1 files changed, 223 insertions, 0 deletions
diff --git a/gn3/auth/authorisation/groups/models.py b/gn3/auth/authorisation/groups/models.py
new file mode 100644
index 0000000..0750419
--- /dev/null
+++ b/gn3/auth/authorisation/groups/models.py
@@ -0,0 +1,223 @@
+"""Handle the management of resource/user groups."""
+import json
+from uuid import UUID, uuid4
+from typing import Any, Sequence, Iterable, Optional, NamedTuple
+
+from flask import g
+from pymonad.maybe import Just, Maybe, Nothing
+
+from gn3.auth import db
+from gn3.auth.dictify import dictify
+from gn3.auth.authentication.users import User
+
+from ..checks import authorised_p
+from ..privileges import Privilege
+from ..errors import AuthorisationError
+from ..roles.models import (
+    Role, create_role, revoke_user_role_by_name, assign_user_role_by_name)
+
+class Group(NamedTuple):
+    """Class representing a group."""
+    group_id: UUID
+    group_name: str
+    group_metadata: dict[str, Any]
+
+    def dictify(self):
+        """Return a dict representation of `Group` objects."""
+        return {
+            "group_id": self.group_id, "group_name": self.group_name,
+            "group_metadata": self.group_metadata
+        }
+
+class GroupRole(NamedTuple):
+    """Class representing a role tied/belonging to a group."""
+    group_role_id: UUID
+    group: Group
+    role: Role
+
+    def dictify(self) -> dict[str, Any]:
+        """Return a dict representation of `GroupRole` objects."""
+        return {
+            "group_role_id": self.group_role_id, "group": dictify(self.group),
+            "role": dictify(self.role)
+        }
+
+class GroupCreationError(AuthorisationError):
+    """Raised whenever a group creation fails"""
+
+class MembershipError(AuthorisationError):
+    """Raised when there is an error with a user's membership to a group."""
+
+    def __init__(self, user: User, groups: Sequence[Group]):
+        """Initialise the `MembershipError` exception object."""
+        groups_str = ", ".join(group.group_name for group in groups)
+        error_message = (
+            f"User '{user.name} ({user.email})' is a member of {len(groups)} "
+            f"groups ({groups_str})")
+        super().__init__(f"{type(self).__name__}: {error_message}.")
+
+def user_membership(conn: db.DbConnection, user: User) -> Sequence[Group]:
+    """Returns all the groups that a member belongs to"""
+    query = (
+        "SELECT groups.group_id, group_name, groups.group_metadata "
+        "FROM group_users INNER JOIN groups "
+        "ON group_users.group_id=groups.group_id "
+        "WHERE group_users.user_id=?")
+    with db.cursor(conn) as cursor:
+        cursor.execute(query, (str(user.user_id),))
+        groups = tuple(Group(row[0], row[1], json.loads(row[2]))
+                       for row in cursor.fetchall())
+
+    return groups
+
+def create_group(
+        conn: db.DbConnection, group_name: str, group_leader: User,
+        group_description: Optional[str] = None) -> Group:
+    """Create a new group."""
+    user_groups = user_membership(conn, group_leader)
+    if len(user_groups) > 0:
+        raise MembershipError(group_leader, user_groups)
+
+    @authorised_p(
+        ("system:group:create-group",), (
+            "You do not have the appropriate privileges to enable you to "
+            "create a new group."),
+        group_leader)
+    def __create_group__():
+        with db.cursor(conn) as cursor:
+            new_group = __save_group__(
+                cursor, group_name,(
+                    {"group_description": group_description}
+                    if group_description else {}))
+            add_user_to_group(cursor, new_group, group_leader)
+            revoke_user_role_by_name(cursor, group_leader, "group-creator")
+            assign_user_role_by_name(cursor, group_leader, "group-leader")
+            return new_group
+
+    return __create_group__()
+
+@authorised_p(("group:role:create-role",),
+              error_message="Could not create the group role")
+def create_group_role(
+        conn: db.DbConnection, group: Group, role_name: str,
+        privileges: Iterable[Privilege]) -> GroupRole:
+    """Create a role attached to a group."""
+    with db.cursor(conn) as cursor:
+        group_role_id = uuid4()
+        role = create_role(cursor, role_name, privileges)
+        cursor.execute(
+            ("INSERT INTO group_roles(group_role_id, group_id, role_id) "
+             "VALUES(?, ?, ?)"),
+            (str(group_role_id), str(group.group_id), str(role.role_id)))
+
+    return GroupRole(group_role_id, group, role)
+
+def authenticated_user_group(conn) -> Maybe:
+    """
+    Returns the currently authenticated user's group.
+
+    Look into returning a Maybe object.
+    """
+    user = g.user
+    with db.cursor(conn) as cursor:
+        cursor.execute(
+            ("SELECT groups.* FROM group_users "
+             "INNER JOIN groups ON group_users.group_id=groups.group_id "
+             "WHERE group_users.user_id = ?"),
+            (str(user.user_id),))
+        groups = tuple(Group(UUID(row[0]), row[1], json.loads(row[2] or "{}"))
+                       for row in cursor.fetchall())
+
+    if len(groups) > 1:
+        raise MembershipError(user, groups)
+
+    if len(groups) == 1:
+        return Just(groups[0])
+
+    return Nothing
+
+def user_group(cursor: db.DbCursor, user: User) -> Maybe[Group]:
+    """Returns the given user's group"""
+    cursor.execute(
+        ("SELECT groups.group_id, groups.group_name, groups.group_metadata "
+         "FROM group_users "
+         "INNER JOIN groups ON group_users.group_id=groups.group_id "
+         "WHERE group_users.user_id = ?"),
+        (str(user.user_id),))
+    groups = tuple(
+        Group(UUID(row[0]), row[1], json.loads(row[2] or "{}"))
+        for row in cursor.fetchall())
+
+    if len(groups) > 1:
+        raise MembershipError(user, groups)
+
+    if len(groups) == 1:
+        return Just(groups[0])
+
+    return Nothing
+
+def is_group_leader(cursor: db.DbCursor, user: User, group: Group):
+    """Check whether the given `user` is the leader of `group`."""
+
+    ugroup = user_group(cursor, user).maybe(
+        False, lambda val: val) # type: ignore[arg-type, misc]
+    if not group:
+        # User cannot be a group leader if not a member of ANY group
+        return False
+
+    if not ugroup == group:
+        # User cannot be a group leader if not a member of THIS group
+        return False
+
+    cursor.execute(
+        ("SELECT roles.role_name FROM user_roles LEFT JOIN roles "
+         "ON user_roles.role_id = roles.role_id WHERE user_id = ?"),
+        (str(user.user_id),))
+    role_names = tuple(row[0] for row in cursor.fetchall())
+
+    return "group-leader" in role_names
+
+def all_groups(conn: db.DbConnection) -> Maybe[Sequence[Group]]:
+    """Retrieve all existing groups"""
+    with db.cursor(conn) as cursor:
+        cursor.execute("SELECT * FROM groups")
+        res = cursor.fetchall()
+        if res:
+            return Just(tuple(
+                Group(row["group_id"], row["group_name"],
+                      json.loads(row["group_metadata"])) for row in res))
+
+    return Nothing
+
+def __save_group__(
+        cursor: db.DbCursor, group_name: str,
+        group_metadata: dict[str, Any]) -> Group:
+    """Save a group to db"""
+    the_group = Group(uuid4(), group_name, group_metadata)
+    cursor.execute(
+        ("INSERT INTO groups "
+         "VALUES(:group_id, :group_name, :group_metadata) "
+         "ON CONFLICT (group_id) DO UPDATE SET "
+         "group_name=:group_name, group_metadata=:group_metadata"),
+    {"group_id": str(the_group.group_id), "group_name": the_group.group_name,
+     "group_metadata": json.dumps(the_group.group_metadata)})
+    return the_group
+
+def add_user_to_group(cursor: db.DbCursor, the_group: Group, user: User):
+    """Add `user` to `the_group` as a member."""
+    cursor.execute(
+        ("INSERT INTO group_users VALUES (:group_id, :user_id) "
+         "ON CONFLICT (group_id, user_id) DO NOTHING"),
+        {"group_id": str(the_group.group_id), "user_id": str(user.user_id)})
+
+def group_users(conn: db.DbConnection, group_id: UUID) -> Iterable[User]:
+    """Retrieve all users that are members of group with id `group_id`."""
+    with db.cursor(conn) as cursor:
+        cursor.execute(
+            "SELECT u.* FROM group_users AS gu INNER JOIN users AS u "
+            "ON gu.user_id = u.user_id WHERE gu.group_id=:group_id",
+            {"group_id": str(group_id)})
+        results = cursor.fetchall()
+
+    return (User(UUID(row["user_id"]), row["email"], row["name"])
+            for row in results)