Bagaimana untuk membangunkan fungsi cadangan muzik mudah menggunakan MySQL dan Ruby on Rails

class CreateSongs < ActiveRecord::Migration[6.0]
  def change
    create_table :songs do |t|
      t.string :title
      t.string :artist
      t.string :genre
    end
  end
end

class CreateUserPreferences < ActiveRecord::Migration[6.0]
  def change
    create_table :user_preferences do |t|
      t.references :user
      t.references :song
      t.integer :rating
    end
  end
end

class Song < ApplicationRecord
  has_many :user_preferences
  has_many :users, through: :user_preferences
end

class User < ApplicationRecord
  has_many :user_preferences
  has_many :songs, through: :user_preferences
end

class UserPreference < ApplicationRecord
  belongs_to :user
  belongs_to :song
end

Song.create(title: 'Song 1', artist: 'Artist 1', genre: 'Pop')
Song.create(title: 'Song 2', artist: 'Artist 2', genre: 'Rock')
Song.create(title: 'Song 3', artist: 'Artist 3', genre: 'Jazz')

User.create(name: 'User 1')
User.create(name: 'User 2')
User.create(name: 'User 3')

UserPreference.create(user_id: 1, song_id: 1, rating: 4)
UserPreference.create(user_id: 1, song_id: 2, rating: 5)
UserPreference.create(user_id: 2, song_id: 2, rating: 3)
UserPreference.create(user_id: 3, song_id: 3, rating: 2)

class RecommendationController < ApplicationController
  def index
    user = User.find(params[:user_id])
    rated_songs = user.songs
    similar_users = User.where.not(id: user.id).joins(:songs)
                   .where('songs.id IN (?)', rated_songs.pluck(:id)).distinct
    recommended_songs = similar_users.joins(:songs).where.not('songs.id IN (?)', rated_songs.pluck(:id))
                       .group(:song_id).average(:rating)
    @recommendations = Song.where(id: recommended_songs.keys)
                       .order(recommended_songs.values.map(&:to_f).reverse)
  end
end

<h1>Recommendations for User <%= @user.name %></h1>

<% @recommendations.each do |song| %>
  <p><%= song.title %></p>
  <p>Artist: <%= song.artist %></p>
  <p>Genre: <%= song.genre %></p>
<% end %>