datomic.clj

(defn sp->transactions-helper
  [db sp deletions-atom]
  (let [{sname :name :as spec} (get-spec sp)
        eid (or (-> sp :db-ref :eid) (get-eid db sp spec))
        db-val (db/entity db (get-eid db sp spec))]
    (with-meta
      (hash-map
       (for [{iname :name [cardinality type] :type :as item} (:items spec)]
         (let [datomic-key (keyword (datomic-ns spec) (name iname))
               is-recursive (= :rec (recursiveness item))
               v (iname sp)
               db-v (datomic-key db-val)]
           (when (and (nil? v) (some? db-v))
             (swap! deletions-atom cons [:db/retract eid datomic-key db-v]))
           ;; TODO: set-difference for :is-many's
           [datomic-key
            (if-not is-recursive v
                    (case cardinality
                      (:is-a :is-an) (sp->transactions-helper db v deletions-atom)
                      :is-many (map #(sp->transactions-helper db % deletions-atom) v)))])))
      {:eid eid :data sp :spec spec})))

(defn sp->transactions
  [db sp]
  (let [deletions (atom '())
        datomic-data (sp->transactions-helper db sp deletions)]
    (with-meta
      (cons datomic-data @deletions)
      (meta datomic-data))))