text: # -*- coding: utf-8 -*-
  """
      flask.ctx
      ~~~~~~~~~
  
      Implements the objects required to keep the context.
  
      :copyright: © 2010 by the Pallets team.
      :license: BSD, see LICENSE for more details.
  """
  
  import sys
  from functools import update_wrapper
  
  from werkzeug.exceptions import HTTPException
  
  from .globals import _request_ctx_stack, _app_ctx_stack
  from .signals import appcontext_pushed, appcontext_popped
  from ._compat import BROKEN_PYPY_CTXMGR_EXIT, reraise
  
  
  # a singleton sentinel value for parameter defaults
  _sentinel = object()
  
  
  class _AppCtxGlobals(object):
      """A plain object. Used as a namespace for storing data during an
      application context.
  
      Creating an app context automatically creates this object, which is
      made available as the :data:`g` proxy.
  
      .. describe:: 'key' in g
  
          Check whether an attribute is present.
  
          .. versionadded:: 0.10
  
      .. describe:: iter(g)
  
          Return an iterator over the attribute names.
  
          .. versionadded:: 0.10
      """
  
      def get(self, name, default=None):
          """Get an attribute by name, or a default value. Like
          :meth:`dict.get`.
  
          :param name: Name of attribute to get.
          :param default: Value to return if the attribute is not present.
  
          .. versionadded:: 0.10
          """
          return self.__dict__.get(name, default)
  
      def pop(self, name, default=_sentinel):
          """Get and remove an attribute by name. Like :meth:`dict.pop`.
  
          :param name: Name of attribute to pop.
          :param default: Value to return if the attribute is not present,
              instead of raise a ``KeyError``.
  
          .. versionadded:: 0.11
          """
          if default is _sentinel:
              return self.__dict__.pop(name)
          else:
              return self.__dict__.pop(name, default)
  
      def setdefault(self, name, default=None):
          """Get the value of an attribute if it is present, otherwise
          set and return a default value. Like :meth:`dict.setdefault`.
  
          :param name: Name of attribute to get.
          :param: default: Value to set and return if the attribute is not
              present.
  
          .. versionadded:: 0.11
          """
          return self.__dict__.setdefault(name, default)
  
      def __contains__(self, item):
          return item in self.__dict__
  
      def __iter__(self):
          return iter(self.__dict__)
  
      def __repr__(self):
          top = _app_ctx_stack.top
          if top is not None:
              return "<flask.g of %r>" % top.app.name
          return object.__repr__(self)
  
  
  def after_this_request(f):
      """Executes a function after this request.  This is useful to modify
      response objects.  The function is passed the response object and has
      to return the same or a new one.
  
      Example::
  
          @app.route('/')
          def index():
              @after_this_request
              def add_header(response):
                  response.headers['X-Foo'] = 'Parachute'
                  return response
              return 'Hello World!'
  
      This is more useful if a function other than the view function wants to
      modify a response.  For instance think of a decorator that wants to add
      some headers without converting the return value into a response object.
  
      .. versionadded:: 0.9
      """
      _request_ctx_stack.top._after_request_functions.append(f)
      return f
  
  
  def copy_current_request_context(f):
      """A helper function that decorates a function to retain the current
      request context.  This is useful when working with greenlets.  The moment
      the function is decorated a copy of the request context is created and
      then pushed when the function is called.  The current session is also
      included in the copied request context.
  
      Example::
  
          import gevent
          from flask import copy_current_request_context
  
          @app.route('/')
          def index():
              @copy_current_request_context
              def do_some_work():
                  # do some work here, it can access flask.request or
                  # flask.session like you would otherwise in the view function.
                  ...
              gevent.spawn(do_some_work)
              return 'Regular response'
  
      .. versionadded:: 0.10
      """
      top = _request_ctx_stack.top
      if top is None:
          raise RuntimeError(
              "This decorator can only be used at local scopes "
              "when a request context is on the stack.  For instance within "
              "view functions."
          )
      reqctx = top.copy()
  
      def wrapper(*args, **kwargs):
          with reqctx:
              return f(*args, **kwargs)
  
      return update_wrapper(wrapper, f)
  
  
  def has_request_context():
      """If you have code that wants to test if a request context is there or
      not this function can be used.  For instance, you may want to take advantage
      of request information if the request object is available, but fail
      silently if it is unavailable.
  
      ::
  
          class User(db.Model):
  
              def __init__(self, username, remote_addr=None):
                  self.username = username
                  if remote_addr is None and has_request_context():
                      remote_addr = request.remote_addr
                  self.remote_addr = remote_addr
  
      Alternatively you can also just test any of the context bound objects
      (such as :class:`request` or :class:`g`) for truthness::
  
          class User(db.Model):
  
              def __init__(self, username, remote_addr=None):
                  self.username = username
                  if remote_addr is None and request:
                      remote_addr = request.remote_addr
                  self.remote_addr = remote_addr
  
      .. versionadded:: 0.7
      """
      return _request_ctx_stack.top is not None
  
  
  def has_app_context():
      """Works like :func:`has_request_context` but for the application
      context.  You can also just do a boolean check on the
      :data:`current_app` object instead.
  
      .. versionadded:: 0.9
      """
      return _app_ctx_stack.top is not None
  
  
  class AppContext(object):
      """The application context binds an application object implicitly
      to the current thread or greenlet, similar to how the
      :class:`RequestContext` binds request information.  The application
      context is also implicitly created if a request context is created
      but the application is not on top of the individual application
      context.
      """
  
      def __init__(self, app):
          self.app = app
          self.url_adapter = app.create_url_adapter(None)
          self.g = app.app_ctx_globals_class()
  
          # Like request context, app contexts can be pushed multiple times
          # but there a basic "refcount" is enough to track them.
          self._refcnt = 0
  
      def push(self):
          """Binds the app context to the current context."""
          self._refcnt += 1
          if hasattr(sys, "exc_clear"):
              sys.exc_clear()
          _app_ctx_stack.push(self)
          appcontext_pushed.send(self.app)
  
      def pop(self, exc=_sentinel):
          """Pops the app context."""
          try:
              self._refcnt -= 1
              if self._refcnt <= 0:
                  if exc is _sentinel:
                      exc = sys.exc_info()[1]
                  self.app.do_teardown_appcontext(exc)
          finally:
              rv = _app_ctx_stack.pop()
          assert rv is self, "Popped wrong app context.  (%r instead of %r)" % (rv, self)
          appcontext_popped.send(self.app)
  
      def __enter__(self):
          self.push()
          return self
  
      def __exit__(self, exc_type, exc_value, tb):
          self.pop(exc_value)
  
          if BROKEN_PYPY_CTXMGR_EXIT and exc_type is not None:
              reraise(exc_type, exc_value, tb)
  
  
  class RequestContext(object):
      """The request context contains all request relevant information.  It is
      created at the beginning of the request and pushed to the
      `_request_ctx_stack` and removed at the end of it.  It will create the
      URL adapter and request object for the WSGI environment provided.
  
      Do not attempt to use this class directly, instead use
      :meth:`~flask.Flask.test_request_context` and
      :meth:`~flask.Flask.request_context` to create this object.
  
      When the request context is popped, it will evaluate all the
      functions registered on the application for teardown execution
      (:meth:`~flask.Flask.teardown_request`).
  
      The request context is automatically popped at the end of the request
      for you.  In debug mode the request context is kept around if
      exceptions happen so that interactive debuggers have a chance to
      introspect the data.  With 0.4 this can also be forced for requests
      that did not fail and outside of ``DEBUG`` mode.  By setting
      ``'flask._preserve_context'`` to ``True`` on the WSGI environment the
      context will not pop itself at the end of the request.  This is used by
      the :meth:`~flask.Flask.test_client` for example to implement the
      deferred cleanup functionality.
  
      You might find this helpful for unittests where you need the
      information from the context local around for a little longer.  Make
      sure to properly :meth:`~werkzeug.LocalStack.pop` the stack yourself in
      that situation, otherwise your unittests will leak memory.
      """
  
      def __init__(self, app, environ, request=None, session=None):
          self.app = app
          if request is None:
              request = app.request_class(environ)
          self.request = request
          self.url_adapter = None
          try:
              self.url_adapter = app.create_url_adapter(self.request)
          except HTTPException as e:
              self.request.routing_exception = e
          self.flashes = None
          self.session = session
  
          # Request contexts can be pushed multiple times and interleaved with
          # other request contexts.  Now only if the last level is popped we
          # get rid of them.  Additionally if an application context is missing
          # one is created implicitly so for each level we add this information
          self._implicit_app_ctx_stack = []
  
          # indicator if the context was preserved.  Next time another context
          # is pushed the preserved context is popped.
          self.preserved = False
  
          # remembers the exception for pop if there is one in case the context
          # preservation kicks in.
          self._preserved_exc = None
  
          # Functions that should be executed after the request on the response
          # object.  These will be called before the regular "after_request"
          # functions.
          self._after_request_functions = []
  
          if self.url_adapter is not None:
              self.match_request()
  
      @property
      def g(self):
          return _app_ctx_stack.top.g
  
      @g.setter
      def g(self, value):
          _app_ctx_stack.top.g = value
  
      def copy(self):
          """Creates a copy of this request context with the same request object.
          This can be used to move a request context to a different greenlet.
          Because the actual request object is the same this cannot be used to
          move a request context to a different thread unless access to the
          request object is locked.
  
          .. versionadded:: 0.10
  
          .. versionchanged:: 1.1
             The current session object is used instead of reloading the original
             data. This prevents `flask.session` pointing to an out-of-date object.
          """
          return self.__class__(
              self.app,
              environ=self.request.environ,
              request=self.request,
              session=self.session,
          )
  
      def match_request(self):
          """Can be overridden by a subclass to hook into the matching
          of the request.
          """
          try:
              url_rule, self.request.view_args = self.url_adapter.match(return_rule=True)
              self.request.url_rule = url_rule
          except HTTPException as e:
              self.request.routing_exception = e
  
      def push(self):
          """Binds the request context to the current context."""
          # If an exception occurs in debug mode or if context preservation is
          # activated under exception situations exactly one context stays
          # on the stack.  The rationale is that you want to access that
          # information under debug situations.  However if someone forgets to
          # pop that context again we want to make sure that on the next push
          # it's invalidated, otherwise we run at risk that something leaks
          # memory.  This is usually only a problem in test suite since this
          # functionality is not active in production environments.
          top = _request_ctx_stack.top
          if top is not None and top.preserved:
              top.pop(top._preserved_exc)
  
          # Before we push the request context we have to ensure that there
          # is an application context.
          app_ctx = _app_ctx_stack.top
          if app_ctx is None or app_ctx.app != self.app:
              app_ctx = self.app.app_context()
              app_ctx.push()
              self._implicit_app_ctx_stack.append(app_ctx)
          else:
              self._implicit_app_ctx_stack.append(None)
  
          if hasattr(sys, "exc_clear"):
              sys.exc_clear()
  
          _request_ctx_stack.push(self)
  
          # Open the session at the moment that the request context is available.
          # This allows a custom open_session method to use the request context.
          # Only open a new session if this is the first time the request was
          # pushed, otherwise stream_with_context loses the session.
          if self.session is None:
              session_interface = self.app.session_interface
              self.session = session_interface.open_session(self.app, self.request)
  
              if self.session is None:
                  self.session = session_interface.make_null_session(self.app)
  
      def pop(self, exc=_sentinel):
          """Pops the request context and unbinds it by doing that.  This will
          also trigger the execution of functions registered by the
          :meth:`~flask.Flask.teardown_request` decorator.
  
          .. versionchanged:: 0.9
             Added the `exc` argument.
          """
          app_ctx = self._implicit_app_ctx_stack.pop()
  
          try:
              clear_request = False
              if not self._implicit_app_ctx_stack:
                  self.preserved = False
                  self._preserved_exc = None
                  if exc is _sentinel:
                      exc = sys.exc_info()[1]
                  self.app.do_teardown_request(exc)
  
                  # If this interpreter supports clearing the exception information
                  # we do that now.  This will only go into effect on Python 2.x,
                  # on 3.x it disappears automatically at the end of the exception
                  # stack.
                  if hasattr(sys, "exc_clear"):
                      sys.exc_clear()
  
                  request_close = getattr(self.request, "close", None)
                  if request_close is not None:
                      request_close()
                  clear_request = True
          finally:
              rv = _request_ctx_stack.pop()
  
              # get rid of circular dependencies at the end of the request
              # so that we don't require the GC to be active.
              if clear_request:
                  rv.request.environ["werkzeug.request"] = None
  
              # Get rid of the app as well if necessary.
              if app_ctx is not None:
                  app_ctx.pop(exc)
  
              assert (
                  rv is self
              ), "Popped wrong request context.  " "(%r instead of %r)" % (rv, self)
  
      def auto_pop(self, exc):
          if self.request.environ.get("flask._preserve_context") or (
              exc is not None and self.app.preserve_context_on_exception
          ):
              self.preserved = True
              self._preserved_exc = exc
          else:
              self.pop(exc)
  
      def __enter__(self):
          self.push()
          return self
  
      def __exit__(self, exc_type, exc_value, tb):
          # do not pop the request stack if we are in debug mode and an
          # exception happened.  This will allow the debugger to still
          # access the request object in the interactive shell.  Furthermore
          # the context can be force kept alive for the test client.
          # See flask.testing for how this works.
          self.auto_pop(exc_value)
  
          if BROKEN_PYPY_CTXMGR_EXIT and exc_type is not None:
              reraise(exc_type, exc_value, tb)
  
      def __repr__(self):
          return "<%s '%s' [%s] of %s>" % (
              self.__class__.__name__,
              self.request.url,
              self.request.method,
              self.app.name,
          )
  