defmodule RangeMap do
  def to_function(in_min, in_max, out_min, out_max) do
    difference_in = in_max - in_min
    difference_out = out_max - out_min
    factor = difference_out / difference_in

    midpoint_in = (in_min + in_max) / 2
    midpoint_out = (out_min + out_max) / 2
    constant = midpoint_out - midpoint_in

    fn input ->
      input * factor + constant
    end
  end

  def map(input, input_min, input_max, output_min, output_max) do
    factor = (output_max - output_min) / (input_max - input_min)
    constant = (output_min + output_max) / 2 - (input_min + input_max) / 2

    input * factor + constant
  end
end