#ifndef GRID_CACHE_H_67BBE74D
#define GRID_CACHE_H_67BBE74D

#include <unordered_map>
#include <unordered_set>
#include "level.h"

template <typename T>
class GridCache {
public:

  explicit GridCache(const Level& level) : width_(level.getSize().w())
  {
  }

  void set(T value, vec2s pos)
  {
    if (reverse_.count(value))
    {
      size_t oldPosIndex = reverse_.at(value);
      lookup_[oldPosIndex].erase(value);
    }

    size_t newPosIndex = getIndex(pos);
    lookup_[newPosIndex].insert(value);
    reverse_[value] = newPosIndex;
  }

  void remove(T value)
  {
    if (reverse_.count(value))
    {
      size_t index = reverse_.at(value);
      lookup_[index].erase(value);
      reverse_.erase(value);
    }
  }

  const std::unordered_set<T>& at(vec2s pos) const
  {
    size_t index = getIndex(pos);

    return lookup_[index];
  }

private:

  inline size_t getIndex(const vec2s& pos) const
  {
    return pos.x() + pos.y() * width_;
  }

  size_t width_;

  mutable std::unordered_map<size_t, std::unordered_set<T>> lookup_;
  std::unordered_map<T, size_t> reverse_;
};

#endif /* end of include guard: GRID_CACHE_H_67BBE74D */