Missing Ratings | Add current rating profile endpoint to Caseflow (#1…

…5172)

Connects #14839 

### Description
This PR integrates the new current rating endpoint from ruby-bgs into Caseflow, and adds a new model for working with data returned by this endpoint.

### Acceptance Criteria
- [x] Add find_current_rating_profile_by_ptcpnt_id to BGSService
- [x] Add a CurrentRating model which can fetch the (single) current rating for a veteran
  - [x] The same "self" classes in the Rating model aren't needed, but the same instance methods are needed
- [x] Add to BGSService fakes

### Testing Plan
- New spec added: `current_rating_spec.rb`
- Testing locally
  - The fake rating store has a list of available participant IDs: `BGSService.rating_store.all_keys`
  - Use `CurrentRating.fetch_by_participant_id` to fetch an instance and play around with it
  - Check the behavior for a non-existent participant ID
- Testing in unmodified UAT (to confirm everything is safe) and prod (to see representative data)
  - Paste the contents of `current_rating.rb` into Rails console
  - Inside a `class ExternalApi::BGSService`/`end` block:
    - Paste the contents of the `def find_current_rating_profile_by_ptcpnt_id` definition
  - Use `CurrentRating.fetch_by_participant_id` with a bunch of `Veteran.participant_id`s and play around. The new test code can provide some inspiration.
  - Check the behavior for a non-existent participant ID

### Code Documentation Updates
- [x] Add or update code comments at the top of the class, module, and/or component.

app/models/current_rating.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+# CurrentRating provides a Rating implementation based on data returned by the BGS endpoint
+# rating_profile.find_current_rating_profile_by_ptcpnt_id. Unlike its siblings RatingAtIssue
+# and PromulgatedRating, this fetches a single rating per call. Thus, fetch_in_range and
+# ratings_from_bgs_response are left unimplemented, and a few other methods aren't used.
+
+class CurrentRating < Rating
+  class << self
+    def fetch_by_participant_id(participant_id)
+      from_bgs_hash(BGSService.new.find_current_rating_profile_by_ptcpnt_id(participant_id))
+    rescue BGS::ShareError
+      nil
+    end
+
+    def from_bgs_hash(data)
+      new(
+        participant_id: data[:ptcpnt_vet_id],
+        profile_date: data[:prfl_dt],
+        promulgation_date: data[:prmlgn_dt],
+        rating_profile: data
+      )
+    end
+  end
+end

app/models/rating.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
-# A Rating can be a PromulgatedRating or a RatingAtIssue. Please see the subclasses for more information.
+# A Rating can be a PromulgatedRating, RatingAtIssue, or CurrentRating.
+# Please see the subclasses for more information.
 
 class Rating
   include ActiveModel::Model

app/services/external_api/bgs_service.rb

@@ -409,6 +409,15 @@ def find_contentions_by_claim_id(claim_id)
     end
   end
 
+  def find_current_rating_profile_by_ptcpnt_id(participant_id)
+    DBService.release_db_connections
+    MetricsService.record("BGS: find current rating profile for veteran by participant_id #{participant_id}",
+                          service: :bgs,
+                          name: "rating_profile.find_current_rating_profile_by_ptcpnt_id") do
+      client.rating_profile.find_current_rating_profile_by_ptcpnt_id(participant_id, true)
+    end
+  end
+
   def pay_grade_list
     DBService.release_db_connections
 

lib/fakes/bgs_service.rb

@@ -135,6 +135,16 @@ def find_contentions_by_claim_id(claim_id)
     format_contentions(contentions)
   end
 
+  # :reek:FeatureEnvy
+  def find_current_rating_profile_by_ptcpnt_id(participant_id)
+    record = get_rating_record(participant_id)
+    fail BGS::ShareError, "No Record Found" if record.blank?
+
+    # We grab the latest promulgated rating, assuming that under the hood BGS also does.
+    rating = record[:ratings].max_by { |rt| rt[:prmlgn_dt] }
+    rating_at_issue_profile_data(rating)
+  end
+
   def format_contentions(contentions)
     { contentions: contentions.map { |contention| format_contention(contention) } }
   end

spec/models/current_rating_spec.rb

@@ -0,0 +1,68 @@
+# frozen_string_literal: true
+
+describe CurrentRating do
+  describe "#fetch_by_participant_id" do
+    let(:bgs) { double("BGSService") }
+    let(:pid) { "12345" }
+    before do
+      allow(BGSService).to receive(:new) { bgs }
+    end
+
+    subject { CurrentRating.fetch_by_participant_id(pid) }
+
+    context "when participant exists" do
+      let(:bgs_hash) do
+        { ptcpnt_vet_id: pid }
+      end
+      before do
+        allow(bgs).to receive(:find_current_rating_profile_by_ptcpnt_id).with(pid).and_return(bgs_hash)
+      end
+
+      it "returns a current rating object" do
+        expect(subject.participant_id).to eq(pid)
+      end
+    end
+
+    context "when participant doesn't exist" do
+      let(:error) { BGS::ShareError.new_from_message("message", 500) }
+      before do
+        allow(bgs).to receive(:find_current_rating_profile_by_ptcpnt_id).with(pid).and_raise(error)
+      end
+
+      it { is_expected.to be_nil }
+    end
+  end
+
+  describe "#from_bgs_hash" do
+    let(:yesterday) { DateTime.yesterday }
+    let(:bgs_hash) do
+      {
+        ptcpnt_vet_id: "participant ID",
+        prfl_dt: yesterday,
+        prmlgn_dt: yesterday,
+        rating_issues: [
+          {
+            rba_issue_id: "rating issue ID",
+            decn_txt: "issue description text"
+          }
+        ],
+        disabilities: [
+          {
+            decn_tn: "Service Connected",
+            dis_sn: "disability ID"
+          }
+        ],
+        associated_claims: { clm_id: "EP claim ID", bnft_clm_tc: "600PRI" }
+      }
+    end
+
+    it "hydrates an object that behaves like a Rating" do
+      rating = CurrentRating.from_bgs_hash(bgs_hash)
+      expect(rating.participant_id).to eq("participant ID")
+      expect(rating.profile_date).to eq(yesterday)
+      expect(rating.promulgation_date).to eq(yesterday)
+      expect(rating.issues[0].reference_id).to eq("rating issue ID")
+      expect(rating.associated_end_products[0].claim_id).to eq("EP claim ID")
+    end
+  end
+end