/*
 * Software License Agreement (BSD License)
 *
 * Copyright (c) 2012, Willow Garage, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
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 *     * Neither the name of the copyright holders nor the names of its
 *       contributors may be used to endorse or promote products derived from
 *       this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 */

#ifndef CLASS_LOADER__CLASS_LOADER_CORE_HPP_
#define CLASS_LOADER__CLASS_LOADER_CORE_HPP_

#include <cstddef>
#include <cstdio>
#include <functional>
#include <map>
#include <memory>
#include <mutex>
#include <string>
#include <typeinfo>
#include <utility>
#include <vector>

// TODO(mikaelarguedas) remove this once console_bridge complies with this
// see https://github.com/ros/console_bridge/issues/55
#ifdef __clang__
# pragma clang diagnostic push
# pragma clang diagnostic ignored "-Wgnu-zero-variadic-macro-arguments"
#endif
#include "console_bridge/console.h"
#ifdef __clang__
# pragma clang diagnostic pop
#endif

#include "class_loader/exceptions.hpp"
#include "class_loader/meta_object.hpp"
#include "class_loader/visibility_control.hpp"

#include "rcpputils/shared_library.hpp"

/**
 * @note This header file is the internal implementation of the plugin system which is exposed
 * via the ClassLoader class
 */

namespace class_loader
{

class ClassLoader;  // Forward declaration

namespace impl
{

// Typedefs
typedef std::string LibraryPath;
typedef std::string ClassName;
typedef std::string BaseClassName;
typedef std::map<ClassName, impl::AbstractMetaObjectBase *> FactoryMap;
typedef std::map<BaseClassName, FactoryMap> BaseToFactoryMapMap;
typedef std::pair<LibraryPath, std::shared_ptr<rcpputils::SharedLibrary>> LibraryPair;
typedef std::vector<LibraryPair> LibraryVector;
typedef std::vector<AbstractMetaObjectBase *> MetaObjectVector;
class MetaObjectGraveyardVector : public MetaObjectVector
{
public:
  ~MetaObjectGraveyardVector()
  {
    // Make sure not to access the pointer value in the static variable of `getMetaObjectGraveyard()
    // when destroying `meta_object` in the unique_ptr deleter. Because the static variable in
    // `getMetaObjectGraveyard()` can be destructed before the static variable
    // `g_register_plugin_ ## UniqueID` in some circumstances.
    // NOTE of the vector dtor in the STL: if the elements themselves are pointers, the pointed-to
    // memory is not touched in any way.  Managing the pointer is the user's responsibility.
    clear();
  }
};

CLASS_LOADER_PUBLIC
void printDebugInfoToScreen();

// Global storage

/**
 * @brief Gets a handle to a global data structure that holds a map of base class names (Base class
 * describes plugin interface) to a FactoryMap which holds the factories for the various different
 * concrete classes that can be instantiated. Note that the Base class is NOT THE LITERAL CLASSNAME,
 * but rather the result of typeid(Base).name() which sometimes is the literal class name
 * (as on Windows) but is often in mangled form (as on Linux).
 *
 * @return A reference to the global base to factory map
 */
CLASS_LOADER_PUBLIC
BaseToFactoryMapMap & getGlobalPluginBaseToFactoryMapMap();

/**
 * @brief Gets a handle to a list of open libraries in the form of LibraryPairs which encode the
 * library path+name and the handle to the underlying shared library
 *
 * @return A reference to the global vector that tracks loaded libraries
 */
CLASS_LOADER_PUBLIC
LibraryVector & getLoadedLibraryVector();

/**
 * @brief When a library is being loaded, in order for factories to know which library they are
 * being associated with, they use this function to query which library is being loaded.
 *
 * @return The currently set loading library name as a string
 */
CLASS_LOADER_PUBLIC
std::string getCurrentlyLoadingLibraryName();

/**
 * @brief When a library is being loaded, in order for factories to know which library they are
 * being associated with, this function is called to set the name of the library currently being loaded.
 * @param library_name - The name of library that is being loaded currently
 */
CLASS_LOADER_PUBLIC
void setCurrentlyLoadingLibraryName(const std::string & library_name);


/**
 * @brief Gets the ClassLoader currently in scope which used when a library is being loaded.
 * @return A pointer to the currently active ClassLoader.
 */
CLASS_LOADER_PUBLIC
ClassLoader * getCurrentlyActiveClassLoader();

/**
 * @brief Sets the ClassLoader currently in scope which used when a library is being loaded.
 *
 * @param loader - pointer to the currently active ClassLoader.
 */
CLASS_LOADER_PUBLIC
void setCurrentlyActiveClassLoader(ClassLoader * loader);


/**
 * @brief This function extracts a reference to the FactoryMap for appropriate base class out of
 *   the global plugin base to factory map. This function should be used by functions in this
 *   namespace that need to access the various factories so as to make sure the right key is
 *   generated to index into the global map.
 *
 * @return A reference to the FactoryMap contained within the global Base-to-FactoryMap map.
 */
CLASS_LOADER_PUBLIC
FactoryMap & getFactoryMapForBaseClass(const std::string & typeid_base_class_name);

/**
 * @brief Same as above but uses a type parameter instead of string for more safety if info is available.
 *
 * @return A reference to the FactoryMap contained within the global Base-to-FactoryMap map.
 */
template<typename Base>
FactoryMap & getFactoryMapForBaseClass()
{
  return getFactoryMapForBaseClass(typeid(Base).name());
}

/**
 * @brief Gets a handle to a list of meta object of graveyard.
 *
 * @return A reference to the MetaObjectGraveyardVector contained within the meta object of graveyard.
 */
CLASS_LOADER_PUBLIC
MetaObjectGraveyardVector & getMetaObjectGraveyard();

/**
 * @brief To provide thread safety, all exposed plugin functions can only be run serially by multiple threads.
 *
 *  This is implemented by using critical sections enforced by a single mutex which is locked and
 *  released with the following two functions.
 *
 * @return A reference to the global mutex
 */
CLASS_LOADER_PUBLIC
std::recursive_mutex & getLoadedLibraryVectorMutex();
CLASS_LOADER_PUBLIC
std::recursive_mutex & getPluginBaseToFactoryMapMapMutex();

/**
 * @brief Indicates if a library containing more than just plugins has been opened by the running process
 *
 * @return True if a non-pure plugin library has been opened, otherwise false
 */
CLASS_LOADER_PUBLIC
bool hasANonPurePluginLibraryBeenOpened();

/**
 * @brief Sets a flag indicating if a library containing more than just plugins has been opened by the running process
 *
 * @param hasIt - The flag
 */
CLASS_LOADER_PUBLIC
void hasANonPurePluginLibraryBeenOpened(bool hasIt);

template<typename Base>
using DeleterType = std::function<void (Base *)>;

template<typename Base>
using UniquePtr = std::unique_ptr<Base, DeleterType<Base>>;

// Plugin Functions

/**
 * @brief This function is called by the CLASS_LOADER_REGISTER_CLASS macro in plugin_register_macro.h to register factories.
 * Classes that use that macro will cause this function to be invoked when the library is loaded.
 * The function will create a MetaObject (i.e. factory) for the corresponding Derived class and
 * insert it into the appropriate FactoryMap in the global Base-to-FactoryMap map.
 * Note that the passed class_name is the literal class name and not the mangled version.
 *
 * @param Derived - parameteric type indicating concrete type of plugin
 * @param Base - parameteric type indicating base type of plugin
 * @param class_name - the literal name of the class being registered (NOT MANGLED)
 * @return A class_loader::impl::UniquePtr<AbstractMetaObjectBase> to newly created meta object.
 */
template<typename Derived, typename Base>
UniquePtr<AbstractMetaObjectBase>
registerPlugin(const std::string & class_name, const std::string & base_class_name)
{
  // Note: This function will be automatically invoked when a dlopen() call
  // opens a library. Normally it will happen within the scope of loadLibrary(),
  // but that may not be guaranteed.
  CONSOLE_BRIDGE_logDebug(
    "class_loader.impl: "
    "Registering plugin factory for class = %s, ClassLoader* = %p and library name %s.",
    class_name.c_str(), getCurrentlyActiveClassLoader(),
    getCurrentlyLoadingLibraryName().c_str());

  if (nullptr == getCurrentlyActiveClassLoader()) {
    CONSOLE_BRIDGE_logDebug(
      "%s",
      "class_loader.impl: ALERT!!! "
      "A library containing plugins has been opened through a means other than through the "
      "class_loader or pluginlib package. "
      "This can happen if you build plugin libraries that contain more than just plugins "
      "(i.e. normal code your app links against). "
      "This inherently will trigger a dlopen() prior to main() and cause problems as class_loader "
      "is not aware of plugin factories that autoregister under the hood. "
      "The class_loader package can compensate, but you may run into namespace collision problems "
      "(e.g. if you have the same plugin class in two different libraries and you load them both "
      "at the same time). "
      "The biggest problem is that library can now no longer be safely unloaded as the "
      "ClassLoader does not know when non-plugin code is still in use. "
      "In fact, no ClassLoader instance in your application will be unable to unload any library "
      "once a non-pure one has been opened. "
      "Please refactor your code to isolate plugins into their own libraries.");
    hasANonPurePluginLibraryBeenOpened(true);
  }

  // Create factory
  UniquePtr<AbstractMetaObjectBase> new_factory(
    new impl::MetaObject<Derived, Base>(class_name, base_class_name),
    [](AbstractMetaObjectBase * p) {
      getPluginBaseToFactoryMapMapMutex().lock();
      MetaObjectGraveyardVector & graveyard = getMetaObjectGraveyard();
      for (auto iter = graveyard.begin(); iter != graveyard.end(); ++iter) {
        if (*iter == p) {
          graveyard.erase(iter);
          break;
        }
      }

      BaseToFactoryMapMap & factory_map_map = getGlobalPluginBaseToFactoryMapMap();
      bool erase_flag = false;
      for (auto & factory_map_item : factory_map_map) {
        FactoryMap & factory_map = factory_map_item.second;
        for (auto iter = factory_map.begin(); iter != factory_map.end(); ++iter) {
          if (iter->second == p) {
            factory_map.erase(iter);
            erase_flag = true;
            break;
          }
        }
        if (erase_flag) {
          break;
        }
      }

      getPluginBaseToFactoryMapMapMutex().unlock();

#ifndef _WIN32
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdelete-non-virtual-dtor"
#endif
      delete (p);  // Note: This is the only place where metaobjects can be destroyed
#ifndef _WIN32
#pragma GCC diagnostic pop
#endif
    });
  new_factory->addOwningClassLoader(getCurrentlyActiveClassLoader());
  new_factory->setAssociatedLibraryPath(getCurrentlyLoadingLibraryName());


  // Add it to global factory map map
  getPluginBaseToFactoryMapMapMutex().lock();
  FactoryMap & factoryMap = getFactoryMapForBaseClass<Base>();
  if (factoryMap.find(class_name) != factoryMap.end()) {
    CONSOLE_BRIDGE_logWarn(
      "class_loader.impl: SEVERE WARNING!!! "
      "A namespace collision has occurred with plugin factory for class %s. "
      "New factory will OVERWRITE existing one. "
      "This situation occurs when libraries containing plugins are directly linked against an "
      "executable (the one running right now generating this message). "
      "Please separate plugins out into their own library or just don't link against the library "
      "and use either class_loader::ClassLoader/MultiLibraryClassLoader to open.",
      class_name.c_str());
  }
  factoryMap[class_name] = new_factory.get();
  getPluginBaseToFactoryMapMapMutex().unlock();

  CONSOLE_BRIDGE_logDebug(
    "class_loader.impl: "
    "Registration of %s complete (Metaobject Address = %p)",
    class_name.c_str(), reinterpret_cast<void *>(new_factory.get()));
  return new_factory;
}

/**
 * @brief This function creates an instance of a plugin class
 *  given the derived name of the class and returns a pointer of the Base class type.
 *
 * @param derived_class_name - The name of the derived class (unmangled)
 * @param loader - The ClassLoader whose scope we are within
 * @return A pointer to newly created plugin, note caller is responsible for object destruction
 */
template<typename Base>
Base * createInstance(const std::string & derived_class_name, ClassLoader * loader)
{
  AbstractMetaObject<Base> * factory = nullptr;

  getPluginBaseToFactoryMapMapMutex().lock();
  FactoryMap & factoryMap = getFactoryMapForBaseClass<Base>();
  if (factoryMap.find(derived_class_name) != factoryMap.end()) {
    factory = dynamic_cast<impl::AbstractMetaObject<Base> *>(factoryMap[derived_class_name]);
  } else {
    CONSOLE_BRIDGE_logError(
      "class_loader.impl: No metaobject exists for class type %s.", derived_class_name.c_str());
  }
  getPluginBaseToFactoryMapMapMutex().unlock();

  Base * obj = nullptr;
  if (factory != nullptr && factory->isOwnedBy(loader)) {
    obj = factory->create();
  }

  if (nullptr == obj) {  // Was never created
    if (factory && factory->isOwnedBy(nullptr)) {
      CONSOLE_BRIDGE_logDebug(
        "%s",
        "class_loader.impl: ALERT!!! "
        "A metaobject (i.e. factory) exists for desired class, but has no owner. "
        "This implies that the library containing the class was dlopen()ed by means other than "
        "through the class_loader interface. "
        "This can happen if you build plugin libraries that contain more than just plugins "
        "(i.e. normal code your app links against) -- that intrinsically will trigger a dlopen() "
        "prior to main(). "
        "You should isolate your plugins into their own library, otherwise it will not be "
        "possible to shutdown the library!");

      obj = factory->create();
    } else {
      throw class_loader::CreateClassException(
              "Could not create instance of type " + derived_class_name);
    }
  }

  CONSOLE_BRIDGE_logDebug(
    "class_loader.impl: Created instance of type %s and object pointer = %p",
    (typeid(obj).name()), obj);

  return obj;
}

/**
 * @brief This function returns all the available class_loader in the plugin system
 * that are derived from Base and within scope of the passed ClassLoader.
 *
 * @param loader - The pointer to the ClassLoader whose scope we are within,
 * @return A vector of strings where each string is a plugin we can create
 */
template<typename Base>
std::vector<std::string> getAvailableClasses(const ClassLoader * loader)
{
  std::lock_guard<std::recursive_mutex> lock(getPluginBaseToFactoryMapMapMutex());

  FactoryMap & factory_map = getFactoryMapForBaseClass<Base>();
  std::vector<std::string> classes;
  std::vector<std::string> classes_with_no_owner;

  for (auto & it : factory_map) {
    AbstractMetaObjectBase * factory = it.second;
    if (factory->isOwnedBy(loader)) {
      classes.push_back(it.first);
    } else if (factory->isOwnedBy(nullptr)) {
      classes_with_no_owner.push_back(it.first);
    }
  }

  // Added classes not associated with a class loader (Which can happen through
  // an unexpected dlopen() to the library)
  classes.insert(classes.end(), classes_with_no_owner.begin(), classes_with_no_owner.end());
  return classes;
}

/**
 * @brief This function returns the names of all libraries in use by a given class loader.
 *
 * @param loader - The ClassLoader whose scope we are within
 * @return A vector of strings where each string is the path+name of each library that are
 *   within a ClassLoader's visible scope
 */
CLASS_LOADER_PUBLIC
std::vector<std::string> getAllLibrariesUsedByClassLoader(const ClassLoader * loader);

/**
 * @brief Indicates if passed library loaded within scope of a ClassLoader.
 * The library maybe loaded in memory, but to the class loader it may not be.
 *
 * @param library_path - The name of the library we wish to check is open
 * @param loader - The pointer to the ClassLoader whose scope we are within
 * @return true if the library is loaded within loader's scope, else false
 */
CLASS_LOADER_PUBLIC
bool isLibraryLoaded(const std::string & library_path, const ClassLoader * loader);

/**
 * @brief Indicates if passed library has been loaded by ANY ClassLoader
 *
 * @param library_path - The name of the library we wish to check is open
 * @return true if the library is loaded in memory, otherwise false
 */
CLASS_LOADER_PUBLIC
bool isLibraryLoadedByAnybody(const std::string & library_path);

/**
 * @brief Loads a library into memory if it has not already been done so.
 * Attempting to load an already loaded library has no effect.
 *
 * @param library_path - The name of the library to open
 * @param loader - The pointer to the ClassLoader whose scope we are within
 */
CLASS_LOADER_PUBLIC
void loadLibrary(const std::string & library_path, ClassLoader * loader);

/**
 * @brief Unloads a library if it loaded in memory and cleans up its corresponding class factories.
 * If it is not loaded, the function has no effect
 *
 * @param library_path - The name of the library to open
 * @param loader - The pointer to the ClassLoader whose scope we are within
 */
CLASS_LOADER_PUBLIC
void unloadLibrary(const std::string & library_path, ClassLoader * loader);

}  // namespace impl
}  // namespace class_loader

#endif  // CLASS_LOADER__CLASS_LOADER_CORE_HPP_