text: """API and implementations for loading templates from different data
  sources.
  """
  import importlib.util
  import os
  import posixpath
  import sys
  import typing as t
  import weakref
  import zipimport
  from collections import abc
  from hashlib import sha1
  from importlib import import_module
  from types import ModuleType
  
  from .exceptions import TemplateNotFound
  from .utils import internalcode
  from .utils import open_if_exists
  
  if t.TYPE_CHECKING:
      from .environment import Environment
      from .environment import Template
  
  
  def split_template_path(template: str) -> t.List[str]:
      """Split a path into segments and perform a sanity check.  If it detects
      '..' in the path it will raise a `TemplateNotFound` error.
      """
      pieces = []
      for piece in template.split("/"):
          if (
              os.path.sep in piece
              or (os.path.altsep and os.path.altsep in piece)
              or piece == os.path.pardir
          ):
              raise TemplateNotFound(template)
          elif piece and piece != ".":
              pieces.append(piece)
      return pieces
  
  
  class BaseLoader:
      """Baseclass for all loaders.  Subclass this and override `get_source` to
      implement a custom loading mechanism.  The environment provides a
      `get_template` method that calls the loader's `load` method to get the
      :class:`Template` object.
  
      A very basic example for a loader that looks up templates on the file
      system could look like this::
  
          from jinja2 import BaseLoader, TemplateNotFound
          from os.path import join, exists, getmtime
  
          class MyLoader(BaseLoader):
  
              def __init__(self, path):
                  self.path = path
  
              def get_source(self, environment, template):
                  path = join(self.path, template)
                  if not exists(path):
                      raise TemplateNotFound(template)
                  mtime = getmtime(path)
                  with open(path) as f:
                      source = f.read()
                  return source, path, lambda: mtime == getmtime(path)
      """
  
      #: if set to `False` it indicates that the loader cannot provide access
      #: to the source of templates.
      #:
      #: .. versionadded:: 2.4
      has_source_access = True
  
      def get_source(
          self, environment: "Environment", template: str
      ) -> t.Tuple[str, t.Optional[str], t.Optional[t.Callable[[], bool]]]:
          """Get the template source, filename and reload helper for a template.
          It's passed the environment and template name and has to return a
          tuple in the form ``(source, filename, uptodate)`` or raise a
          `TemplateNotFound` error if it can't locate the template.
  
          The source part of the returned tuple must be the source of the
          template as a string. The filename should be the name of the
          file on the filesystem if it was loaded from there, otherwise
          ``None``. The filename is used by Python for the tracebacks
          if no loader extension is used.
  
          The last item in the tuple is the `uptodate` function.  If auto
          reloading is enabled it's always called to check if the template
          changed.  No arguments are passed so the function must store the
          old state somewhere (for example in a closure).  If it returns `False`
          the template will be reloaded.
          """
          if not self.has_source_access:
              raise RuntimeError(
                  f"{type(self).__name__} cannot provide access to the source"
              )
          raise TemplateNotFound(template)
  
      def list_templates(self) -> t.List[str]:
          """Iterates over all templates.  If the loader does not support that
          it should raise a :exc:`TypeError` which is the default behavior.
          """
          raise TypeError("this loader cannot iterate over all templates")
  
      @internalcode
      def load(
          self,
          environment: "Environment",
          name: str,
          globals: t.Optional[t.MutableMapping[str, t.Any]] = None,
      ) -> "Template":
          """Loads a template.  This method looks up the template in the cache
          or loads one by calling :meth:`get_source`.  Subclasses should not
          override this method as loaders working on collections of other
          loaders (such as :class:`PrefixLoader` or :class:`ChoiceLoader`)
          will not call this method but `get_source` directly.
          """
          code = None
          if globals is None:
              globals = {}
  
          # first we try to get the source for this template together
          # with the filename and the uptodate function.
          source, filename, uptodate = self.get_source(environment, name)
  
          # try to load the code from the bytecode cache if there is a
          # bytecode cache configured.
          bcc = environment.bytecode_cache
          if bcc is not None:
              bucket = bcc.get_bucket(environment, name, filename, source)
              code = bucket.code
  
          # if we don't have code so far (not cached, no longer up to
          # date) etc. we compile the template
          if code is None:
              code = environment.compile(source, name, filename)
  
          # if the bytecode cache is available and the bucket doesn't
          # have a code so far, we give the bucket the new code and put
          # it back to the bytecode cache.
          if bcc is not None and bucket.code is None:
              bucket.code = code
              bcc.set_bucket(bucket)
  
          return environment.template_class.from_code(
              environment, code, globals, uptodate
          )
  
  
  class FileSystemLoader(BaseLoader):
      """Load templates from a directory in the file system.
  
      The path can be relative or absolute. Relative paths are relative to
      the current working directory.
  
      .. code-block:: python
  
          loader = FileSystemLoader("templates")
  
      A list of paths can be given. The directories will be searched in
      order, stopping at the first matching template.
  
      .. code-block:: python
  
          loader = FileSystemLoader(["/override/templates", "/default/templates"])
  
      :param searchpath: A path, or list of paths, to the directory that
          contains the templates.
      :param encoding: Use this encoding to read the text from template
          files.
      :param followlinks: Follow symbolic links in the path.
  
      .. versionchanged:: 2.8
          Added the ``followlinks`` parameter.
      """
  
      def __init__(
          self,
          searchpath: t.Union[str, os.PathLike, t.Sequence[t.Union[str, os.PathLike]]],
          encoding: str = "utf-8",
          followlinks: bool = False,
      ) -> None:
          if not isinstance(searchpath, abc.Iterable) or isinstance(searchpath, str):
              searchpath = [searchpath]
  
          self.searchpath = [os.fspath(p) for p in searchpath]
          self.encoding = encoding
          self.followlinks = followlinks
  
      def get_source(
          self, environment: "Environment", template: str
      ) -> t.Tuple[str, str, t.Callable[[], bool]]:
          pieces = split_template_path(template)
          for searchpath in self.searchpath:
              # Use posixpath even on Windows to avoid "drive:" or UNC
              # segments breaking out of the search directory.
              filename = posixpath.join(searchpath, *pieces)
              f = open_if_exists(filename)
              if f is None:
                  continue
              try:
                  contents = f.read().decode(self.encoding)
              finally:
                  f.close()
  
              mtime = os.path.getmtime(filename)
  
              def uptodate() -> bool:
                  try:
                      return os.path.getmtime(filename) == mtime
                  except OSError:
                      return False
  
              # Use normpath to convert Windows altsep to sep.
              return contents, os.path.normpath(filename), uptodate
          raise TemplateNotFound(template)
  
      def list_templates(self) -> t.List[str]:
          found = set()
          for searchpath in self.searchpath:
              walk_dir = os.walk(searchpath, followlinks=self.followlinks)
              for dirpath, _, filenames in walk_dir:
                  for filename in filenames:
                      template = (
                          os.path.join(dirpath, filename)[len(searchpath) :]
                          .strip(os.path.sep)
                          .replace(os.path.sep, "/")
                      )
                      if template[:2] == "./":
                          template = template[2:]
                      if template not in found:
                          found.add(template)
          return sorted(found)
  
  
  class PackageLoader(BaseLoader):
      """Load templates from a directory in a Python package.
  
      :param package_name: Import name of the package that contains the
          template directory.
      :param package_path: Directory within the imported package that
          contains the templates.
      :param encoding: Encoding of template files.
  
      The following example looks up templates in the ``pages`` directory
      within the ``project.ui`` package.
  
      .. code-block:: python
  
          loader = PackageLoader("project.ui", "pages")
  
      Only packages installed as directories (standard pip behavior) or
      zip/egg files (less common) are supported. The Python API for
      introspecting data in packages is too limited to support other
      installation methods the way this loader requires.
  
      There is limited support for :pep:`420` namespace packages. The
      template directory is assumed to only be in one namespace
      contributor. Zip files contributing to a namespace are not
      supported.
  
      .. versionchanged:: 3.0
          No longer uses ``setuptools`` as a dependency.
  
      .. versionchanged:: 3.0
          Limited PEP 420 namespace package support.
      """
  
      def __init__(
          self,
          package_name: str,
          package_path: "str" = "templates",
          encoding: str = "utf-8",
      ) -> None:
          package_path = os.path.normpath(package_path).rstrip(os.path.sep)
  
          # normpath preserves ".", which isn't valid in zip paths.
          if package_path == os.path.curdir:
              package_path = ""
          elif package_path[:2] == os.path.curdir + os.path.sep:
              package_path = package_path[2:]
  
          self.package_path = package_path
          self.package_name = package_name
          self.encoding = encoding
  
          # Make sure the package exists. This also makes namespace
          # packages work, otherwise get_loader returns None.
          import_module(package_name)
          spec = importlib.util.find_spec(package_name)
          assert spec is not None, "An import spec was not found for the package."
          loader = spec.loader
          assert loader is not None, "A loader was not found for the package."
          self._loader = loader
          self._archive = None
          template_root = None
  
          if isinstance(loader, zipimport.zipimporter):
              self._archive = loader.archive
              pkgdir = next(iter(spec.submodule_search_locations))  # type: ignore
              template_root = os.path.join(pkgdir, package_path).rstrip(os.path.sep)
          else:
              roots: t.List[str] = []
  
              # One element for regular packages, multiple for namespace
              # packages, or None for single module file.
              if spec.submodule_search_locations:
                  roots.extend(spec.submodule_search_locations)
              # A single module file, use the parent directory instead.
              elif spec.origin is not None:
                  roots.append(os.path.dirname(spec.origin))
  
              for root in roots:
                  root = os.path.join(root, package_path)
  
                  if os.path.isdir(root):
                      template_root = root
                      break
  
          if template_root is None:
              raise ValueError(
                  f"The {package_name!r} package was not installed in a"
                  " way that PackageLoader understands."
              )
  
          self._template_root = template_root
  
      def get_source(
          self, environment: "Environment", template: str
      ) -> t.Tuple[str, str, t.Optional[t.Callable[[], bool]]]:
          # Use posixpath even on Windows to avoid "drive:" or UNC
          # segments breaking out of the search directory. Use normpath to
          # convert Windows altsep to sep.
          p = os.path.normpath(
              posixpath.join(self._template_root, *split_template_path(template))
          )
          up_to_date: t.Optional[t.Callable[[], bool]]
  
          if self._archive is None:
              # Package is a directory.
              if not os.path.isfile(p):
                  raise TemplateNotFound(template)
  
              with open(p, "rb") as f:
                  source = f.read()
  
              mtime = os.path.getmtime(p)
  
              def up_to_date() -> bool:
                  return os.path.isfile(p) and os.path.getmtime(p) == mtime
  
          else:
              # Package is a zip file.
              try:
                  source = self._loader.get_data(p)  # type: ignore
              except OSError as e:
                  raise TemplateNotFound(template) from e
  
              # Could use the zip's mtime for all template mtimes, but
              # would need to safely reload the module if it's out of
              # date, so just report it as always current.
              up_to_date = None
  
          return source.decode(self.encoding), p, up_to_date
  
      def list_templates(self) -> t.List[str]:
          results: t.List[str] = []
  
          if self._archive is None:
              # Package is a directory.
              offset = len(self._template_root)
  
              for dirpath, _, filenames in os.walk(self._template_root):
                  dirpath = dirpath[offset:].lstrip(os.path.sep)
                  results.extend(
                      os.path.join(dirpath, name).replace(os.path.sep, "/")
                      for name in filenames
                  )
          else:
              if not hasattr(self._loader, "_files"):
                  raise TypeError(
                      "This zip import does not have the required"
                      " metadata to list templates."
                  )
  
              # Package is a zip file.
              prefix = (
                  self._template_root[len(self._archive) :].lstrip(os.path.sep)
                  + os.path.sep
              )
              offset = len(prefix)
  
              for name in self._loader._files.keys():  # type: ignore
                  # Find names under the templates directory that aren't directories.
                  if name.startswith(prefix) and name[-1] != os.path.sep:
                      results.append(name[offset:].replace(os.path.sep, "/"))
  
          results.sort()
          return results
  
  
  class DictLoader(BaseLoader):
      """Loads a template from a Python dict mapping template names to
      template source.  This loader is useful for unittesting:
  
      >>> loader = DictLoader({'index.html': 'source here'})
  
      Because auto reloading is rarely useful this is disabled per default.
      """
  
      def __init__(self, mapping: t.Mapping[str, str]) -> None:
          self.mapping = mapping
  
      def get_source(
          self, environment: "Environment", template: str
      ) -> t.Tuple[str, None, t.Callable[[], bool]]:
          if template in self.mapping:
              source = self.mapping[template]
              return source, None, lambda: source == self.mapping.get(template)
          raise TemplateNotFound(template)
  
      def list_templates(self) -> t.List[str]:
          return sorted(self.mapping)
  
  
  class FunctionLoader(BaseLoader):
      """A loader that is passed a function which does the loading.  The
      function receives the name of the template and has to return either
      a string with the template source, a tuple in the form ``(source,
      filename, uptodatefunc)`` or `None` if the template does not exist.
  
      >>> def load_template(name):
      ...     if name == 'index.html':
      ...         return '...'
      ...
      >>> loader = FunctionLoader(load_template)
  
      The `uptodatefunc` is a function that is called if autoreload is enabled
      and has to return `True` if the template is still up to date.  For more
      details have a look at :meth:`BaseLoader.get_source` which has the same
      return value.
      """
  
      def __init__(
          self,
          load_func: t.Callable[
              [str],
              t.Optional[
                  t.Union[
                      str, t.Tuple[str, t.Optional[str], t.Optional[t.Callable[[], bool]]]
                  ]
              ],
          ],
      ) -> None:
          self.load_func = load_func
  
      def get_source(
          self, environment: "Environment", template: str
      ) -> t.Tuple[str, t.Optional[str], t.Optional[t.Callable[[], bool]]]:
          rv = self.load_func(template)
  
          if rv is None:
              raise TemplateNotFound(template)
  
          if isinstance(rv, str):
              return rv, None, None
  
          return rv
  
  
  class PrefixLoader(BaseLoader):
      """A loader that is passed a dict of loaders where each loader is bound
      to a prefix.  The prefix is delimited from the template by a slash per
      default, which can be changed by setting the `delimiter` argument to
      something else::
  
          loader = PrefixLoader({
              'app1':     PackageLoader('mypackage.app1'),
              'app2':     PackageLoader('mypackage.app2')
          })
  
      By loading ``'app1/index.html'`` the file from the app1 package is loaded,
      by loading ``'app2/index.html'`` the file from the second.
      """
  
      def __init__(
          self, mapping: t.Mapping[str, BaseLoader], delimiter: str = "/"
      ) -> None:
          self.mapping = mapping
          self.delimiter = delimiter
  
      def get_loader(self, template: str) -> t.Tuple[BaseLoader, str]:
          try:
              prefix, name = template.split(self.delimiter, 1)
              loader = self.mapping[prefix]
          except (ValueError, KeyError) as e:
              raise TemplateNotFound(template) from e
          return loader, name
  
      def get_source(
          self, environment: "Environment", template: str
      ) -> t.Tuple[str, t.Optional[str], t.Optional[t.Callable[[], bool]]]:
          loader, name = self.get_loader(template)
          try:
              return loader.get_source(environment, name)
          except TemplateNotFound as e:
              # re-raise the exception with the correct filename here.
              # (the one that includes the prefix)
              raise TemplateNotFound(template) from e
  
      @internalcode
      def load(
          self,
          environment: "Environment",
          name: str,
          globals: t.Optional[t.MutableMapping[str, t.Any]] = None,
      ) -> "Template":
          loader, local_name = self.get_loader(name)
          try:
              return loader.load(environment, local_name, globals)
          except TemplateNotFound as e:
              # re-raise the exception with the correct filename here.
              # (the one that includes the prefix)
              raise TemplateNotFound(name) from e
  
      def list_templates(self) -> t.List[str]:
          result = []
          for prefix, loader in self.mapping.items():
              for template in loader.list_templates():
                  result.append(prefix + self.delimiter + template)
          return result
  
  
  class ChoiceLoader(BaseLoader):
      """This loader works like the `PrefixLoader` just that no prefix is
      specified.  If a template could not be found by one loader the next one
      is tried.
  
      >>> loader = ChoiceLoader([
      ...     FileSystemLoader('/path/to/user/templates'),
      ...     FileSystemLoader('/path/to/system/templates')
      ... ])
  
      This is useful if you want to allow users to override builtin templates
      from a different location.
      """
  
      def __init__(self, loaders: t.Sequence[BaseLoader]) -> None:
          self.loaders = loaders
  
      def get_source(
          self, environment: "Environment", template: str
      ) -> t.Tuple[str, t.Optional[str], t.Optional[t.Callable[[], bool]]]:
          for loader in self.loaders:
              try:
                  return loader.get_source(environment, template)
              except TemplateNotFound:
                  pass
          raise TemplateNotFound(template)
  
      @internalcode
      def load(
          self,
          environment: "Environment",
          name: str,
          globals: t.Optional[t.MutableMapping[str, t.Any]] = None,
      ) -> "Template":
          for loader in self.loaders:
              try:
                  return loader.load(environment, name, globals)
              except TemplateNotFound:
                  pass
          raise TemplateNotFound(name)
  
      def list_templates(self) -> t.List[str]:
          found = set()
          for loader in self.loaders:
              found.update(loader.list_templates())
          return sorted(found)
  
  
  class _TemplateModule(ModuleType):
      """Like a normal module but with support for weak references"""
  
  
  class ModuleLoader(BaseLoader):
      """This loader loads templates from precompiled templates.
  
      Example usage:
  
      >>> loader = ChoiceLoader([
      ...     ModuleLoader('/path/to/compiled/templates'),
      ...     FileSystemLoader('/path/to/templates')
      ... ])
  
      Templates can be precompiled with :meth:`Environment.compile_templates`.
      """
  
      has_source_access = False
  
      def __init__(
          self, path: t.Union[str, os.PathLike, t.Sequence[t.Union[str, os.PathLike]]]
      ) -> None:
          package_name = f"_jinja2_module_templates_{id(self):x}"
  
          # create a fake module that looks for the templates in the
          # path given.
          mod = _TemplateModule(package_name)
  
          if not isinstance(path, abc.Iterable) or isinstance(path, str):
              path = [path]
  
          mod.__path__ = [os.fspath(p) for p in path]
  
          sys.modules[package_name] = weakref.proxy(
              mod, lambda x: sys.modules.pop(package_name, None)
          )
  
          # the only strong reference, the sys.modules entry is weak
          # so that the garbage collector can remove it once the
          # loader that created it goes out of business.
          self.module = mod
          self.package_name = package_name
  
      @staticmethod
      def get_template_key(name: str) -> str:
          return "tmpl_" + sha1(name.encode("utf-8")).hexdigest()
  
      @staticmethod
      def get_module_filename(name: str) -> str:
          return ModuleLoader.get_template_key(name) + ".py"
  
      @internalcode
      def load(
          self,
          environment: "Environment",
          name: str,
          globals: t.Optional[t.MutableMapping[str, t.Any]] = None,
      ) -> "Template":
          key = self.get_template_key(name)
          module = f"{self.package_name}.{key}"
          mod = getattr(self.module, module, None)
  
          if mod is None:
              try:
                  mod = __import__(module, None, None, ["root"])
              except ImportError as e:
                  raise TemplateNotFound(name) from e
  
              # remove the entry from sys.modules, we only want the attribute
              # on the module object we have stored on the loader.
              sys.modules.pop(module, None)
  
          if globals is None:
              globals = {}
  
          return environment.template_class.from_module_dict(
              environment, mod.__dict__, globals
          )
  