FileLoaderRegistry.h

#ifndef MANTID_API_FILELOADERREGISTRY_H_
#define MANTID_API_FILELOADERREGISTRY_H_

#include "MantidAPI/AlgorithmFactory.h"
#include "MantidAPI/IFileLoader.h"
#include "MantidKernel/SingletonHolder.h"

#ifndef Q_MOC_RUN
#include <type_traits>
#endif

#include <map>
#include <string>
#include <vector>

namespace Mantid {
// Forward declaration
namespace Kernel {
class Logger;
}
namespace API {
// Forward declaration
class IAlgorithm;

/**
Keeps a registry of algorithm's that are file loading algorithms to allow them
to be searched
to find the correct one to load a particular file.

A macro, DECLARE_FILELOADER_ALGORITHM is defined in RegisterFileLoader.h. Use
this in place of the standard
DECLARE_ALGORITHM macro

Copyright &copy; 2013 ISIS Rutherford Appleton Laboratory, NScD Oak Ridge
National Laboratory & European Spallation Source

This file is part of Mantid.

Mantid 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; either version 3 of the License, or
(at your option) any later version.

Mantid 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 this program.  If not, see <http://www.gnu.org/licenses/>.

File change history is stored at: <https://github.com/mantidproject/mantid>
Code Documentation is available at: <http://doxygen.mantidproject.org>
 */
class MANTID_API_DLL FileLoaderRegistryImpl {
public:
  /// Defines types of possible file
  enum LoaderFormat { Nexus, Generic };

public:
  /// @returns the number of entries in the registry
  inline size_t size() const { return m_totalSize; }

  /**
   * Registers a loader whose format is one of the known formats given in
   * LoaderFormat. It
   * also passes this registration on to the AlgorithmFactory so that it can be
   * created.
   * The template type should be the class being registered. The name is taken
   * from the string
   * returned by the name() method on the object.
   * @param format The type of loader being subscribed, see LoaderFormat
   * @throws std::invalid_argument if an entry with this name already exists
   */
  template <typename Type> void subscribe(LoaderFormat format) {
    SubscriptionValidator<Type>::check(format);
    const auto nameVersion = AlgorithmFactory::Instance().subscribe<Type>();
    // If the factory didn't throw then the name is valid
    m_names[format].insert(nameVersion);
    m_totalSize += 1;
    m_log.debug() << "Registered '" << nameVersion.first << "' version '"
                  << nameVersion.second << "' as file loader\n";
  }

  /// Unsubscribe a named algorithm and version from the loader registration
  void unsubscribe(const std::string &name, const int version = -1);

  /// Returns the name of an Algorithm that can load the given filename
  const boost::shared_ptr<IAlgorithm>
  chooseLoader(const std::string &filename) const;
  /// Checks whether the given algorithm can load the file
  bool canLoad(const std::string &algorithmName,
               const std::string &filename) const;

private:
  /// Friend so that CreateUsingNew
  friend struct Mantid::Kernel::CreateUsingNew<FileLoaderRegistryImpl>;

  /// Default constructor (for singleton)
  FileLoaderRegistryImpl();
  /// Destructor
  ~FileLoaderRegistryImpl();

  /// Helper for subscribe to check base class
  template <typename T> struct SubscriptionValidator {
    static void check(LoaderFormat format) {
      switch (format) {
      case Nexus:
        if (!std::is_base_of<IFileLoader<Kernel::NexusDescriptor>,
                               T>::value) {
          throw std::runtime_error(
              std::string("FileLoaderRegistryImpl::subscribe - Class '") +
              typeid(T).name() + "' registered as Nexus loader but it does not "
                                 "inherit from "
                                 "API::IFileLoader<Kernel::NexusDescriptor>");
        }
        break;
      case Generic:
        if (!std::is_base_of<IFileLoader<Kernel::FileDescriptor>, T>::value) {
          throw std::runtime_error(
              std::string("FileLoaderRegistryImpl::subscribe - Class '") +
              typeid(T).name() + "' registered as Generic loader but it does "
                                 "not inherit from "
                                 "API::IFileLoader<Kernel::FileDescriptor>");
        }
        break;
      default:
        throw std::runtime_error("Invalid LoaderFormat given");
      }
    }
  };

  /// Remove a named algorithm & version from the given map
  void removeAlgorithm(const std::string &name, const int version,
                       std::multimap<std::string, int> &typedLoaders);

  /// The list of names. The index pointed to by LoaderFormat defines a set for
  /// that format
  std::vector<std::multimap<std::string, int>> m_names;
  /// Total number of names registered
  size_t m_totalSize;

  /// Reference to a logger
  mutable Kernel::Logger m_log;
};

/// Type for the actual singleton instance
typedef Mantid::Kernel::SingletonHolder<FileLoaderRegistryImpl>
    FileLoaderRegistry;

} // namespace API
} // namespace Mantid

namespace Mantid {
namespace Kernel {
EXTERN_MANTID_API template class MANTID_API_DLL
    Mantid::Kernel::SingletonHolder<Mantid::API::FileLoaderRegistryImpl>;
}
}

#endif /* MANTID_API_FILELOADERREGISTRY_H_ */