a trailing slash unless a subpath is provided which ends with a trailing slash. Subpaths are expected to begin with a slash, as if returned by :func:`django.core.urlresolvers.reverse`.
                
                :meth:`construct_url` may raise the following exceptions:
                
                - :class:`NoReverseMatch` if "philo-root" is not reversable -- for example, if :mod:`philo.urls` is not included anywhere in your urlpatterns.
                - :class:`Site.DoesNotExist <ObjectDoesNotExist>` if with_domain is True but no :class:`Site` or :class:`RequestSite` can be built.
                - :class:`~philo.exceptions.AncestorDoesNotExist` if the root node of the site isn't an ancestor of the node constructing the URL.
                
                :param string subpath: The subpath to be constructed beyond beyond the node's URL.
                :param request: :class:`HttpRequest` instance. Will be used to construct a :class:`RequestSite` if :meth:`Site.objects.get_current` fails.
                :param with_domain: Whether the constructed URL should include a domain name and protocol.
                :param secure: Whether the protocol, if included, should be http:// or https://.
                :returns: A constructed url for accessing the given subpath of the current node instance.
                
                """
                # Try reversing philo-root first, since we can't do anything if that fails.
                root_url = reverse('philo-root')
                
                try:
                        current_site = Site.objects.get_current()
                except Site.DoesNotExist:
                        if request is not None:
                                current_site = RequestSite(request)
                        elif with_domain:
                                # If they want a domain and we can't figure one out,
                                # best to reraise the error to let them know.
                                raise
                        else:
                                current_site = None
                
                root = getattr(current_site, 'root_node', None)
                path = self.get_path(root=root)
                
                if current_site and with_domain:
                        domain = "http%s://%s" % (secure and "s" or "", current_site.domain)
                else:
                        domain = ""
                
                if not path or subpath == "/":
                        subpath = subpath[1:]
                
                return '%s%s%s%s' % (domain, root_url, path, subpath)
        
        class Meta:
                app_label = 'philo'


# the following line enables the selection of a node as the root for a given django.contrib.sites Site object
models.ForeignKey(Node, related_name='sites', null=True, blank=True).contribute_to_class(Site, 'root_node')


class View(Entity):
        """
        :class:`View` is an abstract model that represents an item which can be "rendered", generally in response to an :class:`HttpRequest`.
        
        """
        #: A generic relation back to nodes.
        nodes = generic.GenericRelation(Node, content_type_field='view_content_type', object_id_field='view_object_id')
        
        #: Property or attribute which defines whether this :class:`View` can handle subpaths. Default: ``False``
        accepts_subpath = False
        
        def handles_subpath(self, subpath):
                """Returns True if the :class:`View` handles the given subpath, and False otherwise."""
                if not self.accepts_subpath and subpath != "/":
                        return False
                return True
        
        def reverse(self, view_name=None, args=None, kwargs=None, node=None, obj=None):
                """
                If :attr:`accepts_subpath` is True, try to reverse a URL using the given parameters using ``self`` as the urlconf.
                
                If ``obj`` is provided, :meth:`get_reverse_params` will be called and the results will be combined with any ``view_name``, ``args``, and ``kwargs`` that may have been passed in.
                
                :param view_name: The name of the view to be reversed.
                :param args: Extra args for reversing the view.
                :param kwargs: A dictionary of arguments for reversing the view.
                :param node: The node whose subpath this is.
                :param obj: An object to be passed to :meth:`get_reverse_params` to generate a view_name, args, and kwargs for reversal.
                :returns: A subpath beyond the node that reverses the view, or an absolute url that reverses the view if a node was passed in.
                :except philo.exceptions.ViewDoesNotProvideSubpaths: if :attr:`accepts_subpath` is False
                :except philo.exceptions.ViewCanNotProvideSubpath: if a reversal is not possible.
                
                """
                if not self.accepts_subpath:
                        raise ViewDoesNotProvideSubpaths
                
                if obj is not None:
                        # Perhaps just override instead of combining?
                        obj_view_name, obj_args, obj_kwargs = self.get_reverse_params(obj)
                        if view_name is None:
                                view_name = obj_view_name
                        args = list(obj_args) + list(args or [])
                        obj_kwargs.update(kwargs or {})
                        kwargs = obj_kwargs
                
                try:
                        subpath = reverse(view_name, urlconf=self, args=args or [], kwargs=kwargs or {})
                except NoReverseMatch, e:
                        raise ViewCanNotProvideSubpath(e.message)
                
                if node is not None:
                        return node.construct_url(subpath)
                return subpath
        
        def get_reverse_params(self, obj):
                """
                This method is not implemented on the base class. It should return a (``view_name``, ``args``, ``kwargs``) tuple suitable for reversing a url for the given ``obj`` using ``self`` as the urlconf. If a reversal will not be possible, this method should raise :class:`~philo.exceptions.ViewCanNotProvideSubpath`.
                
                """
                raise NotImplementedError("View subclasses must implement get_reverse_params to support subpaths.")
        
        def attributes_with_node(self, node, mapper=LazyPassthroughAttributeMapper):
                """
                Returns a :class:`LazyPassthroughAttributeMapper` which can be used to directly retrieve the values of :class:`Attribute`\ s related to the :class:`View`, falling back on the :class:`Attribute`\ s of the passed-in :class:`Node` and its ancestors.
                
                """
                return mapper((self, node))
        
        def render_to_response(self, request, extra_context=None):
                """
                Renders the :class:`View` as an :class:`HttpResponse`. This will raise :const:`~philo.exceptions.MIDDLEWARE_NOT_CONFIGURED` if the `request` doesn't have an attached :class:`Node`. This can happen if the :class:`~philo.middleware.RequestNodeMiddleware` is not in :setting:`settings.MIDDLEWARE_CLASSES` or if it is not functioning correctly.
                
                :meth:`render_to_response` will send the :data:`~philo.signals.view_about_to_render` signal, then call :meth:`actually_render_to_response`, and finally send the :data:`~philo.signals.view_finished_rendering` signal before returning the ``response``.

                """
                if not hasattr(request, 'node'):
                        raise MIDDLEWARE_NOT_CONFIGURED
                
                extra_context = extra_context or {}
                view_about_to_render.send(sender=self, request=request, extra_context=extra_context)
                response = self.actually_render_to_response(request, extra_context)
                view_finished_rendering.send(sender=self, response=response)
                return response
        
        def actually_render_to_response(self, request, extra_context=None):
                """Concrete subclasses must override this method to provide the business logic for turning a ``request`` and ``extra_context`` into an :class:`HttpResponse`."""
                raise NotImplementedError('View subclasses must implement actually_render_to_response.')
        
        class Meta:
                abstract = True


_view_content_type_limiter.cls = View


class MultiView(View):
        """
        :class:`MultiView` is an abstract model which represents a section of related pages - for example, a :class:`~philo.contrib.penfield.BlogView` might have a foreign key to :class:`Page`\ s for an index, an entry detail, an entry archive by day, and so on. :class:`!MultiView` subclasses :class:`View`, and defines the following additional methods and attributes:
        
        """
        #: Same as :attr:`View.accepts_subpath`. Default: ``True``
        accepts_subpath = True
        
        @property
        def urlpatterns(self):
                """Returns urlpatterns that point to views (generally methods on the class). :class:`MultiView`\ s can be thought of as "managing" these subpaths."""
                raise NotImplementedError("MultiView subclasses must implement urlpatterns.")
        
        def handles_subpath(self, subpath):
                if not super(MultiView, self).handles_subpath(subpath):
                        return False
                try:
                        resolve(subpath, urlconf=self)
                except Http404:
                        return False
                return True
        
        def actually_render_to_response(self, request, extra_context=None):
                """
                Resolves the remaining subpath left after finding this :class:`View`'s node using :attr:`self.urlpatterns <urlpatterns>` and renders the view function (or method) found with the appropriate args and kwargs.
                
                """
                clear_url_caches()
                subpath = request.node.subpath
                view, args, kwargs = resolve(subpath, urlconf=self)
                view_args = getargspec(view)
                if extra_context is not None and ('extra_context' in view_args[0] or view_args[2] is not None):
                        if 'extra_context' in kwargs:
                                extra_context.update(kwargs['extra_context'])
                        kwargs['extra_context'] = extra_context
                return view(request, *args, **kwargs)
        
        def get_context(self):
                """Hook for providing instance-specific context - such as the value of a Field - to any view methods on the instance."""
                return {}
        
        def basic_view(self, field_name):
                """
                Given the name of a field on the class, accesses the value of
                that field and treats it as a ``View`` instance. Creates a
                basic context based on self.get_context() and any extra_context
                that was passed in, then calls the ``View`` instance's
                render_to_response() method. This method is meant to be called
                to return a view function appropriate for urlpatterns.
                
                :param field_name: The name of a field on the instance which contains a :class:`View` subclass instance.
                :returns: A simple view function.
                
                Example::
                        
                        class Foo(Multiview):
                                page = models.ForeignKey(Page)
                                
                                @property
                                def urlpatterns(self):
                                        urlpatterns = patterns('',
                                                url(r'^$', self.basic_view('page'))
                                        )
                                        return urlpatterns
                
                """
                field = self._meta.get_field(field_name)
                view = getattr(self, field.name, None)
                
                def inner(request, extra_context=None, **kwargs):
                        if not view:
                                raise Http404
                        context = self.get_context()
                        context.update(extra_context or {})
                        return view.render_to_response(request, extra_context=context)
                
                return inner
        
        class Meta:
                abstract = True


class TargetURLModel(models.Model):
        """An abstract parent class for models which deal in targeting a url."""
        #: An optional :class:`ForeignKey` to a :class:`.Node`. If provided, that node will be used as the basis for the redirect.
        target_node = models.ForeignKey(Node, blank=True, null=True, related_name="%(app_label)s_%(class)s_related")
        #: A :class:`CharField` which may contain an absolute or relative URL, or the name of a node's subpath.
        url_or_subpath = models.CharField(max_length=200, blank=True, help_text="Point to this url or, if a node is defined and accepts subpaths, this subpath of the node.")
        #: A :class:`~philo.models.fields.JSONField` instance. If the value of :attr:`reversing_parameters` is not None, the :attr:`url_or_subpath` will be treated as the name of a view to be reversed. The value of :attr:`reversing_parameters` will be passed into the reversal as args if it is a list or as kwargs if it is a dictionary. Otherwise it will be ignored.
        reversing_parameters = JSONField(blank=True, help_text="If reversing parameters are defined, url_or_subpath will instead be interpreted as the view name to be reversed.")
        
        def clean(self):
                if not self.target_node and not self.url_or_subpath:
                        raise ValidationError("Either a target node or a url must be defined.")
                
                if self.reversing_parameters and not (self.url_or_subpath or self.target_node):
                        raise ValidationError("Reversing parameters require either a view name or a target node.")
                
                try:
                        self.get_target_url()
                except (NoReverseMatch, ViewCanNotProvideSubpath), e:
                        raise ValidationError(e.message)
                
                super(TargetURLModel, self).clean()
        
        def get_reverse_params(self):
                params = self.reversing_parameters
                args = kwargs = None
                if isinstance(params, list):
                        args = params
                elif isinstance(params, dict):
                        # Convert unicode keys to strings for Python < 2.6.5. Compare
                        # http://stackoverflow.com/questions/4598604/how-to-pass-unicode-keywords-to-kwargs
                        kwargs = dict([(smart_str(k, 'ascii'), v) for k, v in params.items()])
                return self.url_or_subpath, args, kwargs
        
        def get_target_url(self):
                """Calculates and returns the target url based on the :attr:`target_node`, :attr:`url_or_subpath`, and :attr:`reversing_parameters`."""
                node = self.target_node
                if node is not None and node.accepts_subpath and self.url_or_subpath:
                        if self.reversing_parameters is not None:
                                view_name, args, kwargs = self.get_reverse_params()
                                subpath = node.view.reverse(view_name, args=args, kwargs=kwargs)
                        else:
                                subpath = self.url_or_subpath
                                if subpath[0] != '/':
                                        subpath = '/' + subpath
                        return node.construct_url(subpath)
                elif node is not None:
                        return node.get_absolute_url()
                else:
                        if self.reversing_parameters is not None:
                                view_name, args, kwargs = self.get_reverse_params()
                                return reverse(view_name, args=args, kwargs=kwargs)
                        return self.url_or_subpath
        target_url = property(get_target_url)
        
        class Meta:
                abstract = True


class Redirect(TargetURLModel, View):
        """Represents a 301 or 302 redirect to a different url on an absolute or relative path."""
        #: A choices tuple of redirect status codes (temporary or permanent).
        STATUS_CODES = (
                (302, 'Temporary'),
                (301, 'Permanent'),
        )
        #: An :class:`IntegerField` which uses :attr:`STATUS_CODES` as its choices. Determines whether the redirect is considered temporary or permanent.
        status_code = models.IntegerField(choices=STATUS_CODES, default=302, verbose_name='redirect type')
        
        def actually_render_to_response(self, request, extra_context=None):
                """Returns an :class:`HttpResponseRedirect` to :attr:`self.target_url`."""
                response = HttpResponseRedirect(self.target_url)
                response.status_code = self.status_code
                return response
        
        class Meta:
                app_label = 'philo'


class File(View):
        """Stores an arbitrary file."""
        #: Defines the mimetype of the uploaded file. This will not be validated.
        mimetype = models.CharField(max_length=255)
        #: Contains the uploaded file. Files are uploaded to ``philo/files/%Y/%m/%d``.
        file = models.FileField(upload_to='philo/files/%Y/%m/%d')
        
        def actually_render_to_response(self, request, extra_context=None):
                wrapper = FileWrapper(self.file)
                response = HttpResponse(wrapper, content_type=self.mimetype)
                response['Content-Length'] = self.file.size
                return response
        
        class Meta:
                app_label = 'philo'
        
        def __unicode__(self):
                """Returns the path of the uploaded file."""
                return self.file.name


register_value_model(Node)