Initialize AutoLibrary website with Gitea deployment

frontend/handlers/errors_handler/handler.go

@@ -0,0 +1,45 @@
+package errors_handler
+
+import (
+	"fmt"
+	"github.com/gin-gonic/gin"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+// Handler renders the same application shell with the actual HTTP error code.
+// It owns its entry data rather than using process-global mutable template state.
+type Handler struct{ entry []byte }
+
+func New(entry []byte) *Handler { return &Handler{entry: entry} }
+
+func (h *Handler) GetErrorsPage(c *gin.Context, status int) {
+	c.Header("Cache-Control", "no-store")
+	c.Data(status, "text/html; charset=utf-8", h.entry)
+}
+
+func (h *Handler) RegisterGetErrorRoutes(r *gin.Engine, statuses []int) {
+	for _, code := range statuses {
+		serve := func(c *gin.Context) { h.GetErrorsPage(c, code) }
+		path := fmt.Sprintf("/errors/%d", code)
+		r.GET(path, serve)
+		r.HEAD(path, serve)
+	}
+}
+
+func (h *Handler) APIAccessMiddleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		if strings.HasPrefix(c.Request.URL.Path, "/api/") {
+			referer := c.GetHeader("Referer")
+			if referer != "" {
+				parsed, err := url.Parse(referer)
+				if err != nil || parsed.Host != c.Request.Host {
+					c.AbortWithStatusJSON(http.StatusForbidden, gin.H{"code": 403, "msg": "Cross-origin API request denied", "data": nil})
+					return
+				}
+			}
+		}
+		c.Next()
+	}
+}