[Reland][Extensions Bindings] Add support for filtered events

extensions/renderer/api_event_listeners.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef EXTENSIONS_RENDERER_API_EVENT_LISTENERS_H_
+#define EXTENSIONS_RENDERER_API_EVENT_LISTENERS_H_
+
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "extensions/common/value_counter.h"
+#include "extensions/renderer/api_binding_types.h"
+#include "v8/include/v8.h"
+
+namespace base {
+class DictionaryValue;
+}
+
+namespace extensions {
+class EventFilter;
+class EventFilteringInfo;
+
+// A base class to hold listeners for a given event. This allows for adding,
+// removing, and querying listeners in the list, and calling a callback when
+// transitioning from 0 -> 1 or 1 -> 0 listeners.
+class APIEventListeners {
+ public:
+  using ListenersUpdated =
+      base::Callback<void(binding::EventListenersChanged,
+                          const base::DictionaryValue* filter,
+                          v8::Local<v8::Context> context)>;
+
+  virtual ~APIEventListeners() = default;
+
+  // Adds the given |listener| to the list, possibly associating it with the
+  // given |filter|. Returns true if the listener is added. Populates |error|
+  // with any errors encountered. Note that |error| is *not* always populated
+  // if false is returned, since we don't consider trying to re-add a listener
+  // to be an error.
+  virtual bool AddListener(v8::Local<v8::Function> listener,
+                           v8::Local<v8::Object> filter,
+                           v8::Local<v8::Context> context,
+                           std::string* error) = 0;
+
+  // Removes the given |listener|, if it's present in the list.
+  virtual void RemoveListener(v8::Local<v8::Function> listener,
+                              v8::Local<v8::Context> context) = 0;
+
+  // Returns true if the given |listener| is in the list.
+  virtual bool HasListener(v8::Local<v8::Function> listener) = 0;
+
+  // Returns the number of listeners in the list.
+  virtual size_t GetNumListeners() = 0;
+
+  // Returns the listeners that should be notified for the given |filter|.
+  virtual std::vector<v8::Local<v8::Function>> GetListeners(
+      const EventFilteringInfo* filter,
+      v8::Local<v8::Context> context) = 0;
+
+  // Invalidates the list.
+  virtual void Invalidate(v8::Local<v8::Context> context) = 0;
+
+ protected:
+  APIEventListeners() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(APIEventListeners);
+};
+
+// A listener list implementation that doesn't support filtering. Each event
+// dispatched is dispatched to all the associated listeners.
+class UnfilteredEventListeners final : public APIEventListeners {
+ public:
+  UnfilteredEventListeners(const ListenersUpdated& listeners_updated);
+  ~UnfilteredEventListeners() override;
+
+  bool AddListener(v8::Local<v8::Function> listener,
+                   v8::Local<v8::Object> filter,
+                   v8::Local<v8::Context> context,
+                   std::string* error) override;
+  void RemoveListener(v8::Local<v8::Function> listener,
+                      v8::Local<v8::Context> context) override;
+  bool HasListener(v8::Local<v8::Function> listener) override;
+  size_t GetNumListeners() override;
+  std::vector<v8::Local<v8::Function>> GetListeners(
+      const EventFilteringInfo* filter,
+      v8::Local<v8::Context> context) override;
+  void Invalidate(v8::Local<v8::Context> context) override;
+
+ private:
+  // The event listeners associated with this event.
+  // TODO(devlin): Having these listeners held as v8::Globals means that we
+  // need to worry about cycles when a listener holds a reference to the event,
+  // e.g. EventEmitter -> Listener -> EventEmitter. Right now, we handle that by
+  // requiring Invalidate() to be called, but that means that events that aren't
+  // Invalidate()'d earlier can leak until context destruction. We could
+  // circumvent this by storing the listeners strongly in a private propery
+  // (thus traceable by v8), and optionally keep a weak cache on this object.
+  std::vector<v8::Global<v8::Function>> listeners_;
+
+  ListenersUpdated listeners_updated_;
+
+  DISALLOW_COPY_AND_ASSIGN(UnfilteredEventListeners);
+};
+
+// A listener list implementation that supports filtering. Events should only
+// be dispatched to those listeners whose filters match. Additionally, the
+// updated callback is triggered any time a listener with a new filter is
+// added, or the last listener with a given filter is removed.
+class FilteredEventListeners final : public APIEventListeners {
+ public:
+  FilteredEventListeners(const ListenersUpdated& listeners_updated,
+                         const std::string& event_name,
+                         EventFilter* event_filter);
+  ~FilteredEventListeners() override;
+
+  bool AddListener(v8::Local<v8::Function> listener,
+                   v8::Local<v8::Object> filter,
+                   v8::Local<v8::Context> context,
+                   std::string* error) override;
+  void RemoveListener(v8::Local<v8::Function> listener,
+                      v8::Local<v8::Context> context) override;
+  bool HasListener(v8::Local<v8::Function> listener) override;
+  size_t GetNumListeners() override;
+  std::vector<v8::Local<v8::Function>> GetListeners(
+      const EventFilteringInfo* filter,
+      v8::Local<v8::Context> context) override;
+  void Invalidate(v8::Local<v8::Context> context) override;
+
+ private:
+  struct ListenerData;
+
+  void InvalidateListener(const ListenerData& listener,
+                          v8::Local<v8::Context> context);
+
+  // Note: See TODO on UnfilteredEventListeners::listeners_.
+  std::vector<ListenerData> listeners_;
+
+  ListenersUpdated listeners_updated_;
+
+  std::string event_name_;
+
+  // The associated EventFilter; required to outlive this object.
+  EventFilter* event_filter_ = nullptr;
+
+  ValueCounter value_counter_;
+
+  DISALLOW_COPY_AND_ASSIGN(FilteredEventListeners);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_RENDERER_API_EVENT_LISTENERS_H_