fairmondo/fairmondo

#   Copyright (c) 2012-2017, Fairmondo eG.  This file is
#   licensed under the GNU Affero General Public License version 3 or later.
#   See the COPYRIGHT file for details.

class Cart < ApplicationRecord
  attr_accessor :cookie_content # temp storage for pundit validation

  # Associations
  has_many :line_item_groups, dependent: :destroy, inverse_of: :cart
  has_many :line_items, through: :line_item_groups, inverse_of: :cart
  has_many :articles, through: :line_item_groups

  belongs_to :user, inverse_of: :carts

  # Scopes
  scope :newest, -> { order(created_at: :desc) }
  scope :open, -> { where.not(sold: true) }

  # Methods
  delegate :total_purchase_donations,
           :belboon_tracking_token,
           :belboon_tracking_token_set_at, to: :user, prefix: true

  # Finds an existing cart for the logged in user or creates a new one
  # @param buyer [User, nil] logged in user or nil if user is not logged in
  # @return [Cart] found or created cart
  def self.current_or_new_for buyer
    if buyer
      current_for(buyer) || create(user: buyer)
    else
      create
    end
  end

  def self.current_for buyer
    newest.open.where(user_id: buyer.id).first
  end

  # In one cart there should only be one LIG per seller; this finds or creates it
  def line_item_group_for seller
    line_item_groups.where(seller: seller).first || LineItemGroup.create(cart: self, seller: seller)
  end

  def contains_all_available_line_items_for? article
    line_item = line_item_for article
    line_item ? line_item.requested_quantity >= article.quantity_available : false
  end

  def line_item_for article
    items = line_items.select { |item| item.article_id == article.id }
    items.any? ? items.first : nil
  end

  def buy
    Article.transaction do
      locked_article_ids_with_quantities = {}
      self.line_item_groups.each do |line_item_group|
        line_item_group.line_items.each do |line_item|
          locked_article_ids_with_quantities[line_item.article.id] =
            line_item.requested_quantity
          line_item.business_transaction.save!
        end
        line_item_group.buyer_id = self.user_id
        line_item_group.sold_at = Time.now
        line_item_group.save!
        line_item_group.generate_purchase_id
      end
      # sort this by article_id to prevent deadlocks
      locked_article_ids_with_quantities.sort.each do |article_id, quantity|
        article = Article.lock.find(article_id) # locks always need to refind records
        article.buy!(quantity)
      end

      self.update_attribute(:sold, true)

      AfterBuyWorker.perform_async self.id
    end

    ###################################################
    # DO NOT PUT ANY CODE HERE THAT CAN FAIL !!!! #####
    # Best would be not to put any code here at all.
    # If you have to do something here that can fail
    # put it into the transaction.
    ###################################################

    return :checked_out
  rescue => e
    Rails.logger.info "cart_error #{e.inspect} - #{e.message}"
    return :checkout_failed
  end

  # checks if cart is empty
  def empty?
    !line_items.any?
  end
end