roguish/collider.cpp

#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) const {
  return table.contains(at);
}

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;

  // 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);
}