Python Entrouvert

"""

Wrapper class that takes a list of template loaders as an argument and attempts

to load templates from them in order, caching the result.

"""

import hashlib

from django.conf import settings

from django.core.exceptions import ImproperlyConfigured

from django.template.base import TemplateDoesNotExist

from django.template.loader import BaseLoader, get_template_from_string, find_template_loader, make_origin

from django.utils.encoding import force_bytes

from django.utils._os import safe_join

from django.db import connection

class CachedLoader(BaseLoader):

    is_usable = True

    def __init__(self, loaders):

        self.template_cache = {}

        self._loaders = loaders

        self._cached_loaders = []

    @property

    def loaders(self):

        # Resolve loaders on demand to avoid circular imports

        if not self._cached_loaders:

            # Set self._cached_loaders atomically. Otherwise, another thread

            # could see an incomplete list. See #17303.

            cached_loaders = []

            for loader in self._loaders:

                cached_loaders.append(find_template_loader(loader))

            self._cached_loaders = cached_loaders

        return self._cached_loaders

    def find_template(self, name, dirs=None):

        for loader in self.loaders:

            try:

                template, display_name = loader(name, dirs)

                return (template, make_origin(display_name, loader, name, dirs))

            except TemplateDoesNotExist:

                pass

        raise TemplateDoesNotExist(name)

    def load_template(self, template_name, template_dirs=None):

        if connection.tenant:

            key = '-'.join([str(connection.tenant.pk), template_name])

        else:

            key = template_name

        if template_dirs:

            # If template directories were specified, use a hash to differentiate

            if connection.tenant:

                key = '-'.join([str(connection.tenant.pk), template_name, hashlib.sha1(force_bytes('|'.join(template_dirs))).hexdigest()])

            else:

                key = '-'.join([template_name, hashlib.sha1(force_bytes('|'.join(template_dirs))).hexdigest()])

        if key not in self.template_cache:

            template, origin = self.find_template(template_name, template_dirs)

            if not hasattr(template, 'render'):

                try:

                    template = get_template_from_string(template, origin, template_name)

                except TemplateDoesNotExist:

                    # If compiling the template we found raises TemplateDoesNotExist,

                    # back off to returning the source and display name for the template

                    # we were asked to load. This allows for correct identification (later)

                    # of the actual template that does not exist.

                    return template, origin

            self.template_cache[key] = template

        return self.template_cache[key], None

    def reset(self):

        "Empty the template cache."

        self.template_cache.clear()

class FilesystemLoader(BaseLoader):

    is_usable = True

    def get_template_sources(self, template_name, template_dirs=None):

        """

        Returns the absolute paths to "template_name", when appended to each

        directory in "template_dirs". Any paths that don't lie inside one of the

        template dirs are excluded from the result set, for security reasons.

        """

        if not connection.tenant:

            return

        if not template_dirs:

            try:

                template_dirs = settings.TENANT_TEMPLATE_DIRS

            except AttributeError:

                raise ImproperlyConfigured('To use %s.%s you must define the TENANT_TEMPLATE_DIRS' % (__name__, FilesystemLoader.__name__))

        for template_dir in template_dirs:

            try:

                yield safe_join(template_dir, connection.tenant.domain_url, template_name)

            except UnicodeDecodeError:

                # The template dir name was a bytestring that wasn't valid UTF-8.

                raise

            except ValueError:

                # The joined path was located outside of this particular

                # template_dir (it might be inside another one, so this isn't

                # fatal).

                pass

    def load_template_source(self, template_name, template_dirs=None):

        tried = []

        for filepath in self.get_template_sources(template_name, template_dirs):

            try:

                with open(filepath, 'rb') as fp:

                    return (fp.read().decode(settings.FILE_CHARSET), filepath)

            except IOError:

                tried.append(filepath)

        if tried:

            error_msg = "Tried %s" % tried

        else:

            error_msg = "Your TENANT_TEMPLATE_DIRS setting is empty. Change it to point to at least one template directory."

        raise TemplateDoesNotExist(error_msg)

    load_template_source.is_usable = True