Refactor mail template and support preview (#34990)

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 + ".mock.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")
+}