facilitate egistering dynamic content scripts with mappings data

1 files changed, 53 insertions, 8 deletions

diff --git a/common/message_server.js b/common/message_server.js
index fd609c7..657e140 100644
--- a/common/message_server.js
+++ b/common/message_server.js
@@ -43,23 +43,68 @@
 
 #FROM common/browser.js IMPORT browser
 
-var listeners = {};
+let listeners = {};
+let listening = false;
 
-/* magic should be one of the constants from /common/connection_types.js */
+function raw_listen(port)
+{
+    if (listeners[port.name] === undefined)
+	return;
+
+    listeners[port.name](port);
+}
 
+/* magic should be one of the constants from /common/connection_types.js */
 function listen_for_connection(magic, cb)
 {
+    if (!listening) {
+	listening = true;
+	browser.runtime.onConnect.addListener(raw_listen);
+    }
     listeners[magic] = cb;
 }
+#EXPORT listen_for_connection
 
-function raw_listen(port)
+/*
+ * Messaging background page from itself might result in messages being silently
+ * discarded. Here we implement an interface (somewhat) compatible with the one
+ * provided by the browser, but which allows for background page to communicate
+ * with itself.
+ */
+function EvTarget()
 {
-    if (listeners[port.name] === undefined)
-	return;
+    this.listeners = new Set();
+    this.addListener    = cb => this.listeners.add(cb);
+    this.removeListener = cb => this.listeners.delete(cb);
+    this.dispatch       = msg => this.listeners.forEach(l => l(msg));
+}
 
-    listeners[port.name](port);
+function Port(magic)
+{
+    this.name = magic;
+    this.onDisconnect = new EvTarget();
+    this.onMessage    = new EvTarget();
+    this.postMessage  = msg => this.other.onMessage.dispatch(msg);
+    this.disconnect   = () => this.other.onDisconnect.dispatch(this.other);
 }
 
-browser.runtime.onConnect.addListener(raw_listen);
+let bg_page_url;
+function connect_to_background(magic)
+{
+    if (bg_page_url === undefined)
+	bg_page_url = browser.runtime.getURL("_generated_background_page.html");
+    if (typeof document === "undefined" || document.URL !== bg_page_url)
+	return browser.runtime.connect({name: magic});
 
-#EXPORT listen_for_connection
+    if (!(magic in listeners))
+	throw `no listener for '${magic}'`
+
+    const ports = [new Port(magic), new Port(magic)];
+    ports[0].other = ports[1];
+    ports[1].other = ports[0];
+
+    listeners[magic](ports[0]);
+    return ports[1];
+}
+
+#EXPORT connect_to_background