feat: add base path configuration

backend/ui/ui_prod.go

@@ -7,7 +7,10 @@ import (
 	"embed"
 	"io/fs"
 	"net/http"
+	"os"
 	"path"
+	"regexp"
+	"strings"
 )
 
 //go:embed dist
@@ -16,19 +19,45 @@ var embeddedFs embed.FS
 func ServeUI(mux *http.ServeMux) {
 	distFs, _ := fs.Sub(embeddedFs, "dist")
 	fileServer := http.FileServer(http.FS(distFs))
+	basePath := os.Getenv("BASE_PATH")
 
-	mux.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	mux.Handle(basePath+"/", http.StripPrefix(basePath, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		_path := path.Clean(r.URL.Path)[1:]
 
 		// Rewrite non-existing paths to index.html
 		if _, err := fs.Stat(distFs, _path); err != nil {
 			index, _ := fs.ReadFile(distFs, "index.html")
+			html := string(index)
+
+			// Set base path for the UI
+			html = strings.ReplaceAll(html, "%BASE_PATH%", basePath)
+			html = addBasePath(html, basePath)
+
 			w.Header().Add("Content-Type", "text/html")
 			w.WriteHeader(http.StatusOK)
-			w.Write(index)
+			w.Write([]byte(html))
+			return
+		}
+
+		// Add prefix to each /assets strings in js
+		if len(basePath) > 0 && strings.HasSuffix(_path, ".js") {
+			data, _ := fs.ReadFile(distFs, _path)
+			html := string(data)
+			html = strings.ReplaceAll(html, "assets/", basePath[1:]+"/assets/")
+
+			w.Header().Add("Content-Type", "text/javascript")
+			w.WriteHeader(http.StatusOK)
+			w.Write([]byte(html))
 			return
 		}
 
 		fileServer.ServeHTTP(w, r)
-	}))
+	})))
+}
+
+func addBasePath(html string, basePath string) string {
+	re := regexp.MustCompile(`(href|src)=["'](/[^"'>]+)["']`)
+	return re.ReplaceAllStringFunc(html, func(match string) string {
+		return re.ReplaceAllString(match, `$1="`+basePath+`$2"`)
+	})
 }