Another test run for https://kaspth.notion.site/Riffing-on-Rails-w-Jeremy-Kasper-8db6196944ac4c999d08f626f81680fb

rip-mix-build.rb

# Spotify Mix Playlists: Assuming we have a history of played songs for a user,
# we have song recommendations via nearest neighbor search,
# and we have categorizations (genre, mood, era, instrumental/vocal, cultural/regional, theme),
# let system admins create mix templates based on music categorizations
# and then generate refreshable custom playlists for each user.

class User
  has_many :playlists
  has_one :history
end

class History
  has_many :listens
  has_many :tracks, through: :listens
end

class History::Listen
  belongs_to :history
  belongs_to :track
end

class Track
  has_many :categorizations
  has_many :categories, through: :categorizations
end

track.inner_joins(Track::Category.genres).nearest(100)

Track::Category.genres.where(value: ["pop", "hiphop"])
Track::Category.eras.where(value: ["80s", "90s"])

class Track::Category
  has_many :categorizations
  has_many :tracks, through: :categorizations

  belongs_to :details
end

class Track::Category::Categorization
  belongs_to :track
  belongs_to :category
end

class Playlist
end

class Mix::Template
  has_many :categories

  def build_for(user)
    from_own_history = user.history.tracks.ordered_by_popularity.joins(:categories).where(categories:).limit(100).flat_map do |track|
      [track, track.nearest(10)]
    end.uniq.first(100)

    if from_own_history >= 100
      from_own_history
    else
      Track.ordered_by_popularity.joins(:categories).where(categories:).limit(100).flat_map do |track|
        [track, track.nearest(10)]
      end.including(from_own_history).uniq.first(100)
    end
  end
end

class Mix::Build
  belongs_to :template
  belongs_to :user

  has_many :links
  has_many :tracks, through: :links

  def regenerate
    update! tracks: template.build_for(user)
  end
end

class Mix::Build::Link
  belongs_to :build
  belongs_to :track
end

This is super cool!.

On the Mix::Template class, you are defining has_many :categories which is used in Mix::Template#build_for(user) method. But I am left wondering how the mix-categories associations would look like. So I thought I would try to fill in the Mix::Template & has_many :categories gap. Let me know what modifications you would do to this.

# template.categories => get all categories for this template
# mix_category.templates => all templates that has this cateogory
class Mix::Category::Categorization
  belongs_to :category, class_name: 'Mix::Category'
  belongs_to :template
end

class Mix::Category
  has_many :categorizations, class_name: 'Mix::Category::Categorization'
  has_many :templates, through: :categorizations
end


# Modified 
class Mix::Template
  has_many :categorizations, class_name: 'Mix::Category::Categorization'
  has_many :categories, through: :categorizations
end

Also I am not sure if belongs_to :details on Track::Category is the same or should be the same with Mix::Category's belongs_to :details

@ziraqyoung hey, thank you so much! It's not the clearest from the gist since we didn't fill in class_name: but Mix::Template.has_many :categories is meant to point to Track::Category, if I recall correctly. And then the details become the same since there's only one class.

I forgot to update it here but @jeremysmithco and I posted how we riffed up this file on YouTube, if you want to see that https://www.youtube.com/watch?v=i1MM2EOniPg

@kaspth, I did watch it (them). They are very educative. Thank you.

@ziraqyoung ah ok, thank you!