rules_to_pred.clj

(ns rules-to-pred)

(def products
  [{:id 1
    :department "bedding"
    :category "pillow"
    :color "white"}
   {:id 2
    :department "cloth"
    :category "shirt"
    :color "red"}
   {:id 3
    :department "kids"
    :category "bottle"}
   {:id 4
    :department "cloth"
    :category "t-shirt"
    :color "white"}
   {:id 5
    :department "kids"
    :category "onesie"
    :color "white"}
   {:id 6
    :department "cloth"
    :category "pants"
    :color "black"}
   {:id 7
    :department "kids"
    :category "pants"
    :color "black"}
   {:id 8
    :department "cloth"
    :category "shirt"
    :color "white"}])

(def rules
  [{:condition :match
    :attr :department
    :value ["cloth" "kids"]
    :required true}
   {:condition :not-match
    :attr :category
    :value ["t-shirt" "shorts"]
    :required true}
   {:condition :not-match
    :attr :department
    :value "kids"
    :required true}
   {:condition :match
    :attr :color
    :value "black"}
   {:condition :match
    :attr :color
    :value "white"}])

; For rules without `:required true`, product needs to be satisfied at least one of them.

(defn rules->pred-fn
  [rules]
  ; Implement me
  )

(= (mapv :id (filter (rules->pred-fn rules) products))
   [6 8])

อันนี้ของผมครับ มีเช็ค empty ไว้ด้วย เพราะในงานที่ทำมีกรณี empty จริงๆ ครับ

(defn rule->pred-fn
  [{:keys [value condition attr]}]
  (let [value-set (if (coll? value) (set value) #{value})]
    (case condition
      :match (fn [item]
               (contains? value-set (get item attr)))
      :not-match (fn [item]
                   (not (contains? value-set (get item attr)))))))

(defn rules->pred-fn
  [rules]
  (let [{:keys [required not-required]} (group-by (fn [{:keys [required]}] (if required :required :not-required)) rules)
        required-fn (when (seq required) (apply every-pred (mapv rule->pred-fn required)))
        not-required-fn (when (seq not-required) (apply some-fn (map rule->pred-fn not-required)))]
    (apply every-pred (remove nil? [required-fn not-required-fn]))))