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(ns aoc.day03
  (:require [clojure.java.io :as io]))

(def example
  "..##.......
#...#...#..
.#....#..#.
..#.#...#.#
.#...##..#.
..#.##.....
.#.#.#....#
.#........#
#.##...#...
#...##....#
.#..#...#.#")

(def paths
  [[1 1]
   [3 1]
   [5 1]
   [7 1]
   [1 2]])

(defn read-input []
  (->> (slurp (io/resource "input03.txt"))
       clojure.string/split-lines))

(defn all-coordinates [[x y]]
  (iterate (fn [[xx yy]]
             [(+ x xx)
              (+ y yy)])
           [0 0]))

(defn tree? [s]
  (= s \#))

(defn count-trees [lines]
  (fn [acc [x y]]
    (let [line (nth lines y)
          spot (nth line x)]
      (if (tree? spot)
        (inc acc)
        acc))))

(defn compute [input coords]
  (let [infinite-lines (map cycle input)
        needed-coords (take-while #(< (second %)
                                      (count input))
                                  coords)]
    (reduce (count-trees infinite-lines) 0 needed-coords)))

;; ----------------------------------------------------------------------------

(defn compute-1 [input]
  (let [infinite-lines (map cycle input)
        infinite-coords (all-coordinates [3 1])
        needed-coords (take-while #(< (second %)
                                      (count input)) infinite-coords)]
    (reduce (count-trees infinite-lines) 0 needed-coords)))

(defn compute-2 [input]
  (let [c (partial compute input)
        coords (map all-coordinates paths)]
    (->> coords
         (map c)
         (apply *))))

(defn main []
  (let [input (read-input)]
    (println (compute-1 input))
    (println (compute-2 input))))

(main)