• rake db:migrate (et rake db:rollback), dès que je souhaite modifier la structure de ma base de données ;
  
• rake routes, que l'on a vu rapidement sur le tutorial précédent ;
  
• rake gems:install, qui installe les gem dont l'application a besoin. C'est très utile quand on récupère un projet : je récupère les sources d'un projet puis je lance ça pour mettre à jour ou installer les gems (dans leur bonne version) nécessaires ;
  

task :hello_world do

  puts "Hello World!"

end



task :introduce => :hello_world do

  puts "My name is Bond. James Bond."

end

task :open_the_door do

  puts "I open the door of the car."

end



task tart_engine do

  puts "I start the engine."

end



task :go_on_baby => [ :open_the_door, tart_engine ] do

  puts "Vroooom!"

end

require 'open-uri' # Lib to simplify HTTP request.

require 'hpricot'  # Amazing HTML (and XML) parser.



# We put the task in a namespace, to be clean.

# To call a namespaced task, simply use the following notation :

# rake namespace_name:task_name

namespace :trailers do

  

  # Perl syntax to declare array of strings.

  CHANELS_TO_SEARCH = %w( tf-1 france-2 france-3 m6 canal canal-cinema w9 nt-1 tmc )

  

  # In this case, it's sexier than pure litteral notation...

  CHANELS_TO_SEARCH = [ 'tf-1', 'france-2', 'france-3', 'm6', 'canal', 'canal-cinema', 'w9', 'nt-1', 'tmc' ]

  

  # The desc is only a human readable comment displayed in the tasks list.

  desc "Search for trailers for films of the day"

  task earch => :environment do

    # earch is the name of the task.

    # We will call it with : rake trailersearch

    # The "=> :environment" mean that when the task is fired,

    # the task :environment (default defined in Rails) is fired before

    # to initialize ActiveRecord and other Rails cool stuff.

    

    # We want the trailers of today movies.

    date_from = Date.today

    date_to   = date_from + 24.hours

  

    # Find the channel for which we want trailers.

    channels = Channel.find_all_by_pretty_name(CHANELS_TO_SEARCH)

    

    # We want only trailers for movies subsets (thriller, horror, porn ?).

    # Don't care about "Plus belle la vie"...

    tv_program_kinds = TvProgramKind.find_by_name('Cinéma').children

    

    # We have few ways to build the query. I decided to use dynamic scopes.

    # The dynamics scopes are just a cool way to build the WHERE condition.

    tv_programs = TvProgram.scoped_by_air_time(date_from..date_to).

                            scoped_by_tv_program_kind_id(tv_program_kinds.map(&:id)).

                            scoped_by_channel_id(channels.map(&:id)).

                            all

    

    # Iterate through the TV programs found.

    tv_programs.each do |tv_program|

      

      # Database is encoded in latin1 and we need UTF-8 to send to YouTube API.

      # Iconv is designed to receive many string after the two first arguments

      # and return an array. The first string we passed (tv_program.title) is

      # the first of the result. So we call "first" on this array.

      utf8_title = Iconv.iconv('UTF-8', 'LATIN1', tv_program.title).first

      

      # We add quotes to the "q" param to search the exact terms.

      url = build_url_for_youtube_api({ 'q' => '"' + utf8_title + '"' })

      

      # We send the HTTP request passing a URL to open, thanks to open-uri.

      # The we parse the XML stream returned by YouTube with the amazing Hpricot.

      xml_stream = open(url) do |stream|

        Hpricot.XML(stream)

      end

      

      # Explore the XML feed as documented in :

      # code.google.com/intl/fr-FR/apis/youtube/2.0/developers_guide_protocol_understanding_video_feeds.html     

      xml_stream.search('/feed/entry').each do |entry|

        

        # TODO: Try to do it with pure XPath instead of Ruby condition.

        # It should be something like :

        # //media:content[@yt:format='5']

        entry.search("//media:content").each do |e|

          if e.attributes['yt:format'] == '5'

            # It's the link we want to embed the video player.

            # No we can save it into the database.

            trailer_url = e.attributes['url']

            Trailer.create! :title => utf8_title,

                            :url   => trailer_url

          end

        end

      end

      

    end

    

  end

  

  

  # Return the URL to query the YouTube API.

  def build_url_for_youtube_api(options = {})

    # Default options.

    # format 5 say that only embeddable videos should be selected.

    options.reverse_merge! 'lr'          => 'fr',

                           'max-results' => 1,

                           'strict'      => true,

                           'format'      => 5

    

    service_url = 'http://gdata.youtube.com/feeds/api/videos'

    query_array = [ ] # [ "foo=bar", "foo2=bar2" ]

    options.each do |key, value|

      query_array << "#{key}=#{ERB::Util::url_encode(value)}"

    end

    query_string = query_array.join("&")



    "#{service_url}?#{query_string}"

  end

  

  

end

rake trailersearch                 # Search for trailers for films of the day

0 2 * * * cd /path/to/application && /path/to/ruby rake trailersearch RAILS_ENV=production

tv_programs = TvProgram.find_all_by_air_time_and_tv_program_kind_id_and_channel_id(from..to, tv_program_kinds, channel_ids)

condition = "air_time IN(?) AND tv_program_kind_id IN (?) AND channel_id IN (?)"

tv_programs = TvProgram.all :conditions => [ 

                                             condition,

                                             from..to,

                                             tv_program_kind_ids,

                                             channel_ids

                                           ]

condition = "air_time IN(:time) AND tv_program_kind_id IN (:tv_program_kind_ids) AND channel_id IN (:channel_ids)"

tv_programs = TvProgram.all :conditions => [ 

                                             condition,

                                             {

                                               :time => from..to,

                                               :tv_program_kind_ids => tv_program_kind_ids,

                                               :channel_ids => channel_ids

                                             }

                                           ]

tv_programs = TvProgram.find :all,

                            :conditions => {

                              :air_time => date_from..date_to,

                              :tv_program_kind_id => tv_program_kind_ids,

                              :channel_id => channel_ids

                            }