feat: add native fnOS gateway socket and base path support

internal/app/app.go

@@ -2,13 +2,16 @@ package app
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"io/fs"
 	"log/slog"
+	"net"
 	"net/http"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 
 	"github.com/havline/havline/internal/acme"
@@ -144,6 +147,9 @@ func New(cfg config.Config, staticFS fs.FS, migrationsDir string) (*App, error)
 		StaticFS:   staticFS,
 		StartedAt:  startedAt,
 	})
+	if prefix := strings.TrimSpace(cfg.GatewayPrefix); prefix != "" {
+		handler = stripPrefixIfPresent(prefix, handler)
+	}
 	server := &http.Server{
 		Addr:              cfg.ListenAddr,
 		Handler:           handler,
@@ -235,7 +241,33 @@ func (a *App) bootstrapNginx(ctx context.Context, proxySvc *service.ProxyService
 }
 
 func (a *App) Run() error {
-	return a.server.ListenAndServe()
+	errCh := make(chan error, 2)
+	go func() {
+		errCh <- a.server.ListenAndServe()
+	}()
+
+	if socket := strings.TrimSpace(a.cfg.GatewaySocket); socket != "" {
+		if err := os.Remove(socket); err != nil && !os.IsNotExist(err) {
+			return err
+		}
+		listener, err := net.Listen("unix", socket)
+		if err != nil {
+			return err
+		}
+		if err := os.Chmod(socket, 0o660); err != nil {
+			_ = listener.Close()
+			return err
+		}
+		go func() {
+			errCh <- a.server.Serve(listener)
+		}()
+	}
+
+	err := <-errCh
+	if errors.Is(err, http.ErrServerClosed) {
+		return nil
+	}
+	return err
 }
 
 func (a *App) Shutdown(ctx context.Context) error {
@@ -246,6 +278,9 @@ func (a *App) Shutdown(ctx context.Context) error {
 	if err := a.server.Shutdown(ctx); err != nil {
 		return err
 	}
+	if socket := strings.TrimSpace(a.cfg.GatewaySocket); socket != "" {
+		_ = os.Remove(socket)
+	}
 	if err := a.nginx.Stop(ctx); err != nil {
 		a.logger.Error("nginx stop failed", "module", "NGINX", "error", err.Error())
 	}
@@ -260,6 +295,18 @@ func (a *App) Shutdown(ctx context.Context) error {
 	return nil
 }
 
+func stripPrefixIfPresent(prefix string, next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if strings.HasPrefix(r.URL.Path, prefix) {
+			r.URL.Path = strings.TrimPrefix(r.URL.Path, prefix)
+			if r.URL.Path == "" {
+				r.URL.Path = "/"
+			}
+		}
+		next.ServeHTTP(w, r)
+	})
+}
+
 func ResolveMigrationsDir() (string, error) {
 	candidates := []string{
 		"migrations",