FEATURE: allow admins to choose a group as a primary group

FEATURE: allow admins to set a default title for a group

app/models/group.rb

@@ -12,6 +12,8 @@ class Group < ActiveRecord::Base
 
   after_save :destroy_deletions
   after_save :automatic_group_membership
+  after_save :update_primary_group
+  after_save :update_title
 
   validate :name_format_validator
   validates_uniqueness_of :name, case_sensitive: false
@@ -301,6 +303,59 @@ class Group < ActiveRecord::Base
       end
     end
 
+    def update_title
+      return if new_record? && !self.title.present?
+
+      if self.title_changed?
+        sql = <<SQL
+        UPDATE users SET title = :title
+        WHERE (title = :title_was OR
+              title = '' OR
+              title IS NULL) AND
+              COALESCE(title,'') <> COALESCE(:title,'') AND
+              id IN (
+                SELECT user_id
+                FROM group_users
+                WHERE group_id = :id
+              )
+SQL
+
+        self.class.exec_sql(sql,
+              title: title,
+              title_was: title_was,
+              id: id
+        )
+      end
+    end
+
+    def update_primary_group
+      return if new_record? && !self.primary_group?
+
+      if self.primary_group_changed?
+        sql = <<SQL
+        UPDATE users
+        /*set*/
+        /*where*/
+SQL
+
+        builder = SqlBuilder.new(sql)
+        builder.where("
+              id IN (
+                SELECT user_id
+                FROM group_users
+                WHERE group_id = :id
+              )", id: id)
+
+        if primary_group
+          builder.set("primary_group_id = :id")
+        else
+          builder.set("primary_group_id = NULL")
+          builder.where("primary_group_id = :id")
+        end
+
+        builder.exec
+      end
+    end
 end
 
 # == Schema Information