/**
 * Orthanc - A Lightweight, RESTful DICOM Store
 * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
 * Department, University Hospital of Liege, Belgium
 * Copyright (C) 2017-2023 Osimis S.A., Belgium
 * Copyright (C) 2021-2023 Sebastien Jodogne, ICTEAM UCLouvain, Belgium
 *
 * This program is free software: you can redistribute it and/or
 * modify it under the terms of the GNU Affero General Public License
 * as published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * This program 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
 * Affero General Public License for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 **/


#include "IndexConnectionsPool.h"

namespace OrthancDatabases
{
  class IndexConnectionsPool::ManagerReference : public Orthanc::IDynamicObject
  {
  private:
    DatabaseManager*  manager_;

  public:
    ManagerReference(DatabaseManager& manager) :
      manager_(&manager)
    {
    }

    DatabaseManager& GetManager()
    {
      assert(manager_ != NULL);
      return *manager_;
    }
  };


  IndexConnectionsPool::IndexConnectionsPool(IndexBackend* backend,
                                             size_t countConnections) :
    backend_(backend),
    countConnections_(countConnections)
  {
    if (countConnections == 0)
    {
      throw Orthanc::OrthancException(Orthanc::ErrorCode_ParameterOutOfRange,
                                      "There must be a non-zero number of connections to the database");
    }
    else if (backend == NULL)
    {
      throw Orthanc::OrthancException(Orthanc::ErrorCode_NullPointer);
    }
    else
    {
      context_ = backend_->GetContext();
    }
  }

  
  IndexConnectionsPool::~IndexConnectionsPool()
  {
    for (std::list<DatabaseManager*>::iterator
           it = connections_.begin(); it != connections_.end(); ++it)
    {
      assert(*it != NULL);
      delete *it;
    }
  }


  void IndexConnectionsPool::OpenConnections()
  {
    boost::unique_lock<boost::shared_mutex>  lock(connectionsMutex_);

    if (connections_.size() == 0)
    {
      assert(backend_.get() != NULL);

      {
        std::unique_ptr<DatabaseManager> manager(new DatabaseManager(backend_->CreateDatabaseFactory()));
        manager->GetDatabase();  // Make sure to open the database connection
          
        backend_->ConfigureDatabase(*manager);
        connections_.push_back(manager.release());
      }

      for (size_t i = 1; i < countConnections_; i++)
      {
        connections_.push_back(new DatabaseManager(backend_->CreateDatabaseFactory()));
        connections_.back()->GetDatabase();  // Make sure to open the database connection
      }

      for (std::list<DatabaseManager*>::iterator
             it = connections_.begin(); it != connections_.end(); ++it)
      {
        assert(*it != NULL);
        availableConnections_.Enqueue(new ManagerReference(**it));
      }        
    }
    else
    {
      throw Orthanc::OrthancException(Orthanc::ErrorCode_BadSequenceOfCalls);
    }
  }


  void IndexConnectionsPool::CloseConnections()
  {
    boost::unique_lock<boost::shared_mutex>  lock(connectionsMutex_);

    if (connections_.size() != countConnections_)
    {
      throw Orthanc::OrthancException(Orthanc::ErrorCode_BadSequenceOfCalls);
    }
    else if (availableConnections_.GetSize() != countConnections_)
    {
      throw Orthanc::OrthancException(Orthanc::ErrorCode_Database, "Some connections are still in use, bug in the Orthanc core");
    }
    else
    {
      for (std::list<DatabaseManager*>::iterator
             it = connections_.begin(); it != connections_.end(); ++it)
      {
        assert(*it != NULL);
        (*it)->Close();
      }
    }
  }


  IndexConnectionsPool::Accessor::Accessor(IndexConnectionsPool& pool) :
    lock_(pool.connectionsMutex_),
    pool_(pool),
    manager_(NULL)
  {
    for (;;)
    {
      std::unique_ptr<Orthanc::IDynamicObject> manager(pool.availableConnections_.Dequeue(100));
      if (manager.get() != NULL)
      {
        manager_ = &dynamic_cast<ManagerReference&>(*manager).GetManager();
        return;
      }
    }
  }

  
  IndexConnectionsPool::Accessor::~Accessor()
  {
    assert(manager_ != NULL);
    pool_.availableConnections_.Enqueue(new ManagerReference(*manager_));
  }

  
  IndexBackend& IndexConnectionsPool::Accessor::GetBackend() const
  {
    return *pool_.backend_;
  }

  
  DatabaseManager& IndexConnectionsPool::Accessor::GetManager() const
  {
    assert(manager_ != NULL);
    return *manager_;
  }
}