(ns day01)

(defn fuel-needed
  "calculates fuel needed for given mass"
  [mass]
  (max (-> mass
           (/ 3)
           long
           (- 2))
       0))

(defn total-fuel-needed
  "calculates total fuel needed accounting for weight of gas as well"
  ([mass]
   (total-fuel-needed mass 0))
  ([mass acc]
   (let [f (fuel-needed mass)]
     (if (= f 0)
       acc
       (recur f (+ acc f))))))

(comment
  (require '[clojure.string :as str])

  ; part 1
  (->> input
       str/split-lines
       (map parse-long)
       (map fuel-needed)
       (reduce +))

  ; part 2
  (->> input
       str/split-lines
       (map parse-long)
       (map total-fuel-needed)
       (reduce +))

  (def input "83453
89672
81336
74923
71474
117060
55483
116329
123515
99383
80314
108221
128335
72860
139235
127843
140120
63561
68854
109062
146211
59096
123085
105763
127657
142212
111007
100166
63641
59010
108575
93619
144095
74561
95059
145318
81404
96567
91799
92987
107137
87678
126842
85594
116330
104714
128117
132641
75602
90747
69038
67322
146147
147535
83266
85908
124634
51681
104430
56202
68631
69970
116985
140878
125357
126229
66379
103213
108210
73855
130992
113363
82298
111468
110751
52272
103661
122262
114363
80881
65183
125291
100119
56995
101634
55467
136284
107433
95647
71462
133265
104554
62499
61347
68675
123501
113954
135798
80825
128235"))