[GRC] Coordination Unit Graph Observer

services/resource_coordinator/coordination_unit/coordination_unit_impl.h

Index: services/resource_coordinator/coordination_unit/coordination_unit_impl.h
diff --git a/services/resource_coordinator/coordination_unit/coordination_unit_impl.h b/services/resource_coordinator/coordination_unit/coordination_unit_impl.h
index d8b3fe24fdb9721d8bb51e73513408e58d5bc720..fe3bc9bfb39d2d57b8f1caba58249530549e264b 100644
--- a/services/resource_coordinator/coordination_unit/coordination_unit_impl.h
+++ b/services/resource_coordinator/coordination_unit/coordination_unit_impl.h
@@ -11,19 +11,89 @@
 #include <unordered_map>
 #include <utility>
 
+#include <vector>
+#include "base/callback.h"
+
 #include "base/optional.h"
 #include "base/values.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "services/resource_coordinator/public/cpp/coordination_unit_id.h"
+#include "services/resource_coordinator/public/cpp/coordination_unit_types.h"
 #include "services/resource_coordinator/public/interfaces/coordination_unit.mojom.h"
 #include "services/resource_coordinator/public/interfaces/coordination_unit_provider.mojom.h"
 #include "services/service_manager/public/cpp/service_context_ref.h"
 
 namespace resource_coordinator {
 
+// Collection to manage CoordinationUnitEvent listeners.
+// It is naive prototype with lots of room for improvement.
+template <typename Listener, typename Filter>
+class CoordinationUnitEventListenerList {
+ public:
+  CoordinationUnitEventListenerList() = default;
+  ~CoordinationUnitEventListenerList() = default;
+
+  // callbacks paired with this kWildcardFilter will always be invoked
+  static const Filter kWildcardFilter = static_cast<Filter>(0);
+
+  void AddListener(Listener listener, Filter filter) {
+    listeners_.push_back(std::make_pair(filter, listener));
+  }
+
+  void AddListener(Listener listener) {
+    AddListener(listener, kWildcardFilter);
+  }
+
+  // Get the listeners who are are either registered to be invoked for a
+  // specific filter or were registered with the kWildcardFilter.
+  // TODO(matthalp) add iterator support to replace this call and
+  // avoid excessive copying that currently occurs
+  std::vector<Listener> GetListeners(Filter filter) {
+    std::vector<Listener> listeners;
+
+    for (auto& listener_info : listeners_) {
+      if (listener_info.first == filter ||
+          listener_info.first == kWildcardFilter) {
+        listeners.push_back(listener_info.second);
+      }
+    }
+
+    return listeners;
+  }
+
+  std::vector<Listener> GetListeners() { return GetListeners(kWildcardFilter); }

[zhenw, 2017/06/13 18:38:41]

There can be 2 ways to interpret this:
1. Get the listeners that do not have filter (the intended implementation).
2. Get all listeners. (My 1st impression was this one).

Maybe rename this function to be more specific.

[matthalp, 2017/06/13 20:57:11]

I see the ambiguity. I don't believe this method is used,
so it might just be a good idea to get rid of it and add
a comment to say that kWildcardFilter (or a better-named
variable) that gets all of the listeners without a filter.

Otherwise I can do GetListenersWithoutFilter.

+
+ private:
+  std::vector<std::pair<Filter, Listener>> listeners_;

[zhenw, 2017/06/13 18:38:41]

A map of vectors is probably more efficient.

[matthalp, 2017/06/13 20:57:11]

I can do this.

+
+  DISALLOW_COPY_AND_ASSIGN(CoordinationUnitEventListenerList);
+};
+
 class CoordinationUnitImpl : public mojom::CoordinationUnit {
+  typedef base::Callback<void(
+      const CoordinationUnitImpl* coordination_unit,
+      const CoordinationUnitImpl* child_coordination_unit)>
+      AddChildEventListener;

[zhenw, 2017/06/13 18:38:41]

Those should follow On*() style.

[matthalp, 2017/06/13 20:57:11]

I can do this.

+  typedef base::Callback<void(
+      const CoordinationUnitImpl* coordination_unit,
+      const CoordinationUnitImpl* parent_coordination_unit)>
+      AddParentEventListener;
+  typedef base::Callback<void(
+      const CoordinationUnitImpl* coordination_unit,
+      const CoordinationUnitImpl* removed_child_coordination_unit)>
+      RemoveChildEventListener;
+  typedef base::Callback<void(
+      const CoordinationUnitImpl* coordination_unit,
+      const CoordinationUnitImpl* removed_parent_coordination_unit)>
+      RemoveParentEventListener;
+  typedef base::Callback<void(const CoordinationUnitImpl* coordination_unit,
+                              mojom::PropertyType property)>
+      PropertyChangedEventListener;
+  typedef base::Callback<void(const CoordinationUnitImpl* coordination_unit)>
+      WillBeDestroyedEventListener;
+
  public:
   CoordinationUnitImpl(
       const CoordinationUnitID& id,
@@ -55,10 +125,45 @@ class CoordinationUnitImpl : public mojom::CoordinationUnit {
   // Clear property from internal key-value store
   void ClearProperty(mojom::PropertyType property);
   // Retrieve property from internal key-value store
-  base::Value GetProperty(mojom::PropertyType property);
+  base::Value GetProperty(mojom::PropertyType property) const;
   // Set property from internal key-value store
   void SetProperty(mojom::PropertyType property, base::Value value);
 
+  // Notify an instance it will be destroyed before its destructor is
+  // actually called.
+  void WillBeDestroyed();
+
+  CoordinationUnitEventListenerList<AddChildEventListener,
+                                    CoordinationUnitType>&
+  on_add_child_event_listeners() {
+    return on_add_child_event_listeners_;
+  }
+  CoordinationUnitEventListenerList<AddParentEventListener,
+                                    CoordinationUnitType>&
+  on_add_parent_event_listeners() {
+    return on_add_parent_event_listeners_;
+  }
+  CoordinationUnitEventListenerList<RemoveChildEventListener,
+                                    CoordinationUnitType>&
+  on_remove_child_event_listeners() {
+    return on_remove_child_event_listeners_;
+  }
+  CoordinationUnitEventListenerList<RemoveParentEventListener,
+                                    CoordinationUnitType>&
+  on_remove_parent_event_listeners() {
+    return on_remove_parent_event_listeners_;
+  }
+  CoordinationUnitEventListenerList<PropertyChangedEventListener,
+                                    mojom::PropertyType>&
+  on_property_changed_event_listeners() {
+    return on_property_changed_event_listeners_;
+  }
+  CoordinationUnitEventListenerList<WillBeDestroyedEventListener,
+                                    CoordinationUnitType>&
+  on_will_be_destroyed_event_listeners() {
+    return on_will_be_destroyed_event_listeners_;
+  }
+
  protected:
   const CoordinationUnitID id_;
   std::set<CoordinationUnitImpl*> children_;
@@ -93,6 +198,26 @@ class CoordinationUnitImpl : public mojom::CoordinationUnit {
 
   base::Optional<bool> state_flags_[kNumStateFlags];
 
+  CoordinationUnitEventListenerList<AddChildEventListener, CoordinationUnitType>
+      on_add_child_event_listeners_;
+  CoordinationUnitEventListenerList<AddParentEventListener,
+                                    CoordinationUnitType>
+      on_add_parent_event_listeners_;
+  CoordinationUnitEventListenerList<RemoveChildEventListener,
+                                    CoordinationUnitType>
+      on_remove_child_event_listeners_;
+  CoordinationUnitEventListenerList<RemoveParentEventListener,
+                                    CoordinationUnitType>
+      on_remove_parent_event_listeners_;
+  CoordinationUnitEventListenerList<PropertyChangedEventListener,
+                                    mojom::PropertyType>
+      on_property_changed_event_listeners_;
+  // There is nothing to filter WillBeDestroyedEventCallbacks on so the
+  // CoordinationUnitType is used as a filter placeholder
+  CoordinationUnitEventListenerList<WillBeDestroyedEventListener,
+                                    CoordinationUnitType>
+      on_will_be_destroyed_event_listeners_;
+
   DISALLOW_COPY_AND_ASSIGN(CoordinationUnitImpl);
 };