import gleam/list
import gleam/dict.{type Dict}
import gleam/string
import gleam/int
import gleam/result

pub type Posn {
  Posn(r: Int, c: Int)
}

pub type Array2D(a) =
  Dict(Posn, a)

pub fn add_posns(p1: Posn, p2: Posn) -> Posn {
  case p1, p2 {
    Posn(r1, c1), Posn(r2, c2) -> Posn(r1 + r2, c1 + c2)
  }
}

pub fn ortho_neighbors(p: Posn) -> List(Posn) {
  let Posn(r, c) = p
  [Posn(r + 1, c), Posn(r - 1, c), Posn(r, c + 1), Posn(r, c - 1)]
}

pub fn to_2d_array(xss: List(List(a))) -> Array2D(a) {
  to_2d_array_using(xss, fn(x) { Ok(x) })
}

pub fn to_2d_array_using(
  xss: List(List(a)),
  f: fn(a) -> Result(b, Nil),
) -> Array2D(b) {
  {
    use r, row <- list.index_map(xss)
    use c, cell <- list.index_map(row)
    case f(cell) {
      Ok(contents) -> Ok(#(Posn(r, c), contents))
      Error(Nil) -> Error(Nil)
    }
  }
  |> list.flatten
  |> result.values
  |> dict.from_list
}

pub fn to_2d_intarray(xss: List(List(String))) -> Array2D(Int) {
  {
    use r, row <- list.index_map(xss)
    use c, cell <- list.index_map(row)
    let assert Ok(n) = int.parse(cell)
    #(Posn(r, c), n)
  }
  |> list.flatten
  |> dict.from_list
}

pub fn to_list_of_lists(str: String) -> List(List(String)) {
  str
  |> string.split("\n")
  |> list.map(string.to_graphemes)
}

pub fn parse_grid(str: String) -> Array2D(String) {
  parse_grid_using(str, fn(x) { Ok(x) })
}

pub fn parse_grid_using(
  str: String,
  f: fn(String) -> Result(a, Nil),
) -> Array2D(a) {
  str
  |> to_list_of_lists
  |> to_2d_array_using(f)
}