// src/backend/cpu_policies_gatekeeper.cc - Copyright 2005, 2006, University
//               of Padova, dept. of Pure and Applied
//               Mathematics
//
// This file is part of SGPEMv2.
//
// This 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 2 of the License, or
// (at your option) any later version.
//
// SGPEMv2 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 SGPEMv2; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

#include "config.h"

#include "cpu_policies_gatekeeper.hh"
#include "cpu_policy_manager.hh"
#include "cpu_policy.hh"

// Include full template definition only in implementation files:
#include "singleton.tcc"

#include <algorithm>
#include <cassert>

using std::vector;
using std::map;
using std::find;
using std::runtime_error;
using namespace sgpem;

// Explicit template instantiation to allow to export symbols from the DSO.
template class SG_DLLEXPORT Singleton<CPUPoliciesGatekeeper>;

typedef vector<CPUPolicyManager*>::iterator ManagerIterator;
typedef map<History*, CPUPolicy*>::iterator ActiveIterator;

vector<CPUPolicyManager*>
CPUPoliciesGatekeeper::get_registered() const
{
  return _registered;
}

void
CPUPoliciesGatekeeper::register_manager(CPUPolicyManager* manager)
{
  assert(manager != NULL);

  ManagerIterator end = _registered.end();

  if (find(_registered.begin(), end, manager) == end)
    _registered.push_back(manager);
}

void
CPUPoliciesGatekeeper::unregister_manager(CPUPolicyManager* manager)
{
  assert(manager != NULL);

  ManagerIterator end = _registered.end();
  ManagerIterator pos = find(_registered.begin(), end, manager);

  if (pos != end)
  {
    deactivate_policies(*pos);
    _registered.erase(pos);
  }
}

CPUPolicy*
CPUPoliciesGatekeeper::get_current_policy(History* history) throw(runtime_error)
{
  assert(history != NULL);

  ActiveIterator policy = _active_policies.find(history);

  if (policy == _active_policies.end())
    throw runtime_error("No active policy associated with this "
                        "history is available.");

  return policy->second;
}

void
CPUPoliciesGatekeeper::activate_policy(History *history, CPUPolicy* policy)
{
  assert(history != NULL);

  ActiveIterator end = _active_policies.end();
  ActiveIterator pos = _active_policies.find(history);

  if (pos != end && pos->second != policy)
    _active_policies[history]->deactivate();

  if(policy == NULL)
  {
    _active_policies.erase(pos);
    return;
  }
  
  if (pos == end || pos->second != policy)
  {
    try
    {
      // policy->activate() needs already an active policy, because:
      //   * it calls the configure() method on the 
      //     insert-your-favourite-scripting-language-here-policy
      //   * which in turn calls the configure() method in the 
      //     code written by the user
      //   * which probably uses Simulation to get the _active_ C++ policy,
      //     so it can get its policy_parameters()
      //  ... so **DON'T** play Mr. Clever Dick and swap the following two
      //    lines in an optimization frenzy! Or the user policy WILL fail.
      _active_policies[history] = policy;
      policy->activate();
    }
    catch(const CPUPolicyException& e)
    {
      // See the comment above to understand why we do this
      // in this way
      _active_policies.erase(_active_policies.find(history));
    }
  }
}

CPUPoliciesGatekeeper::CPUPoliciesGatekeeper()
{}

void
CPUPoliciesGatekeeper::deactivate_policies(CPUPolicyManager* manager)
{
  typedef vector<CPUPolicy*>::iterator CPUPolicyIterator;

  vector<CPUPolicy*> avail_policies = manager->get_avail_policies();

  CPUPolicyIterator avail_it = avail_policies.begin();
  CPUPolicyIterator avail_end = avail_policies.end();

  for (; avail_it != avail_end; ++avail_it)
  {
    // TODO isn't there a way to write more compact code by using
    // library utilities?
    ActiveIterator act_it = _active_policies.begin();

    while (act_it != _active_policies.end())
    {
      if (act_it->second == *avail_it)
      {
        ActiveIterator removable = act_it++;
        removable->second->deactivate();
        _active_policies.erase(removable);
      }
      else
        act_it++;
    }
  } //~ for(avail_it)
}