require 'net/http'
 
# Tinifies a URL. That is, take a long URL and makes it shorter using an API
# for a service like TinyURL.
class Tinifier
  # TODO Refine this regular expression, or find one that someone smarter has already come up with.
  @@url_matcher = /(https?)[\w\.\/\+\@\#\$\%\&\=\?\|\:\-\~\[\]]+[\w\/\+\@\#\$\%\&\=\?\|\:\-\~\[\]]/
  
  @@apis = {
      :tinyurl => "http://tinyurl.com/api-create.php?url=%s",
      :snipurl => "http://snipr.com/site/snip?r=simple&link=%s",
      :is_gd   => "http://is.gd/api.php?longurl=%s",
    }        
  
  @@default_api = :tinyurl
  
  cattr_accessor :url_matcher, :apis, :default_api
  
  def initialize(api=Tinifier.default_api)
    @api = api
  end
  
  # Tinifies a single URL using the specified API. Returns the short URL,
  # or the original URL if the API call fails.
  def tinify_url(long_url, api=nil, &block)
    tinify_url!(long_url, api, &block) rescue long_url    
  end
  
  # Tinifies a single URL, raising an error if the URL could not be 
  # tinified.
  def tinify_url!(long_url, api=nil)
    api ||= @api
    
    if block_given?
      block.call(long_url)
    else
      api_template = Tinifier.apis[api]
      raise "Unknown API specified: #{api}" if api_template.nil?
 
      uri = URI.parse(api_template % long_url)
      response = Net::HTTP.get_response(uri)
    
      if response.class == Net::HTTPOK
        short_url = response.body            
        logger.debug "Tinified #{long_url} => #{short_url}"
        return short_url
      else
        raise "Failed to tinify #{long_url} via #{api}"
      end
    end
  end
  
  # Turns all urls found in +text+ string into tinified urls. Calls out
  # to tinyurl API to replace the url. If a block is given, each url is 
  # yielded and the result replaces the url.
  #
  # tinify_urls('Visit http://www.mylongurl.com for more details.')
  # tinify_urls('Visit http://www.mylongurl.com for more details.') { |url| MyUrlTinifier.tinify(url) }
  def tinify_urls(text, api=nil, &block)
    text.gsub(Tinifier.url_matcher) do |url|
      tinify_url(url, api, &block)
    end
  end
  
  def tinify_urls!(text, api=nil, &block)
    text.gsub(Tinifier.url_matcher) do |url|
      tinify_url!(url, api, &block)
    end
  end
 
  protected
  
    def logger
      RAILS_DEFAULT_LOGGER      
    end
    
end