bookstore/app/controllers/books_controller.rb

class BooksController < ApplicationController
  before_action :set_book, only: [:show, :edit, :update, :add_to_cart]
  before_action :ensure_admin, only: [:edit, :update]

  def index
    if current_user&.admin?
      books = Book.all
    else
      books = Book.published
    end
    @books = books.map { |book| BooksPresenter.new(book) }
  end

  def show
  end

  def edit
  end

  def update
    if @book.update(book_params)
      redirect_to '/books'
    end
  end

  def add_to_cart
    @book = Book.find(params[:id])
    return unless @book.quantity.positive?

    current_user.books << @book
    @book.decrement!(:quantity)
    redirect_to '/books', notice: 'Book added to your cart'
  end

  def shopping_cart
    @books = current_user.books.map { |book| BooksPresenter.new(book) }
  end

  private

  def set_book
    @book = BooksPresenter.new(Book.find(params[:id]))
  end

  def book_params
    result = params.require(:book).permit(:title, :price, :published)
    result['price'] = result['price'].to_d * 100
    result
  end
end