Managing Roles Memberships in Fauna (DB)

readme.md

Managing Roles Memberships in Fauna (DB) (the hacky way)

The above definitions are a hacky way to manage base role memberships while still being able to do proper check of a Ref roles.

You would manage the memberships predicates by modifying a User-Defined Function. (It doesn't sound amazing but well, until we're able to read a predicate and use it as a Lambda, I see no other way.)

Let me know if you see optimizations ;)

HasRoleUDF.js

// HasRole - User-Defined Function
CreateFunction({
  name: 'HasRole',
  body: Query(Lambda(['role', 'ref'], Select(Var('role'), Call('RolesMemberships', [Var('ref')]), false)))
})

RolesMembershipsUDF.js

// RolesMemberships - User-Defined Function
CreateFunction({
  name: 'RolesMemberships',
  body: Query(
    Lambda(
      ['ref'],
      Let(
        {
          doc: Get(Var('ref')),
          collection: Select('collection', Var('ref'), null)
        },
        If(IsNull(Var('collection')), Abort('No collection found in the Ref'), {
          // Roles Memberships predicates
          user: If(Equals(Var('collection'), Collection('users')), true, false)
        })
      )
    )
  )
})

UserRole.js

// Example of a "user" Role - using the RolesMemberships UDF via HasRole UDF
CreateRole({
  name: 'user',
  membership: [
    {
      resource: Collection('users'),
      predicate: Lambda('ref', Call('HasRole', 'user', 'ref'))
    }
  ],
  // example of privileges
  privileges: [
    {
      resource: Collection('users'),
      action: {
        read: Lambda(
          'ref',
          Equals(
            Identity(),
            Select(['data', 'owner'], Get(Var('ref')))
          )
        )
      }
    }
  ]
})