F2: Feed model scopes and helpers (#599)

* Dry exceptions handling

* Test coverage

* Clean up

* Rename constant

* `Feed.stale` scope

* `Feed.ordered_by` scope

* Formatting

* Implement `Feed.stale?`

* Bump Ruby from 3.3.5 to 3.3.6

.ruby-version

@@ -1 +1 @@
-ruby-3.3.5
+ruby-3.3.6

.tool-versions

@@ -1 +1 @@
-ruby 3.3.5
+ruby 3.3.6

Gemfile

@@ -1,6 +1,6 @@
 source "https://rubygems.org"
 
-ruby "3.3.5"
+ruby "3.3.6"
 
 gem "aasm", "~> 5.5"
 gem "amazing_print"

Gemfile.lock

@@ -438,7 +438,7 @@ DEPENDENCIES
   yaml-lint (~> 0.1.2)
 
 RUBY VERSION
-   ruby 3.3.5p100
+   ruby 3.3.6p108
 
 BUNDLED WITH
    2.5.16

app/models/feed.rb

@@ -1,7 +1,7 @@
 class Feed < ApplicationRecord
   include AASM
 
-  MAX_LIMIT_LIMIT = 100
+  MAX_IMPORT_LIMIT = 100
   IMPORT_LIMIT_RANGE = 0..(86400 * 7)
   NAME_LENGTH_RANGE = 3..80
   MAX_URL_LENGTH = 4096
@@ -14,7 +14,7 @@ class Feed < ApplicationRecord
   validates :name, presence: true, length: NAME_LENGTH_RANGE, format: /\A[\w\-]+\z/
   normalizes :name, with: ->(name) { name.to_s.strip.downcase }
 
-  validates :import_limit, numericality: {less_than_or_equal_to: MAX_LIMIT_LIMIT}
+  validates :import_limit, numericality: {less_than_or_equal_to: MAX_IMPORT_LIMIT}
   validates :refresh_interval, presence: true, numericality: {greater_than_or_equal_to: 0}
   validates :loader, :normalizer, :processor, presence: true, format: /\A\w+\z/
   validates :url, length: {maximum: MAX_URL_LENGTH}, allow_nil: true
@@ -46,17 +46,33 @@ class Feed < ApplicationRecord
     end
   end
 
+  scope :ordered_by, ->(attribute, direction) { order(sanitize_sql_for_order("#{attribute} #{direction} NULLS LAST")) }
+
+  scope :stale, lambda {
+    where(refresh_interval: 0)
+      .or(where(refreshed_at: nil))
+      .or(where("age(now(), refreshed_at) > make_interval(secs => refresh_interval)"))
+  }
+
   def configurable?
     updated_at.blank? || configured_at.blank? || updated_at.change(usec: 0) <= configured_at.change(usec: 0)
   end
 
+  # @return [true, false] true when the feed needs a refresh
+  def stale?
+    refresh_interval.zero? || refreshed_at.blank? || time_to_refresh?
+  end
+
   def reference
     [self.class.name.underscore, id, name].compact_blank.join("-")
   end
 
   def ensure_supported
-    return true if loader_class && processor_class && normalizer_class
-    raise FeedConfigurationError
+    if loader_class && processor_class && normalizer_class
+      true
+    else
+      raise FeedConfigurationError
+    end
   end
 
   def service_classes
@@ -69,8 +85,6 @@ def service_classes
 
   def loader_class
     ClassResolver.new(loader, suffix: "loader").resolve
-  rescue NameError
-    nil
   end
 
   def loader_instance
@@ -79,8 +93,6 @@ def loader_instance
 
   def processor_class
     ClassResolver.new(processor, suffix: "processor").resolve
-  rescue NameError
-    nil
   end
 
   def processor_instance
@@ -89,13 +101,19 @@ def processor_instance
 
   def normalizer_class
     ClassResolver.new(normalizer, suffix: "normalizer").resolve
-  rescue NameError
-    nil
   end
 
   private
 
   def options_must_be_hash
     errors.add(:options, :not_a_hash, message: "must be a hash") unless options.is_a?(Hash)
   end
+
+  def time_to_refresh?
+    seconds_since_last_refresh > refresh_interval
+  end
+
+  def seconds_since_last_refresh
+    (Time.now.utc.to_i - refreshed_at.to_i).abs
+  end
 end

app/services/class_resolver.rb

@@ -15,5 +15,7 @@ def initialize(class_name, suffix: nil)
   # @raise [NameError] if the target class is missing
   def resolve
     [class_name, suffix].join("_").classify.constantize
+  rescue NameError
+    nil
   end
 end

app/services/feed_processor.rb

@@ -10,7 +10,6 @@ def initialize(feeds:)
     @feeds = feeds
   end
 
-  # TBD: This should receive "stale enabled" feeds; test Feed model scopes
   def perform
     feeds.each do |feed|
       Importer.new(feed).import

spec/models/feed_spec.rb

@@ -1,4 +1,6 @@
 RSpec.describe Feed do
+  before { freeze_time }
+
   describe "relations" do
     subject(:feed) { build(:feed) }
 
@@ -42,7 +44,7 @@
 
     describe "#import_limit" do
       it "validates numericality" do
-        expect(feed).to validate_numericality_of(:import_limit).is_less_than_or_equal_to(Feed::MAX_LIMIT_LIMIT)
+        expect(feed).to validate_numericality_of(:import_limit).is_less_than_or_equal_to(Feed::MAX_IMPORT_LIMIT)
       end
     end
 
@@ -128,6 +130,58 @@
     end
   end
 
+  describe ".ordered_by" do
+    it "orders records by the specified attribute and direction" do
+      create(:feed, name: "bbb", refreshed_at: 2.days.ago)
+      create(:feed, name: "aaa", refreshed_at: 1.day.ago)
+      feeds = described_class.ordered_by("name", "ASC")
+
+      expect(feeds.map(&:name)).to eq(%w[aaa bbb])
+    end
+
+    it "puts null values last when descending" do
+      create(:feed, name: "bbb", refreshed_at: nil)
+      create(:feed, name: "aaa", refreshed_at: 1.day.ago)
+      feeds = described_class.ordered_by("refreshed_at", "DESC")
+
+      expect(feeds.map(&:name)).to eq(%w[aaa bbb])
+    end
+
+    it "puts null values last when ascending" do
+      create(:feed, name: "bbb", refreshed_at: nil)
+      create(:feed, name: "aaa", refreshed_at: 1.day.ago)
+      feeds = described_class.ordered_by("refreshed_at", "ASC")
+
+      expect(feeds.map(&:name)).to eq(%w[aaa bbb])
+    end
+  end
+
+  describe ".stale" do
+    it "includes feeds with zero refresh_interval" do
+      feed = create(:feed, refresh_interval: 0, refreshed_at: 1.minute.ago)
+
+      expect(described_class.stale).to eq([feed])
+    end
+
+    it "includes feeds with nil refreshed_at" do
+      feed = create(:feed, refresh_interval: 1.hour.to_i, refreshed_at: nil)
+
+      expect(described_class.stale).to eq([feed])
+    end
+
+    it "includes feeds that are past their refresh interval" do
+      feed = create(:feed, refresh_interval: 1.hour.to_i, refreshed_at: 2.hours.ago)
+
+      expect(described_class.stale).to eq([feed])
+    end
+
+    it "excludes fresh feeds" do
+      create(:feed, refresh_interval: 1.hour.to_i, refreshed_at: 30.minutes.ago)
+
+      expect(described_class.stale).to be_empty
+    end
+  end
+
   describe "#configurable?" do
     let(:arbitrary_time) { Time.current }
 
@@ -152,6 +206,24 @@
     end
   end
 
+  describe "#stale?" do
+    context "when refresh_interval is zero" do
+      it { expect(build(:feed, refresh_interval: 0)).to be_stale }
+    end
+
+    context "when refreshed_at is nil" do
+      it { expect(build(:feed, refresh_interval: 1.hour.to_i, refreshed_at: nil)).to be_stale }
+    end
+
+    context "when past refresh interval" do
+      it { expect(build(:feed, refresh_interval: 1.hour.to_i, refreshed_at: 2.hours.ago)).to be_stale }
+    end
+
+    context "when within refresh interval" do
+      it { expect(build(:feed, refresh_interval: 1.hour.to_i, refreshed_at: 30.minutes.ago)).not_to be_stale }
+    end
+  end
+
   describe "#reference" do
     it "returns expected value" do
       actual = build(:feed, id: 1, name: "sample").reference

spec/services/class_resolver_spec.rb

@@ -28,7 +28,7 @@
 
     it "raises a NameError for missing class" do
       resolver = described_class.new("non_existent")
-      expect { resolver.resolve }.to raise_error(NameError)
+      expect(resolver.resolve).to be_nil
     end
   end
 end