Implemented a simple collision hash table.

collider.cpp

@@ -0,0 +1,38 @@
+#include "collider.hpp"
+
+using DinkyECS::Entity;
+
+void SpatialHashTable::insert(Point pos, Entity ent) {
+  table[pos] = ent;
+}
+
+void SpatialHashTable::remove(Point pos) {
+  table.erase(pos);
+}
+
+void SpatialHashTable::move(Point from, Point to, Entity ent) {
+  remove(from);
+  insert(to, ent);
+}
+
+bool SpatialHashTable::occupied(Point at) {
+  return table[at];
+}
+
+std::tuple<bool, FoundList> SpatialHashTable::neighbors(Point cell) {
+  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);
+      }
+    }
+  }
+
+  return std::tuple(!result.empty(), result);
+}