From 444dc49aec188a3b34fab3cc5d7c0ce2df26fabf Mon Sep 17 00:00:00 2001
From: Craig Savolainen <dev+craig@influitive.com>
Date: Wed, 10 Aug 2016 18:41:04 -0400
Subject: [PATCH] Allow update suppression to be configurable

Currently updates will be suppressed if the model
responds to #previous_changes and return an #empty?
object. This allows each publisher to specify an
:update_unless proc that will accept the record
being processed.
---
 lib/multiple_man/mixins/publisher.rb |  6 +-----
 lib/multiple_man/model_publisher.rb  | 14 +++++++++++---
 spec/model_publisher_spec.rb         | 19 +++++++++++++++++--
 3 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/lib/multiple_man/mixins/publisher.rb b/lib/multiple_man/mixins/publisher.rb
index 3a0751b..d8ea7dd 100644
--- a/lib/multiple_man/mixins/publisher.rb
+++ b/lib/multiple_man/mixins/publisher.rb
@@ -6,11 +6,7 @@ def Publisher.included(base)
       base.extend(ClassMethods)
       if base.respond_to?(:after_commit)
         base.after_commit(on: :create) { |r| r.multiple_man_publish(:create) }
-        base.after_commit(on: :update) do |r|
-          if !r.respond_to?(:previous_changes) || r.previous_changes.any?
-            r.multiple_man_publish(:update)
-          end
-        end
+        base.after_commit(on: :update) { |r| r.multiple_man_publish(:update) }
         base.after_commit(on: :destroy) { |r| r.multiple_man_publish(:destroy) }
       end
 
diff --git a/lib/multiple_man/model_publisher.rb b/lib/multiple_man/model_publisher.rb
index 921ba98..b6cd4c7 100644
--- a/lib/multiple_man/model_publisher.rb
+++ b/lib/multiple_man/model_publisher.rb
@@ -2,17 +2,25 @@
 
 module MultipleMan
   class ModelPublisher
+    DEFAULT_OPTIONS = {
+      update_unless: ->(r) {
+        r.respond_to?(:previous_changes) && r.previous_changes.blank?
+      }
+    }.freeze
 
     def initialize(options = {})
-      self.options = options.with_indifferent_access
+      @options = DEFAULT_OPTIONS.merge(options).with_indifferent_access
+      @update_unless = @options[:update_unless]
     end
 
-    def publish(records, operation=:create)
+    def publish(records, operation = :create)
       return unless MultipleMan.configuration.enabled
 
       Connection.connect do |connection|
         ActiveSupport::Notifications.instrument('multiple_man.publish_messages') do
           all_records(records) do |record|
+            next if :update == operation && update_unless.call(record)
+
             ActiveSupport::Notifications.instrument('multiple_man.publish_message') do
               push_record(connection, record, operation)
             end
@@ -25,7 +33,7 @@ def publish(records, operation=:create)
 
   private
 
-    attr_accessor :options
+    attr_reader :options, :update_unless
 
     def push_record(connection, record, operation)
       data = PayloadGenerator.new(record, operation, options)
diff --git a/spec/model_publisher_spec.rb b/spec/model_publisher_spec.rb
index 52fd763..0607029 100644
--- a/spec/model_publisher_spec.rb
+++ b/spec/model_publisher_spec.rb
@@ -1,6 +1,6 @@
 require 'spec_helper'
 
-describe MultipleMan::ModelPublisher do 
+describe MultipleMan::ModelPublisher do
   let(:channel_stub) { double(Bunny::Channel, topic: topic_stub)}
   let(:topic_stub) { double(Bunny::Exchange, publish: nil) }
 
@@ -34,6 +34,21 @@ def model_name
       described_class.new(fields: [:foo]).publish(MockObject.new)
     end
 
+    it 'skips updates for models with no changes by default' do
+      expect(topic_stub).to_not receive(:publish)
+
+      model = OpenStruct.new(previous_changes: [])
+      described_class.new(fields: [:foo]).publish(model, :update)
+    end
+
+    it 'allows skipping updates' do
+      expect(topic_stub).to_not receive(:publish)
+
+      model = OpenStruct.new(previous_changes: [])
+      described_class.new(fields: [:foo], update_unless: ->(r) { true })
+        .publish(model, :update)
+    end
+
     it "should call the error handler on error" do
       ex = Exception.new("Bad stuff happened")
       topic_stub.stub(:publish) { raise ex }
@@ -60,4 +75,4 @@ def as_json
     end
   end
 
-end
\ No newline at end of file
+end