Add cache for abbreviated city names (#9)

flights/city.go

@@ -58,6 +58,10 @@ func decodeInnerObject(body *bufio.Reader) ([][][][]interface{}, error) {
 }
 
 func (s *Session) AbbrCity(city string, lang language.Tag) (string, error) {
+	if abbrCity, ok := s.Cities.Load(city); ok {
+		return abbrCity, nil
+	}
+
 	resp, err := s.doRequestCity(city, lang)
 	if err != nil {
 		return "", err
@@ -95,6 +99,8 @@ func (s *Session) AbbrCity(city string, lang language.Tag) (string, error) {
 		return "", fmt.Errorf("the requested city name didn't match the found. requested: %s found: %s", city, foundCity)
 	}
 
+	s.Cities.Store(city, serializedCity)
+
 	return serializedCity, nil
 }
 

flights/city_test.go

@@ -86,27 +86,34 @@ func TestAbbrCity(t *testing.T) {
 		"testdata/city_athens.resp",
 		"testdata/city_warsaw.resp",
 	)
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	session := &Session{
-		httpClientMock,
+		client: httpClientMock,
 	}
 
 	cityA := "Athens"
 	cityB := "Warsaw"
 
-	a, err := session.AbbrCity(cityA, language.English)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if a != abbrA {
-		t.Fatalf("wrong abbreviated city name, expected: %s received: %s", abbrA, a)
-	}
-
-	b, err := session.AbbrCity(cityB, language.English)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if b != abbrB {
-		t.Fatalf("wrong abbreviated city name, expected: %s received: %s", abbrB, b)
+	// Since httpClientMock has only two responses, run it twice to check whether
+	// the cache for abbreviated city names works properly
+	for i := 0; i < 2; i++ {
+		a, err := session.AbbrCity(cityA, language.English)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if a != abbrA {
+			t.Fatalf("wrong abbreviated city name, expected: %s received: %s", abbrA, a)
+		}
+
+		b, err := session.AbbrCity(cityB, language.English)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if b != abbrB {
+			t.Fatalf("wrong abbreviated city name, expected: %s received: %s", abbrB, b)
+		}
 	}
 }

flights/price_graph_test.go

@@ -47,7 +47,7 @@ func TestGetPriceGraph(t *testing.T) {
 	)
 
 	session := &Session{
-		httpClientMock,
+		client: httpClientMock,
 	}
 
 	offers, err := session.GetPriceGraph(time.Now().AddDate(0, 0, 2), time.Now().AddDate(0, 0, 5), 0, "Athens", "Warsaw", currency.PLN, language.English)

flights/session.go

@@ -2,19 +2,37 @@ package flights
 
 import (
 	"net/http"
+	"sync"
 	"time"
 )
 
-type Client interface {
+type Map[K comparable, V any] struct {
+	m sync.Map
+}
+
+func (m *Map[K, V]) Load(key K) (value V, ok bool) {
+	v, ok := m.m.Load(key)
+	if !ok {
+		return value, ok
+	}
+	return v.(V), ok
+}
+
+func (m *Map[K, V]) Store(key K, value V) { m.m.Store(key, value) }
+
+type HttpClient interface {
 	Do(req *http.Request) (*http.Response, error)
 }
 
 type Session struct {
-	client Client
+	Cities Map[string, string]
+
+	client HttpClient
 }
 
 func New() *Session {
 	return &Session{
+		Cities: Map[string, string]{},
 		client: &http.Client{
 			Timeout: 30 * time.Second,
 		},