From facbf4130798b4772877f69ff6a6dbff605ea8e3 Mon Sep 17 00:00:00 2001
From: Thomas Leese <thomas@leese.io>
Date: Mon, 16 Dec 2024 18:48:42 +0000
Subject: [PATCH] Raise NHS::PDS::TooManyMatches

This updates the PDS search client code to handle getting a too many
matches error response and raise a suitable exception.

This doesn't handle the error, as we need to decide how to handle this
case, but having its own error means we can easily filter these out in
Sentry.
---
 app/lib/nhs/pds.rb                            | 31 ++++++--
 spec/fixtures/files/pds/too-many-matches.json | 19 +++++
 spec/lib/nhs/pds_spec.rb                      | 72 +++++++++++++------
 3 files changed, 93 insertions(+), 29 deletions(-)
 create mode 100644 spec/fixtures/files/pds/too-many-matches.json

diff --git a/app/lib/nhs/pds.rb b/app/lib/nhs/pds.rb
index c82043326..9d0f9e494 100644
--- a/app/lib/nhs/pds.rb
+++ b/app/lib/nhs/pds.rb
@@ -26,6 +26,9 @@ class InvalidNHSNumber < StandardError
   class PatientNotFound < StandardError
   end
 
+  class TooManyMatches < StandardError
+  end
+
   class << self
     def get_patient(nhs_number)
       NHS::API.connection.get(
@@ -52,18 +55,32 @@ def search_patients(attributes)
         raise "Unrecognised attributes: #{missing_attrs.join(", ")}"
       end
 
-      NHS::API.connection.get(
-        "personal-demographics/FHIR/R4/Patient",
-        attributes
-      )
+      response =
+        NHS::API.connection.get(
+          "personal-demographics/FHIR/R4/Patient",
+          attributes
+        )
+
+      if is_error?(response, "TOO_MANY_MATCHES")
+        raise TooManyMatches
+      else
+        response
+      end
     end
 
     private
 
-    def is_error?(error, code)
-      response = JSON.parse(error.response_body)
+    def is_error?(error_or_response, code)
+      response =
+        if error_or_response.is_a?(Faraday::ClientError)
+          JSON.parse(error_or_response.response_body)
+        elsif error_or_response.is_a?(Faraday::Response)
+          error_or_response.body
+        end
+
+      return false if (issues = response["issue"]).blank?
 
-      response["issue"].any? do |issue|
+      issues.any? do |issue|
         issue["details"]["coding"].any? { |coding| coding["code"] == code }
       end
     end
diff --git a/spec/fixtures/files/pds/too-many-matches.json b/spec/fixtures/files/pds/too-many-matches.json
new file mode 100644
index 000000000..468363ce5
--- /dev/null
+++ b/spec/fixtures/files/pds/too-many-matches.json
@@ -0,0 +1,19 @@
+{
+  "issue": [
+    {
+      "code": "multiple-matches",
+      "details": {
+        "coding": [
+          {
+            "code": "TOO_MANY_MATCHES",
+            "display": "Too Many Matches",
+            "system": "https://fhir.nhs.uk/R4/CodeSystem/Spine-ErrorOrWarningCode",
+            "version": "1"
+          }
+        ]
+      },
+      "severity": "information"
+    }
+  ],
+  "resourceType": "OperationOutcome"
+}
diff --git a/spec/lib/nhs/pds_spec.rb b/spec/lib/nhs/pds_spec.rb
index d9969e417..ead873553 100644
--- a/spec/lib/nhs/pds_spec.rb
+++ b/spec/lib/nhs/pds_spec.rb
@@ -82,33 +82,61 @@
   end
 
   describe "#search_patients" do
-    before do
-      stub_request(
-        :get,
-        "https://sandbox.api.service.nhs.uk/personal-demographics/FHIR/R4/Patient"
-      ).with(
-        query: {
-          birthdate: "eq1939-01-09",
-          family: "Lawman",
-          gender: "female"
-        }
-      ).to_return(
-        body: file_fixture("pds/search-patients-response.json"),
-        headers: {
-          "Content-Type" => "application/fhir+json"
-        }
+    subject(:search_patients) do
+      described_class.search_patients(
+        family: "Lawman",
+        gender: "female",
+        birthdate: "eq1939-01-09"
       )
     end
 
-    it "sends a GET request to with the provided attributes" do
-      response =
-        described_class.search_patients(
-          family: "Lawman",
-          gender: "female",
-          birthdate: "eq1939-01-09"
+    context "with a successful response" do
+      before do
+        stub_request(
+          :get,
+          "https://sandbox.api.service.nhs.uk/personal-demographics/FHIR/R4/Patient"
+        ).with(
+          query: {
+            birthdate: "eq1939-01-09",
+            family: "Lawman",
+            gender: "female"
+          }
+        ).to_return(
+          body: file_fixture("pds/search-patients-response.json"),
+          headers: {
+            "Content-Type" => "application/fhir+json"
+          }
         )
+      end
+
+      it "sends a GET request to with the provided attributes" do
+        response = search_patients
+        expect(response.body).to include("total" => 1)
+      end
+    end
 
-      expect(response.body).to include("total" => 1)
+    context "with a too many matches response" do
+      before do
+        stub_request(
+          :get,
+          "https://sandbox.api.service.nhs.uk/personal-demographics/FHIR/R4/Patient"
+        ).with(
+          query: {
+            birthdate: "eq1939-01-09",
+            family: "Lawman",
+            gender: "female"
+          }
+        ).to_return(
+          body: file_fixture("pds/too-many-matches.json"),
+          headers: {
+            "Content-Type" => "application/fhir+json"
+          }
+        )
+      end
+
+      it "raises an error" do
+        expect { search_patients }.to raise_error(NHS::PDS::TooManyMatches)
+      end
     end
 
     it "raises an error if an unrecognised attribute is provided" do