thin wrapper around xrandr to determine the primary output (among others)

monitors

#!/usr/bin/env ruby
# frozen_string_literal: true

# Detect the monitor setup
#
# rubocop:disable Metrics/LineLength,Lint/MissingCopEnableDirective
command = ARGV[0]
# subcommand = ARGV[1]

# value-object with high-end regex string-parsing power
class XrandrInfo
  attr_reader :output, :primary, :width, :height

  def initialize(xrandr_string)
    matches = xrandr_string.match(
      /^(?<output>\S+) connected(?<primary> primary)? (?<width>\d+)x(?<height>\d+)/
    ) || {}

    @output  = matches[:output]
    @primary = matches[:primary] == ' primary'
    @width   = matches[:width].to_i
    @height  = matches[:height].to_i
  end

  def to_s
    "<XrandrInfo output:#{@output} primary:#{@primary} dimensions:#{@width}x#{@height}>"
  end

  def width_class
    case @width
    when 0...1024      then 'tiny'
    when 1024...1920   then 'small'
    when 1920...3440   then 'medium'
    when 3440...10_000 then 'wide'
    end
  end

  def device
    case @output
    when 'eDP1' then :laptop
    end
  end
end

def rescan_monitors
  `xrandr | grep ' connected'`
    .each_line.map(&:chomp)
    .map { |output| XrandrInfo.new(output) }
end

monitors = rescan_monitors
primary = monitors.find(&:primary)

puts case command
     when 'width'  then primary.width_class
     when 'output' then primary.output
     when 'set'
       if monitors.size == 1 && primary.device == :laptop
         system "xrandr --output #{primary.output} --mode 1600x900"
       end

       system '~/.fehbg'
       "Resolution set: #{rescan_monitors.find(&:primary)}"
     else primary
     end

exit