defmodule Orb.I32.UnsafePointer do
  @moduledoc """
  Custom `Orb.CustomType` for pointer to 32-bit integer in memory.
  """

  alias Orb.{Memory, I32, VariableReference}

  @behaviour Orb.CustomType
  @behaviour Access

  @impl Orb.CustomType
  def wasm_type(), do: :i32

  @impl Orb.CustomType
  def byte_count(), do: 4

  @impl Access
  def fetch(%VariableReference{} = var_ref, at!: offset) do
    address =
      offset
      |> then(&Orb.Numeric.Multiply.optimized(I32, &1, 4))
      |> then(&Orb.Numeric.Add.optimized(I32, &1, var_ref))

    ast = Memory.load!(I32, address)
    {:ok, ast}
  end

  @impl Access
  def get_and_update(_data, _key, _function) do
    raise UndefinedFunctionError, module: __MODULE__, function: :get_and_update, arity: 3
  end

  @impl Access
  def pop(_data, _key) do
    raise UndefinedFunctionError, module: __MODULE__, function: :pop, arity: 2
  end
end