2 files changed, 59 insertions, 1 deletions
diff --git a/routers/web/devtest/devtest.go b/routers/web/devtest/devtest.go
index 765931a730..a22d376579 100644
--- a/routers/web/devtest/devtest.go
+++ b/routers/web/devtest/devtest.go
@@ -132,7 +132,7 @@ func prepareMockDataBadgeActionsSvg(ctx *context.Context) {
 	selectedStyle := ctx.FormString("style", badge.DefaultStyle)
 	var badges []badge.Badge
 	badges = append(badges, badge.GenerateBadge("啊啊啊啊啊啊啊啊啊啊啊啊", "🌞🌞🌞🌞🌞", "green"))
-	for r := rune(0); r < 256; r++ {
+	for r := range rune(256) {
 		if unicode.IsPrint(r) {
 			s := strings.Repeat(string(r), 15)
 			badges = append(badges, badge.GenerateBadge(s, util.TruncateRunes(s, 7), "green"))
diff --git a/routers/web/devtest/mail_preview.go b/routers/web/devtest/mail_preview.go
new file mode 100644
index 0000000000..d6bade15d7
--- /dev/null
+++ b/routers/web/devtest/mail_preview.go
@@ -0,0 +1,58 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package devtest
+
+import (
+	"net/http"
+	"strings"
+
+	"code.gitea.io/gitea/modules/templates"
+	"code.gitea.io/gitea/services/context"
+	"code.gitea.io/gitea/services/mailer"
+
+	"gopkg.in/yaml.v3"
+)
+
+func MailPreviewRender(ctx *context.Context) {
+	tmplName := ctx.PathParam("*")
+	mockDataContent, err := templates.AssetFS().ReadFile("mail/" + tmplName + ".devtest.yml")
+	mockData := map[string]any{}
+	if err == nil {
+		err = yaml.Unmarshal(mockDataContent, &mockData)
+		if err != nil {
+			http.Error(ctx.Resp, "Failed to parse mock data: "+err.Error(), http.StatusInternalServerError)
+			return
+		}
+	}
+	mockData["locale"] = ctx.Locale
+	err = mailer.LoadedTemplates().BodyTemplates.ExecuteTemplate(ctx.Resp, tmplName, mockData)
+	if err != nil {
+		_, _ = ctx.Resp.Write([]byte(err.Error()))
+	}
+}
+
+func prepareMailPreviewRender(ctx *context.Context, tmplName string) {
+	tmplSubject := mailer.LoadedTemplates().SubjectTemplates.Lookup(tmplName)
+	if tmplSubject == nil {
+		ctx.Data["RenderMailSubject"] = "default subject"
+	} else {
+		var buf strings.Builder
+		err := tmplSubject.Execute(&buf, nil)
+		if err != nil {
+			ctx.Data["RenderMailSubject"] = err.Error()
+		} else {
+			ctx.Data["RenderMailSubject"] = buf.String()
+		}
+	}
+	ctx.Data["RenderMailTemplateName"] = tmplName
+}
+
+func MailPreview(ctx *context.Context) {
+	ctx.Data["MailTemplateNames"] = mailer.LoadedTemplates().TemplateNames
+	tmplName := ctx.FormString("tmpl")
+	if tmplName != "" {
+		prepareMailPreviewRender(ctx, tmplName)
+	}
+	ctx.HTML(http.StatusOK, "devtest/mail-preview")
+}