"""

Wrapper for loading templates from "templates" directories in INSTALLED_APPS

packages.

"""

import os

import sys

from django.conf import settings

from django.core.exceptions import ImproperlyConfigured

from django.template import TemplateDoesNotExist

from django.template.loader import BaseLoader

from django.utils._os import safe_join

from django.utils.importlib import import_module

# At compile time, cache the directories to search.

fs_encoding = sys.getfilesystemencoding() or sys.getdefaultencoding()

app_template_dirs = []

for app in settings.INSTALLED_APPS:

    try:

        mod = import_module(app)

    except ImportError, e:

        raise ImproperlyConfigured('ImportError %s: %s' % (app, e.args[0]))

    template_dir = os.path.join(os.path.dirname(mod.__file__), 'templates')

    if os.path.isdir(template_dir):

        app_template_dirs.append(template_dir.decode(fs_encoding))

# It won't change, so convert it to a tuple to save memory.

app_template_dirs = tuple(app_template_dirs)

class Loader(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 template_dirs:

            template_dirs = app_template_dirs

        for template_dir in template_dirs:

            try:

                yield safe_join(template_dir, 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 template_dir.

                pass

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

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

            try:

                file = open(filepath)

                try:

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

                finally:

                    file.close()

            except IOError:

                pass

        raise TemplateDoesNotExist(template_name)

_loader = Loader()

def load_template_source(template_name, template_dirs=None):

    # For backwards compatibility

    import warnings

    warnings.warn(

        "'django.template.loaders.app_directories.load_template_source' is deprecated; use 'django.template.loaders.app_directories.Loader' instead.",

        PendingDeprecationWarning

    )

    return _loader.load_template_source(template_name, template_dirs)

load_template_source.is_usable = True