1 files changed, 72 insertions, 0 deletions
diff --git a/packages/integrations/lit/server.js b/packages/integrations/lit/server.js
new file mode 100644
index 000000000..1622ef619
--- /dev/null
+++ b/packages/integrations/lit/server.js
@@ -0,0 +1,72 @@
+import './server-shim.js';
+import '@lit-labs/ssr/lib/render-lit-html.js';
+import { LitElementRenderer } from '@lit-labs/ssr/lib/lit-element-renderer.js';
+
+function isCustomElementTag(name) {
+	return typeof name === 'string' && /-/.test(name);
+}
+
+function getCustomElementConstructor(name) {
+	if (typeof customElements !== 'undefined' && isCustomElementTag(name)) {
+		return customElements.get(name) || null;
+	}
+	return null;
+}
+
+async function isLitElement(Component) {
+	const Ctr = getCustomElementConstructor(Component);
+	return !!(Ctr && Ctr._$litElement$);
+}
+
+async function check(Component, _props, _children) {
+	// Lit doesn't support getting a tagName from a Constructor at this time.
+	// So this must be a string at the moment.
+	return !!(await isLitElement(Component));
+}
+
+function* render(tagName, attrs, children) {
+	const instance = new LitElementRenderer(tagName);
+
+	// LitElementRenderer creates a new element instance, so copy over.
+	const Ctr = getCustomElementConstructor(tagName);
+	for (let [name, value] of Object.entries(attrs)) {
+		// check if this is a reactive property
+		if (name in Ctr.prototype) {
+			instance.setProperty(name, value);
+		} else {
+			instance.setAttribute(name, value);
+		}
+	}
+
+	instance.connectedCallback();
+
+	yield `<${tagName}`;
+	yield* instance.renderAttributes();
+	yield `>`;
+	const shadowContents = instance.renderShadow({});
+	if (shadowContents !== undefined) {
+		yield '<template shadowroot="open">';
+		yield* shadowContents;
+		yield '</template>';
+	}
+	yield children || ''; // don’t print “undefined” as string
+	yield `</${tagName}>`;
+}
+
+async function renderToStaticMarkup(Component, props, children) {
+	let tagName = Component;
+
+	let out = '';
+	for (let chunk of render(tagName, props, children)) {
+		out += chunk;
+	}
+
+	return {
+		html: out,
+	};
+}
+
+export default {
+	check,
+	renderToStaticMarkup,
+};