Refactoring Tickets

- Tickets now independent from registration
- Implemented money gem
#419

app/models/ticket_purchase.rb

@@ -0,0 +1,51 @@
+class TicketPurchase < ActiveRecord::Base
+  belongs_to :ticket
+  belongs_to :user
+  belongs_to :conference
+
+  attr_accessible :ticket_id, :user_id, :conference_id, :paid, :quantity
+
+  validates :ticket_id, :user_id, :conference_id, :quantity, presence: true
+
+  validates_numericality_of :quantity, greater_than: 0
+
+  validates_uniqueness_of :user_id,
+                          scope: :ticket_id,
+                          message: 'already bought this ticket!'
+
+  def self.purchase(conference, user, purchases)
+    errors = []
+    ActiveRecord::Base.transaction do
+      conference.tickets.each do |ticket|
+        quantity = purchases[ticket.id.to_s].to_i
+        if ticket.bought?(user)
+          purchase = update_quantity(conference, quantity, ticket, user)
+        else
+          purchase = purchase_ticket(conference, quantity, ticket, user)
+        end
+
+        if purchase && !purchase.save
+          errors.push(purchase.errors.full_messages)
+        end
+      end
+    end
+    errors.join('. ')
+  end
+
+  def self.purchase_ticket(conference, quantity, ticket, user)
+    purchase = new(ticket_id: ticket.id,
+                   conference_id: conference.id,
+                   user_id: user.id,
+                   quantity: quantity) if quantity > 0
+    purchase
+  end
+
+  def self.update_quantity(conference, quantity, ticket, user)
+    purchase = TicketPurchase.where(ticket_id: ticket.id,
+                                    conference_id: conference.id,
+                                    user_id: user.id).first
+
+    purchase.quantity = quantity if quantity > 0
+    purchase
+  end
+end