dark launch with mixin

dark_launch.rb

module DarkLaunch

  FEATURES = %w(feature_a feature_b feature_c) # could load this from a config file
  def self.included(base)
    FEATURES.each do |f|
      base.send(:define_method, "has_access_to_#{f}?") { DarkLaunch.feature_visible(f, self) }
    end
    # could add a method_missing handler for the same prefix, for things that aren't explicitly defined
  end

 
  def self.feature_visible(feature_id, current_user)
  
    if !current_user
      # Only logged in users should have access to Dark Launch features
      return false
    end
    
    if Rails.env.development? || Rails.env.test?
      # On Dev and Test these features should always be visible (for now at least)
      return true
    end
    
    # We're prefixing the ENV var ourselves with 'FEATURE_'
    # this can be be loaded from anywhere, if you don't like environment variables
    env_var = ENV["FEATURE_#{feature_id}"]
    
    if env_var
    
      # If it equals the string "PUBLIC" then return true and don't check invidiual user_ids anymore
      return true if env_var == "PUBLIC" 
        
      # If we've got an array then we'll check whether the user ID is in there
      # Note: this is the actual piece of logic that allows us to control who to launch a feature to. Right now we're basing this
      # off of customer IDs. This could as well be 10% of our users, traffic from a certain country, only users with an email
      # of ...@my_own_company.com or whatever.
      return env_var.split(',').include?(current_user.id.to_s) unless !env_var
    
    end
    
    # Apparently nothing succeeded before so let's be safe and return false for now
    false
    
  end
end