add disk space usage failsafe

spec/components/cooked_post_processor_spec.rb

@@ -275,6 +275,8 @@ describe CookedPostProcessor do
     let(:post) { build(:post) }
     let(:cpp) { CookedPostProcessor.new(post) }
 
+    before { cpp.stubs(:available_disk_space).returns(90) }
+
     it "does not run when download_remote_images_to_local is disabled" do
       SiteSetting.stubs(:download_remote_images_to_local).returns(false)
       Jobs.expects(:cancel_scheduled_job).never
@@ -291,6 +293,13 @@ describe CookedPostProcessor do
         cpp.pull_hotlinked_images
       end
 
+      it "disables download when disk space is low" do
+        SiteSetting.expects(:download_remote_images_threshold).returns(20)
+        cpp.expects(:available_disk_space).returns(10)
+        Jobs.expects(:cancel_scheduled_job).never
+        cpp.pull_hotlinked_images
+      end
+
       context "and the post has been updated by a user" do
 
         before { post.id = 42 }
@@ -310,4 +319,25 @@ describe CookedPostProcessor do
 
   end
 
+  context ".disable_if_low_on_disk_space" do
+
+    let(:post) { build(:post) }
+    let(:cpp) { CookedPostProcessor.new(post) }
+
+    before { cpp.expects(:available_disk_space).returns(50) }
+
+    it "does nothing when there's enough disk space" do
+      SiteSetting.expects(:download_remote_images_threshold).returns(20)
+      SiteSetting.expects(:download_remote_images_to_local).never
+      cpp.disable_if_low_on_disk_space.should == false
+    end
+
+    it "disables download_remote_images_threshold when there's not enough disk space" do
+      SiteSetting.expects(:download_remote_images_threshold).returns(75)
+      cpp.disable_if_low_on_disk_space.should == true
+      SiteSetting.download_remote_images_to_local.should == false
+    end
+
+  end
+
 end