unfinished.ml

open Containers

type state =
  | Empty
  | Head
  | Tail
  | Conductor
type cell = {
  mutable state : state;
  mutable neighbors : cell list
}

let tick (board : cell array array) : unit =
  for y = 0 to Array.length board do
    for x = 0 to Array.length board.(0) do
      let cell_cur = board.(y).(x) in
      cell_cur.state <-
        match cell_cur.state with
        | Head -> Tail
        | Tail -> Conductor
        | Conductor ->
          let num_heads = List.length (List.filter (fun c -> Equal.physical c.state Head) cell_cur.neighbors) in
          if num_heads = 2 || num_heads = 1 then Head else Conductor
        | Empty -> Empty
    done
  done

let decode_board str =
  let decode_variant = function
    | 'O' -> Head
    | 'o' -> Tail
    | '#' -> Conductor
    | _   -> Empty in
  let justify xs =
    let longest = Array.fold_left (fun acc x -> Int.max acc (Array.length x)) 0 xs in
    Array.map (fun x ->
        if Array.length x < longest then
          Array.concat [ x; Array.init (longest - Array.length x) (fun _ -> ' ') ]
        else x) xs in
  let board =
    str
    |> String.split ~by:"\n"
    |> Array.of_list
    |> Array.map String.to_array
    |> justify
    |> Array.mapi (fun posx x->
        Array.mapi (fun posy y ->
            {
              state = decode_variant y;
              neighbors = []
            }
          ) x) in
  let ymax = Array.length board - 1 in
  let xmax = Array.length board.(0) - 1 in
  for y = 0 to ymax do
    for x = 0 to xmax do
      board.(y).(x).neighbors <- List.filter_map (fun a -> (* This essentially checks whether a potential neighbor is within bounds of the board *)
          let (x', y', el) = a in
          let yrel = match y with
            | 0 -> -1
            | _ -> if y = ymax then 1 else 0 in
          let xrel = match x with
            | 0 -> -1
            | _ -> if x = xmax then 1 else 0 in
          match (y', x', y' - yrel, x' - xrel) with
          | (_, _, 0, 0) -> Some el
          | (0, _, _, 0) -> Some el
          | (_, 0, 0, _) -> Some el
          | _            -> None
        ) [
          (-1,  0, board.(y-1).(x));
          ( 1,  0, board.(y+1).(x));
          (-1, -1, board.(y-1).(x-1));
          ( 1, -1, board.(y+1).(x-1));
          ( 1,  1, board.(y+1).(x+1));
          (-1,  1, board.(y-1).(x+1));
          ( 0, -1, board.(y).(x-1));
          ( 0,  1, board.(y).(x+1));
        ]
    done
  done;
  board

let () =
  let is = if Array.length Sys.argv >= 3 then open_in Sys.argv.(2) else stdin in
  let board = decode_board @@ IO.read_all is in
  for gen = 0 to int_of_string (Sys.argv.(1)) do
    tick board
  done