gnuplot.ex

defmodule Api.Slack.Gnuplot do
  alias Porcelain.Process, as: Proc
  alias Porcelain.Result
  require Logger

  def line do
    proc = %Proc{pid: pid} = setup

    plot(proc,
    """
      a = 0.9
      f(x) = a * sin(x)
      g(x) = a * cos(x)

      # Plot
      plot f(x) title 'sin(x)' with lines linestyle 1, \
      g(x) notitle with lines linestyle 2
    """
    )
  end

  def setup do
    Porcelain.spawn_shell("gnuplot", in: :receive, out: {:send, self()})
  end

  def plot(proc, msg) do
    Proc.send_input(proc,
      """
        # Clean basis for SVG
        set terminal svg enhanced font 'Verdana,10'

        # Line width of the axes
        set border linewidth 1.5

        # Line styles
        set style line 1 linecolor rgb '#0060ad' linetype 1 linewidth 2
        set style line 2 linecolor rgb '#dd181f' linetype 1 linewidth 2

        # Output
        set terminal svg

        #{msg}
      """
    )

    receive do
      {^pid, :data, :out, data} -> data
    end
  end

end