Blacklist distracting websites while working

iam.rb

#!/opt/local/bin/ruby
#
# iam -  block distracting websites while working
#
# Examples:
#
#   Switch to work mode -- disable distracting websites
#   % iam working
#
#   Switch to play mode -- enable distracting websites
#   % iam playing
#
#   Block some distracting sites
#   % iam add facebook.com
#   % iam add reddit.com
#
#   Unblock something:
#   % iam remove reddit.com
#
#   List database
#   % iam list
#   facebook.com
#
#   Find out which mode you're in
#   % iam
#   playing
#
#
# Notes:
# 1. /etc/hosts must be writable by you
# 2. iam creates two hidden files--  ~/.iam and ~/.iamdb to store the mode and database, respectively
#

# Files we need
MODE_FILE = ENV['HOME'] + '/.iam'
DATABASE_FILE = ENV['HOME'] + '/.iamdb'
HOSTS_FILE = '/etc/hosts'

# Default to playing with empty blacklist
database = [ ]
hosts = [ ]
mode = 'playing'

File.open(DATABASE_FILE, 'r').each { |host| database << host.strip } if File.exists? DATABASE_FILE
File.open(MODE_FILE, 'r').each { |line| mode = line.strip } if File.exists? MODE_FILE
File.open(HOSTS_FILE, 'r').each { |line| hosts << line.strip }

hosts.delete_if { |line| line.match(/\#iam$/) }

# Do stuff
case ARGV[0]
  when 'working', 'playing'
    mode = ARGV[0]
  when 'list'
    puts database.join "\n"
  when 'add'
    database << ARGV[1]
  when 'remove'
    database.delete_if { |h| h == ARGV[1] }
  else
    puts mode
end

# Clean up database
database.delete_if { |h| h.nil? || h.length == 0 }

# Build working database
if mode == 'working'
  hosts = hosts + database.map { |h| "127.0.0.1\t#{h} #iam" }
end

# Write working DB
File.open(DATABASE_FILE, 'w+') { |f| f.write database.join "\n" }

# Write mode
File.open(MODE_FILE, 'w+') { |f| f.write mode }

# Write hosts file
File.open(HOSTS_FILE, "w") { |f| f.write hosts.join "\n" }