Convert watch page to flask framework

1 files changed, 385 insertions, 0 deletions

diff --git a/python/flask/sessions.py b/python/flask/sessions.py
new file mode 100644
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+++ b/python/flask/sessions.py
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+# -*- coding: utf-8 -*-
+"""
+    flask.sessions
+    ~~~~~~~~~~~~~~
+
+    Implements cookie based sessions based on itsdangerous.
+
+    :copyright: © 2010 by the Pallets team.
+    :license: BSD, see LICENSE for more details.
+"""
+
+import hashlib
+import warnings
+from datetime import datetime
+
+from itsdangerous import BadSignature, URLSafeTimedSerializer
+from werkzeug.datastructures import CallbackDict
+
+from flask._compat import collections_abc
+from flask.helpers import is_ip, total_seconds
+from flask.json.tag import TaggedJSONSerializer
+
+
+class SessionMixin(collections_abc.MutableMapping):
+    """Expands a basic dictionary with session attributes."""
+
+    @property
+    def permanent(self):
+        """This reflects the ``'_permanent'`` key in the dict."""
+        return self.get('_permanent', False)
+
+    @permanent.setter
+    def permanent(self, value):
+        self['_permanent'] = bool(value)
+
+    #: Some implementations can detect whether a session is newly
+    #: created, but that is not guaranteed. Use with caution. The mixin
+    # default is hard-coded ``False``.
+    new = False
+
+    #: Some implementations can detect changes to the session and set
+    #: this when that happens. The mixin default is hard coded to
+    #: ``True``.
+    modified = True
+
+    #: Some implementations can detect when session data is read or
+    #: written and set this when that happens. The mixin default is hard
+    #: coded to ``True``.
+    accessed = True
+
+
+class SecureCookieSession(CallbackDict, SessionMixin):
+    """Base class for sessions based on signed cookies.
+
+    This session backend will set the :attr:`modified` and
+    :attr:`accessed` attributes. It cannot reliably track whether a
+    session is new (vs. empty), so :attr:`new` remains hard coded to
+    ``False``.
+    """
+
+    #: When data is changed, this is set to ``True``. Only the session
+    #: dictionary itself is tracked; if the session contains mutable
+    #: data (for example a nested dict) then this must be set to
+    #: ``True`` manually when modifying that data. The session cookie
+    #: will only be written to the response if this is ``True``.
+    modified = False
+
+    #: When data is read or written, this is set to ``True``. Used by
+    # :class:`.SecureCookieSessionInterface` to add a ``Vary: Cookie``
+    #: header, which allows caching proxies to cache different pages for
+    #: different users.
+    accessed = False
+
+    def __init__(self, initial=None):
+        def on_update(self):
+            self.modified = True
+            self.accessed = True
+
+        super(SecureCookieSession, self).__init__(initial, on_update)
+
+    def __getitem__(self, key):
+        self.accessed = True
+        return super(SecureCookieSession, self).__getitem__(key)
+
+    def get(self, key, default=None):
+        self.accessed = True
+        return super(SecureCookieSession, self).get(key, default)
+
+    def setdefault(self, key, default=None):
+        self.accessed = True
+        return super(SecureCookieSession, self).setdefault(key, default)
+
+
+class NullSession(SecureCookieSession):
+    """Class used to generate nicer error messages if sessions are not
+    available.  Will still allow read-only access to the empty session
+    but fail on setting.
+    """
+
+    def _fail(self, *args, **kwargs):
+        raise RuntimeError('The session is unavailable because no secret '
+                           'key was set.  Set the secret_key on the '
+                           'application to something unique and secret.')
+    __setitem__ = __delitem__ = clear = pop = popitem = \
+        update = setdefault = _fail
+    del _fail
+
+
+class SessionInterface(object):
+    """The basic interface you have to implement in order to replace the
+    default session interface which uses werkzeug's securecookie
+    implementation.  The only methods you have to implement are
+    :meth:`open_session` and :meth:`save_session`, the others have
+    useful defaults which you don't need to change.
+
+    The session object returned by the :meth:`open_session` method has to
+    provide a dictionary like interface plus the properties and methods
+    from the :class:`SessionMixin`.  We recommend just subclassing a dict
+    and adding that mixin::
+
+        class Session(dict, SessionMixin):
+            pass
+
+    If :meth:`open_session` returns ``None`` Flask will call into
+    :meth:`make_null_session` to create a session that acts as replacement
+    if the session support cannot work because some requirement is not
+    fulfilled.  The default :class:`NullSession` class that is created
+    will complain that the secret key was not set.
+
+    To replace the session interface on an application all you have to do
+    is to assign :attr:`flask.Flask.session_interface`::
+
+        app = Flask(__name__)
+        app.session_interface = MySessionInterface()
+
+    .. versionadded:: 0.8
+    """
+
+    #: :meth:`make_null_session` will look here for the class that should
+    #: be created when a null session is requested.  Likewise the
+    #: :meth:`is_null_session` method will perform a typecheck against
+    #: this type.
+    null_session_class = NullSession
+
+    #: A flag that indicates if the session interface is pickle based.
+    #: This can be used by Flask extensions to make a decision in regards
+    #: to how to deal with the session object.
+    #:
+    #: .. versionadded:: 0.10
+    pickle_based = False
+
+    def make_null_session(self, app):
+        """Creates a null session which acts as a replacement object if the
+        real session support could not be loaded due to a configuration
+        error.  This mainly aids the user experience because the job of the
+        null session is to still support lookup without complaining but
+        modifications are answered with a helpful error message of what
+        failed.
+
+        This creates an instance of :attr:`null_session_class` by default.
+        """
+        return self.null_session_class()
+
+    def is_null_session(self, obj):
+        """Checks if a given object is a null session.  Null sessions are
+        not asked to be saved.
+
+        This checks if the object is an instance of :attr:`null_session_class`
+        by default.
+        """
+        return isinstance(obj, self.null_session_class)
+
+    def get_cookie_domain(self, app):
+        """Returns the domain that should be set for the session cookie.
+
+        Uses ``SESSION_COOKIE_DOMAIN`` if it is configured, otherwise
+        falls back to detecting the domain based on ``SERVER_NAME``.
+
+        Once detected (or if not set at all), ``SESSION_COOKIE_DOMAIN`` is
+        updated to avoid re-running the logic.
+        """
+
+        rv = app.config['SESSION_COOKIE_DOMAIN']
+
+        # set explicitly, or cached from SERVER_NAME detection
+        # if False, return None
+        if rv is not None:
+            return rv if rv else None
+
+        rv = app.config['SERVER_NAME']
+
+        # server name not set, cache False to return none next time
+        if not rv:
+            app.config['SESSION_COOKIE_DOMAIN'] = False
+            return None
+
+        # chop off the port which is usually not supported by browsers
+        # remove any leading '.' since we'll add that later
+        rv = rv.rsplit(':', 1)[0].lstrip('.')
+
+        if '.' not in rv:
+            # Chrome doesn't allow names without a '.'
+            # this should only come up with localhost
+            # hack around this by not setting the name, and show a warning
+            warnings.warn(
+                '"{rv}" is not a valid cookie domain, it must contain a ".".'
+                ' Add an entry to your hosts file, for example'
+                ' "{rv}.localdomain", and use that instead.'.format(rv=rv)
+            )
+            app.config['SESSION_COOKIE_DOMAIN'] = False
+            return None
+
+        ip = is_ip(rv)
+
+        if ip:
+            warnings.warn(
+                'The session cookie domain is an IP address. This may not work'
+                ' as intended in some browsers. Add an entry to your hosts'
+                ' file, for example "localhost.localdomain", and use that'
+                ' instead.'
+            )
+
+        # if this is not an ip and app is mounted at the root, allow subdomain
+        # matching by adding a '.' prefix
+        if self.get_cookie_path(app) == '/' and not ip:
+            rv = '.' + rv
+
+        app.config['SESSION_COOKIE_DOMAIN'] = rv
+        return rv
+
+    def get_cookie_path(self, app):
+        """Returns the path for which the cookie should be valid.  The
+        default implementation uses the value from the ``SESSION_COOKIE_PATH``
+        config var if it's set, and falls back to ``APPLICATION_ROOT`` or
+        uses ``/`` if it's ``None``.
+        """
+        return app.config['SESSION_COOKIE_PATH'] \
+               or app.config['APPLICATION_ROOT']
+
+    def get_cookie_httponly(self, app):
+        """Returns True if the session cookie should be httponly.  This
+        currently just returns the value of the ``SESSION_COOKIE_HTTPONLY``
+        config var.
+        """
+        return app.config['SESSION_COOKIE_HTTPONLY']
+
+    def get_cookie_secure(self, app):
+        """Returns True if the cookie should be secure.  This currently
+        just returns the value of the ``SESSION_COOKIE_SECURE`` setting.
+        """
+        return app.config['SESSION_COOKIE_SECURE']
+
+    def get_cookie_samesite(self, app):
+        """Return ``'Strict'`` or ``'Lax'`` if the cookie should use the
+        ``SameSite`` attribute. This currently just returns the value of
+        the :data:`SESSION_COOKIE_SAMESITE` setting.
+        """
+        return app.config['SESSION_COOKIE_SAMESITE']
+
+    def get_expiration_time(self, app, session):
+        """A helper method that returns an expiration date for the session
+        or ``None`` if the session is linked to the browser session.  The
+        default implementation returns now + the permanent session
+        lifetime configured on the application.
+        """
+        if session.permanent:
+            return datetime.utcnow() + app.permanent_session_lifetime
+
+    def should_set_cookie(self, app, session):
+        """Used by session backends to determine if a ``Set-Cookie`` header
+        should be set for this session cookie for this response. If the session
+        has been modified, the cookie is set. If the session is permanent and
+        the ``SESSION_REFRESH_EACH_REQUEST`` config is true, the cookie is
+        always set.
+
+        This check is usually skipped if the session was deleted.
+
+        .. versionadded:: 0.11
+        """
+
+        return session.modified or (
+            session.permanent and app.config['SESSION_REFRESH_EACH_REQUEST']
+        )
+
+    def open_session(self, app, request):
+        """This method has to be implemented and must either return ``None``
+        in case the loading failed because of a configuration error or an
+        instance of a session object which implements a dictionary like
+        interface + the methods and attributes on :class:`SessionMixin`.
+        """
+        raise NotImplementedError()
+
+    def save_session(self, app, session, response):
+        """This is called for actual sessions returned by :meth:`open_session`
+        at the end of the request.  This is still called during a request
+        context so if you absolutely need access to the request you can do
+        that.
+        """
+        raise NotImplementedError()
+
+
+session_json_serializer = TaggedJSONSerializer()
+
+
+class SecureCookieSessionInterface(SessionInterface):
+    """The default session interface that stores sessions in signed cookies
+    through the :mod:`itsdangerous` module.
+    """
+    #: the salt that should be applied on top of the secret key for the
+    #: signing of cookie based sessions.
+    salt = 'cookie-session'
+    #: the hash function to use for the signature.  The default is sha1
+    digest_method = staticmethod(hashlib.sha1)
+    #: the name of the itsdangerous supported key derivation.  The default
+    #: is hmac.
+    key_derivation = 'hmac'
+    #: A python serializer for the payload.  The default is a compact
+    #: JSON derived serializer with support for some extra Python types
+    #: such as datetime objects or tuples.
+    serializer = session_json_serializer
+    session_class = SecureCookieSession
+
+    def get_signing_serializer(self, app):
+        if not app.secret_key:
+            return None
+        signer_kwargs = dict(
+            key_derivation=self.key_derivation,
+            digest_method=self.digest_method
+        )
+        return URLSafeTimedSerializer(app.secret_key, salt=self.salt,
+                                      serializer=self.serializer,
+                                      signer_kwargs=signer_kwargs)
+
+    def open_session(self, app, request):
+        s = self.get_signing_serializer(app)
+        if s is None:
+            return None
+        val = request.cookies.get(app.session_cookie_name)
+        if not val:
+            return self.session_class()
+        max_age = total_seconds(app.permanent_session_lifetime)
+        try:
+            data = s.loads(val, max_age=max_age)
+            return self.session_class(data)
+        except BadSignature:
+            return self.session_class()
+
+    def save_session(self, app, session, response):
+        domain = self.get_cookie_domain(app)
+        path = self.get_cookie_path(app)
+
+        # If the session is modified to be empty, remove the cookie.
+        # If the session is empty, return without setting the cookie.
+        if not session:
+            if session.modified:
+                response.delete_cookie(
+                    app.session_cookie_name,
+                    domain=domain,
+                    path=path
+                )
+
+            return
+
+        # Add a "Vary: Cookie" header if the session was accessed at all.
+        if session.accessed:
+            response.vary.add('Cookie')
+
+        if not self.should_set_cookie(app, session):
+            return
+
+        httponly = self.get_cookie_httponly(app)
+        secure = self.get_cookie_secure(app)
+        samesite = self.get_cookie_samesite(app)
+        expires = self.get_expiration_time(app, session)
+        val = self.get_signing_serializer(app).dumps(dict(session))
+        response.set_cookie(
+            app.session_cookie_name,
+            val,
+            expires=expires,
+            httponly=httponly,
+            domain=domain,
+            path=path,
+            secure=secure,
+            samesite=samesite
+        )