#use "lib/utils.ml" ;;

let priority_of_item c =
  (* ASCII lower case is 97-122, upper case is 65-90 *)
  (* Lower case start at 1, upper case at 27 *)
  let code = Char.code c in
  if code > 90
  then code - 96
  else code - 65 + 27
in

let sum_of_priorities fn str =
  let chars = List.sort_uniq compare (list_of_chars str) in
  List.fold_left fn 0 chars
in

let sum_rucksack_priorities lines =
  let rucksack_priority str =
    let len2 = (String.length str)/2 in
    let comp1 = String.sub str 0 len2 in
    let comp2 = String.sub str len2 len2 in
    let char_priority agg c =
      if String.contains comp2 c
      then (agg + priority_of_item c)
      else agg
    in
    sum_of_priorities char_priority comp1
  in
  List.fold_left (+) 0 (List.map rucksack_priority lines)
in

let rec sum_badge_priorities sum lines =
  let common_badge_priority str1 str2 str3 =
    let char_priority agg c =
      if String.contains str2 c && String.contains str3 c
      then (agg + priority_of_item c)
      else agg
    in
    sum_of_priorities char_priority str1
  in
  match lines with
    | [] -> sum
    | hd1 :: tl1 -> match tl1 with
      | [] -> failwith "number of rows must be divisible by 3"
      | hd2 :: tl2 -> match tl2 with
        | [] -> failwith "number of rows must be divisible by 3"
        | hd3 :: tl3 -> sum_badge_priorities (sum + common_badge_priority hd1 hd2 hd3) tl3
in

let contents = read_file "inputs/3.txt" in
let lines = List.filter (fun l -> String.trim l <> "") (String.split_on_char '\n' contents) in
let sum1 = sum_rucksack_priorities lines in
let sum2 = sum_badge_priorities 0 lines in
Printf.printf "Part 1: %d\n" sum1;
Printf.printf "Part 2: %d\n" sum2