Downloader for TED

gistfile1.rb

# Use
#   ruby download.rb http://www.ted.com/search?q=any+query

require 'rubygems'
require 'mechanize'

agent = Mechanize.new { |agent| agent.user_agent_alias = 'Linux Firefox' }

pages = ARGV
loaded = []

class DummyObject
  def method_missing(*a)
  end
end

class <<agent
  def absolute_url(uri)
    hash = { :uri => uri, :referer => current_page }
    Mechanize::Chain::URIResolver.new(@scheme_handlers).tap {|o| o.chain = DummyObject.new }.handle(nil, hash)
    hash[:uri].to_s
  end
end

while not pages.empty?

  current_url = pages.shift
  next if loaded.include?(current_url)
  loaded << current_url

  puts "Loading #{current_url}..."
  current_page = agent.get(current_url)
  download_links = current_page.search(".downloads a")

  if not download_links.empty?
    Process.wait(fork do
      video_link = download_links.last[:href]
      dest_file = current_url.split("/").last.sub(/\.html$/i, "") + ".mp4"

      if File.exist?(dest_file)
        puts "#{dest_file} exists"
      else
        exec "wget", "-O", dest_file, agent.absolute_url(video_link)
      end
    end)
  else
    current_page.search("dt a").each do |next_link|
      pages << next_link[:href]
    end
    if next_page = current_page.at("li.next a")
      pages << next_page[:ref]
    end
  end

end