//          Copyright Oliver Kowalke 2013.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          http://www.boost.org/LICENSE_1_0.txt)

#include "boost/fiber/round_robin.hpp"

#include <algorithm>
#include <cmath>
#include <memory>
#include <utility>

#include <boost/assert.hpp>
#include <boost/bind.hpp>
#include <boost/foreach.hpp>
#include <boost/scope_exit.hpp>
#include <boost/thread/locks.hpp>

#include "boost/fiber/detail/scheduler.hpp"
#include "boost/fiber/exceptions.hpp"
#include "boost/fiber/interruption.hpp"

#ifdef BOOST_HAS_ABI_HEADERS
#  include BOOST_ABI_PREFIX
#endif

namespace boost {
namespace fibers {

round_robin::round_robin() BOOST_NOEXCEPT :
    active_fiber_(),
    wqueue_(),
    rqueue_()
{}

round_robin::~round_robin() BOOST_NOEXCEPT
{
    // fibers will be destroyed (stack-unwinding)
    // if last reference goes out-of-scope
    // therefore destructing wqueue_ && rqueue_
    // will destroy the fibers in this scheduler
    // if not referenced on other places
    if ( detail::scheduler::instance() == this)
        detail::scheduler::replace( 0);
}

void
round_robin::spawn( detail::fiber_base::ptr_t const& f)
{
    BOOST_ASSERT( f);
    BOOST_ASSERT( f->is_ready() );

    // store active fiber in local var
    detail::fiber_base::ptr_t tmp = active_fiber_;
    try
    {
        // assign new fiber to active fiber
        active_fiber_ = f;
        // set active fiber to state_running
        active_fiber_->set_running();
        // resume active fiber
        active_fiber_->resume();
        // fiber is resumed

        BOOST_ASSERT( f == active_fiber_);
    }
    catch (...)
    {
        // reset active fiber to previous
        active_fiber_ = tmp;
        throw;
    }
    // reset active fiber to previous
    active_fiber_ = tmp;
}

bool
round_robin::run()
{
    wqueue_t wqueue;
    // move all fibers witch are ready (state_ready)
    // from waiting-queue to the runnable-queue
    BOOST_FOREACH( schedulable const& s, wqueue_)
    {
        detail::fiber_base::ptr_t f( s.f);

        BOOST_ASSERT( ! f->is_running() );
        BOOST_ASSERT( ! f->is_terminated() );

        // set fiber to state_ready if dead-line was reached
        if ( s.tp <= clock_type::now() )
            f->set_ready();
        // set fiber to state_ready if interruption was requested
        if ( f->interruption_requested() )
            f->set_ready();
        if ( f->is_ready() )
            rqueue_.push_back( f);
        else wqueue.push_back( s);
    }
    // exchange local with global waiting queue
    wqueue_.swap( wqueue);

    // pop new fiber from ready-queue which is not complete
    // (example: fiber in ready-queue could be canceled by active-fiber)
    detail::fiber_base::ptr_t f;
    do
    {
        if ( rqueue_.empty() ) return false;
        f.swap( rqueue_.front() );
        rqueue_.pop_front();

        if ( f->is_ready() ) break;
        //else if ( f->is_waiting() ) wqueue_.push_back( schedulable( f) );
        else BOOST_ASSERT_MSG( false, "fiber with invalid state in ready-queue");
    }
    while ( true);

    // resume fiber
    spawn( f);

    return true;
}

void
round_robin::wait()
{ wait_until( clock_type::time_point( (clock_type::duration::max)() ) ); }

bool
round_robin::wait_until( clock_type::time_point const& timeout_time)
{
    clock_type::time_point start( clock_type::now() );

    BOOST_ASSERT( active_fiber_);
    BOOST_ASSERT( active_fiber_->is_running() );

    // set active fiber to state_waiting
    active_fiber_->set_waiting();
    // push active fiber to wqueue_
    wqueue_.push_back( schedulable( active_fiber_, timeout_time) );
    // store active fiber in local var
    detail::fiber_base::ptr_t tmp = active_fiber_;
    // suspend active fiber
    active_fiber_->suspend();
    // fiber is resumed

    BOOST_ASSERT( tmp == active_fiber_);
    BOOST_ASSERT( active_fiber_->is_running() );

    return clock_type::now() < timeout_time;
}

void
round_robin::yield()
{
    BOOST_ASSERT( active_fiber_);
    BOOST_ASSERT( active_fiber_->is_running() );

    // set active fiber to state_waiting
    active_fiber_->set_ready();
    // push active fiber to wqueue_
    wqueue_.push_back( schedulable( active_fiber_) );
    // store active fiber in local var
    detail::fiber_base::ptr_t tmp = active_fiber_;
    // suspend acitive fiber
    active_fiber_->suspend();
    // fiber is resumed

    BOOST_ASSERT( tmp == active_fiber_);
    BOOST_ASSERT( active_fiber_->is_running() );
}

void
round_robin::join( detail::fiber_base::ptr_t const& f)
{
    BOOST_ASSERT( f);
    BOOST_ASSERT( f != active_fiber_);

    if ( active_fiber_)
    {
        // set active fiber to state_waiting
        active_fiber_->set_waiting();
        // push active fiber to wqueue_
        wqueue_.push_back( schedulable( active_fiber_) );
        // add active fiber to joinig-list of f
        if ( ! f->join( active_fiber_) )
            // f must be already terminated therefore we set
            // active fiber to state_ready
            // FIXME: better state_running and no suspend
            active_fiber_->set_ready();
        // store active fiber in local var
        detail::fiber_base::ptr_t tmp = active_fiber_;
        // suspend fiber until f terminates
        active_fiber_->suspend();
        // fiber is resumed by f

        BOOST_ASSERT( tmp == active_fiber_);
        BOOST_ASSERT( active_fiber_->is_running() );

        // check if fiber was interrupted
        this_fiber::interruption_point();
    }
    else
    {
        while ( ! f->is_terminated() )
            run();
    }

    // check if joined fiber has an exception
    // and rethrow exception
    if ( f->has_exception() ) f->rethrow();

    BOOST_ASSERT( f->is_terminated() );
}

void
round_robin::priority( detail::fiber_base::ptr_t const& f, int prio)
{
    BOOST_ASSERT( f);

    // set only priority to fiber
    // round-robin does not respect priorities
    f->priority( prio);
}

}}

#ifdef BOOST_HAS_ABI_HEADERS
#  include BOOST_ABI_SUFFIX
#endif