Add Coffee Shops Finder service

Author: Alexandru Popescu

app/services/coffee_shop_finder_service.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require 'csv'
+require 'httparty'
+
+class CoffeeShopFinderService
+  def closest_shops(user_lat, user_lon, limit = 3)
+    coffee_shops = fetch_and_parse_coffee_shops
+
+    # Used for faster distance retrieval
+    distances = Hash.new { |h, shop| h[shop] = shop.distance_to(user_lat, user_lon) }
+    closest_shops = coffee_shops.min_by(limit) { |shop| distances[shop] }
+
+    closest_shops.map { |shop| { shop: shop, distance: distances[shop] } }
+  end
+
+  private
+
+  def fetch_and_parse_coffee_shops
+    response = fetch_csv
+    parse_coffee_shops(response)
+  end
+
+  def parse_coffee_shops(response)
+    CSV.parse(response.body, headers: true).map do |row|
+      validate_csv_row!(row)
+      CoffeeShop.new(row['Name'], row['X Coordinate'], row['Y Coordinate'])
+    end
+  rescue CSV::MalformedCSVError => e
+    raise "Malformed CSV: #{e.message}"
+  end
+
+  def fetch_csv
+    url = ENV['CSV_URL'] || APP_CONFIG[:csv_url]
+    response = HTTParty.get(url)
+    raise "Failed to fetch CSV: #{response.code}" unless response.success?
+
+    response
+  end
+
+  # Validate CSV row structure
+  def validate_csv_row!(row)
+    missing = %w[Name X Coordinate Y Coordinate].reject { |h| row[h] }
+    raise "Invalid CSV headers: #{missing.join(', ')}" if missing.any?
+  end
+end

spec/services/coffee_shop_finder_service_spec.rb

@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+require_relative '../../app/services/coffee_shop_finder_service'
+require_relative '../../app/models/coffee_shop'
+
+RSpec.describe CoffeeShopFinderService do # rubocop:disable RSpec/BlockLength
+  let(:finder) { CoffeeShopFinderService.new }
+
+  context '#closest_shops' do # rubocop:disable RSpec/BlockLength
+    subject { finder.closest_shops(user_lat, user_lon) }
+
+    let(:user_lat) { 40.7128 }
+    let(:user_lon) { -74.0060 }
+
+    let(:shop_same) { CoffeeShop.new('Same Location', user_lat, user_lon) } # 0.0 distance
+    let(:shop_near) { CoffeeShop.new('Starbucks Seattle', 47.5869, -122.316) }
+    let(:shop_mid) { CoffeeShop.new('Starbucks Moscow', 55.752047, 37.595242) }
+    let(:shop_far) { CoffeeShop.new('Starbucks Sydney', -33.871843, 151.206767) }
+    let(:all_shops) { [shop_far, shop_near, shop_mid, shop_same] }
+
+    before do
+      allow_any_instance_of(CoffeeShopFinderService)
+        .to receive(:fetch_and_parse_coffee_shops)
+        .and_return(all_shops)
+    end
+
+    describe 'limit functionality' do
+      it 'returns the specified number of shops' do
+        results = finder.closest_shops(user_lat, user_lon, 2)
+        expect(results.size).to eq(2)
+      end
+
+      it 'returns all shops if limit is greater than the number of shops' do
+        results = finder.closest_shops(user_lat, user_lon, 20)
+        expect(results.size).to eq(4)
+      end
+    end
+
+    describe 'normal functionality' do
+      it 'returns shops in ascending order' do
+        expect(subject).to eq(
+          [
+            { shop: shop_same, distance: 0.0 },
+            { shop: shop_near, distance: 48.7966 },
+            { shop: shop_mid, distance: 112.61 }
+          ]
+        )
+      end
+    end
+
+    describe 'edge cases' do
+      context 'with empty shop list' do
+        it 'returns empty array' do
+          allow_any_instance_of(CoffeeShopFinderService)
+            .to receive(:fetch_and_parse_coffee_shops).and_return([])
+
+          expect(subject).to be_empty
+        end
+      end
+
+      context 'with identical locations' do
+        let(:dupe_shop) { CoffeeShop.new('Dupe', user_lat, user_lon) }
+
+        it 'returns all matching shops' do
+          allow_any_instance_of(CoffeeShopFinderService)
+            .to receive(:fetch_and_parse_coffee_shops).and_return([shop_same, dupe_shop])
+
+          expect(subject.size).to eq(2)
+          expect(subject.map { |r| r[:distance] }).to all(eq(0.0))
+        end
+      end
+    end
+  end
+end