Add LocationPositionUpdater

This adds a class which handles updating the position of a location by
fetching the information from the Ordnance Survey Places API.

Jira-Issue: MAV-6379

Author: thomasleese

app/lib/location_position_updater.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+##
+# This class fetches the latitude and longitude of a location's address
+# using the +OrdnanceSurvey::PlacesAPI+ and stores it in the position column.
+class LocationPositionUpdater
+  class MissingAddress < StandardError
+  end
+
+  class NoResults < StandardError
+  end
+
+  def initialize(location)
+    @location = location
+  end
+
+  attr_reader :location
+
+  def call
+    raise MissingAddress unless location.has_address?
+
+    location.update!(position:)
+  end
+
+  def self.call(...) = new(...).call
+
+  private_class_method :new
+
+  private
+
+  def full_address = location.address_parts.join(", ")
+
+  def position
+    response = OrdnanceSurvey::PlacesAPI.find(full_address)
+
+    results = response[:results]
+    raise NoResults if results.blank?
+
+    first_result = results.first
+
+    latitude = first_result.dig(:dpa, :lat)
+    longitude = first_result.dig(:dpa, :lng)
+
+    raise NoResults if latitude.blank? || longitude.blank?
+
+    "POINT(#{longitude} #{latitude})"
+  end
+end

spec/factories/locations.rb

@@ -58,6 +58,14 @@
       end
     end
 
+    trait :without_address do
+      address_line_1 { nil }
+      address_line_2 { nil }
+      address_town { nil }
+      address_postcode { nil }
+      position { nil }
+    end
+
     factory :community_clinic do
       type { :community_clinic }
       name { "#{Faker::University.name} Clinic" }

spec/lib/location_position_updater_spec.rb

@@ -0,0 +1,132 @@
+# frozen_string_literal: true
+
+describe LocationPositionUpdater do
+  describe "#call" do
+    subject(:call) { described_class.call(location) }
+
+    let(:location) do
+      create(
+        :community_clinic,
+        address_line_1: "1 High Street",
+        address_town: "London",
+        address_postcode: "SW1A 1AA",
+        position: nil
+      )
+    end
+
+    context "when location has no address" do
+      let(:location) { create(:community_clinic, :without_address) }
+
+      it "raises an error" do
+        expect { call }.to raise_error(LocationPositionUpdater::MissingAddress)
+      end
+
+      it "does not call the API" do
+        expect(OrdnanceSurvey::PlacesAPI).not_to receive(:find)
+        expect { call }.to raise_error(LocationPositionUpdater::MissingAddress)
+      end
+
+      it "does not update the position" do
+        expect { call }.to raise_error(
+          LocationPositionUpdater::MissingAddress
+        ).and not_change(location, :position)
+      end
+    end
+
+    context "when API returns coordinates" do
+      let(:response) do
+        {
+          header: {
+            total_results: 1
+          },
+          results: [{ dpa: { lat: 51.5074, lng: -0.1278 } }]
+        }
+      end
+
+      before do
+        allow(OrdnanceSurvey::PlacesAPI).to receive(:find).and_return(response)
+      end
+
+      it "calls the API with the address" do
+        expect(OrdnanceSurvey::PlacesAPI).to receive(:find).with(
+          "1 High Street, London, SW1A 1AA"
+        )
+        call
+      end
+
+      it "updates the location's position" do
+        expect { call }.to change(location, :position).from(nil).to(
+          an_instance_of(RGeo::Geographic::SphericalPointImpl)
+        )
+        expect(location.position.x).to eq(-0.1278)
+        expect(location.position.y).to eq(51.5074)
+      end
+    end
+
+    context "when API returns no results" do
+      let(:response) { { header: { total_results: 0 }, results: [] } }
+
+      before do
+        allow(OrdnanceSurvey::PlacesAPI).to receive(:find).and_return(response)
+      end
+
+      it "raises an error" do
+        expect { call }.to raise_error(LocationPositionUpdater::NoResults)
+      end
+    end
+
+    context "when API returns a result without coordinates" do
+      let(:response) do
+        { header: { total_results: 1 }, results: [{ dpa: {} }] }
+      end
+
+      before do
+        allow(OrdnanceSurvey::PlacesAPI).to receive(:find).and_return(response)
+      end
+
+      it "raises an error" do
+        expect { call }.to raise_error(LocationPositionUpdater::NoResults)
+      end
+    end
+
+    context "when location has partial address" do
+      let(:location) do
+        create(
+          :community_clinic,
+          address_line_1: "1 High Street",
+          address_town: nil,
+          address_postcode: "SW1A 1AA",
+          position: nil
+        )
+      end
+
+      let(:response) do
+        {
+          header: {
+            total_results: 1
+          },
+          results: [{ dpa: { lat: 51.5074, lng: -0.1278 } }]
+        }
+      end
+
+      before do
+        allow(OrdnanceSurvey::PlacesAPI).to receive(:find).and_return(response)
+      end
+
+      it "calls the API with partial address" do
+        expect(OrdnanceSurvey::PlacesAPI).to receive(:find).with(
+          "1 High Street, SW1A 1AA"
+        )
+        call
+      end
+
+      it "updates the location position" do
+        expect { call }.to change(location, :position).from(nil).to(
+          an_instance_of(RGeo::Geographic::SphericalPointImpl)
+        )
+        expect(location.position.x).to eq(-0.1278)
+        expect(location.position.y).to eq(51.5074)
+      end
+    end
+  end
+end