Implemented a simple collision hash table.

tests/collider.cpp

@@ -0,0 +1,95 @@
+#include <catch2/catch_test_macros.hpp>
+#include <fmt/core.h>
+#include <string>
+#include "collider.hpp"
+#include "dinkyecs.hpp"
+
+using DinkyECS::Entity;
+using namespace fmt;
+
+TEST_CASE("confirm basic collision operations", "[collision]") {
+  DinkyECS::World world;
+  Entity player = world.entity();
+  Entity enemy = world.entity();
+
+  SpatialHashTable coltable;
+  coltable.insert({11,11}, player);
+  coltable.insert({21,21}, enemy);
+
+  { // not found
+    auto [found, nearby] = coltable.neighbors({1,1});
+    REQUIRE(!found);
+    REQUIRE(nearby.empty());
+  }
+
+  { // found
+    auto [found, nearby] = coltable.neighbors({10,10});
+
+    REQUIRE(found);
+    REQUIRE(nearby[0] == player);
+  }
+
+  { // removed
+    coltable.remove({11,11});
+    auto [found, nearby] = coltable.neighbors({10,10});
+    REQUIRE(!found);
+    REQUIRE(nearby.empty());
+  }
+
+  coltable.insert({11,11}, player); // setup for the move test
+
+  { // moving
+    coltable.move({11,11}, {12, 12}, player);
+    auto [found, nearby] = coltable.neighbors({10,10});
+    REQUIRE(!found);
+    REQUIRE(nearby.empty());
+  }
+
+  { // find it after move
+    auto [found, nearby] = coltable.neighbors({11,11});
+    REQUIRE(found);
+    REQUIRE(nearby[0] == player);
+  }
+
+  {
+    REQUIRE(coltable.occupied({12,12}));
+    REQUIRE(coltable.occupied({21,21}));
+    REQUIRE(!coltable.occupied({1,10}));
+  }
+}
+
+
+
+TEST_CASE("confirm multiple entities moving", "[collision]") {
+  DinkyECS::World world;
+  Entity player = world.entity();
+  Entity e1 = world.entity();
+  Entity e2 = world.entity();
+  Entity e3 = world.entity();
+
+  SpatialHashTable coltable;
+  coltable.insert({11,11}, player);
+  coltable.insert({10,10}, e2);
+  coltable.insert({11,10}, e3);
+  coltable.insert({21,21}, e1);
+
+  { // find e3 and e2
+    auto [found, nearby] = coltable.neighbors({11, 11});
+    REQUIRE(found);
+    REQUIRE(nearby.size() == 3);
+    // BUG: replace this with std::find/std::search
+    REQUIRE(nearby[0] == e2);
+    REQUIRE(nearby[1] == e3);
+    REQUIRE(nearby[2] == player);
+  }
+
+  coltable.move({11,11}, {20,20}, player);
+  { // should only find the e1
+    auto [found, nearby] = coltable.neighbors({20,20});
+    REQUIRE(found);
+    REQUIRE(nearby.size() == 2);
+    // BUG: replace this with std::find/std::search
+    REQUIRE(nearby[0] == player);
+    REQUIRE(nearby[1] == e1);
+  }
+}