#
# Copyright Michael Orlitzky
#
# http://michael.orlitzky.com/
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# http://www.fsf.org/licensing/licenses/gpl.html
#

require 'src/website'


class Youtube < Website

  VALID_YOUTUBE_URL_REGEX = /^(http:\/\/)?([a-z0-9]+\.)?youtube\.com\/((watch\?v=)|(v\/))[a-z0-9_\-]+(\&.*)?\#?$/i
  
  def self.owns_url?(url)
    return url =~ VALID_YOUTUBE_URL_REGEX
  end

  
  def get_video_url()
    video_id = self.parse_video_id()

    # The video's URL (the "page data" URL) may be different from the
    # URL that was passed to the program. We support the /v/video_id
    # URL format, but that is *not* the main video page where we can
    # retrieve the "t" parameter. We can only get that from the
    # /watch?v=video_id form.
    page_data_url = "http://www.youtube.com/watch?v=#{video_id}"
    page_data = self.get_page_data(page_data_url)

    # Magic.
    t_parameter = self.parse_t_parameter(page_data)
    
    video_url = "http://www.youtube.com/get_video?video_id=#{video_id}&t=#{t_parameter}"
      
    return video_url
  end


  def get_video_filename()
    return (self.parse_video_id() + '.flv')
  end

  
  protected;

  # Get the video id from the URL. Should be relatively easy,
  # unless Youtube supports some URL formats of which I'm unaware.
  def parse_video_id()
    # Return nil if we get no matches below.
    video_id = nil
    
    # Both URLs are fairly easy to parse if you handle
    # them one at a time. The only tricky situation is when
    # parameters like "&hl=en" are tacked on to the end.
    # We'll call /watch?v=video_id the "first form."
    first_form_video_id_regex = /v=([0-9a-z_\-]+)/i
    first_form_matches = first_form_video_id_regex.match(@url)
    return first_form_matches[1] if not (first_form_matches.nil? ||
                                         first_form_matches.length < 2)

    # First form didn't work? Try the second.
    second_form_video_id_regex = /\/v\/([0-9a-z_\-]+)/i
    second_form_matches = second_form_video_id_regex.match(@url)
    video_id = second_form_matches[1] if not (second_form_matches.nil? ||
                                              second_form_matches.length < 2)
    
    return video_id
  end


  # Parse out the "t" parameter from the video's page. I'm not sure
  # what "t" stands for, but it's located in some JSON, and is required
  # for the final video URL to work.
  def parse_t_parameter(page_data)
    t_parameter = nil
    
    t_parameter_regex = /\"t\"\:[[:space:]]\"([^\"]+?)\"/
    matches = t_parameter_regex.match(page_data)
    t_parameter = matches[1] if not (matches.nil? || matches.length < 2)

    return t_parameter
  end
  
  
end