Add min_trust_to_create_topic setting to require a certain trust level before users can start new topics

app/models/min_trust_to_create_topic_setting.rb

@@ -0,0 +1,18 @@
+require_dependency 'enum_site_setting'
+
+class MinTrustToCreateTopicSetting < EnumSiteSetting
+
+  def self.valid_value?(val)
+    valid_values.any? { |v| v.to_s == val.to_s }
+  end
+
+  def self.values
+    @values ||= valid_values.map {|x| {name: x.to_s, value: x} }
+  end
+
+  private
+
+  def self.valid_values
+    TrustLevel.levels.values.sort
+  end
+end

app/models/site_setting.rb

@@ -205,6 +205,8 @@ class SiteSetting < ActiveRecord::Base
   setting(:regular_requires_likes_given, 1)
   setting(:regular_requires_topic_reply_count, 3)
 
+  setting(:min_trust_to_create_topic, 0, enum: 'MinTrustToCreateTopicSetting')
+
   # Reply by Email Settings
   setting(:reply_by_email_enabled, false)
   setting(:reply_by_email_address, '')

config/locales/server.en.yml

@@ -611,6 +611,8 @@ en:
     regular_requires_likes_given: "How many likes a basic user must cast before promotion to regular (2) trust level"
     regular_requires_topic_reply_count: "How many topics a basic user must reply to before promotion to regular (2) trust level"
 
+    min_trust_to_create_topic: "The minimum trust level required to create a new topic."
+
     newuser_max_links: "How many links a new user can add to a post"
     newuser_max_images: "How many images a new user can add to a post"
     newuser_max_attachments: "How many attachments a new user can add to a post"

lib/guardian.rb

@@ -229,11 +229,11 @@ class Guardian
   end
 
   def can_create_topic?(parent)
-    can_create_post?(parent)
+    user && user.trust_level >= SiteSetting.min_trust_to_create_topic.to_i && can_create_post?(parent)
   end
 
   def can_create_topic_on_category?(category)
-    can_create_post?(nil) && (
+    can_create_topic?(nil) && (
       !category ||
       Category.topic_create_allowed(self).where(:id => category.id).count == 1
     )

spec/components/guardian_spec.rb

@@ -283,6 +283,21 @@ describe Guardian do
         category.save
         Guardian.new(user).can_create?(Topic,category).should be_false
       end
+
+      it "is true for new users by default" do
+        Guardian.new(user).can_create?(Topic,Fabricate(:category)).should be_true
+      end
+
+      it "is false if user has not met minimum trust level" do
+        SiteSetting.stubs(:min_trust_to_create_topic).returns(1)
+        Guardian.new(build(:user, trust_level: 0)).can_create?(Topic,Fabricate(:category)).should be_false
+      end
+
+      it "is true if user has met or exceeded the minimum trust level" do
+        SiteSetting.stubs(:min_trust_to_create_topic).returns(1)
+        Guardian.new(build(:user, trust_level: 1)).can_create?(Topic,Fabricate(:category)).should be_true
+        Guardian.new(build(:user, trust_level: 2)).can_create?(Topic,Fabricate(:category)).should be_true
+      end
     end
 
     describe 'a Post' do