(ns question-4
  (:require [inputs]
            [clojure.set]
            [clojure.string :as strings]))
(def mock-input "..@@.@@@@.\n@@@.@.@.@@\n@@@@@.@.@@\n@.@@@@..@.\n@@.@@@@.@@\n.@@@@@@@.@\n.@.@.@.@@@\n@.@@@.@@@@\n.@@@@@@@@.\n@.@.@@@.@.")

(defn parse-input [document]
  (let [x (map vec (strings/split-lines document))]
    (apply hash-set (for [[line-idx line] (map-indexed vector x)
                          [col-idx e] (map-indexed vector line)
                          :when (= e \@)] [line-idx col-idx]))))

(defn neighbourhood [[row col]]
  (for [delta-row [-1 0 1]
        delta-col [-1 0 1]
        :when (not= 0 delta-row delta-col)]
    [(+ delta-row row) (+ col delta-col)]))

(defn accessible? [roll all-rolls]
  (< (count (filter #(contains? all-rolls %) (neighbourhood roll))) 4))

(defn how-many-accessible [all-rolls]
  (count (filter #(accessible? % all-rolls) all-rolls)))

(defn remove-all [all-rolls]
  (let [to-remove (filter #(accessible? % all-rolls) all-rolls)]
    (if (empty? to-remove)
      all-rolls
      (recur (clojure.set/difference all-rolls to-remove)))))

(defn question-4-a [document]
  (-> document parse-input how-many-accessible))

(defn question-4-b [document]
  (let [all-rolls (parse-input document)
        final-rolls (remove-all all-rolls)]
    (- (count all-rolls) (count final-rolls))))

(defn -main [& args]
  (println "Solution to question 4-a is: " (question-4-a inputs/question-4))
  (println "Solution to question 4-b is: " (question-4-b inputs/question-4)))