let input = Reuse.split "inputs/day01.txt" '\n'


let convert (s : string): int =
  let first_char = s.[0] in 
  let remainder = String.sub s 1 (String.length s - 1) in 
  let distance = int_of_string remainder in
  match first_char with 
  | 'L' -> -distance
  | 'R' -> distance
  | _ -> raise (Invalid_argument "Invalid input") 

  
let count_if_zero (counter: int) (position: int) =
  if position == 0 then counter + 1 else counter
  
let normalize_position (pos : int) (modulus : int) =
  let result = pos mod modulus in
  if result >= 0 then result else result + modulus

let count_boundary_crossings (counter: int) (position: int) (movement: int) = 
  let full_rotations = abs movement / 100 in
  let remaining_movement = movement mod 100 in
  let new_position = position + remaining_movement in
  let boundary_crossings = 
    if (new_position >= 100 && position < 100) || 
       (new_position <= 0 && position > 0) then 1 else 0
  in
  counter + full_rotations + boundary_crossings



let rec update (values: int list) (position: int) (counter: int) : int =
  match values with
  | [] -> counter
  | x :: xs -> let new_position = normalize_position (position + x) 100 in 
  update xs new_position (count_if_zero counter new_position)
  
let rec update_part2 (values: int list) (position: int) (counter: int) : int =
  match values with
  | [] -> counter
  | x :: xs -> let new_position = normalize_position (position + x) 100 in
  update_part2 xs new_position (count_boundary_crossings counter position x)

let solve_part1 (lines: string list) : int =
  update (List.map convert lines) 50 0

let solve_part2 (lines: string list) : int =
  update_part2 (List.map convert lines) 50 0

let day1_part1 : int =
  solve_part1 input
  
let day1_part2 : int =
  solve_part2 input

module Tests = struct
let test_input = "L268
L30
R48
L5
R60
L55
L1
L99
R14
L82"

let test_lines = String.split_on_char '\n' test_input

let run_tests () = 
  let part1_result = solve_part1 test_lines in
  let part2_result = solve_part2 test_lines in
  if part1_result <> 3 then
    failwith ("Day 1 Part 1 test failed: expected 3, got " ^ string_of_int part1_result);
    
  if part2_result <> 8 then
      failwith ("Day 1 Part 2 test failed: expected 8, got " ^ string_of_int part2_result);
    
  Printf.printf "All Day 1 tests passed!\n"
end

let () = Tests.run_tests()