add helper i18n.ListLanguages()

i18n.ListLanguages() returns a map, mapping language tags ('en', 'sv')
to the names of their corresponding languages (as translated by the
language itself).

This functionality will be used in the language picker, to present a
nice list of the translated languages.

I renamed testing.go to conform to go's testing conventions, and
added a test for i18n.ListLanguages().

web/i18n/defaults/active.en.toml

@@ -1,4 +1,5 @@
 # default localiztion file for english
+MetaLanguage = "English"
 
 # generic terms
 GenericConfirm = "Yes"

web/i18n/helper.go

@@ -22,11 +22,11 @@ import (
 )
 
 type Helper struct {
-	bundle *i18n.Bundle
+	bundle    *i18n.Bundle
+	languages map[string]string
 }
 
 func New(r repo.Interface) (*Helper, error) {
-
 	bundle := i18n.NewBundle(language.English)
 	bundle.RegisterUnmarshalFunc("toml", toml.Unmarshal)
 
@@ -114,22 +114,36 @@ func New(r repo.Interface) (*Helper, error) {
 		return nil, fmt.Errorf("i18n: failed to iterate localizations: %w", err)
 	}
 
-	return &Helper{bundle: bundle}, nil
+	// create a mapping of language tags to the translated language names
+	langmap := listLanguages(bundle)
+	return &Helper{bundle: bundle, languages: langmap}, nil
 }
 
-func (h Helper) GetRenderFuncs() []render.Option {
-	var opts = []render.Option{
-		render.InjectTemplateFunc("i18npl", func(r *http.Request) interface{} {
-			loc := h.FromRequest(r)
-			return loc.LocalizePlurals
-		}),
+func listLanguages(bundle *i18n.Bundle) map[string]string {
+	langmap := make(map[string]string)
 
-		render.InjectTemplateFunc("i18n", func(r *http.Request) interface{} {
-			loc := h.FromRequest(r)
-			return loc.LocalizeSimple
-		}),
+	for _, langTag := range bundle.LanguageTags() {
+		var l Localizer
+		l.loc = i18n.NewLocalizer(bundle, langTag.String())
+
+		msg, err := l.loc.Localize(&i18n.LocalizeConfig{
+			MessageID: "MetaLanguage",
+		})
+		if err != nil {
+			msg = langTag.String()
+		}
+
+		langmap[langTag.String()] = msg
 	}
-	return opts
+
+	return langmap
+}
+
+// ListLanguages returns a mapping between the room's translated languages.
+// The keys are language tags (as strings) and the values are the name of the language tag, as translated in the original language.
+// For example: en -> English, sv -> Svenska, de -> Deutsch
+func (h Helper) ListLanguages() map[string]string {
+	return h.languages
 }
 
 type Localizer struct {
@@ -153,6 +167,21 @@ func (h Helper) FromRequest(r *http.Request) *Localizer {
 	return h.newLocalizer(lang, accept)
 }
 
+func (h Helper) GetRenderFuncs() []render.Option {
+	var opts = []render.Option{
+		render.InjectTemplateFunc("i18npl", func(r *http.Request) interface{} {
+			loc := h.FromRequest(r)
+			return loc.LocalizePlurals
+		}),
+
+		render.InjectTemplateFunc("i18n", func(r *http.Request) interface{} {
+			loc := h.FromRequest(r)
+			return loc.LocalizeSimple
+		}),
+	}
+	return opts
+}
+
 func (l Localizer) LocalizeSimple(messageID string) string {
 	msg, err := l.loc.Localize(&i18n.LocalizeConfig{
 		MessageID: messageID,

web/i18n/i18ntesting/i18n_test.go

@@ -3,6 +3,7 @@ package i18ntesting
 import (
 	"bytes"
 	"fmt"
+	"github.com/stretchr/testify/assert"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -66,7 +67,17 @@ func justTheKeys(t *testing.T) []byte {
 	return buf.Bytes()
 }
 
-func WriteReplacement(t *testing.T) {
+func TestListAllLanguages(t *testing.T) {
+	r := repo.New(filepath.Join("testrun", t.Name()))
+	a := assert.New(t)
+	helper, err := i18n.New(r)
+	a.NoError(err)
+	t.Log(helper)
+	langmap := helper.ListLanguages()
+	a.Equal(langmap["en"], "English")
+}
+
+func TestWriteReplacement(t *testing.T) {
 	r := repo.New(filepath.Join("testrun", t.Name()))
 
 	testOverride := filepath.Join(r.GetPath("i18n"), "active.en.toml")