Fallback received city names to latin (#25)

This PR enables you to pass latin letters for city names that do not
contain only latin letters.
e.g.:
All the following AbbrCity calls will successfully receive the
abbreviated "Łódź" city name.
```
session.AbbrCity(context.Background(), "Łódź", language.English)
session.AbbrCity(context.Background(), "łódź", language.English)
session.AbbrCity(context.Background(), "lodz", language.English)
```

flights/location.go

@@ -9,8 +9,10 @@ import (
 	"net/http"
 	"net/url"
 	"strconv"
+	"strings"
 	"time"
 
+	anyascii "github.com/anyascii/go"
 	"github.com/hashicorp/go-retryablehttp"
 	"golang.org/x/text/language"
 )
@@ -47,6 +49,28 @@ func abbrCitySchema(city, abbrCity *string) *[][][][]interface{} {
 	return &[][][][]interface{}{{{{nil, nil, city, nil, abbrCity}}}}
 }
 
+func compareStrLatin(lv, rv string) bool {
+	if lv == rv {
+		return true
+	}
+
+	lv = anyascii.Transliterate(lv)
+	rv = anyascii.Transliterate(rv)
+
+	lv = strings.ToLower(lv)
+	rv = strings.ToLower(rv)
+
+	if len(lv) != len(rv) {
+		return false
+	}
+	for i := range lv {
+		if lv[i] != rv[i] {
+			return false
+		}
+	}
+	return true
+}
+
 // AbbrCity serializes the city name by requesting it from the Google Flights API. The city name should
 // be provided in the language described by [language.Tag].
 //
@@ -79,7 +103,7 @@ func (s *Session) AbbrCity(ctx context.Context, city string, lang language.Tag)
 		return "", fmt.Errorf("AbbrCity error during decoding: %v", err)
 	}
 
-	if city != receivedCity {
+	if !compareStrLatin(city, receivedCity) {
 		return "", fmt.Errorf("the requested city name didn't match the found. requested: %s found: %s", city, receivedCity)
 	}
 

flights/city_test.go → flights/location_test.go

@@ -135,3 +135,36 @@ func TestAbbrCity(t *testing.T) {
 		t.Fatalf("Warsaw abbreviated city name not stored in cache")
 	}
 }
+
+func TestAbbrCityLatin(t *testing.T) {
+	session, err := New()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expectedAbbrCity := "/m/0c6fz"
+
+	abbrCity, err := session.AbbrCity(context.Background(), "Łódź", language.English)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if abbrCity != expectedAbbrCity {
+		t.Fatalf("wrong abbreviated city name, expected: %s received: %s", expectedAbbrCity, abbrCity)
+	}
+
+	abbrCity, err = session.AbbrCity(context.Background(), "łódź", language.English)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if abbrCity != expectedAbbrCity {
+		t.Fatalf("wrong abbreviated city name, expected: %s received: %s", expectedAbbrCity, abbrCity)
+	}
+
+	abbrCity, err = session.AbbrCity(context.Background(), "lodz", language.English)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if abbrCity != expectedAbbrCity {
+		t.Fatalf("wrong abbreviated city name, expected: %s received: %s", expectedAbbrCity, abbrCity)
+	}
+}

go.mod

@@ -5,6 +5,7 @@ go 1.20
 require golang.org/x/text v0.11.0
 
 require (
+	github.com/anyascii/go v0.3.2
 	github.com/go-test/deep v1.1.0
 	github.com/hashicorp/go-retryablehttp v0.7.4
 	google.golang.org/protobuf v1.31.0

go.sum

@@ -1,3 +1,5 @@
+github.com/anyascii/go v0.3.2 h1:87uFISteh7vwofK02srrPKtAvG6Wx7ozRjNh8uhfa7w=
+github.com/anyascii/go v0.3.2/go.mod h1:HDvbMmSpqJyIe+xtSkHmAYTjc8PzvO3l1Jmgx/IFUPs=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/go-test/deep v1.1.0 h1:WOcxcdHcvdgThNXjw0t76K42FXTU7HpNQWHpA2HHNlg=
 github.com/go-test/deep v1.1.0/go.mod h1:5C2ZWiW0ErCdrYzpqxLbTX7MG14M9iiw8DgHncVwcsE=