birthday_liker.rb

require 'date'
require 'koala'

class BirthdayLiker
  FACEBOOK_TOKEN   = 'your_oauth_key'
  BIRTHDAY_WORDS   = %w(birthday bday birfday birth born)
  THANKS_OPTIONS   = ['Thank you!', 'Thanks!', 'Appreciate it!']
  DATE_TIME_FORMAT = '%Y-%m-%d'

  def initialize(birthdate, opts={})
    @api  = Koala::Facebook::API.new(FACEBOOK_TOKEN)
    @uid  = @api.get_object('me')['id']
    @bday = DateTime.strptime(birthdate, DATE_TIME_FORMAT)
    @opts = {
      limit: 1000,
      range: 1
    }.merge!(opts)

    retrieve_comments
  end

  def show_appreciation
    @comments.each do |comment|
      @api.put_like(comment['id'])
      @api.put_comment(comment['id'], THANKS_OPTIONS.sample)
    end
    p "Liked #{@comments.length} comments. You're so kind!"
  end

  private
  
  def retrieve_comments
    pre_bday  = (@bday - @opts[:range]).strftime(DATE_TIME_FORMAT)
    post_bday = (@bday + @opts[:range] + 1).strftime(DATE_TIME_FORMAT)
    @comments = @api.get_connections("me", "feed", :since => pre_bday, :until => post_bday, :limit => @opts[:limit])

    filter_comments
  end

  def filter_comments
    remove_user_comments
    remove_non_birthday
    remove_already_liked
  end

  def remove_user_comments
    @comments.delete_if { |comment| comment['from']['id'] == @uid }
  end

  def remove_non_birthday
    @comments.delete_if do |comment| 
      (comment['message'].downcase.gsub(/[\.,;:!\?]/, '').split & BIRTHDAY_WORDS).empty?
    end
  end

  def remove_already_liked
    @comments.delete_if do |comment|
      comment.has_key?('likes') && comment['likes']['data'].any? do |like| 
        like['id'] == @uid
      end
    end
  end
end

liker = BirthdayLiker.new('2014-08-13')
liker.show_appreciation