rework template load/generation + add generic error on template error

handlers/download/handler.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"librapi/services"
 	"net/http"
+	"os"
 	"path/filepath"
 
 	"github.com/rs/zerolog/log"
@@ -27,7 +28,7 @@ func getDownload(w http.ResponseWriter, r *http.Request, bs services.IStore) {
 	downloadFiles, ok := queryParams["file"]
 	if !ok {
 		log.Error().Msg("file query param does not exist")
-		http.Error(w, "file does not exists", http.StatusBadRequest)
+		http.Error(w, "file query param does not exist", http.StatusBadRequest)
 		return
 	}
 
@@ -40,6 +41,15 @@ func getDownload(w http.ResponseWriter, r *http.Request, bs services.IStore) {
 	filename := downloadFiles[0]
 	filePath := filepath.Join(bs.GetStoreDir(), filename)
 
+	if _, err := os.Stat(filePath); err != nil {
+		if os.IsNotExist(err) {
+			http.Error(w, "file does not exist", http.StatusInternalServerError)
+			return
+		}
+		http.Error(w, "unexpected error occurred", http.StatusInternalServerError)
+		return
+	}
+
 	http.ServeFile(w, r, filePath)
 
 	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=%s", filename))