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+/* 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/. */
+
+#ifndef DOM_MEDIA_MEDIACONTROL_MEDIAPLAYBACKSTATUS_H_
+#define DOM_MEDIA_MEDIACONTROL_MEDIAPLAYBACKSTATUS_H_
+
+#include "mozilla/Maybe.h"
+#include "mozilla/RefPtr.h"
+#include "nsISupportsImpl.h"
+#include "nsTArray.h"
+#include "nsTHashMap.h"
+
+namespace mozilla::dom {
+
+/**
+ * This enum is used to update controlled media state to the media controller in
+ * the chrome process.
+ * `eStarted`: media has successfully registered to the content media controller
+ * `ePlayed` : media has started playing
+ * `ePaused` : media has paused playing, but still can be resumed by content
+ * media controller
+ * `eStopped`: media has unregistered from the content media controller, we can
+ * not control it anymore
+ */
+enum class MediaPlaybackState : uint32_t {
+ eStarted,
+ ePlayed,
+ ePaused,
+ eStopped,
+};
+
+/**
+ * This enum is used to update controlled media audible audible state to the
+ * media controller in the chrome process.
+ */
+enum class MediaAudibleState : bool {
+ eInaudible = false,
+ eAudible = true,
+};
+
+/**
+ * MediaPlaybackStatus is an internal module for the media controller, it
+ * represents a tab's media related status, such like "does the tab contain any
+ * controlled media? is the tab playing? is the tab audible?".
+ *
+ * The reason we need this class is that we would like to encapsulate the
+ * details of determining the tab's media status. A tab can contains multiple
+ * browsing contexts, and each browsing context can have different media status.
+ * The final media status would be decided by checking all those context status.
+ *
+ * Use `UpdateMediaXXXState()` to update controlled media status, and use
+ * `IsXXX()` methods to acquire the playback status of the tab.
+ *
+ * As we know each context's audible state, we can decide which context should
+ * owns the audio focus when multiple contexts are all playing audible media at
+ * the same time. In that cases, the latest context that plays media would own
+ * the audio focus. When the context owning the audio focus is destroyed, we
+ * would see if there is another other context still playing audible media, and
+ * switch the audio focus to another context.
+ */
+class MediaPlaybackStatus final {
+ public:
+ void UpdateMediaPlaybackState(uint64_t aContextId, MediaPlaybackState aState);
+ void UpdateMediaAudibleState(uint64_t aContextId, MediaAudibleState aState);
+
+ bool IsPlaying() const;
+ bool IsAudible() const;
+ bool IsAnyMediaBeingControlled() const;
+
+ Maybe<uint64_t> GetAudioFocusOwnerContextId() const;
+
+ private:
+ /**
+ * This internal class stores detailed media status of controlled media for
+ * a browsing context.
+ */
+ class ContextMediaInfo final {
+ public:
+ explicit ContextMediaInfo(uint64_t aContextId) : mContextId(aContextId) {}
+ ~ContextMediaInfo() = default;
+
+ void IncreaseControlledMediaNum() {
+ MOZ_DIAGNOSTIC_ASSERT(mControlledMediaNum < UINT_MAX);
+ mControlledMediaNum++;
+ }
+ void DecreaseControlledMediaNum() {
+ MOZ_DIAGNOSTIC_ASSERT(mControlledMediaNum > 0);
+ mControlledMediaNum--;
+ }
+ void IncreasePlayingMediaNum() {
+ MOZ_DIAGNOSTIC_ASSERT(mPlayingMediaNum < mControlledMediaNum);
+ mPlayingMediaNum++;
+ }
+ void DecreasePlayingMediaNum() {
+ MOZ_DIAGNOSTIC_ASSERT(mPlayingMediaNum > 0);
+ mPlayingMediaNum--;
+ }
+ void IncreaseAudibleMediaNum() {
+ MOZ_DIAGNOSTIC_ASSERT(mAudibleMediaNum < mPlayingMediaNum);
+ mAudibleMediaNum++;
+ }
+ void DecreaseAudibleMediaNum() {
+ MOZ_DIAGNOSTIC_ASSERT(mAudibleMediaNum > 0);
+ mAudibleMediaNum--;
+ }
+ bool IsPlaying() const { return mPlayingMediaNum > 0; }
+ bool IsAudible() const { return mAudibleMediaNum > 0; }
+ bool IsAnyMediaBeingControlled() const { return mControlledMediaNum > 0; }
+ uint64_t Id() const { return mContextId; }
+
+ private:
+ /**
+ * The possible value for those three numbers should follow this rule,
+ * mControlledMediaNum >= mPlayingMediaNum >= mAudibleMediaNum
+ */
+ uint32_t mControlledMediaNum = 0;
+ uint32_t mAudibleMediaNum = 0;
+ uint32_t mPlayingMediaNum = 0;
+ uint64_t mContextId = 0;
+ };
+
+ ContextMediaInfo& GetNotNullContextInfo(uint64_t aContextId);
+ void DestroyContextInfo(uint64_t aContextId);
+
+ void ChooseNewContextToOwnAudioFocus();
+ void SetOwningAudioFocusContextId(Maybe<uint64_t>&& aContextId);
+ bool IsContextOwningAudioFocus(uint64_t aContextId) const;
+ bool ShouldRequestAudioFocusForInfo(const ContextMediaInfo& aInfo) const;
+ bool ShouldAbandonAudioFocusForInfo(const ContextMediaInfo& aInfo) const;
+
+ // This contains all the media status of browsing contexts within a tab.
+ nsTHashMap<uint64_t, UniquePtr<ContextMediaInfo>> mContextInfoMap;
+ Maybe<uint64_t> mOwningAudioFocusContextId;
+};
+
+} // namespace mozilla::dom
+
+#endif // DOM_MEDIA_MEDIACONTROL_MEDIAPLAYBACKSTATUS_H_