Bug 1721443 - Implement gtest helper TakeN that return a MozPromise wrapping the first N events from a MediaEventSource. r=bwc

Differential Revision: https://phabricator.services.mozilla.com/D129625

dom/media/gtest/WaitFor.h

@@ -6,9 +6,10 @@
 #define WAITFOR_H_
 
 #include "MediaEventSource.h"
+#include "MediaUtils.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/MozPromise.h"
-#include "mozilla/Result.h"
+#include "mozilla/ResultVariant.h"
 #include "mozilla/SpinEventLoopUntil.h"
 
 namespace mozilla {
@@ -81,6 +82,36 @@ void WaitUntil(MediaEventSource<T>& aEvent, const CallbackFunction& aF) {
   listener.Disconnect();
 }
 
+template <typename... Args>
+using TakeNPromise = MozPromise<std::vector<std::tuple<Args...>>, bool, true>;
+
+template <ListenerPolicy Lp, typename... Args>
+auto TakeN(MediaEventSourceImpl<Lp, Args...>& aEvent, size_t aN)
+    -> RefPtr<TakeNPromise<Args...>> {
+  using Storage = std::vector<std::tuple<Args...>>;
+  using Promise = TakeNPromise<Args...>;
+  using Values = media::Refcountable<Storage>;
+  using Listener = media::Refcountable<MediaEventListener>;
+  RefPtr<Values> values = MakeRefPtr<Values>();
+  values->reserve(aN);
+  RefPtr<Listener> listener = MakeRefPtr<Listener>();
+  auto promise = InvokeAsync(
+      AbstractThread::GetCurrent(), __func__, [values, aN]() mutable {
+        SpinEventLoopUntil<ProcessFailureBehavior::IgnoreAndContinue>(
+            "TakeN(MediaEventSourceImpl<Lp, Args...>& aEvent, size_t aN)"_ns,
+            [&] { return values->size() == aN; });
+        return Promise::CreateAndResolve(std::move(*values), __func__);
+      });
+  *listener = aEvent.Connect(AbstractThread::GetCurrent(),
+                             [values, listener, aN](Args... aValue) {
+                               values->push_back({aValue...});
+                               if (values->size() == aN) {
+                                 listener->Disconnect();
+                               }
+                             });
+  return promise;
+}
+
 /**
  * Helper that, given that canonicals have just been updated on the current
  * thread, will block its execution until mirrors and their watchers have

dom/media/gtest/moz.build

@@ -10,6 +10,7 @@ DEFINES["ENABLE_SET_CUBEB_BACKEND"] = True
 
 LOCAL_INCLUDES += [
     "/dom/media/mediasink",
+    "/dom/media/systemservices",
     "/dom/media/webrtc/common/",
     "/third_party/libwebrtc",
     "/third_party/libwebrtc/third_party/abseil-cpp",

media/webrtc/signaling/gtest/moz.build

@@ -22,6 +22,7 @@ if (
     LOCAL_INCLUDES += [
         "/dom/media",
         "/dom/media/gtest",
+        "/dom/media/systemservices",
         "/dom/media/webrtc",
         "/dom/media/webrtc/common",
         "/dom/media/webrtc/common/time_profiling",