add permission service, add validations to map.rb

app/models/map.rb

@@ -13,6 +13,9 @@ class Map < ActiveRecord::Base
    #:full => ['940x630#', :png]
   },
   :default_url => 'https://s3.amazonaws.com/metamaps-assets/site/missing-map.png'
+  validates_presence_of :name
+  validates_presence_of :arranged
+  validate_presence_of :permission
     
   # Validate the attached image is image/jpg, image/png, etc
   validates_attachment_content_type :screenshot, :content_type => /\Aimage\/.*\Z/
@@ -22,13 +25,7 @@ class Map < ActiveRecord::Base
   end
 
   def mk_permission
-    if self.permission == "commons"
+    Perm.short(permission)
-      "co"
-    elsif self.permission == "public"
-      "pu"
-    elsif self.permission == "private"
-      "pr"
-    end
   end
 
   #return an array of the contributors to the map

app/services/perm.rb

@@ -0,0 +1,36 @@
+class Perm
+  class << self
+    # e.g. Perm::ISSIONS
+    ISSIONS = [:commons, :public, :private]
+  
+    def short(permission)
+      case permission
+      when :commons
+        "co"
+      when :public
+        "pu"
+      when :private
+        "pr"
+      else
+        fail "Invalid permission"
+      end
+    end
+
+    def long(perm)
+      case perm
+      when "co"
+        :commons
+      when "pu"
+        :public
+      when "pr"
+        :private
+      else
+        fail "Invalid short permission"
+      end
+    end
+  
+    def valid?(permission)
+      ISSIONS.include? permission
+    end
+  end
+end