File SelectionManager.h

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#pragma once

#include <algorithm>
#include <string>
#include <vector>
#include <unordered_set>

template<class _Base>
class SelectionManager
{
private:
    std::vector<_Base*> selected_objects;        
    _Base* hovered_object{ nullptr };            
    std::unordered_set<_Base*> _selection_cache; 

public:
    void Select(_Base* obj, bool increment)
    {
        if (obj == nullptr) return;

        if (increment) {
            auto idx = std::find(selected_objects.begin(), selected_objects.end(), obj);
            if (idx == selected_objects.end()) {
                selected_objects.push_back(obj);
                _selection_cache.insert(obj);
            }
            else {
                std::swap(*idx, selected_objects[selected_objects.size() - 1]);
            }
        }
        else {
            selected_objects.clear();
            selected_objects.push_back(obj);
            _selection_cache.clear();
            _selection_cache.insert(obj);
        }
    }

    void Deselect(_Base* obj, bool increment) {
        if (obj == nullptr) 
            return;

        auto idx = std::find(selected_objects.begin(), selected_objects.end(), obj);
        if (idx == selected_objects.end()) 
            return;
        selected_objects.erase(idx);
        _selection_cache.erase(obj);
    }

    _Base* GetActiveObject() const
    {
        if (selected_objects.empty())
            return nullptr;
        else
            return selected_objects[selected_objects.size() - 1];
    }

    _Base* GetSelectedObjects() const
    {
        if (selected_objects.empty())
            return nullptr;
        else
            return selected_objects[0];
    }

    bool IsSelected(_Base* obj) const
    {
        return _selection_cache.contains(obj);
    }
};