script.gleam

import gleam/int
import gleam/io
import gleam/list
import gleam/string
import simplifile

pub fn execute() -> Nil {
  case simplifile.read(from: "./inputs/day1.txt") {
    Error(e) -> io.println("cannot read input " <> string.inspect(e))
    Ok(content) -> {
      let result =
        string.trim(content)
        |> string.split("\n")
        |> list.filter(fn(it) { !string.is_empty(it) })
        |> list.map(fn(it) {
          let #(multiplier, text) = case string.pop_grapheme(it) {
            Ok(#("R", rest)) -> #(1, rest)
            Ok(#("L", rest)) -> #(-1, rest)
            Ok(#(it, _)) -> panic as {"Expected R or L but got " <> it}
            Error(e) -> panic as {"cannot parse " <> string.inspect(e)}
          }
          let assert Ok(i) = int.parse(text)
          multiplier * i
        })
        |> list.fold(#(50, 0), fn(acc, curr) {
          let #(previous_state, counter) = acc
          let state_after_rotation = previous_state + curr
          let normalized_state = normalize(state_after_rotation)
          case normalized_state {
            0 -> #(normalized_state, counter + 1)
            _ -> #(normalized_state, counter)
          }
        })

      let #(_, counter) = result
      io.println("result is " <> int.to_string(counter))
    }
  }
}

fn normalize(state: Int) -> Int {
  let state = state % 100
  case state {
    100 -> 0
    it if it < 0 -> it + 100
    _ -> state
  }
}