Externally batching and updating the working memory state

clara-batched-updates.clj

(defrecord PrevFetchedItems [item-ids])
(defrecord ToFetch [items])

(r/defrule find-items-to-fetch
  [PrevFetchedItems (= ?item-ids item-ids)]
  [?items <- (acc/all) :from [Item (not (contains? ?items id))]]
  =>
  (r/insert! (->ToFetch ?items)))

(r/defquery get-items-to-fetch []
  [?to-fetch <- ToFetch])

(defn run-fetch-rules [new-items prev-fetched-ids]
  (let [s (-> (r/mk-session)
              (r/insert-all new-items)
              (r/insert (->PrevFetchedItems prev-fetched-ids))
              r/fire-rules)]
    (-> s
        (r/query get-items-to-fetch)
        :?to-fetch
        :items)))

(defn fetch-items! [items]
  (do-fetching items))

(defn batched-fetching [batches]
  (reduce (fn [[all-fetched-vals prev-fetched-ids] items]
            (let [to-fetch-items (run-fetch-rules items prev-fetched-ids)
                  fetched-vals (fetch-items! to-fetch-items)]
              [(into all-fetched-vals fetched-vals)
               (into prev-fetched-ids (map :id) to-fetch-items)]))
          [[] #{}]
          batches))