liquid

defmodule Liquid.Expression do
  alias Liquid.Variable
  alias Liquid.RangeLookup

  @literal_list [nil, "nil", "null", "", "true", "false", "blank", "empty"]
  @literals %{

    nil: nil, "nil": nil, "null": nil, "": nil,

    "true": true,

    "false": false,

    "blank": :blank?,

    "empty": :empty?

  }

  def parse(markup) when markup in @literal_list, do: @literals[markup]
  def parse(markup) do
    cond do
      Regex.match?(~r/\A'(.*)'\z/m, markup) -> # Single quoted strings

        [result] = Regex.run(~r/\A'(.*)'\z/m, markup, capture: :all_but_first)
        result
      Regex.match?(~r/\A"(.*)"\z/m, markup) ->  # Double quoted strings

        [result] = Regex.run(~r/\A"(.*)"\z/m, markup, capture: :all_but_first)
        result
      Regex.match?(~r/\A(-?\d+)\z/, markup) ->  # Integer and floats

        [result] = Regex.run(~r/\A(-?\d+)\z/, markup, capture: :all_but_first)
        String.to_integer(result)
      Regex.match?(~r/\A\((\S+)\.\.(\S+)\)\z/, markup) -> # Ranges

        [left_range, right_range] = Regex.run(~r/\A\((\S+)\.\.(\S+)\)\z/, markup, capture: :all_but_first)
        RangeLookup.parse(left_range, right_range)
      Regex.match?(~r/\A(-?\d[\d\.]+)\z/, markup) -> # Floats

        [result] = Regex.run(~r/\A(-?\d[\d\.]+)\z/, markup, capture: :all_but_first)
        result
      true -> Variable.create(markup)
    end
  end
end