ascii_bar_meter.exs

defmodule AudioPlayground.Visualization.AsciiBarMeter do
  # Expects a half-width and a value between -1 and 1
  # FIXME: Typespecs
  def output(half_width, value) do
    inner = for x <- 1..width(half_width), into: "" do
              cond do
                x == string_position(half_width, value) -> "x"
                true -> " "
              end
            end
    "[#{inner}]"
  end

  def width(half_width), do: (half_width * 2) + 1

  def string_position(half_width, value) do
    position = :erlang.round(value * half_width)
    half_width + position + 1
  end
end

defmodule AudioPlayground.Visualization.AsciiBarMeterTest do
  use ExUnit.Case
  alias AudioPlayground.Visualization.AsciiBarMeter

  test "it places the x in the center for a value of 0" do
    assert AsciiBarMeter.output(2, 0) == "[  x  ]"
  end

  test "it places the x on the right for a value of 1" do
    assert AsciiBarMeter.output(2, 1) == "[    x]"
  end

  test "it places the x on the left for a value of -1" do
    assert AsciiBarMeter.output(2, -1) == "[x    ]"
  end
end