Resize e-mail iframe with content

plugins/base/public/assets/script.js

@@ -0,0 +1,8 @@
+var emailFrame = document.getElementById("email-frame");
+if (emailFrame) {
+	var resizeFrame = function() {
+		emailFrame.style.height = emailFrame.contentWindow.document.documentElement.scrollHeight + "px";
+	};
+	emailFrame.addEventListener("load", resizeFrame);
+	emailFrame.contentWindow.addEventListener("resize", resizeFrame);
+}

plugins/base/public/foot.html

@@ -1,2 +1,3 @@
+    <script src="/plugins/base/assets/script.js"></script>
   </body>
 </html>

plugins/base/public/message.html

@@ -114,7 +114,8 @@
 	<p><a href="{{.Message.Uid}}/reply?part={{.PartPath}}">Reply</a></p>
 	{{if .IsHTML}}
 		<!-- TODO: add a src fallback -->
-		<iframe srcdoc="{{.Body}}" sandbox></iframe>
+		<!-- allow-same-origin is required to resize the frame with its content -->
+		<iframe id="email-frame" srcdoc="{{.Body}}" sandbox="allow-same-origin"></iframe>
 	{{else}}
 		<pre>{{.Body}}</pre>
 	{{end}}

plugins/base/routes.go

@@ -247,6 +247,9 @@ func handleGetPart(ctx *koushin.Context, raw bool) error {
 	isHTML := false
 	if strings.EqualFold(mimeType, "text/html") {
 		p := bluemonday.UGCPolicy()
+		// TODO: be more strict
+		p.AllowElements("style")
+		p.AllowAttrs("style")
 		body = p.Sanitize(body)
 		isHTML = true
 	}