fix models designs

app/models/movie.rb

@@ -1,2 +1,5 @@
 class Movie < ApplicationRecord
+  has_many :users, through: :purchases
+  has_many :purchases, as: :content
+  has_many :purchase_options, as: :content
 end

app/models/purchase.rb

@@ -1,4 +1,22 @@
 class Purchase < ApplicationRecord
   belongs_to :user
-  belongs_to :content, polymorphic: true
+  belongs_to :purchase_option
+
+  delegate :content, to: :purchase_option
+
+  def alive?
+    remaining_time > 0
+  end
+
+  private
+
+  # in minutes
+  # if is expired return 0
+  def remaining_time
+    [(expire_date - Time.now).to_i / 1.minute, 0].max
+  end
+
+  def expire_date
+    (self.created_at + 2.days)
+  end
 end

app/models/purchase_option.rb

@@ -1,2 +1,4 @@
 class PurchaseOption < ApplicationRecord
+  has_many :purchases
+  belongs_to :content, polymorphic: true
 end

app/models/season.rb

@@ -1,3 +1,7 @@
 class Season < ApplicationRecord
-  belongs_to :episodes
+  has_many :users, through: :purchases
+  has_many :purchases, as: :content
+  has_many :purchase_options, as: :content
+
+  has_many :episodes
 end

app/models/user.rb

@@ -1,2 +1,26 @@
 class User < ApplicationRecord
+
+  class AlreadyPurchasedError < StandardError; end
+
+  has_many :purchases
+
+  def library
+    self.purchases.select {|p| p.alive? }
+  end
+
+  def purchase(purchase_option)
+    # todo: remove content assoc from Purchase
+    #       check if content is already purchased
+    if is_in_library?(purchase_option.content)
+      raise AlreadyPurchasedError
+    else
+      self.purchases << Purchase.create(purchase_option: purchase_option)
+    end
+  end
+
+  private
+
+  def is_in_library?(content)
+    library.any? {|purchase| purchase.content.title == content.title }
+  end
 end

db/migrate/20190703103723_create_purchases.rb

@@ -2,7 +2,6 @@ class CreatePurchases < ActiveRecord::Migration[5.2]
   def change
     create_table :purchases do |t|
       t.references :user, foreign_key: true
-      t.references :content, polymorphic: true
 
       t.timestamps
     end

db/migrate/20190703104503_create_seasons.rb

@@ -3,7 +3,6 @@ def change
     create_table :seasons do |t|
       t.string :title
       t.text :plot
-      t.references :episodes, foreign_key: true
 
       t.timestamps
     end

db/migrate/20190703105304_create_purchase_options.rb

@@ -3,6 +3,7 @@ def change
     create_table :purchase_options do |t|
       t.float :price
       t.string :video_quality
+      t.references :content, polymorphic: true
 
       t.timestamps
     end

db/migrate/20190705120624_add_content_to_purchase_option.rb

@@ -0,0 +1,5 @@
+class AddContentToPurchaseOption < ActiveRecord::Migration[5.2]
+  def change
+    add_reference :purchase_options, :content, polymorphic: true
+  end
+end

db/migrate/20190706162714_add_purchase_option_to_purchase.rb

@@ -0,0 +1,5 @@
+class AddPurchaseOptionToPurchase < ActiveRecord::Migration[5.2]
+  def change
+    add_reference :purchases, :purchase_option, foreign_key: true
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2019_07_03_104503) do
+ActiveRecord::Schema.define(version: 2019_07_06_162714) do
 
   create_table "episodes", force: :cascade do |t|
     t.string "title"
@@ -28,13 +28,27 @@
     t.datetime "updated_at", null: false
   end
 
+  create_table "purchase_options", force: :cascade do |t|
+    t.float "price"
+    t.string "video_quality"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.string "content_type"
+    t.integer "content_id"
+    t.index ["content_type", "content_id"], name: "index_purchase_options_on_content_type_and_content_id"
+  end
+
   create_table "purchases", force: :cascade do |t|
     t.integer "user_id"
     t.string "content_type"
     t.integer "content_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.integer "purchase_id"
+    t.integer "purchase_option_id"
     t.index ["content_type", "content_id"], name: "index_purchases_on_content_type_and_content_id"
+    t.index ["purchase_id"], name: "index_purchases_on_purchase_id"
+    t.index ["purchase_option_id"], name: "index_purchases_on_purchase_option_id"
     t.index ["user_id"], name: "index_purchases_on_user_id"
   end