provider_manager.h

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

 
#ifndef PROVIDER_MANAGER_H
#define PROVIDER_MANAGER_H

template <typename TProviderType>
class ProviderManager {
public:
  /* Avoid copying this object; it is a singleton object. */
  ProviderManager(ProviderManager const &) = delete;
 
  ProviderManager &operator=(ProviderManager const &) = delete;
 
  static void Register(const TProviderType &instance)
  {
    /* Insert according to comparator. */
    auto &providers = GetProviders();
    auto it = std::ranges::lower_bound(providers, &instance, typename TProviderType::ProviderSorter());
    providers.insert(it, &instance);
  }
 
  static void Unregister(const TProviderType &instance)
  {
    auto &providers = GetProviders();
    providers.erase(std::find(std::begin(providers), std::end(providers), &instance));
  }

  static std::vector<const TProviderType *> &GetProviders()
  {
    static std::vector<const TProviderType *> providers{};
    return providers;
  }
};
 
template <typename T>
class BaseProvider {
public:
  constexpr BaseProvider(std::string_view name, std::string_view description) : name(name), description(description) {}
  virtual ~BaseProvider() = default;
 
  inline std::string_view GetName() const { return this->name; }
  inline std::string_view GetDescription() const { return this->description; }

  struct ProviderSorter {
    bool operator()(const T *a, const T *b) const
    {
      if (a->GetName() == b->GetName()) return a < b;
      return a->GetName() < b->GetName();
    }
  };
 
protected:
  const std::string_view name;
  const std::string_view description;
};
 
template <typename T>
class PriorityBaseProvider : public BaseProvider<T> {
public:
  constexpr PriorityBaseProvider(std::string_view name, std::string_view description, int priority) : BaseProvider<T>(name, description), priority(priority) {}
 
  inline int GetPriority() const { return this->priority; }

  struct ProviderSorter {
    bool operator()(const T *a, const T *b) const
    {
      if (a->GetPriority() == b->GetPriority()) return a < b;
      return a->GetPriority() < b->GetPriority();
    }
  };
 
protected:
  const int priority;
};
 
#endif /* PROVIDER_MANAGER_H */