;; Show history of an entity
;;
;; useful for interactively inspecting what happened to a datomic entity in its lifetime
;;
;; use `entity-history` to get a list of transactions that have touched the entity (assertions, retractions)
;;
;; use `explain-tx` to find out what else was transacted in the txs

(defn entity-history
  "Takes an entity and shows all the transactions that touched this entity.

  Pairs well with clojure.pprint/print-table"
  [db eid]
  (->> eid
       (d/q
        '[:find ?e ?a ?v ?tx ?added
          :in $ ?e
          :where
          [?e ?a ?v ?tx ?added]]
        (datomic.api/history db))
       (map #(->> %
                  (map vector [:e :a :v :tx :added])
                  (into {})))
       (sort-by :tx)))

(defn pretty-datom [d] (into {} (map (fn [x] [x (x d)]) [:e :a :v :tx :added])))

(defn resolve-attr [db {:keys [a] :as datom}]
  (assoc datom
         :a
         (->> a (d/entity db) :db/ident)))

(defn explain-tx
  "Takes a tx id and returns a prettified list of all datoms contained in the
  transaction. N.b. takes a conn, not a db.

  Pairs well with clojure.pprint/print-table"
  [conn tx]
  (->> (d/tx-range (d/log conn) tx nil)
       first
       :data
       (map pretty-datom)
       (map (partial resolve-attr (d/db conn)))
       (sort-by :e)))