#!/usr/bin/env ruby
# dwm-d.rb: a simple app that periodically emits text to standard output, controllable by
# DRb. Suitable for use with dwm's stdin status bar.

class DwmStatus

  STATUS_LINE_INTERPOLATION_REGEX = Regexp.new(/:([A-Za-z\-_]+)(\((.+?)\))?/)

  # The format of the status line is "blah blah :blah :time(%c) etc."  where:
  # - any colon followed by [A-Za-z\-_] will be interpolated
  # - any parentheses following that chunk will be interpreted as wrapping arguments
  # - The contents of those parentheses will be split on semicolons and passed as arguments, if reasonable
  attr_accessor :status_line

  # Interpolation can be drawn from one of two sources:
  # - The status_items hash
  #   Items in status_items are either a Proc or something with to_s. If the item is a Proc, it's eligible
  #   to have arguments passed in.
  #   You can set a Proc over DRb by using 'set_status_item_proc' and passing a string which evaluates to
  #   a proc. That's the best I can do right now.
  # - Built-in methods
  #   These are tried after trying the hash and are simply methods on DwmStatus. date(fmt) is the most obvious.
  attr_accessor :status_items

  # The DwmStatus will emit to this IO. All it has to do is support puts.
  attr_accessor :output

  # The DwmStatus will wait this many seconds between emitting.
  attr_accessor :timeout

  def initialize
    self.status_line  = "STATUS :date(%-I:%M %p | %d %B %Y)"
    self.status_items = {}
    self.output = $stdout
    self.timeout = 1
  end

  def interpolate_status
    @status_line.gsub(STATUS_LINE_INTERPOLATION_REGEX) do |match|
      interpolator = find_interpolator($1)
      if interpolator
        if interpolator.respond_to?(:call)
          if $3
            interpolator.call(*($3.split(';'))) rescue '$ERROR$'
          else
            interpolator.call rescue '$ERROR$'
          end
        else
          interpolator
        end
      else
        match
      end
    end
  end
  
  def insert_date(fmt)
    Time.now.strftime(fmt)
  end

  def insert_exec(cmd, *args)
    `#{cmd} #{args.join(' ')}`
  end

  def insert_mpd_now_playing(trailer = ' |', leader = nil)
    mpd_info = `mpc status`.split("\n")
    if mpd_info.length == 3
      leader.to_s + mpd_info[0].chomp + ' ' + (mpd_info[1].split(' ', 2).first) + trailer.to_s
    end
  end

  def find_interpolator(term)
    status_items.fetch(term) { self.method('insert_' + term) rescue nil }
  end

  def set_status_item_proc(term, proc_str)
    status_items[term] = eval(proc_str)
  end

  def set_status_item(term, item)
    status_items[term] = item
  end

  def emit
    self.output.puts(interpolate_status)
    self.output.flush
  end

  def emit_loop
    until defined? @time_to_die
      emit
      sleep self.timeout
    end
  end

  def quit
    @time_to_die = true
  end

end

def start_drb(status, uri = 'druby://localhost:12120')
  require 'drb/drb'
  dserv = DRb.start_service(uri, status)
  status.emit_loop
  dserv.stop_service
end

if ARGV.empty?
  start_drb(DwmStatus.new)
else
  require 'drb'
  dobj = DRbObject.new_with_uri('druby://localhost:12120')
  meth = ARGV.shift
  puts dobj.send(meth, *ARGV)
end