Read-Only Joined Collection in NHibernate - nhibernate

Question

Here is the basic situation. In our application, we have Roles and Permissions. There is a many-to-many relationship between roles and permission. The catch is, that a user can be assigned roles directly, or they can have a role that they have acquired by paying for a service. To make things more interesting, if the user cancels the paid service, or it expires, then they should no longer have that role. My issue is that I would like to have a (read-only) collection of the Effective Permissions on any given user, and I'd like to be able to query against it. Some mapping details:
public ApplicationPermissionMap()
{
Table("CLSYS_ApplicationPermissions");
Id(ap => ap.ID)
.Column("ApplicationPermissionID")
.GeneratedBy.Assigned();
//...
}
public ApplicationRoleMap()
{
Table("CLSYS_ApplicationRole");
Id(role => role.ID)
.Column("ApplicationRoleID");
HasManyToMany(r => r.Permissions)
.Table("CLSYS_ApplicationRolePermissions")
.ParentKeyColumn("ApplicationRoleID")
.ChildKeyColumn("PermissionID")
.Cascade.None();
//...
}
public PaidServiceMap()
{
Table("ECOM_PaidService");
Id(ps => ps.ID)
.Column("PaidServiceID");
Component(ps => ps.Status, statusMapping =>
{
statusMapping.Map(status => status.ID)
.Column("StatusID")
.Not.Nullable();
});
HasManyToMany(ps => ps.ApplicationRoles)
.Table("ECOM_PaidServiceRoles")
.ParentKeyColumn("PaidServiceID")
.ChildKeyColumn("RoleID")
.Cascade.None();
//....
}
public UserMap()
{
Table("CLSYS_User");
Id(user => user.ID)
.Column("UserID");
HasManyToMany(user => user.Roles)
.Table("CLSYS_User_ApplicationRoles")
.ParentKeyColumn("UserID")
.ChildKeyColumn("RoleID")
.Cascade.None();
//...
}
What I need is something like this (an addition to UserMap above)
public UserMap()
{
//...
HasMany(user => user.EffectivePermissions)
//Union ( user -> ApplicationRoles -> permissions)
//Union ( user -> PaidServices [with active status] -> permissions)
//Distinct
}
And I would like to be able to query on these permissions like so
_session.Linq<User>().Where(u => u.EffectivePermssions.Contains(somePermission) && user.SomeOtherCriteria == something);
I understand that I wouldn't be able to modify this collection directly, and that is perfectly acceptable. Can anyone help me out with this mapping?

Answer 1

As a short term solution, I have created a view that handles the union logic, and have the following mapping:
HasManyToMany(user => user.EffectivePermissions)
.Table("VW_CLSYS_User_EffectiveApplicationPermissions")
.ParentKeyColumn("UserID")
.ChildKeyColumn("ApplicationPermissionID")
.Inverse();
This is not ideal, as I'd prefer to have the logic in the mapping for the user. Any other suggestions are welcome.