focus.rb

#!/usr/bin/env ruby

# The script that give you focus!
# Create a text file that contains sites you only want to give yourself
# access to during certain times of day.
# The file will look like this:
# 12 news.ycombinator.com
# 11-13,19-21 twitter.com
#
# In this case, I can visit hacker news only over the lunch hour,
# and twitter between 11-1pm and 7-9pm.
#
# Next, create an hourly cron to run the script, passing it the location
# of your focus file (use root's crontab since it's writing to /etc/hosts).
# 0 * * * * /Users/robert/focus.rb /Users/robert/.focus
class Focus
  FOCUS_LINE_START = "#--START FOCUS--(do not remove)\n"
  FOCUS_LINE_END = "#--END FOCUS--(do not remove)\n"
  def initialize(focus_file_path)
    unless focus_file_path && File.exist?(focus_file_path) && File.file?(focus_file_path)
      raise IOError, "Focus file not found!"
    end
    @focus_file = focus_file_path
  end
  
  def update_hosts_file
    host_file_contents = IO.readlines("/etc/hosts")
    focus_section_start = host_file_contents.index(FOCUS_LINE_START)
    focus_section_end = host_file_contents.index(FOCUS_LINE_END)
    host_file_entries = host_file_contents[0...(focus_section_start || -1)].concat(focus_lines.unshift(FOCUS_LINE_START).push(FOCUS_LINE_END))
    if focus_section_end
      host_file_entries << host_file_contents[focus_section_end+1, host_file_contents.size]
    end
    open("/etc/hosts", "w") {|out| out.write(host_file_entries.join)}
    `dscacheutil -flushcache` # otherwise apps don't seem to bother to check
  end
  
  private
  def focus_lines
    # allow anything on the weekends
    return [] if %w{ 0 6 }.include?(Time.now.strftime('%w'))

    lines = IO.readlines(@focus_file)
    hour = Time.now.hour
    sites_to_ignore = []
    lines.each do |line|
      case line
      when /^#/
        next
      when /^([0-9,-]+) (\w.*)/
        site = $2
        groups = $1.split(",")
        intervals = groups.collect {|g| s = g.split("-"); s.size == 1 ? s[0].to_i : (s[0].to_i...s[-1].to_i)}
        sites_to_ignore << site unless intervals.any? {|i| i === hour}
      end
    end
    sites_to_ignore.collect {|site| "127.0.0.1 #{site}\n"}
  end
    
end

if __FILE__ == $0
  file = ARGV.first
  if ARGV.size == 0
    puts "Usage: path/to/focus.rb path/to/.focus"
    exit(1)
  end
  begin
    Focus.new(file).update_hosts_file
  rescue Exception
    puts "Problem! #{$!.message}"
  end
end