src/website.rb

   1 #
   2 # Copyright Michael Orlitzky
   3 #
   4 # http://michael.orlitzky.com/
   5 #
   6 # This program is free software: you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation, either version 3 of the License, or
   9 # (at your option) any later version.
  10 #
  11 # This program is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 # GNU General Public License for more details.
  15 #
  16 # http://www.fsf.org/licensing/licenses/gpl.html
  17 #
  18
  19 # This class keeps track of all its subclasses
  20 # We use this to loop through every "website" in an
  21 # attempt to determine to which site a URL belongs.
  22 class Website
  23
  24   protected;
  25
  26   @url = nil
  27
  28
  29   def self.inherited(subclass)
  30     if superclass.respond_to? :inherited
  31       superclass.inherited(subclass)
  32     end
  33
  34     # Every time we're subclassed, add the new
  35     # subclass to our list of subclasses.
  36     @subclasses ||= []
  37     @subclasses << subclass
  38   end
  39
  40
  41   public;
  42
  43   def initialize(url)
  44     @url = url
  45   end
  46
  47
  48   def self.create(url)
  49     # Factory method returning an instance of
  50     # the appropriate subclass.
  51
  52     # Check the URL against each website's class.
  53     # The class will know whether or not the URL
  54     # "belongs" to its website.
  55     @subclasses.each do |w|
  56       if w.owns_url?(url)
  57         return w.new(url)
  58       end
  59     end
  60
  61     # If nothing matched, we don't return an instance
  62     # of anything.
  63     return nil
  64   end
  65
  66
  67   # Abstract definition. Each subclass of Website
  68   # should support it on its own.
  69   def self.owns_url?(url)
  70     raise NotImplementedError
  71   end
  72
  73
  74   # Same here. Abstract.
  75   def get_video_url()
  76     raise NotImplementedError
  77   end
  78
  79
  80   # The website class should be responsible for determining the
  81   # video's filename. By default, we can take the last component
  82   # of the video URL, but in some cases, subclasses will want
  83   # to override this behavior.
  84   def get_video_filename()
  85     # Use whatever comes after the final front slash.
  86     return get_video_url().split('/').pop()
  87   end
  88
  89 end