Setup i18n

Author: nicolashery

README.md

@@ -52,6 +52,7 @@ Install tools:
 - [Templ](https://templ.guide/): `go install github.com/a-h/templ/cmd/templ@latest`
 - [sqlc](https://docs.sqlc.dev/): `brew install sqlc`
 - [Dbmate](https://github.com/amacneil/dbmate): `brew install dbmate`
+- [goi18n](https://github.com/nicksnyder/go-i18n): `go install github.com/nicksnyder/go-i18n/v2/goi18n@latest`
 
 Install Node and upgrade npm, for example with [mise](https://mise.jdx.dev/lang/node.html):
 

Taskfile.yaml

@@ -101,3 +101,19 @@ tasks:
       - task: drop
       - task: migrate
       - task: seed
+
+  i18n-extract:
+    desc: Extract messages from Go source files to the default `active.en.toml` file
+    cmds:
+      - goi18n extract -outdir locales app
+
+  i18n-translate:
+    desc: Generate updated `translate.*.toml` files to be translated
+    cmds:
+      - goi18n merge -outdir locales locales/active.*.toml
+
+  i18n-merge:
+    desc: Merge translated messages back into `active.*.toml` files and clean up translation files
+    cmds:
+      - goi18n merge -outdir locales locales/active.*.toml locales/translate.*.toml
+      - rm locales/translate.*.toml

app/app.go

@@ -11,12 +11,13 @@ import (
 	"github.com/nicolashery/simply-shared-notes/app/config"
 	"github.com/nicolashery/simply-shared-notes/app/db"
 	"github.com/nicolashery/simply-shared-notes/app/email"
+	"github.com/nicolashery/simply-shared-notes/app/intl"
 	"github.com/nicolashery/simply-shared-notes/app/server"
 	"github.com/nicolashery/simply-shared-notes/app/session"
 	"github.com/nicolashery/simply-shared-notes/app/vite"
 )
 
-func Run(ctx context.Context, distFS embed.FS, pragmasSQL string) error {
+func Run(ctx context.Context, distFS embed.FS, pragmasSQL string, localesFS embed.FS) error {
 	ctx, stop := signal.NotifyContext(ctx, os.Interrupt)
 	defer stop()
 
@@ -51,7 +52,12 @@ func Run(ctx context.Context, distFS embed.FS, pragmasSQL string) error {
 		return err
 	}
 
-	s := server.New(cfg, logger, sqlDB, queries, vite, sessionStore, email)
+	i18nBundle, err := intl.NewBundle(localesFS)
+	if err != nil {
+		return err
+	}
+
+	s := server.New(cfg, logger, sqlDB, queries, vite, sessionStore, email, i18nBundle)
 
 	return server.Run(ctx, s, logger, cfg.Port)
 }

app/handlers/identity.handlers.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"strings"
 
+	"github.com/nicksnyder/go-i18n/v2/i18n"
 	"github.com/nicolashery/simply-shared-notes/app/db"
 	"github.com/nicolashery/simply-shared-notes/app/rctx"
 	"github.com/nicolashery/simply-shared-notes/app/session"
@@ -84,11 +85,23 @@ func handleIdentitySet(logger *slog.Logger, queries *db.Queries) http.HandlerFun
 			return
 		}
 
+		intl := rctx.GetIntl(r.Context())
+		msg := intl.Localize(&i18n.LocalizeConfig{
+			DefaultMessage: &i18n.Message{
+				ID:    "Spaces.Show.Flash",
+				Other: "{{.Member}}, welcome to the space {{.Space}}!",
+			},
+			TemplateData: map[string]any{
+				"Member": member.Name,
+				"Space":  space.Name,
+			},
+		})
+
 		sess := rctx.GetSession(r.Context())
 		sess.Values[session.IdentityKey] = member.ID
 		sess.AddFlash(session.FlashMessage{
 			Type:    session.FlashType_Info,
-			Content: fmt.Sprintf("%s, welcome to the space %s!", member.Name, space.Name),
+			Content: msg,
 		})
 
 		redirectURL := fmt.Sprintf("/s/%s", access.Token)

app/handlers/routes.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/go-chi/chi/v5"
 	"github.com/gorilla/sessions"
+	"github.com/nicksnyder/go-i18n/v2/i18n"
 	"github.com/nicolashery/simply-shared-notes/app/access"
 	"github.com/nicolashery/simply-shared-notes/app/config"
 	"github.com/nicolashery/simply-shared-notes/app/db"
@@ -21,9 +22,11 @@ func RegisterRoutes(
 	queries *db.Queries,
 	sessionStore *sessions.CookieStore,
 	email *email.Email,
+	i18nBundle *i18n.Bundle,
 ) {
 	r.Use(rctx.SessionCtxMiddleware(logger, sessionStore))
 	r.Use(rctx.ThemeCtxMiddleware())
+	r.Use(rctx.IntlCtxMiddleware(logger, i18nBundle))
 
 	r.Get("/", handleHome(logger))
 

app/handlers/spaces.handlers.go

@@ -112,7 +112,7 @@ func handleSpacesCreate(cfg *config.Config, logger *slog.Logger, sqlDB *sql.DB,
 			return
 		}
 
-		emailSubject := emails.SpaceCreatedSubject(space)
+		emailSubject := emails.SpaceCreatedSubject(r.Context(), space)
 		baseURL := baseUrlFromRequest(r)
 		emailText := emails.SpaceCreatedText(member.Name, space, baseURL, tokens)
 		err = email.Send(space.Email, emailSubject, emailText)

app/intl/intl.go

@@ -0,0 +1,78 @@
+package intl
+
+import (
+	"embed"
+	"fmt"
+	"log/slog"
+	"strings"
+
+	"github.com/BurntSushi/toml"
+	"github.com/nicksnyder/go-i18n/v2/i18n"
+	"golang.org/x/text/language"
+)
+
+var DefaultLang language.Tag = language.English
+
+var SupportedLangs = []language.Tag{
+	language.English,
+	language.French,
+}
+
+const LocalizeErrorMessage string = "<failed to localize>"
+
+type Intl struct {
+	CurrentLang language.Tag
+	localizer   *i18n.Localizer
+	logger      *slog.Logger
+}
+
+func NewBundle(localesFS embed.FS) (*i18n.Bundle, error) {
+	b := i18n.NewBundle(DefaultLang)
+	b.RegisterUnmarshalFunc("toml", toml.Unmarshal)
+
+	for _, tag := range SupportedLangs {
+		path := fmt.Sprintf("locales/active.%s.toml", tag.String())
+		// debug: check if path exists in localFS
+		// if _, err := localeFS.Open(path); err != nil {
+		// 	return nil, fmt.Errorf("loading i18n file %q: %w", path, err)
+		// }
+		if _, err := b.LoadMessageFileFS(localesFS, path); err != nil {
+			return nil, fmt.Errorf("loading i18n file %q: %w", path, err)
+		}
+	}
+
+	return b, nil
+}
+
+func New(logger *slog.Logger, i18nBundle *i18n.Bundle, lang language.Tag) *Intl {
+	localizer := i18n.NewLocalizer(i18nBundle, lang.String())
+
+	return &Intl{
+		CurrentLang: lang,
+		localizer:   localizer,
+		logger:      logger,
+	}
+}
+
+func (i *Intl) Localize(lc *i18n.LocalizeConfig) string {
+	msg, err := i.localizer.Localize(lc)
+	if err != nil {
+		i.logger.Error(
+			"failed to localize",
+			slog.Any("error", err),
+			slog.String("lang", i.CurrentLang.String()),
+			slog.String("key", lc.MessageID),
+		)
+		return LocalizeErrorMessage
+	}
+
+	return msg
+}
+
+func (i *Intl) SplitOnSlot(s, slot string) (string, string) {
+	j := strings.Index(s, slot)
+	if j < 0 {
+		return s, ""
+	}
+	return s[:j], s[j+len(slot):]
+}

app/rctx/context_keys.go

@@ -6,6 +6,7 @@ const (
 	viteContextKey       contextKey = "vite"
 	sessionContextKey    contextKey = "session"
 	themeContextKey      contextKey = "theme"
+	intlContextKey       contextKey = "intl"
 	spaceContextKey      contextKey = "space"
 	spaceStatsContextKey contextKey = "space_stats"
 	accessContextKey     contextKey = "access"

app/rctx/intl.context.go

@@ -0,0 +1,54 @@
+package rctx
+
+import (
+	"context"
+	"log/slog"
+	"net/http"
+	"slices"
+
+	"github.com/nicksnyder/go-i18n/v2/i18n"
+	"github.com/nicolashery/simply-shared-notes/app/intl"
+	"golang.org/x/text/language"
+)
+
+func IntlCtxMiddleware(logger *slog.Logger, i18nBundle *i18n.Bundle) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			lang := selectLanguage(r.Header.Get("Accept-Language"))
+
+			intl := intl.New(logger, i18nBundle, lang)
+
+			ctx := context.WithValue(r.Context(), intlContextKey, intl)
+			next.ServeHTTP(w, r.WithContext(ctx))
+		})
+	}
+}
+
+func selectLanguage(acceptLang string) language.Tag {
+	if acceptLang == "" {
+		return intl.DefaultLang
+	}
+
+	tags, _, err := language.ParseAcceptLanguage(acceptLang)
+	if err != nil {
+		return intl.DefaultLang
+	}
+
+	// Find the first tag that matches one of our supported languages
+	for _, tag := range tags {
+		if slices.Contains(intl.SupportedLangs, tag) {
+			return tag
+		}
+	}
+
+	return intl.DefaultLang
+}
+
+func GetIntl(ctx context.Context) *intl.Intl {
+	intl, ok := ctx.Value(intlContextKey).(*intl.Intl)
+	if !ok {
+		panic("intl not found in context, make sure to use middleware")
+	}
+
+	return intl
+}

app/server/server.go

@@ -10,6 +10,7 @@ import (
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/gorilla/sessions"
+	"github.com/nicksnyder/go-i18n/v2/i18n"
 	"github.com/nicolashery/simply-shared-notes/app/config"
 	"github.com/nicolashery/simply-shared-notes/app/db"
 	"github.com/nicolashery/simply-shared-notes/app/email"
@@ -26,6 +27,7 @@ func New(
 	vite *vite.Vite,
 	sessionStore *sessions.CookieStore,
 	email *email.Email,
+	i18nBundle *i18n.Bundle,
 ) http.Handler {
 	router := chi.NewRouter()
 
@@ -35,7 +37,7 @@ func New(
 		rctx.ViteCtxMiddleware(vite),
 	)
 
-	handlers.RegisterRoutes(router, cfg, logger, sqlDB, queries, sessionStore, email)
+	handlers.RegisterRoutes(router, cfg, logger, sqlDB, queries, sessionStore, email, i18nBundle)
 
 	StaticDir(router, "/assets", vite.AssetsFS)
 	StaticFile(router, "/robots.txt", vite.PublicFS)