structure Parser =
struct
  structure T = Tokens

  fun parseItems (tokens, grid) =
    case tokens of
      T.L_BRACE ::
        T.INT x ::
          T.INT y ::
            T.INT ex ::
              T.INT ey ::
                T.INT r :: T.INT g :: T.INT b :: T.INT a :: T.R_BRACE :: tl =>
        let
          val colour = {r = r, g = g, b = b, a = a}
          val grid = ParseGrid.applyItem (grid, x, y, ex, ey, colour)
        in
          parseItems (tl, grid)
        end
    | _ => SOME (tokens, grid)

  fun parse string =
    case Lexer.scan string of
      SOME tokens =>
        (case tokens of
           T.INT canvasWidth :: T.INT canvasHeight :: T.L_BRACE :: tl =>
             let
               val grid = ParseGrid.make (canvasWidth, canvasHeight)
             in
               case parseItems (tl, grid) of
                 SOME (tokens, grid) =>
                   (case tokens of
                      [T.R_BRACE] => SOME (canvasWidth, canvasHeight, grid)
                    | _ => NONE)
               | NONE => NONE
             end
         | _ => NONE)
    | NONE => NONE
end