Refactor i18n middleware language finders

* Split language finders into separate functions
* Refactor LanguageFinder type
* Generalize Language finders options
* Add a new path prefix language finding strategy
* Ensure setups with default config won't break

middleware/i18n/i18n.go

@@ -18,23 +18,23 @@ import (
 // languages. This can be useful if you want to load a user's language
 // from something like a database. See Middleware() for more information
 // on how the default implementation searches for languages.
-type LanguageFinder func(*Translator, buffalo.Context) []string
+type LanguageFinder func(LanguageFinderOptions, buffalo.Context) []string
+
+// LanguageFinderOptions is a map of options for a LanguageFinder.
+type LanguageFinderOptions map[string]interface{}
 
 // Translator for handling all your i18n needs.
 type Translator struct {
 	// Box - where are the files?
 	Box packr.Box
 	// DefaultLanguage - default is passed as a parameter on New.
 	DefaultLanguage string
-	// CookieName - name of the cookie to find the desired language.
-	// default is "lang"
-	CookieName string
-	// SessionName - name of the session to find the desired language.
-	// default is "lang"
-	SessionName string
 	// HelperName - name of the view helper. default is "t"
-	HelperName     string
-	LanguageFinder LanguageFinder
+	HelperName string
+	// LanguageFinders - a sorted list of user language extractors.
+	LanguageFinders []LanguageFinder
+	// LanguageFinderOptions - a map with options to give to LanguageFinders.
+	LanguageFinderOptions LanguageFinderOptions
 }
 
 // Load translations from the t.Box.
@@ -70,10 +70,17 @@ func New(box packr.Box, language string) (*Translator, error) {
 	t := &Translator{
 		Box:             box,
 		DefaultLanguage: language,
-		CookieName:      "lang",
-		SessionName:     "lang",
 		HelperName:      "t",
-		LanguageFinder:  defaultLanguageFinder,
+		LanguageFinderOptions: LanguageFinderOptions{
+			"CookieName":    "lang",
+			"SessionName":   "lang",
+			"URLPrefixName": "lang",
+		},
+		LanguageFinders: []LanguageFinder{
+			CookieLanguageFinder,
+			SessionLanguageFinder,
+			HeaderLanguageFinder,
+		},
 	}
 	return t, t.Load()
 }
@@ -102,7 +109,7 @@ func (t *Translator) Middleware() buffalo.MiddlewareFunc {
 
 			// set languages in context, if not set yet
 			if langs := c.Value("languages"); langs == nil {
-				c.Set("languages", t.LanguageFinder(t, c))
+				c.Set("languages", t.LanguageFinder(c))
 			}
 
 			// set translator
@@ -156,31 +163,72 @@ func (t *Translator) AvailableLanguages() []string {
 	return lt
 }
 
-func defaultLanguageFinder(t *Translator, c buffalo.Context) []string {
+// LanguageFinder calls each LanguageFinder in the sorted list, then gather
+// the result languages slice.
+func (t *Translator) LanguageFinder(c buffalo.Context) []string {
 	langs := []string{}
+	for _, finder := range t.LanguageFinders {
+		langs = append(langs, finder(t.LanguageFinderOptions, c)...)
+	}
+	// Add default language, even if no language finder is defined
+	langs = append(langs, t.DefaultLanguage)
+	return langs
+}
 
-	r := c.Request()
-
+// CookieLanguageFinder is a LanguageFinder implementation, using a cookie.
+func CookieLanguageFinder(o LanguageFinderOptions, c buffalo.Context) []string {
+	langs := make([]string, 0)
 	// try to get the language from a cookie:
-	if cookie, err := r.Cookie(t.CookieName); err == nil {
-		if cookie.Value != "" {
-			langs = append(langs, cookie.Value)
+	if cookieName := o["CookieName"].(string); cookieName != "" {
+		if cookie, err := c.Request().Cookie(cookieName); err == nil {
+			if cookie.Value != "" {
+				langs = append(langs, cookie.Value)
+			}
 		}
+	} else {
+		c.Logger().Error("i18n middleware: \"CookieName\" is not defined in LanguageFinderOptions")
 	}
+	return langs
+}
 
+// SessionLanguageFinder is a LanguageFinder implementation, using a session.
+func SessionLanguageFinder(o LanguageFinderOptions, c buffalo.Context) []string {
+	langs := make([]string, 0)
 	// try to get the language from the session
-	if s := c.Session().Get(t.SessionName); s != nil {
-		langs = append(langs, s.(string))
+	if sessionName := o["SessionName"].(string); sessionName != "" {
+		if s := c.Session().Get(sessionName); s != nil {
+			langs = append(langs, s.(string))
+		}
+	} else {
+		c.Logger().Error("i18n middleware: \"SessionName\" is not defined in LanguageFinderOptions")
 	}
+	return langs
+}
 
+// HeaderLanguageFinder is a LanguageFinder implementation, using a HTTP Accept-Language
+// header.
+func HeaderLanguageFinder(o LanguageFinderOptions, c buffalo.Context) []string {
+	langs := make([]string, 0)
 	// try to get the language from a header:
-	acceptLang := r.Header.Get("Accept-Language")
+	acceptLang := c.Request().Header.Get("Accept-Language")
 	if acceptLang != "" {
 		langs = append(langs, parseAcceptLanguage(acceptLang)...)
 	}
+	return langs
+}
 
-	// finally set the default app language as fallback
-	langs = append(langs, t.DefaultLanguage)
+// URLPrefixLanguageFinder is a LanguageFinder implementation, using a prefix in the URL.
+func URLPrefixLanguageFinder(o LanguageFinderOptions, c buffalo.Context) []string {
+	langs := make([]string, 0)
+	// try to get the language from an URL prefix:
+	if urlPrefixName := o["URLPrefixName"].(string); urlPrefixName != "" {
+		paramLang := c.Param(urlPrefixName)
+		if paramLang != "" && strings.HasPrefix(c.Request().URL.Path, fmt.Sprintf("/%s", paramLang)) {
+			langs = append(langs, paramLang)
+		}
+	} else {
+		c.Logger().Error("i18n middleware: \"URLPrefixName\" is not defined in LanguageFinderOptions")
+	}
 	return langs
 }
 

middleware/i18n/i18n_test.go

@@ -29,6 +29,9 @@ func app() *buffalo.App {
 	if err != nil {
 		log.Fatal(err)
 	}
+	// Setup URL prefix Language finder
+	t.LanguageFinders = append(t.LanguageFinders, URLPrefixLanguageFinder)
+
 	app.Use(t.Middleware())
 	app.GET("/", func(c buffalo.Context) error {
 		return c.Render(200, r.HTML("index.html"))
@@ -58,6 +61,9 @@ func app() *buffalo.App {
 	}
 	app.Middleware.Skip(t.Middleware(), noI18n)
 	app.GET("/localized-disabled", noI18n)
+	app.GET("/{lang:fr|en}/index", func(c buffalo.Context) error {
+		return c.Render(200, r.HTML("index.html"))
+	})
 	return app
 }
 
@@ -160,3 +166,16 @@ func Test_i18n_availableLanguages(t *testing.T) {
 	res := w.Request("/languages-list").Get()
 	r.Equal("[\"en-us\",\"fr-fr\"]", strings.TrimSpace(res.Body.String()))
 }
+
+func Test_i18n_URL_prefix(t *testing.T) {
+	r := require.New(t)
+
+	w := willie.New(app())
+	req := w.Request("/fr/index")
+	res := req.Get()
+	r.Equal("Bonjour à tous !", strings.TrimSpace(res.Body.String()))
+
+	req = w.Request("/en/index")
+	res = req.Get()
+	r.Equal("Hello, World!", strings.TrimSpace(res.Body.String()))
+}