1 files changed, 57 insertions, 0 deletions
diff --git a/dom/manifest/ManifestFinder.sys.mjs b/dom/manifest/ManifestFinder.sys.mjs
new file mode 100644
index 0000000000..1f8a23462b
--- /dev/null
+++ b/dom/manifest/ManifestFinder.sys.mjs
@@ -0,0 +1,57 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+export var ManifestFinder = {
+  /**
+   * Check from content process if DOM Window has a conforming
+   * manifest link relationship.
+   * @param aContent DOM Window to check.
+   * @return {Promise<Boolean>}
+   */
+  contentHasManifestLink(aContent) {
+    if (!aContent || isXULBrowser(aContent)) {
+      throw new TypeError("Invalid input.");
+    }
+    return checkForManifest(aContent);
+  },
+
+  /**
+   * Check from a XUL browser (parent process) if it's content document has a
+   * manifest link relationship.
+   * @param aBrowser The XUL browser to check.
+   * @return {Promise}
+   */
+  async browserHasManifestLink(aBrowser) {
+    if (!isXULBrowser(aBrowser)) {
+      throw new TypeError("Invalid input.");
+    }
+
+    const actor =
+      aBrowser.browsingContext.currentWindowGlobal.getActor("ManifestMessages");
+    const reply = await actor.sendQuery("DOM:WebManifest:hasManifestLink");
+    return reply.result;
+  },
+};
+
+function isXULBrowser(aBrowser) {
+  if (!aBrowser || !aBrowser.namespaceURI || !aBrowser.localName) {
+    return false;
+  }
+  const XUL_NS =
+    "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
+  return aBrowser.namespaceURI === XUL_NS && aBrowser.localName === "browser";
+}
+
+function checkForManifest(aWindow) {
+  // Only top-level browsing contexts are valid.
+  if (!aWindow || aWindow.top !== aWindow) {
+    return false;
+  }
+  const elem = aWindow.document.querySelector("link[rel~='manifest']");
+  // Only if we have an element and a non-empty href attribute.
+  if (!elem || !elem.getAttribute("href")) {
+    return false;
+  }
+  return true;
+}