Add optional Datastar plumbing

site/examples/uce-starter/README.md

@@ -33,3 +33,9 @@ The example uses query-string routing in the same style as the PHP starter, but
 Direct requests to `/examples/uce-starter/index.uce` still work, but self-links are canonicalized back to `/examples/uce-starter/`.
 
 The demo account pages use a small file-backed user store under `/tmp/uce-starter-data/` with session-based login state.
+
+
+## Optional Datastar Assets
+
+This starter vendors Datastar v1.0.2 as `js/datastar.js` for future server-rendered interactive islands. It is not loaded by the default page shell. `lib/datastar.uce` contains small Datastar SSE formatting helpers, and `views/datastar-example.uce` is an unlinked opt-in example route.
+

site/examples/uce-starter/lib/datastar.uce

@@ -0,0 +1,38 @@
+String datastar_data_lines(String field, String value)
+{
+	String out = "";
+	for(String line : split(value, "\n"))
+		out += "data: " + field + " " + line + "\n";
+	return(out);
+}
+
+void datastar_sse_headers(Request& context)
+{
+	context.call["app"]["page_type"] = "blank";
+	context.header["Content-Type"] = "text/event-stream; charset=utf-8";
+	context.header["Cache-Control"] = "no-cache, no-store, must-revalidate";
+	context.header["X-Accel-Buffering"] = "no";
+}
+
+String datastar_event(String event_name, StringMap fields)
+{
+	String out = "event: " + event_name + "\n";
+	for(const auto& field : fields)
+		out += datastar_data_lines(field.first, field.second);
+	out += "\n";
+	return(out);
+}
+
+String datastar_patch_elements(String html)
+{
+	StringMap fields;
+	fields["elements"] = html;
+	return(datastar_event("datastar-patch-elements", fields));
+}
+
+String datastar_patch_signals(String signals_json)
+{
+	StringMap fields;
+	fields["signals"] = signals_json;
+	return(datastar_event("datastar-patch-signals", fields));
+}

site/examples/uce-starter/views/datastar-example.uce

@@ -0,0 +1,20 @@
+#load "../lib/app.uce"
+#load "../lib/datastar.uce"
+
+COMPONENT(Request& context)
+{
+	if(context.get["stream"] == "1")
+	{
+		datastar_sse_headers(context);
+		print(datastar_patch_elements("<div id=\"datastar-example-result\">Server-rendered UCE Datastar fragment</div>"));
+		return;
+	}
+
+	<>
+		<h1>Datastar optional example</h1>
+		<p>Datastar is vendored beside the starter client libraries for future server-rendered islands. It is not loaded globally.</p>
+		<script type="module" src="<?= app_asset_url("js/datastar.js", context) ?>"></script>
+		<button class="btn" data-on:click="@get('<?= app_link("datastar-example", context) ?>&amp;stream=1')">Patch a fragment</button>
+		<div id="datastar-example-result">Waiting for a server patch.</div>
+	</>;
+}