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

@@ -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

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"
+}

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