(ns adventofcode2019.day16
  [:require [adventofcode2019.lib :refer :all]
   [clojure.string :as str]])

(defn parse-input [input]
  (map (comp parse-int str) input))

(defn phase [input]
  (let [pattern (fn [n]
                  (->> [0 1 0 -1]
                       (mapcat (partial repeat n))
                       (cycle)
                       (rest)))
        transform (fn [i n]
                    (->> (map * input (pattern (inc i)))
                         (reduce +)
                         (str)
                         (last)
                         (str)
                         (parse-int)))]
    (map-indexed transform input)))

(defn result-of 
  ([input]
    (result-of 0 input))
  ([offset input]
    (as-> (parse-input input) it
          (iterate phase it)
          (nth it 100)
          (drop offset it)
          (take 8 it)
          (str/join it))))

(defn fft [input]
  (->> (repeat 10000 input)
       (str/join)
       (result-of (->> input
                       (take 7)
                       (str/join)
                       (parse-int)))))

(defn day16 []
  (let [[input] (get-list-from-file (input-file))]
    (part1 (result-of input))
    (part2 (fft input))))