Make DependencyGroup::State an enum

The previous struct used two bools to represent three useful states. Make this
more explicit by having these three states as an enum.

lib/icinga/checkable-dependency.cpp

@@ -206,7 +206,7 @@ bool Checkable::IsReachable(DependencyType dt, int rstack) const
 	}
 
 	for (auto& dependencyGroup : GetDependencyGroups()) {
-		if (auto state(dependencyGroup->GetState(this, dt, rstack + 1)); !state.Reachable || !state.OK) {
+		if (auto state(dependencyGroup->GetState(this, dt, rstack + 1)); state != DependencyGroup::State::Ok) {
 			Log(LogDebug, "Checkable")
 				<< "Dependency group '" << dependencyGroup->GetRedundancyGroupName() << "' have failed for checkable '"
 				<< GetName() << "': Marking as unreachable.";

lib/icinga/dependency-group.cpp

@@ -325,14 +325,24 @@ DependencyGroup::State DependencyGroup::GetState(const Checkable* child, Depende
 
 	if (IsRedundancyGroup()) {
 		// The state of a redundancy group is determined by the best state of any parent. If any parent ist reachable,
-		// the redundancy group is reachable, analogously for availability. Note that an unreachable group cannot be
+		// the redundancy group is reachable, analogously for availability.
-		// available as reachable = 0 implies available = 0.
+		if (reachable == 0) {
-		return {reachable > 0, available > 0};
+			return State::Unreachable;
+		} else if (available == 0) {
+			return State::Failed;
+		} else {
+			return State::Ok;
+		}
 	} else {
 		// For dependencies without a redundancy group, dependencies.size() will be 1 in almost all cases. It will only
 		// contain more elements if there are duplicate dependency config objects between two checkables. In this case,
-		// all of them have to be reachable or available as they don't provide redundancy. Note that unreachable implies
+		// all of them have to be reachable/available as they don't provide redundancy.
-		// unavailable here as well as only reachable parents count towards the number of available parents.
+		if (reachable < dependencies.size()) {
-		return {reachable == dependencies.size(), available == dependencies.size()};
+			return State::Unreachable;
+		} else if (available < dependencies.size()) {
+			return State::Failed;
+		} else {
+			return State::Ok;
+		}
 	}
 }

lib/icinga/dependency.hpp

@@ -163,12 +163,7 @@ public:
 	const String& GetRedundancyGroupName() const;
 	String GetCompositeKey();
 
-	struct State
+	enum class State { Ok, Failed, Unreachable };
-	{
-		bool Reachable; // Whether the dependency group is reachable.
-		bool OK; // Whether the dependency group is reachable and OK.
-	};
-
 	State GetState(const Checkable* child, DependencyType dt = DependencyState, int rstack = 0) const;
 
 	static boost::signals2::signal<void(const Checkable::Ptr&, const DependencyGroup::Ptr&)> OnChildRegistered;

lib/icingadb/icingadb-utility.cpp

@@ -213,8 +213,8 @@ Dictionary::Ptr IcingaDB::SerializeRedundancyGroupState(const Checkable::Ptr& ch
 		{"id", redundancyGroup->GetIcingaDBIdentifier()},
 		{"environment_id", m_EnvironmentId},
 		{"redundancy_group_id", redundancyGroup->GetIcingaDBIdentifier()},
-		{"failed", !state.Reachable || !state.OK},
+		{"failed", state != DependencyGroup::State::Ok},
-		{"is_reachable", state.Reachable},
+		{"is_reachable", state != DependencyGroup::State::Unreachable},
 		{"last_state_change", TimestampToMilliseconds(Utility::GetTime())},
 	};
 }