set strong ETag for responses

i18n/locale/en/template.json

@@ -137,6 +137,7 @@
   "assets/views/fragments/small-tn.jet.html:yTQShm_bVeU": "Deleted or Private",
   "assets/views/fragments/thumbnail-dt.jet.html:0wMo7aB_ylE": "{{ if .XRestrict == 1 }}R-18{{ else }}R-18G{{ end }}",
   "assets/views/fragments/thumbnail-dt.jet.html:R20Dy5iCS58": "AI",
+  "assets/views/index.jet.html:6103Lobv_EM": "Trending!",
   "assets/views/index.jet.html:8lMwxcLFwfQ": "R-18",
   "assets/views/index.jet.html:Awt3bDxDL0U": "View more",
   "assets/views/index.jet.html:D-LKBPd3-uc": "Today's illustration rankings",
@@ -145,6 +146,7 @@
   "assets/views/index.jet.html:Sccoo133FQI": "All",
   "assets/views/index.jet.html:lEVH3Ram904": "Newest works",
   "assets/views/index.jet.html:lv5wuj1vx98": "Latest works by followed",
+  "assets/views/index.jet.html:n-1FZQng9rs": "Popular tags",
   "assets/views/index.jet.html:n7zdClpaR18": "Recommended illustrations tagged",
   "assets/views/index.jet.html:s7Bp-mQhmg0": "Recommended users",
   "assets/views/index.jet.html:v1aAHggOM7M": "Recommended works",

server/routes/types.go

@@ -14,9 +14,20 @@ func RenderHTML[T any](w http.ResponseWriter, r *http.Request, data T) error {
 }
 
 func RenderWithContentType[T any](w http.ResponseWriter, r *http.Request, contentType string, data T) error {
-	w.Header().Set("content-type", contentType)
-	w.WriteHeader(request_context.Get(r).RenderStatusCode)
-	return template.Render(w, template.GetTemplatingVariables(r), data)
+  w.Header().Set("Content-Type", contentType)
+
+  // Render and get ETag
+  etag, err := template.Render(w, template.GetTemplatingVariables(r), data)
+  if err != nil {
+      return err
+  }
+
+  // Set strong ETag
+  w.Header().Set("ETag", `"`+etag+`"`)
+
+  w.WriteHeader(request_context.Get(r).RenderStatusCode)
+
+  return nil
 }
 
 // Tutorial: adding new types in this file

server/template/render.go

@@ -1,12 +1,17 @@
 package template
 
 import (
+	"bytes"
+	"encoding/base64"
+	"encoding/binary"
 	"io"
 	"log"
 	"net/http"
 	"reflect"
 	"strings"
 
+	"github.com/zeebo/xxh3"
+
 	"codeberg.org/vnpower/pixivfe/v2/server/session"
 	"codeberg.org/vnpower/pixivfe/v2/server/utils"
 
@@ -32,7 +37,7 @@ func Init(DisableCache bool, assetsLocation string) {
 	}
 }
 
-func Render[T any](w io.Writer, variables jet.VarMap, data T) error {
+func Render[T any](w io.Writer, variables jet.VarMap, data T) (string, error) {
 	template_name, found := strings.CutPrefix(reflect.TypeFor[T]().Name(), "Data_")
 	if !found {
 		log.Panicf("struct name does not start with 'Data_': %s", template_name)
@@ -40,12 +45,31 @@ func Render[T any](w io.Writer, variables jet.VarMap, data T) error {
 
 	template, err := views.GetTemplate(template_name + ".jet.html")
 	if err != nil {
-		return err
+		return "", err
 	}
 
 	views.Parse(template_name+".jet.html", template.String())
 
-	return template.Execute(w, variables, data)
+	// Create buffer to capture rendered output
+	buf := &bytes.Buffer{}
+
+	// Execute template to buffer
+	if err := template.Execute(buf, variables, data); err != nil {
+		return "", err
+	}
+
+	// Generate ETag
+	hash := xxh3.Hash(buf.Bytes())
+	hash_bytes := make([]byte, 8)
+	binary.LittleEndian.PutUint64(hash_bytes, uint64(hash))
+	etag := template_name + ":" + base64.RawURLEncoding.EncodeToString(hash_bytes)
+
+	// Write buffer to original writer
+	if _, err := io.Copy(w, buf); err != nil {
+		return "", err
+	}
+
+	return etag, nil
 }
 
 func GetTemplatingVariables(r *http.Request) jet.VarMap {