yo.clj

(ns adoc.core
  (:require [clojure.string :as str]))

(defn parse-name [room]
  (let [parsed (str/split room #"-")
        name (drop-last parsed)
        sector-checksum (str/split (last parsed) #"\[")
        sector (first sector-checksum)
        checksum (str/replace (last sector-checksum) "]" "")]
    {:room-name name
     :sector-id sector
     :checksum checksum}))

(defn get-frequencies [room-name]
  (reduce #(conj %1 [(first %2)  (count %2)])
          []
          (partition-by identity (sort (str/join room-name)))))

(defn extract-checksum [frequencies]
  (->> frequencies
       (group-by last)
       (sort-by key)
       reverse
       flatten
       (filter char?)
       (take 5)
       (apply str)))

(defn sector-val [input]
  (let [room (parse-name input)
        room-name (:room-name room)
        checksum (extract-checksum (get-frequencies room-name))]
    (if (= checksum (:checksum room))
      (Integer/valueOf (:sector-id room))
      0)))

(defn shift-cipher [a s]
  (let [v (int a)
        r (rem s 26)]
    (char (+ v r))))

(defn -main [& args]
  (with-open [rdr (clojure.java.io/reader "input.txt")]
    (reduce #(+ %1 (sector-val %2))
            0
            (line-seq rdr))))

(comment
  (def t1 "not-a-real-room-404[oarel]")

  (shift-cipher \b 26)
  (shift-cipher \z 343)

  (letter-counts (:room-name (parse-name t1)))
  (extract-checksum (letter-counts (:room-name (parse-name t1))))
  (is-real? t1)
  (def t2 "totally-real-room-200[decoy]")
  (extract-checksum (letter-counts (:room-name (parse-name t2))))
  (is-real? t2)

  (-main)
  ;;COMMENT
  )