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(require '[clojure.core.reducers :as r])
(require 'clojure.string)
(def orientation-vectors
[[[1 0 0] [0 1 0] [0 0 1]]
[[1 0 0] [0 0 -1] [0 1 0]]
[[1 0 0] [0 -1 0] [0 0 -1]]
[[1 0 0] [0 0 1] [0 -1 0]]
[[-1 0 0] [0 -1 0] [0 0 1]]
[[-1 0 0] [0 0 -1] [0 -1 0]]
[[-1 0 0] [0 1 0] [0 0 -1]]
[[-1 0 0] [0 0 1] [0 1 0]]
[[0 0 -1] [1 0 0] [0 -1 0]]
[[0 1 0] [1 0 0] [0 0 -1]]
[[0 0 1] [1 0 0] [0 1 0]]
[[0 -1 0] [1 0 0] [0 0 1]]
[[0 0 1] [-1 0 0] [0 -1 0]]
[[0 1 0] [-1 0 0] [0 0 1]]
[[0 0 -1] [-1 0 0] [0 1 0]]
[[0 -1 0] [-1 0 0] [0 0 -1]]
[[0 -1 0] [0 0 -1] [1 0 0]]
[[0 0 1] [0 -1 0] [1 0 0]]
[[0 1 0] [0 0 1] [1 0 0]]
[[0 0 -1] [0 1 0] [1 0 0]]
[[0 0 1] [0 1 0] [-1 0 0]]
[[0 -1 0] [0 0 1] [-1 0 0]]
[[0 0 -1] [0 -1 0] [-1 0 0]]
[[0 1 0] [0 0 -1] [-1 0 0]]])
(defn build-scanner-reports
"Splits slurped, split-line'd input by scanner."
[input-lines]
(loop [scanners [] rem-input input-lines]
(if (empty? rem-input)
scanners
(let [[this nxt] (split-with (comp not empty?) rem-input)]
(recur (->> (rest this)
(map #(read-string (clojure.string/join ["[" % "]"])))
(conj scanners))
(rest nxt))))))
(defn point-add [[a b c] [d e f]] [(+ a d) (+ b e) (+ c f)])
(defn orient [[x y z] [[a b c] [d e f] [g h i]]]
[(+ (* x a) (* y d) (* z g)) (+ (* x b) (* y e) (* z h)) (+ (* x c) (* y f) (* z i))])
(defn scanner-orientation [report or-index]
(map #(orient (map - %) (get orientation-vectors or-index)) report))
(defn scanner-orientations
"Builds list of scanner reports adjusted for all possible orientations."
[report]
(for [or-vec orientation-vectors]
(map #(orient (map - %) or-vec) report)))
(defn scanner-build-potential-links
"Builds a list for each s2 orientation that contains lists of each s1 point
added to the corresponding s2 point."
[s1 s2]
(for [s2-or (scanner-orientations s2)]
(for [i (range 0 (count s1))]
(for [j (range 0 (count s2-or))]
(point-add (nth s1 i) (nth s2-or j))))))
(defn scanner-find-connection
"Attempt to determine if s1 and s2 are linked through common beacons."
[s1 s2]
(loop [potential-links (as-> (scanner-build-potential-links s1 s2) $
(for [i (range 0 (count $))] [i (nth $ i)])
(into [] $))]
(when-let [[orientation link] (first potential-links)]
(if-let [match (first (drop-while #(< (val %) 12) (frequencies (reduce concat link))))]
[orientation (key match)]
(recur (rest potential-links))))))
(defn scanner-merge
"Merges the report of linked scanner s2 into scanner s1."
[s1 s2 s2-or s2-coord]
(vec (into (set s1) (map #(point-add s2-coord (map - %)) (scanner-orientation s2 s2-or)))))
(let [[beacon-count scanner-coords]
(loop [new-reps (->> (slurp "./in") clojure.string/split-lines build-scanner-reports)
sc-coords '([0 0 0])
next-reps (rest new-reps)]
(if-let [next-rep (first next-reps)]
(if-let [[found-or found-coord] (scanner-find-connection (first new-reps) next-rep)]
(let [new-base (scanner-merge (first new-reps) next-rep found-or found-coord)
newest-reps (->> (assoc new-reps 0 new-base) (filterv (partial not= next-rep)))]
(println "found" found-coord)
(recur newest-reps (conj sc-coords found-coord) (rest newest-reps)))
(recur new-reps sc-coords (rest next-reps)))
[(count (first new-reps)) sc-coords]))]
(println "Part 1:" beacon-count)
(println "Part 2:"
(apply max
(for [p1 scanner-coords p2 scanner-coords :when (not= p1 p2)]
(apply + (map #(Math/abs %) (point-add (map - p1) p2)))))))
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