point_ledger.rb

class PointLedger
  attr_reader :user

  def initialize(user)
    @user = user
  end

  def add(amount, item)
    user.point_transactions.build(amount: amount, item_type: item.class, item_name: item.name)
    user.points += amount
    user.save
  end

  def deduct(amount, item)
    user.point_transactions.build(amount: -amount, item_type: item.class, item_name: item.name)
    user.points -= amount
    user.save
  end
end

# will eventually have a "Trip" calc that will
# take current users location and end location and see
# if _that_ is .possible?
class PurchaseCalc
  def possible?(user, item)
    user.points >= item.price
  end
end

class PurchaseService
  attr_reader :user

  def initialize(user)
    @user = user
  end

  def purchase(item)
    if PurchaseCalc.new.possible?(user, item)
      point_ledger = PointLedger.new(user)
      point_ledger.deduct(10, item)
    end
  end
end

location = Location.find(1)
if Service::Purchase.new(user).purchase(location)
  Service::UserLocation.new(user).update(location)
else
  render :back, alert: "error"
end