Now using a simple collision map to track entities and then determine if they're near the player for attacking.

collider.cpp

@@ -15,23 +15,32 @@ void SpatialHashTable::move(Point from, Point to, Entity ent) {
   insert(to, ent);
 }
 
-bool SpatialHashTable::occupied(Point at) {
-  return table[at];
+bool SpatialHashTable::occupied(Point at) const {
+  return table.contains(at);
 }
 
-std::tuple<bool, FoundList> SpatialHashTable::neighbors(Point cell) {
+inline void find_neighbor(const PointEntityMap &table, FoundList &result, Point at) {
+  auto it = table.find(at);
+  if (it != table.end()) {
+    result.insert(result.end(), it->second);
+  }
+}
+
+std::tuple<bool, FoundList> SpatialHashTable::neighbors(Point cell, bool diag) const {
   FoundList result;
 
-  // Check the current cell and its 8 neighbors
-  // BUG: this can sign underflow, assert it won't
-  for (size_t x = cell.x - 1; x <= cell.x + 1; x++) {
-    for (size_t y = cell.y - 1; y <= cell.y + 1; y++) {
-      Point neighborCell = {x, y};
-      auto it = table.find(neighborCell);
-      if (it != table.end()) {
-        result.insert(result.end(), it->second);
-      }
-    }
+  // just unroll the loop since we only check four directions
+  // this also solves the problem that it was detecting that the cell was automatically included as a "neighbor" but it's not
+  find_neighbor(table, result, {cell.x, cell.y+1}); // north
+  find_neighbor(table, result, {cell.x, cell.y-1}); // south
+  find_neighbor(table, result, {cell.x+1, cell.y}); // east
+  find_neighbor(table, result, {cell.x-1, cell.y}); // west
+  find_neighbor(table, result, {cell.x+1, cell.y-1}); // south east
+
+  if(diag) {
+    find_neighbor(table, result, {cell.x-1, cell.y-1}); // south west
+    find_neighbor(table, result, {cell.x+1, cell.y+1}); // north east
+    find_neighbor(table, result, {cell.x-1, cell.y+1}); // north west
   }
 
   return std::tuple(!result.empty(), result);

collider.hpp

@@ -12,21 +12,18 @@ struct PointHash {
 };
 
 typedef std::vector<DinkyECS::Entity> FoundList;
+typedef std::unordered_map<Point, DinkyECS::Entity, PointHash> PointEntityMap;
 
 class SpatialHashTable {
   public:
     SpatialHashTable() {}
 
-    // disable copying, I think?
-    SpatialHashTable(SpatialHashTable &other) = delete;
-
     void insert(Point pos, DinkyECS::Entity obj);
     void move(Point from, Point to, DinkyECS::Entity ent);
     void remove(Point pos);
-    bool occupied(Point pos);
-
-    std::tuple<bool, FoundList> neighbors(Point position);
+    bool occupied(Point pos) const;
+    std::tuple<bool, FoundList> neighbors(Point position, bool diag=false) const;
 
   private:
-    std::unordered_map<Point, DinkyECS::Entity, PointHash> table;
+    PointEntityMap table;
 };

gui.cpp

@@ -22,6 +22,7 @@
 #include "rand.hpp"
 #include "components.hpp"
 #include "systems.hpp"
+#include "collider.hpp"
 
 using std::string;
 using namespace fmt;
@@ -277,6 +278,9 @@ void GUI::configure_world() {
   ActionLog log{{"Welcome to the game!"}};
   $world.set<ActionLog>(log);
 
+  SpatialHashTable collider;
+  $world.set<SpatialHashTable>(collider);
+
   $world.assign<Position>(player.entity, {$game_map.place_entity(0)});
   $world.assign<Motion>(player.entity, {0, 0});
   $world.assign<Combat>(player.entity, {100, 10});
@@ -298,6 +302,8 @@ void GUI::configure_world() {
   $world.assign<Position>(gold, {$game_map.place_entity($game_map.room_count() - 1)});
   $world.assign<Treasure>(gold, {100});
   $world.assign<Tile>(gold, {"$"});
+
+  System::init_positions($world);
 }
 
 void GUI::render_scene() {

systems.cpp

@@ -3,6 +3,7 @@
 #include <string>
 #include <cmath>
 #include "rand.hpp"
+#include "collider.hpp"
 
 using std::string;
 using namespace fmt;
@@ -24,8 +25,17 @@ void System::enemy_pathing(DinkyECS::World &world, Map &game_map, Player &player
   game_map.clear_target(player_position.location);
 }
 
+void System::init_positions(DinkyECS::World &world) {
+  auto &collider = world.get<SpatialHashTable>();
+
+  world.system<Position>([&](const auto &ent, auto &pos) {
+      collider.insert(pos.location, ent);
+  });
+}
 
 void System::motion(DinkyECS::World &world, Map &game_map) {
+  auto &collider = world.get<SpatialHashTable>();
+
   world.system<Position, Motion>([&](const auto &ent, auto &position, auto &motion) {
     // don't process entities that don't move
     if(motion.dx != 0 || motion.dy != 0) {
@@ -36,8 +46,10 @@ void System::motion(DinkyECS::World &world, Map &game_map) {
       motion = {0,0}; // clear it after getting it
 
       if(game_map.inmap(move_to.x, move_to.y) &&
-          !game_map.iswall(move_to.x,move_to.y))
+          !game_map.iswall(move_to.x, move_to.y) &&
+          !collider.occupied(move_to))
       {
+        collider.move(position.location, move_to, ent);
         position.location = move_to;
       }
     }
@@ -46,25 +58,27 @@ void System::motion(DinkyECS::World &world, Map &game_map) {
 
 
 void System::combat(DinkyECS::World &world, Player &player) {
+  const auto& collider = world.get<SpatialHashTable>();
   const auto& player_position = world.component<Position>(player.entity);
   auto& player_combat = world.component<Combat>(player.entity);
   auto& log = world.get<ActionLog>();
 
-  world.system<Position, Combat>([&](const auto &ent, auto &pos, auto &combat) {
-      if(ent != player.entity) {
-        int dx = std::abs(int(pos.location.x) - int(player_position.location.x));
-        int dy = std::abs(int(pos.location.y) - int(player_position.location.y));
-
-        if(dx <= 1 && dy <= 1) {
-          if(player_combat.hp > -1) {
-            int dmg = Random::uniform<int>(1, combat.damage);
-            player_combat.hp -= dmg;
-
-            log.log(format("HIT! You took {} damage.", dmg));
-          }
-        }
+  // this is guaranteed to not return the given position
+  auto [found, nearby] = collider.neighbors(player_position.location);
+
+  if(found) {
+    for(auto entity : nearby) {
+      int attack = Random::uniform<int>(0,1);
+      if(attack) {
+        const auto& enemy_dmg = world.component<Combat>(entity);
+        int dmg = Random::uniform<int>(1, enemy_dmg.damage);
+        player_combat.hp -= dmg;
+        log.log(format("HIT! You took {} damage.", dmg));
+      } else {
+        log.log("You dodged! Run!");
       }
-  });
+    }
+  }
 };
 
 void System::draw_entities(DinkyECS::World &world, Map &game_map, ftxui::Canvas &canvas, const Point &cam_orig, size_t view_x, size_t view_y) {

systems.hpp

@@ -12,4 +12,5 @@ namespace System {
   void enemy_pathing(DinkyECS::World &world, Map &game_map, Player &player);
   void draw_map(DinkyECS::World &world, Map &game_map, ftxui::Canvas &canvas, size_t view_x, size_t view_y);
   void draw_entities(DinkyECS::World &world, Map &game_map, ftxui::Canvas &canvas, const Point &cam_orig, size_t view_x, size_t view_y);
+  void init_positions(DinkyECS::World &world);
 }

tests/collider.cpp

@@ -23,7 +23,7 @@ TEST_CASE("confirm basic collision operations", "[collision]") {
   }
 
   { // found
-    auto [found, nearby] = coltable.neighbors({10,10});
+    auto [found, nearby] = coltable.neighbors({10,10}, true);
 
     REQUIRE(found);
     REQUIRE(nearby[0] == player);
@@ -31,7 +31,7 @@ TEST_CASE("confirm basic collision operations", "[collision]") {
 
   { // removed
     coltable.remove({11,11});
-    auto [found, nearby] = coltable.neighbors({10,10});
+    auto [found, nearby] = coltable.neighbors({10,10}, true);
     REQUIRE(!found);
     REQUIRE(nearby.empty());
   }
@@ -40,13 +40,13 @@ TEST_CASE("confirm basic collision operations", "[collision]") {
 
   { // moving
     coltable.move({11,11}, {12, 12}, player);
-    auto [found, nearby] = coltable.neighbors({10,10});
+    auto [found, nearby] = coltable.neighbors({10,10}, true);
     REQUIRE(!found);
     REQUIRE(nearby.empty());
   }
 
   { // find it after move
-    auto [found, nearby] = coltable.neighbors({11,11});
+    auto [found, nearby] = coltable.neighbors({11,11}, true);
     REQUIRE(found);
     REQUIRE(nearby[0] == player);
   }
@@ -59,7 +59,6 @@ TEST_CASE("confirm basic collision operations", "[collision]") {
 }
 
 
-
 TEST_CASE("confirm multiple entities moving", "[collision]") {
   DinkyECS::World world;
   Entity player = world.entity();
@@ -74,22 +73,20 @@ TEST_CASE("confirm multiple entities moving", "[collision]") {
   coltable.insert({21,21}, e1);
 
   { // find e3 and e2
-    auto [found, nearby] = coltable.neighbors({11, 11});
+    auto [found, nearby] = coltable.neighbors({11, 11}, true);
     REQUIRE(found);
-    REQUIRE(nearby.size() == 3);
+    REQUIRE(nearby.size() == 2);
     // BUG: replace this with std::find/std::search
-    REQUIRE(nearby[0] == e2);
-    REQUIRE(nearby[1] == e3);
-    REQUIRE(nearby[2] == player);
+    REQUIRE(nearby[0] == e3);
+    REQUIRE(nearby[1] == e2);
   }
 
   coltable.move({11,11}, {20,20}, player);
   { // should only find the e1
-    auto [found, nearby] = coltable.neighbors({20,20});
+    auto [found, nearby] = coltable.neighbors({20,20}, true);
     REQUIRE(found);
-    REQUIRE(nearby.size() == 2);
+    REQUIRE(nearby.size() == 1);
     // BUG: replace this with std::find/std::search
-    REQUIRE(nearby[0] == player);
-    REQUIRE(nearby[1] == e1);
+    REQUIRE(nearby[0] == e1);
   }
 }