hook up has_many relations

app/models/author.rb

@@ -1,2 +1,6 @@
 class Author < ApplicationRecord
+  has_many :books
+  has_many :characters, through: :books
+  has_many :genres,     through: :books
+  has_many :metrics,    through: :books
 end

app/models/book.rb

@@ -1,2 +1,15 @@
 class Book < ApplicationRecord
+  has_many :book_has_genres
+  has_many :genres, through: :book_has_genres
+
+  has_many :publish_dates
+  has_many :publishers, through: :publish_dates
+  has_many :authors,    through: :publish_dates
+
+  has_many :chapters
+
+  has_many :character_appearances
+  has_many :characters, through: :character_appearances
+
+  has_many :metrics, as: :prose
 end

app/models/chapter.rb

@@ -1,3 +1,8 @@
 class Chapter < ApplicationRecord
   belongs_to :book
+
+  has_many :character_appearances
+  has_many :characters, through: :character_appearances
+
+  has_many :metrics, as: :prose
 end

app/models/character.rb

@@ -1,2 +1,9 @@
 class Character < ApplicationRecord
+  has_many :character_appearances
+  has_many :books, through: :character_appearances,
+    source: :prose, source_type: Book.name
+  has_many :chapters, through: :character_appearances,
+    source: :prose, source_type: Chapter.name
+
+  has_many :metrics
 end

app/models/genre.rb

@@ -1,2 +1,5 @@
 class Genre < ApplicationRecord
+  has_many :book_has_genres
+  has_many :books,   through: :book_has_genres
+  has_many :authors, through: :book_has_genres
 end

app/models/publisher.rb

@@ -1,2 +1,8 @@
 class Publisher < ApplicationRecord
+  has_many :books
+  has_many :authors, through: :books
+  has_many :metrics, through: :books
+  has_many :genres,  through: :books
+
+  has_many :publish_dates
 end