class Favorite < ApplicationRecord
  class Error < StandardError; end

  belongs_to :post
  belongs_to :user

  scope :for_user, ->(user_id) { where("favorites.user_id % 100 = ? AND favorites.user_id = ?", user_id.to_i % 100, user_id) }
  scope :public_favorites, -> { where(user: User.bit_prefs_match(:enable_private_favorites, false)) }

  def self.visible(user)
    user.is_admin? ? all : for_user(user.id).or(public_favorites)
  end

  def self.search(params)
    q = search_attributes(params, :id, :post)

    if params[:user_id].present?
      q = q.for_user(params[:user_id])
    end

    q.order(post_id: :desc)
  end

  def self.available_includes
    [:post, :user]
  end

  def self.add(post:, user:)
    Favorite.transaction do
      User.where(id: user.id).select("id").lock("FOR UPDATE").first

      if user.favorite_count >= user.favorite_limit
        raise Error, "You can only keep up to #{user.favorite_limit} favorites. Upgrade your account to save more."
      elsif Favorite.for_user(user.id).where(:user_id => user.id, :post_id => post.id).exists?
        raise Error, "You have already favorited this post"
      end

      Favorite.create!(:user_id => user.id, :post_id => post.id)
      Post.where(:id => post.id).update_all("fav_count = fav_count + 1")
      post.append_user_to_fav_string(user.id)
      User.where(:id => user.id).update_all("favorite_count = favorite_count + 1")
      user.favorite_count += 1
    end
  end

  def self.remove(user:, post: nil, post_id: nil)
    Favorite.transaction do
      if post && post_id.nil?
        post_id = post.id
      end

      User.where(id: user.id).select("id").lock("FOR UPDATE").first

      return unless Favorite.for_user(user.id).where(:user_id => user.id, :post_id => post_id).exists?
      Favorite.for_user(user.id).where(post_id: post_id).delete_all
      Post.where(:id => post_id).update_all("fav_count = fav_count - 1")
      post&.delete_user_from_fav_string(user.id)
      User.where(:id => user.id).update_all("favorite_count = favorite_count - 1")
      user.favorite_count -= 1
      post.fav_count -= 1 if post
    end
  end
end
