Add CacheService

app/services/cache_service.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class CacheService
+  def self.cache(cache_key, options = {})
+    Rails.cache.fetch cache_key.to_s, options do
+      yield
+    end
+  end
+
+  # Yields a cached query, expired by the most recently updated record for a given class.
+  # E.g: if *any* Spree::Taxon record is updated, all keys based on Spree::Taxon will auto-expire.
+  def self.cached_data_by_class(cache_key, cached_class)
+    Rails.cache.fetch "#{cache_key}-#{cached_class}-#{latest_timestamp_by_class(cached_class)}" do
+      yield
+    end
+  end
+
+  # Gets the :updated_at value of the most recently updated record for a given class, and returns
+  # it as a timestamp, eg: `1583836069`.
+  def self.latest_timestamp_by_class(cached_class)
+    cached_class.maximum(:updated_at).to_i
+  end
+end

spec/services/cache_service_spec.rb

@@ -0,0 +1,50 @@
+require 'spec_helper'
+
+describe CacheService do
+  let(:rails_cache) { Rails.cache }
+
+  describe "#cache" do
+    before do
+      rails_cache.stub(:fetch)
+    end
+
+    it "provides a wrapper for basic #fetch calls to Rails.cache" do
+      CacheService.cache("test-cache-key", expires_in: 10.seconds) do
+        "TEST"
+      end
+
+      expect(rails_cache).to have_received(:fetch).with("test-cache-key", expires_in: 10.seconds)
+    end
+  end
+
+  describe "#cached_data_by_class" do
+    let(:timestamp) { Time.now.to_i }
+
+    before do
+      rails_cache.stub(:fetch)
+      CacheService.stub(:latest_timestamp_by_class) { timestamp }
+    end
+
+    it "caches data by timestamp for last record of that class" do
+      CacheService.cached_data_by_class("test-cache-key", Enterprise) do
+        "TEST"
+      end
+
+      expect(CacheService).to have_received(:latest_timestamp_by_class).with(Enterprise)
+      expect(rails_cache).to have_received(:fetch).with("test-cache-key-Enterprise-#{timestamp}")
+    end
+  end
+
+  describe "#latest_timestamp_by_class" do
+    let!(:taxon1) { create(:taxon) }
+    let!(:taxon2) { create(:taxon) }
+
+    it "gets the :updated_at value of the last record for a given class and returns a timestamp" do
+      taxon1.touch
+      expect(CacheService.latest_timestamp_by_class(Spree::Taxon)).to eq taxon1.updated_at.to_i
+
+      taxon2.touch
+      expect(CacheService.latest_timestamp_by_class(Spree::Taxon)).to eq taxon2.updated_at.to_i
+    end
+  end
+end