Parser for tmux's layout string (tmux display -p "#{window_visible_layout}")

tmux_layout_parser.rb

class Parser
  def initialize(input)
    @input = input
    @s = 0
  end

  def parse
    wid = scan_wid
    pick
    w, h = scan_wh; pick
    x = scan_d; pick
    y = scan_d
    c = case pick
    when '['; scan_panes :vert, ']'
    when '{'; scan_panes :horz, '}'
    else []
    end
    [:win, wid, w, h, x, y, c]
  end

private
  def scan_panes(type, last)
    panes = []
    loop do
      panes << scan_pane
      case peek
      when ','; pick
      when last; pick; break
      end
    end
    [type, panes]
  end
  def scan_pane
    w, h = scan_wh; pick
    x = scan_d; pick
    y = scan_d 
    c = case pick
    when '['; scan_panes :vert, ']'
    when '{'; scan_panes :horz, '}'
    else scan_d
    end
    [:pane, w, h, x, y, c]
  end

  def scan_wid
    case peek
    when /\h/; pick + scan_wid
    when ','; ''
    end
  end

  def scan_wh
    w = scan_d
    pick
    h = scan_d
    [w, h]
  end
  def scan_d
    case peek
    when /\d/; pick + scan_d
    else ''
    end
  end

  def pick
    @input[@s]
  ensure
    @s += 1
  end
  def peek; @input[@s] end
end

require 'pp'
pp Parse.new.parse(<<EOH)
a158,80x64,0,0[81x16,0,0{40x16,0,0,108,40x16,41,0,127},81x15,0,17,126,81x32,0,33{31x32,0,33[31x16,0,33,122,31x15,0,50,128],49x32,32,33,123}]  
EOH #=>
# [:win,
# "a158",
# "80",
# "64",
# "0",
# "0",
# [:vert,
#  [[:pane,
#    "81",
#    "16",
#    "0",
#    "0",
#    [:horz,
#     [[:pane, "40", "16", "0", "0", "108"],
#      [:pane, "40", "16", "41", "0", "127"]]]],
#   [:pane, "81", "15", "0", "17", "126"],
#   [:pane,
#    "81",
#    "32",
#    "0",
#    "33",
#    [:horz,
#     [[:pane,
#       "31",
#       "32",
#       "0",
#       "33",
#       [:vert,
#        [[:pane, "31", "16", "0", "33", "122"],
#         [:pane, "31", "15", "0", "50", "128"]]]],
#      [:pane, "49", "32", "32", "33", "123"]]]]]]]