basic invitation model with domain class

atst/domain/invitations.py

@@ -0,0 +1,62 @@
+import datetime
+from sqlalchemy.orm.exc import NoResultFound
+
+from atst.database import db
+from atst.models import Invitation
+
+from .exceptions import NotFoundError
+
+
+class InvitationExpired(Exception):
+    def __init__(self, invite_id):
+        self.invite_id = invite_id
+
+    @property
+    def message(self):
+        return "{} has expired".format(self.invite_id)
+
+
+class Invitations(object):
+    EXPIRATION_LIMIT = 360
+
+    @classmethod
+    def _get(cls, invite_id):
+        try:
+            invite = db.session.query(Invitation).filter_by(id=invite_id).one()
+        except NoResultFound:
+            raise NotFoundError("invite")
+
+        return invite
+
+    @classmethod
+    def create(cls, workspace, user):
+        invite = Invitation(workspace=workspace, user=user, valid=True)
+        db.session.add(invite)
+        db.session.commit()
+
+        return invite
+
+    @classmethod
+    def accept(cls, invite_id):
+        invite = Invitations._get(invite_id)
+        valid = Invitations._is_valid(invite)
+
+        invite.valid = False
+        db.session.add(invite)
+        db.session.commit()
+
+        if not valid:
+            raise InvitationExpired(invite_id)
+
+        return invite
+
+    @classmethod
+    def _is_valid(cls, invite):
+        if not invite.valid:
+            return False
+        else:
+            time_created = invite.time_created
+            expiration = datetime.datetime.now(
+                time_created.tzinfo
+            ) - datetime.timedelta(minutes=Invitations.EXPIRATION_LIMIT)
+            return invite.time_created > expiration