Check whether the given text is in 140 character limit. URL is taken into account.

tweetable.rb

# -*- coding: utf-8 -*-

TWEET_MAX_LEN = 140

def tweetable?(text)
  text = text.dup
  len = 0
  while text.sub!(/http:\/\/[^\s]*/, '')
    len += 20
  end
  while text.sub!(/https:\/\/[^\s]*/, '')
    len += 21
  end
  (len + text.length) <= TWEET_MAX_LEN
end

tweetable?('こんにちは')        # => true
tweetable?('あ' * 140)          # => true
tweetable?('あ'*119 + " http://mikutter.hachune.net/")  # => true
tweetable?('あ'*120 + " http://mikutter.hachune.net/")  # => false
tweetable?('あ'*118 + " https://mikutter.hachune.net/") # => true
tweetable?('あ'*119 + " https://mikutter.hachune.net/") # => false