Enforce 1024 character limit on description value

README.md

@@ -126,7 +126,8 @@ data = { start_time: DateTime.now + 4.hours }
 mail(to: to_email, subject: "Test", body: "test", sparkpost_data: data)
 ```
 
-You can set a description for a transmission via the "sparkpost_data" as well:
+You can set a description for a transmission via the "sparkpost_data" as well.  The maximum length of the decription is 1024 characters - values
+longer than the maxium will be truncated.
 
 ```
 data = { description: "My Important Message" }

lib/sparkpost_rails/delivery_method.rb

@@ -267,7 +267,7 @@ def prepare_skip_suppression_from sparkpost_data
 
     def prepare_description_from sparkpost_data
       if sparkpost_data[:description]
-        @data[:description] = sparkpost_data[:description]
+        @data[:description] = sparkpost_data[:description].truncate(1024)
       end
     end
 

spec/description_spec.rb

@@ -15,6 +15,17 @@
       expect(@delivery_method.data[:description]).to eq("Test Email")
     end
 
+    it "truncates values longer than 1024 characters" do
+      raw_description = "X" * 1050
+      truncated_description = ("X" * 1021) + "..."
+
+      test_email = Mailer.test_email sparkpost_data: {description: raw_description}
+
+      @delivery_method.deliver!(test_email)
+
+      expect(@delivery_method.data[:description]).to eq(truncated_description)
+    end
+
     it "does not include description element if not supplied" do
       test_email = Mailer.test_email
       @delivery_method.deliver!(test_email)