follow relationship

friendship.rb

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  # Activate the gem you are reporting the issue against.
  gem "activerecord", "6.0.0"
  gem "sqlite3"
  gem "byebug"
end

require "active_record"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do

  create_table :users, force: true do |t|
    t.string :name, null: false
  end

  create_table :friendships, force: true do |t|
    t.belongs_to :follower
    t.belongs_to :followed
  end

  add_index :friendships, [:follower_id, :followed_id], unique: true

  create_table :books, force: true do |t|

    t.string :user_id
    t.string :name
  end

end

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
end

class User < ApplicationRecord
  has_many :books
  has_many :friendships, foreign_key: "follower_id", dependent: :destroy
  has_many :reverse_friendships, foreign_key: "followed_id", class_name: "Friendship", dependent: :destroy
  has_many :following, through: :friendships, source: :followed, class_name: "User"
  has_many :followers, through: :reverse_friendships, class_name: "User"
  has_many :following_books, through: :following, source: :books, class_name: "Book"

  def follow!(user)
#    friendships.create!(followed_id: user.id)
    following << user
  end

  def unfollow!(user)
    friendships.find_by!(followed_id: user.id).destroy!
  end

  def following?(user)
    following.include?(user)
  end
end

class Friendship < ApplicationRecord
  belongs_to :follower, class_name: "User"
  belongs_to :followed, class_name: "User"
end

class Book < ApplicationRecord
  belongs_to :user

  default_scope -> { order('create_at DESC') }

  def self.friend_feeds(user)
    # 自分の持つ書籍とフォローユーザーが持つ書籍を取得する
    following_ids = "select followed_id from friendships where follower_id = :user_id"
    where("user_id in (#{following_ids}) or user_id = :user_id", user_id: user.id)
  end
end

class FriendshipTest < Minitest::Test
  def test_association
    # テストデータ作成
    mh = User.create!(name: "mh")
    ruby_book = Book.create!(name: "ruby", user_id: mh.id) 
    js_book = Book.create!(name: "js", user_id: mh.id)

    miro = User.create!(name: "miro")
    php_book = Book.create!(name: "php", user_id: miro.id) 
    python_book = Book.create!(name: "python", user_id: miro.id)
    swift_book = Book.create!(name: "swift", user_id: miro.id)

    haru = User.create!(name: "haru")
    rust_book = Book.create!(name: "rust", user_id: haru.id)
    typescript_book = Book.create!(name: "typescript", user_id: haru.id)
    go_book = Book.create!(name: "go", user_id: haru.id)
    kotlin = Book.create!(name: "kotlin", user_id: haru.id)

    # フォローの関連付け
    assert_equal false, mh.following?(miro)
    assert_equal false, mh.following?(haru)
    mh.follow!(miro)
    mh.follow!(haru)
    assert_equal true, mh.following?(miro)
    assert_equal true, mh.following?(haru)

    # フォローユーザーの取得
    following =  mh.following

    # フォローが正しい
    assert_equal 2, following.count
    assert_equal miro, following[0]
    assert_equal haru, following[1]

    # フォローユーザーの書籍の数が正しい
    following_books = mh.following_books
    assert_equal 7, following_books.count

    # 自分を含めたフォローユーザーの書籍のフィードを取得
    feeds = Book.friend_feeds(mh)
    assert_equal 9, feeds.count

    # フォローを解除
    mh.unfollow!(miro)
    mh.reload

    following =  mh.following

    # フォローが正しい
    assert_equal 1, following.count
    assert_equal haru, following[0]
    assert_equal false, mh.following?(miro)
    assert_equal true, mh.following?(haru)

    # mhユーザーを削除
    mh.destroy

    # Friendshipのデータ数が０になる
    assert_equal 0, Friendship.all.count
  end
end