perf(security): cache assets checksum

2 files changed, 18 insertions, 9 deletions

diff --git a/backend/data.go b/backend/data.go
index a1b2dba..d98c8b0 100644
--- a/backend/data.go
+++ b/backend/data.go
@@ -134,34 +134,41 @@ type assetData struct {
 	Checksum string
 }
 
+var assets = map[string]*assetData{}
+
 func getAsset(ctx context.Context, path string) *assetData {
-	var asset assetData
+	asset, ok := assets[path]
+	if ok && !ctx.Value(debugKey).(bool) {
+		return asset
+	}
+	asset = &assetData{}
 	var b []byte
-	var err error
 	if regexIsHttp.MatchString(path) {
 		asset.Src = path
 		resp, err := http.Get(path)
 		if err != nil {
 			slog.Warn("get remote asset", "error", err)
-			return &asset
+			return asset
 		}
 		defer resp.Body.Close()
 		b, err = io.ReadAll(resp.Body)
 		if err != nil {
 			slog.Warn("read remote asset", "error", err)
-			return &asset
+			return asset
 		}
 	} else {
 		asset.Src = fmt.Sprintf("/assets/%s", path)
-		aFS := ctx.Value(assetsFS).(fs.FS)
+		aFS := ctx.Value(assetsFSKey).(fs.FS)
+		var err error
 		b, err = fs.ReadFile(aFS, path)
 		if err != nil {
 			slog.Warn("read asset", "error", err)
-			return &asset
+			return asset
 		}
 	}
 	sum := sha256.Sum256(b)
 	checksum := base64.StdEncoding.EncodeToString(sum[:])
 	asset.Checksum = fmt.Sprintf("sha256-%s", checksum)
-	return &asset
+	assets[path] = asset
+	return asset
 }
diff --git a/backend/router.go b/backend/router.go
index 1231fdf..fb43845 100644
--- a/backend/router.go
+++ b/backend/router.go
@@ -20,7 +20,8 @@ const (
 	Version     = "0.2.0"
 	configKey   = "config"
 	isUpdateKey = "is_update"
-	assetsFS    = "assets_fs"
+	assetsFSKey = "assets_fs"
+	debugKey    = "debug"
 )
 
 //go:embed templates
@@ -78,7 +79,8 @@ func NewRouter(debug bool, cfg *Config, assets fs.FS) *chi.Mux {
 	r.Use(func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			ctx := context.WithValue(r.Context(), configKey, cfg)
-			ctx = context.WithValue(ctx, assetsFS, assets)
+			ctx = context.WithValue(ctx, assetsFSKey, assets)
+			ctx = context.WithValue(ctx, debugKey, debug)
 			next.ServeHTTP(w, r.WithContext(ctx))
 		})
 	})