// 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 3 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, see http://www.gnu.org/licenses/.


#include "concrete_history.hh"
#include <sgpemv2/cpu_policies_gatekeeper.hh>
#include <sgpemv2/cpu_policy.hh>
#include <sgpemv2/cpu_policy_manager.hh>

// Include full template definition only in implementation files:
#include <sgpemv2/templates/singleton.tcc>

#include <sgpemv2/templates/down_cast.tcc>

#include <algorithm>
#include <cassert>
#include <iostream>

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

// Explicit template instantiation to allow to export symbols from the DSO.
template class sgpem::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 != nullptr);

    ManagerIterator end = _registered.end ();

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

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

    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)
{
    assert (history != nullptr);

    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 != nullptr);

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

    // deactivate the policy, if necessary
    if (pos != end)
    {
        // nothing to do in this case
        if (pos->second == policy)
            return;

        pos->second->deactivate ();
    }

    // if policy is nullptr, simply erase the entry and return, since we are sure the policy is
    // not active due to the previous lines
    if (policy == nullptr)
    {
        // this is a no-op if history is not a key used in the map
        _active_policies.erase (history);
        return;
    }

    try
    {
        policy->activate ();
        _active_policies[history] = policy;
        // the content of history (if any) is not vaild any more.
        down_cast<ConcreteHistory *> (history)->reset ();
    }
    catch (const CPUPolicyException &e)
    {
        // the caller need to know if it failed
        throw;
    }
}

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)
    {
        ActiveIterator act_it = _active_policies.begin ();

        while (act_it != _active_policies.end ())
        {
            if (act_it->second == *avail_it)
            {
                act_it->second->deactivate ();
                // Please note the postfix increment
                // (operating on the old, now invalidated by
                // erase, iterator object):
                _active_policies.erase (act_it++);
            }
            else
                ++act_it;
        }
    } //~ for(avail_it)
}