1 files changed, 65 insertions, 0 deletions
diff --git a/browser/extensions/webcompat/lib/shim_messaging_helper.js b/browser/extensions/webcompat/lib/shim_messaging_helper.js
new file mode 100644
index 0000000000..ee109713a5
--- /dev/null
+++ b/browser/extensions/webcompat/lib/shim_messaging_helper.js
@@ -0,0 +1,65 @@
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/* globals browser */
+
+if (!window.Shims) {
+  window.Shims = new Map();
+}
+
+if (!window.ShimsHelperReady) {
+  window.ShimsHelperReady = true;
+
+  browser.runtime.onMessage.addListener(details => {
+    const { shimId, warning } = details;
+    if (!shimId) {
+      return;
+    }
+    window.Shims.set(shimId, details);
+    if (warning) {
+      console.warn(warning);
+    }
+  });
+
+  async function handleMessage(port, shimId, messageId, message) {
+    let response;
+    const shim = window.Shims.get(shimId);
+    if (shim) {
+      const { needsShimHelpers, origin } = shim;
+      if (origin === location.origin) {
+        if (needsShimHelpers?.includes(message)) {
+          const msg = { shimId, message };
+          try {
+            response = await browser.runtime.sendMessage(msg);
+          } catch (_) {}
+        }
+      }
+    }
+    port.postMessage({ messageId, response });
+  }
+
+  window.addEventListener(
+    "ShimConnects",
+    e => {
+      e.stopPropagation();
+      e.preventDefault();
+      const { port, pendingMessages, shimId } = e.detail;
+      const shim = window.Shims.get(shimId);
+      if (!shim) {
+        return;
+      }
+      port.onmessage = ({ data }) => {
+        handleMessage(port, shimId, data.messageId, data.message);
+      };
+      for (const [messageId, message] of pendingMessages) {
+        handleMessage(port, shimId, messageId, message);
+      }
+    },
+    true
+  );
+
+  window.dispatchEvent(new CustomEvent("ShimHelperReady"));
+}