Refactor sorting path cache

It'll be easier to experiment on with the cache storage abstracted away.

src/api/sorting/plugin_graph.cpp

@@ -115,8 +115,14 @@ std::string describeEdgeType(EdgeType edgeType) {
   }
 }
 
-bool operator==(const GraphPath& lhs, const GraphPath& rhs) {
-  return lhs.from == rhs.from && lhs.to == rhs.to;
+bool PathsCache::IsPathCached(const vertex_t& fromVertex,
+                              const vertex_t& toVertex) const {
+  return pathsCache_.count({fromVertex, toVertex});
+}
+
+void PathsCache::CachePath(const vertex_t& fromVertex,
+                           const vertex_t& toVertex) {
+  pathsCache_.insert({fromVertex, toVertex});
 }
 
 size_t PluginGraph::CountVertices() const {
@@ -306,7 +312,7 @@ void PluginGraph::CheckForCycles() const {
 
 bool PluginGraph::PathExists(const vertex_t& fromVertex,
                              const vertex_t& toVertex) {
-  if (pathsCache_.count(GraphPath{fromVertex, toVertex}) != 0) {
+  if (pathsCache_.IsPathCached(fromVertex, toVertex)) {
     return true;
   }
 
@@ -330,7 +336,7 @@ bool PluginGraph::PathExists(const vertex_t& fromVertex,
       for (const auto adjacentV :
            boost::make_iterator_range(boost::adjacent_vertices(v, graph_))) {
         if (forwardVisited.count(adjacentV) == 0) {
-          pathsCache_.insert(GraphPath{fromVertex, adjacentV});
+          pathsCache_.CachePath(fromVertex, adjacentV);
 
           forwardVisited.insert(adjacentV);
           forwardQueue.push(adjacentV);
@@ -346,7 +352,7 @@ bool PluginGraph::PathExists(const vertex_t& fromVertex,
       for (const auto adjacentV : boost::make_iterator_range(
                boost::inv_adjacent_vertices(v, graph_))) {
         if (reverseVisited.count(adjacentV) == 0) {
-          pathsCache_.insert(GraphPath{adjacentV, toVertex});
+          pathsCache_.CachePath(adjacentV, toVertex);
 
           reverseVisited.insert(adjacentV);
           reverseQueue.push(adjacentV);
@@ -361,9 +367,7 @@ bool PluginGraph::PathExists(const vertex_t& fromVertex,
 void PluginGraph::AddEdge(const vertex_t& fromVertex,
                           const vertex_t& toVertex,
                           EdgeType edgeType) {
-  const auto graphPath = GraphPath{fromVertex, toVertex};
-
-  if (pathsCache_.count(graphPath) != 0) {
+  if (pathsCache_.IsPathCached(fromVertex, toVertex)) {
     return;
   }
 
@@ -376,7 +380,7 @@ void PluginGraph::AddEdge(const vertex_t& fromVertex,
   }
 
   boost::add_edge(fromVertex, toVertex, edgeType, graph_);
-  pathsCache_.insert(graphPath);
+  pathsCache_.CachePath(fromVertex, toVertex);
 }
 
 void PluginGraph::AddHardcodedPluginEdges(Game& game) {

src/api/sorting/plugin_graph.h

@@ -39,6 +39,19 @@
 #include "api/sorting/plugin_sorting_data.h"
 #include "loot/exception/cyclic_interaction_error.h"
 
+namespace std {
+template<typename A, typename B>
+struct hash<pair<A, B>> {
+  size_t operator()(const pair<A, B>& pair) const {
+    size_t seed = 0;
+    boost::hash_combine(seed, pair.first);
+    boost::hash_combine(seed, pair.second);
+
+    return seed;
+  }
+};
+}
+
 namespace loot {
 typedef boost::adjacency_list<boost::listS,
                               boost::listS,
@@ -52,28 +65,15 @@ typedef boost::associative_property_map<std::map<vertex_t, size_t>>
 
 std::string describeEdgeType(EdgeType edgeType);
 
-struct GraphPath {
-  vertex_t from;
-  vertex_t to;
+class PathsCache {
+public:
+  bool IsPathCached(const vertex_t& fromVertex, const vertex_t& toVertex) const;
+  void CachePath(const vertex_t& fromVertex, const vertex_t& toVertex);
+
+private:
+  std::unordered_set<std::pair<vertex_t, vertex_t>> pathsCache_;
 };
 
-bool operator==(const GraphPath& lhs, const GraphPath& rhs);
-}
-
-namespace std {
-template<>
-struct hash<loot::GraphPath> {
-  size_t operator()(const loot::GraphPath& graphPath) const {
-    size_t seed = 0;
-    boost::hash_combine(seed, graphPath.from);
-    boost::hash_combine(seed, graphPath.to);
-
-    return seed;
-  }
-};
-}
-
-namespace loot {
 class PluginGraph {
 public:
   size_t CountVertices() const;
@@ -97,7 +97,7 @@ private:
                EdgeType edgeType);
 
   RawPluginGraph graph_;
-  std::unordered_set<GraphPath> pathsCache_;
+  PathsCache pathsCache_;
 };
 }