1 files changed, 142 insertions, 0 deletions
diff --git a/dom/media/mediacontrol/MediaPlaybackStatus.cpp b/dom/media/mediacontrol/MediaPlaybackStatus.cpp
new file mode 100644
index 0000000000..80dedf8599
--- /dev/null
+++ b/dom/media/mediacontrol/MediaPlaybackStatus.cpp
@@ -0,0 +1,142 @@
+/* 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/. */
+
+#include "MediaPlaybackStatus.h"
+
+#include "MediaControlUtils.h"
+
+namespace mozilla::dom {
+
+#undef LOG
+#define LOG(msg, ...)                        \
+  MOZ_LOG(gMediaControlLog, LogLevel::Debug, \
+          ("MediaPlaybackStatus=%p, " msg, this, ##__VA_ARGS__))
+
+void MediaPlaybackStatus::UpdateMediaPlaybackState(uint64_t aContextId,
+                                                   MediaPlaybackState aState) {
+  LOG("Update playback state '%s' for context %" PRIu64,
+      ToMediaPlaybackStateStr(aState), aContextId);
+  MOZ_ASSERT(NS_IsMainThread());
+
+  ContextMediaInfo& info = GetNotNullContextInfo(aContextId);
+  if (aState == MediaPlaybackState::eStarted) {
+    info.IncreaseControlledMediaNum();
+  } else if (aState == MediaPlaybackState::eStopped) {
+    info.DecreaseControlledMediaNum();
+  } else if (aState == MediaPlaybackState::ePlayed) {
+    info.IncreasePlayingMediaNum();
+  } else {
+    MOZ_ASSERT(aState == MediaPlaybackState::ePaused);
+    info.DecreasePlayingMediaNum();
+  }
+
+  // The context still has controlled media, we should keep its alive.
+  if (info.IsAnyMediaBeingControlled()) {
+    return;
+  }
+  MOZ_ASSERT(!info.IsPlaying());
+  MOZ_ASSERT(!info.IsAudible());
+  // DO NOT access `info` after this line.
+  DestroyContextInfo(aContextId);
+}
+
+void MediaPlaybackStatus::DestroyContextInfo(uint64_t aContextId) {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG("Remove context %" PRIu64, aContextId);
+  mContextInfoMap.Remove(aContextId);
+  // If the removed context is owning the audio focus, we would find another
+  // context to take the audio focus if it's possible.
+  if (IsContextOwningAudioFocus(aContextId)) {
+    ChooseNewContextToOwnAudioFocus();
+  }
+}
+
+void MediaPlaybackStatus::UpdateMediaAudibleState(uint64_t aContextId,
+                                                  MediaAudibleState aState) {
+  LOG("Update audible state '%s' for context %" PRIu64,
+      ToMediaAudibleStateStr(aState), aContextId);
+  MOZ_ASSERT(NS_IsMainThread());
+  ContextMediaInfo& info = GetNotNullContextInfo(aContextId);
+  if (aState == MediaAudibleState::eAudible) {
+    info.IncreaseAudibleMediaNum();
+  } else {
+    MOZ_ASSERT(aState == MediaAudibleState::eInaudible);
+    info.DecreaseAudibleMediaNum();
+  }
+  if (ShouldRequestAudioFocusForInfo(info)) {
+    SetOwningAudioFocusContextId(Some(aContextId));
+  } else if (ShouldAbandonAudioFocusForInfo(info)) {
+    ChooseNewContextToOwnAudioFocus();
+  }
+}
+
+bool MediaPlaybackStatus::IsPlaying() const {
+  MOZ_ASSERT(NS_IsMainThread());
+  return std::any_of(mContextInfoMap.Values().cbegin(),
+                     mContextInfoMap.Values().cend(),
+                     [](const auto& info) { return info->IsPlaying(); });
+}
+
+bool MediaPlaybackStatus::IsAudible() const {
+  MOZ_ASSERT(NS_IsMainThread());
+  return std::any_of(mContextInfoMap.Values().cbegin(),
+                     mContextInfoMap.Values().cend(),
+                     [](const auto& info) { return info->IsAudible(); });
+}
+
+bool MediaPlaybackStatus::IsAnyMediaBeingControlled() const {
+  MOZ_ASSERT(NS_IsMainThread());
+  return std::any_of(
+      mContextInfoMap.Values().cbegin(), mContextInfoMap.Values().cend(),
+      [](const auto& info) { return info->IsAnyMediaBeingControlled(); });
+}
+
+MediaPlaybackStatus::ContextMediaInfo&
+MediaPlaybackStatus::GetNotNullContextInfo(uint64_t aContextId) {
+  MOZ_ASSERT(NS_IsMainThread());
+  return *mContextInfoMap.GetOrInsertNew(aContextId, aContextId);
+}
+
+Maybe<uint64_t> MediaPlaybackStatus::GetAudioFocusOwnerContextId() const {
+  return mOwningAudioFocusContextId;
+}
+
+void MediaPlaybackStatus::ChooseNewContextToOwnAudioFocus() {
+  for (const auto& info : mContextInfoMap.Values()) {
+    if (info->IsAudible()) {
+      SetOwningAudioFocusContextId(Some(info->Id()));
+      return;
+    }
+  }
+  // No context is audible, so no one should the own audio focus.
+  SetOwningAudioFocusContextId(Nothing());
+}
+
+void MediaPlaybackStatus::SetOwningAudioFocusContextId(
+    Maybe<uint64_t>&& aContextId) {
+  if (mOwningAudioFocusContextId == aContextId) {
+    return;
+  }
+  mOwningAudioFocusContextId = aContextId;
+}
+
+bool MediaPlaybackStatus::ShouldRequestAudioFocusForInfo(
+    const ContextMediaInfo& aInfo) const {
+  return aInfo.IsAudible() && !IsContextOwningAudioFocus(aInfo.Id());
+}
+
+bool MediaPlaybackStatus::ShouldAbandonAudioFocusForInfo(
+    const ContextMediaInfo& aInfo) const {
+  // The owner becomes inaudible and there is other context still playing, so we
+  // should switch the audio focus to the audible context.
+  return !aInfo.IsAudible() && IsContextOwningAudioFocus(aInfo.Id()) &&
+         IsAudible();
+}
+
+bool MediaPlaybackStatus::IsContextOwningAudioFocus(uint64_t aContextId) const {
+  return mOwningAudioFocusContextId ? *mOwningAudioFocusContextId == aContextId
+                                    : false;
+}
+
+}  // namespace mozilla::dom