First (test) Rack app: Generates random numbers.

config.ru

# RESULT CAN BE SEEN AT http://furious-day-14.heroku.com/
#
#
# Sat down to watch this video about rack    http://confreaks.net/videos/49-mwrc2009-in-a-world-of-middleware-who-needs-monolithic-applications
# About 17 min in at the moment, figured I'd verify what the guy was saying. Ended up with this simple script to generate random numbers.
# Figured I'd see if I could get it on heroku, looked up this blog I had read a few months ago   http://blog.heroku.com/archives/2009/3/5/32_deploy_merb_sinatra_or_any_rack_app_to_heroku/
# Tried it all out, and it worked!
#
# Regarding the code, I don't think it would scale well. I'll need to spend some time thinking about the implications of this sort of environment.
# For example: validating urls, handling exceptions, giving help file, generating content all in one class gets some ugly coupling between methods.
# Though, I think rack is supposed to be at a lower level than I as a user would ever experience, so I don't think it's really meant for this type of use.
# They just point out that you can use it like this, b/c it's a cool enough idea to get people like me to go try it out.


class RandomNumberGenerator

  MAX_COUNT = 1000
    
  def call(env)
    begin
      set_path env['PATH_INFO']
      raise ArgumentError.new("Min is greater than max") if rand_min > rand_max
      [ 200 , { 'Content-Type' => 'text/plain' } , content(env) ] 
    rescue => e
      [ 400 , { 'Content-Type' => 'text/plain' } , usage(env,e) ]
    end
  end
  
  def content(env)
    min         =  rand_min
    max         =  rand_max
    count       =  rand_count
    difference  =  max - min
    raise ArgumentError.new("Count is too large") if count > MAX_COUNT
    (0...count).map { min + rand(difference).to_i }.join(' ')
  end
  
  def set_path(path)
    @path = path.split('/').reject { |segment| !segment || segment.empty? }
    raise ArgumentError.new("Too many path parameters") if @path.size > 3
    raise ArgumentError.new("Path must only contain numbers") if @path.any? { |segment| segment !~ /^-?\d+$/ }
  end
  
  def rand_count
    if @path.first 
      @path.first.to_i 
    else 
      raise ArgumentError.new("No Arguments")
    end
  end

  def default_max
    1000
  end

  def rand_max
    case @path.length 
    when 2 , 3
      @path[-1].to_i
    else
      default_max
    end
  end
  
  def default_min
    0
  end
  
  def rand_min
    case @path.length
    when 3
      @path[1].to_i
    else
      default_min
    end
  end
  
  def usage( env , error )
    url = env["HTTP_HOST"]
    <<-USAGE.gsub(/^      /,'')
      Your request should look like one of the following:
      #{url}/10        implies count => 10 , min => #{default_min} , max => #{default_max}
      #{url}/10/30     implies count => 10 , min => #{default_min} , max => 30
      #{url}/10/20/30  implies count => 10 , min => 20 , max => 30
      
      The min must be less than the max.
      Only digits are allowed.
      Count may not exceed #{MAX_COUNT}
      
      Your values were: 
        count  =>  #{(rand_count rescue nil) || 'missing'}
        min    =>  #{rand_min}
        max    =>  #{rand_max}
      
      Your request was not fulfilled because:
        #{error.message}
    USAGE
  end
  
end


run RandomNumberGenerator.new