(ns lol.core
  (:gen-class))

(defn return [value] (fn [state] (assoc state :value value)))

(defn satisfy [f]
  (fn [state]
    (let [input (:input state)]
      (if (empty? input)
        {:input nil :ok false}
        (let [c (first input)]
          (if (f c)
            {:input (next (:input state)) :ok true :value c}
            {:input (:input state) :ok false}))))))

(defn sym [x]
  (satisfy (fn [c] (.equals c x))))

(defn >>= [parser f]
  (fn [state]
    (let [result (parser state)]
      (if (:ok result)
        ((f (:value result)) result)
        result))))

(defn >>
  ([p q]
    (>>= p (fn [_] q)))
  ([p q & more]
    (reduce >> (list* p q more))))

(defn toker [xs]
  (fn [state]
    (let [result ((reduce >> (map sym xs)) state)]
      (if (:ok result)
        result
        (assoc result :ok false)))))

(def pillu (>> (toker "muna") (return "LAPSI")))

(defn -main
  "I don't do a whole lot ... yet."
  [& args]
  (println "Hello, World!"))