feat: add HTTP HEAD method support (#1135)

backend/internal/bootstrap/router_bootstrap.go

@@ -63,6 +63,7 @@ func initRouterInternal(db *gorm.DB, svc *services) (utils.Service, error) {
 	rateLimitMiddleware := middleware.NewRateLimitMiddleware().Add(rate.Every(time.Second), 60)
 
 	// Setup global middleware
+	r.Use(middleware.HeadMiddleware())
 	r.Use(middleware.NewCacheControlMiddleware().Add())
 	r.Use(middleware.NewCorsMiddleware().Add())
 	r.Use(middleware.NewCspMiddleware().Add())
@@ -111,7 +112,17 @@ func initRouterInternal(db *gorm.DB, svc *services) (utils.Service, error) {
 	srv := &http.Server{
 		MaxHeaderBytes:    1 << 20,
 		ReadHeaderTimeout: 10 * time.Second,
-		Handler:           r,
+		Handler: http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+			// HEAD requests don't get matched by Gin routes, so we convert them to GET
+			// middleware.HeadMiddleware will convert them back to HEAD later
+			if req.Method == http.MethodHead {
+				req.Method = http.MethodGet
+				ctx := context.WithValue(req.Context(), middleware.IsHeadRequestCtxKey{}, true)
+				req = req.WithContext(ctx)
+			}
+
+			r.ServeHTTP(w, req)
+		}),
 	}
 
 	// Set up the listener

backend/internal/middleware/head_middleware.go

@@ -0,0 +1,40 @@
+package middleware
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+)
+
+type IsHeadRequestCtxKey struct{}
+
+type headWriter struct {
+	gin.ResponseWriter
+	size int
+}
+
+func (w *headWriter) Write(b []byte) (int, error) {
+	w.size += len(b)
+	return w.size, nil
+}
+
+func HeadMiddleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		// Only process if it's a HEAD request
+		if c.Request.Context().Value(IsHeadRequestCtxKey{}) != true {
+			c.Next()
+			return
+		}
+
+		// Replace the ResponseWriter with our headWriter to swallow the body
+		hw := &headWriter{ResponseWriter: c.Writer}
+		c.Writer = hw
+
+		c.Next()
+
+		c.Writer.Header().Set("Content-Length", strconv.Itoa(hw.size))
+		c.Request.Method = http.MethodHead
+
+	}
+}