(defn addr [program idx]
  (nth program idx))

(defn value [program idx]
  (nth program (addr program idx)))

(defn next-op [idx]
  (+ 4 idx))

(defn eval-op [program op idx]
  (assoc program
         (addr program (+ 3 idx))
         (op (value program (inc idx))
             (value program (+ 2 idx)))))

(defn execute [program]
  (loop [program program
         i 0]
    (let [opcode (get program i)]
      (case opcode
        1 (recur (eval-op program + i)
                 (next-op i))
        2 (recur (eval-op program * i)
                 (next-op i))
        99 program))))

(defn restore [program]
  (assoc program
         1 12
         2 2))

(defn parse-input [content]
  (->> (clojure.string/split (clojure.string/trim-newline content) #",")
       (map #(Integer/valueOf %))
       vec))

(-> (slurp "/tmp/input")
    parse-input
    restore
    execute
    first) ;; => 5534943