ptc_runner

defmodule PtcRunner.Lisp.ParserHelpers do
  @moduledoc "Helper functions for parser reductions"

  alias PtcRunner.Lisp.AST

  # ============================================================
  # Number parsing
  # ============================================================

  def parse_integer(parts) do
    parts
    |> Enum.map_join(&to_string_part/1)
    |> String.to_integer()
  end

  def parse_float(parts) do
    parts
    |> Enum.map_join(&to_string_part/1)
    |> String.to_float()
  end

  defp to_string_part(part) when is_integer(part), do: <<part::utf8>>
  defp to_string_part(part) when is_binary(part), do: part

  # ============================================================
  # String building
  # ============================================================

  def build_string(chars) do
    str = Enum.map_join(chars, &to_string_part/1)
    {:string, str}
  end

  # ============================================================
  # Keyword/Symbol building
  # ============================================================

  def build_keyword([name]), do: {:keyword, String.to_atom(name)}

  def build_symbol(parts) do
    name = Enum.join(parts)
    AST.symbol(name)
  end

  # ============================================================
  # Collection building
  # ============================================================

  def build_vector({:vector, elements}), do: {:vector, elements}

  def build_set({:set, elements}), do: {:set, elements}

  def build_map({:map, elements}) do
    if rem(length(elements), 2) != 0 do
      raise ArgumentError, "Map literal requires even number of forms, got #{length(elements)}"
    end

    pairs =
      elements
      |> Enum.chunk_every(2)
      |> Enum.map(fn [k, v] -> {k, v} end)

    {:map, pairs}
  end

  def build_list({:list, elements}), do: {:list, elements}
end