/*! \file timer.cpp
 * \brief Mini-task scheduler for timed events.
 *
 */

#include "copyright.h"
#include "autoconf.h"
#include "config.h"
#include "externs.h"
#include <new>
#include <exception>

CScheduler scheduler;

// Run one recurring system task's body, containing any exception (#2011).
//
// #2009 stopped a throwing task from killing the game.  It did not stop a
// throwing task from killing ITSELF: every dispatcher below re-defers its
// next run on its LAST line, and the #2009 barrier unwinds straight past
// that line, so the task is never scheduled again and silently stops
// forever.
//
// Measured with a one-shot throw on the third cache tick at
// cache_tick_period 1: three ticks in thirty seconds, then nothing.  With
// the body wrapped, twenty-nine.
//
// For dispatch_DatabaseDump that difference is the whole point -- a game
// that survives the exception and then quietly stops dumping is losing the
// database slowly instead of all at once, which is not the trade #2009 was
// meant to buy.
//
// Wrapping only the body leaves each reschedule tail unconditional.
//
template<typename F>
static void run_task_body(F body, const UTF8 *pWhich)
{
    try
    {
        body();
    }
    catch (const std::exception &e)
    {
        STARTLOG(LOG_BUGS, T("BUG"), T("TASK"));
        log_printf(T("Exception in system task %s (%s); rescheduled anyway."),
            pWhich, reinterpret_cast<const UTF8 *>(e.what()));
        ENDLOG;
    }
    catch (...)
    {
        STARTLOG(LOG_BUGS, T("BUG"), T("TASK"));
        log_printf(T("Unknown exception in system task %s; rescheduled anyway."),
            pWhich);
        ENDLOG;
    }
}

// Free List Reconstruction Task routine.
//
void dispatch_FreeListReconstruction(void *pUnused, int iUnused)
{
    UNUSED_PARAMETER(pUnused);
    UNUSED_PARAMETER(iUnused);

    run_task_body([]()
    {
        if (mudconf.control_flags & CF_DBCHECK)
        {
            const UTF8 *cmdsave = g_debug_cmd;
            g_debug_cmd = T("< dbck >");
            do_dbck(NOTHING, NOTHING, NOTHING, 0, 0);
            Guest.CleanUp();
            pcache_trim();
            pool_reset();
            g_debug_cmd = cmdsave;
        }
    }, T("dbck"));

    // Schedule ourselves again.
    //
    CLinearTimeAbsolute ltaNow;
    ltaNow.GetUTC();
    CLinearTimeDelta ltd;
    ltd.SetSeconds(mudconf.check_interval);
    mudstate.check_counter = ltaNow + ltd;
    scheduler.DeferTask(mudstate.check_counter, PRIORITY_SYSTEM,
        dispatch_FreeListReconstruction, 0, 0);
}

// Database Dump Task routine.
//
void dispatch_DatabaseDump(void *pUnused, int iUnused)
{
    UNUSED_PARAMETER(pUnused);
    UNUSED_PARAMETER(iUnused);

    int nNextTimeInSeconds = mudconf.dump_interval;

    run_task_body([&nNextTimeInSeconds]()
    {
        if (mudconf.control_flags & CF_CHECKPOINT)
        {
            const UTF8 *cmdsave = g_debug_cmd;
            g_debug_cmd = T("< dump >");
#if defined(HAVE_WORKING_FORK)
            if (mudstate.dumping)
            {
                // There is a dump in progress. These usually happen very
                // quickly.  We will reschedule ourselves to try again in 20
                // seconds.  Ordinarily, you would think "...a dump is a
                // dump...", but some dumps might not be the type of dump
                // we're going to do.
                //
                nNextTimeInSeconds = 20;
            }
            else
#endif // HAVE_WORKING_FORK
            {
                fork_and_dump(0);
            }
            g_debug_cmd = cmdsave;
        }
    }, T("dump"));

    // Schedule ourselves again.
    //
    CLinearTimeAbsolute ltaNow;
    ltaNow.GetUTC();
    CLinearTimeDelta ltd;
    ltd.SetSeconds(nNextTimeInSeconds);
    mudstate.dump_counter = ltaNow + ltd;
    scheduler.DeferTask(mudstate.dump_counter, PRIORITY_SYSTEM, dispatch_DatabaseDump, 0, 0);
}

// Idle Check Task routine.
//
void dispatch_IdleCheck(void *pUnused, int iUnused)
{
    UNUSED_PARAMETER(pUnused);
    UNUSED_PARAMETER(iUnused);

    run_task_body([]()
    {
        if (mudconf.control_flags & CF_IDLECHECK)
        {
            const UTF8 *cmdsave = g_debug_cmd;
            g_debug_cmd = T("< idlecheck >");
            check_idle();
            g_debug_cmd = cmdsave;
        }
    }, T("idlecheck"));

    // Schedule ourselves again.
    //
    CLinearTimeAbsolute ltaNow;
    ltaNow.GetUTC();
    CLinearTimeDelta ltd;
    ltd.SetSeconds(mudconf.idle_interval);
    mudstate.idle_counter = ltaNow + ltd;
    scheduler.DeferTask(mudstate.idle_counter, PRIORITY_SYSTEM, dispatch_IdleCheck, 0, 0);
}

void dispatch_KeepAlive(void *pUnused, int iUnused)
{
    UNUSED_PARAMETER(pUnused);
    UNUSED_PARAMETER(iUnused);

    run_task_body([]() { send_keepalive_nops(); }, T("keepalive"));

    // Schedule ourselves again.
    //
    CLinearTimeAbsolute ltaNow;
    ltaNow.GetUTC();
    CLinearTimeDelta ltd;
    ltd.SetSeconds(mudconf.keepalive_interval);
    mudstate.keepalive_counter = ltaNow + ltd;
    scheduler.DeferTask(mudstate.keepalive_counter, PRIORITY_SYSTEM, dispatch_KeepAlive, 0, 0);
}

// Check Events Task routine.
//
void dispatch_CheckEvents(void *pUnused, int iUnused)
{
    UNUSED_PARAMETER(pUnused);
    UNUSED_PARAMETER(iUnused);

    run_task_body([]()
    {
        if (mudconf.control_flags & CF_EVENTCHECK)
        {
            const UTF8 *cmdsave = g_debug_cmd;
            g_debug_cmd = T("< eventcheck >");
            check_events();
            g_debug_cmd = cmdsave;
        }
    }, T("eventcheck"));

    // Schedule ourselves again.
    //
    CLinearTimeAbsolute ltaNow;
    ltaNow.GetUTC();
    CLinearTimeDelta ltd = time_15m;
    mudstate.events_counter = ltaNow + ltd;
    scheduler.DeferTask(mudstate.events_counter, PRIORITY_SYSTEM, dispatch_CheckEvents, 0, 0);
}

void dispatch_CacheTick(void *pUnused, int iUnused)
{
    UNUSED_PARAMETER(pUnused);
    UNUSED_PARAMETER(iUnused);

    const UTF8 *cmdsave = g_debug_cmd;
    g_debug_cmd = T("< cachetick >");

    CLinearTimeDelta ltd = 0;
    if (mudconf.cache_tick_period <= ltd)
    {
        mudconf.cache_tick_period.SetSeconds(1);
    }

    run_task_body([]() { cache_tick(); }, T("cachetick"));

    // Schedule ourselves again.
    //
    CLinearTimeAbsolute ltaNextTime;
    ltaNextTime.GetUTC();
    ltaNextTime += mudconf.cache_tick_period;
    scheduler.DeferTask(ltaNextTime, PRIORITY_SYSTEM, dispatch_CacheTick, 0, 0);
    g_debug_cmd = cmdsave;
}

static void dispatch_CanRestart(void *pUnused, int iUnused)
{
    UNUSED_PARAMETER(pUnused);
    UNUSED_PARAMETER(iUnused);
    mudstate.bCanRestart = true;
}

void init_timer(void)
{
    CLinearTimeAbsolute ltaNow;
    ltaNow.GetUTC();

    // Setup re-occuring Free List Reconstruction task.
    //
    CLinearTimeDelta ltd;
    ltd.SetSeconds((mudconf.check_offset == 0) ? mudconf.check_interval : mudconf.check_offset);
    mudstate.check_counter  = ltaNow + ltd;
    scheduler.DeferTask(mudstate.check_counter, PRIORITY_SYSTEM,
        dispatch_FreeListReconstruction, 0, 0);

    // Setup re-occuring Database Dump task.
    //
    ltd.SetSeconds((mudconf.dump_offset == 0) ? mudconf.dump_interval : mudconf.dump_offset);
    mudstate.dump_counter  = ltaNow + ltd;
    scheduler.DeferTask(mudstate.dump_counter, PRIORITY_SYSTEM,
        dispatch_DatabaseDump, 0, 0);

    // Setup re-occuring Idle Check task.
    //
    ltd.SetSeconds(mudconf.idle_interval);
    mudstate.idle_counter   = ltaNow + ltd;
    scheduler.DeferTask(mudstate.idle_counter, PRIORITY_SYSTEM,
        dispatch_IdleCheck, 0, 0);

    // Setup re-occuring Check Events task.
    //
    mudstate.events_counter = ltaNow + time_15s;
    scheduler.DeferTask(mudstate.events_counter, PRIORITY_SYSTEM,
        dispatch_CheckEvents, 0, 0);

    // Setup re-occuring KeepAlive task.
    //
    ltd.SetSeconds(mudconf.keepalive_interval);
    mudstate.keepalive_counter = ltaNow + ltd;
    scheduler.DeferTask(mudstate.keepalive_counter, PRIORITY_SYSTEM, dispatch_KeepAlive, 0, 0);

    // Setup re-occuring cache_tick task.
    //
    ltd.SetSeconds(0);
    if (mudconf.cache_tick_period <= ltd)
    {
        mudconf.cache_tick_period.SetSeconds(1);
    }
    scheduler.DeferTask(ltaNow+mudconf.cache_tick_period, PRIORITY_SYSTEM,
        dispatch_CacheTick, 0, 0);

    // Setup one-shot task to enable restarting 15 seconds after startmux.
    //
    // PRIORITY_SYSTEM, deliberately (#2131).  This is maintenance — it arms
    // the @restart throttle — but it sat at PRIORITY_OBJECT, inside the band
    // CScheduler::HasPendingUserTasks counts as user work.  muxscript's
    // post-EOF exit predicate therefore saw "pending user tasks" until this
    // timer expired, and every scripted invocation idled ~15 seconds doing
    // nothing: five thousand JIT compilations moved muxscript's wall clock
    // by 22 ms while this task held it for 15.15 s.  SYSTEM also means the
    // throttle arms even while @disable'd dequeuing blocks the user band,
    // which is the right behaviour for a safety timer.
    //
    scheduler.DeferTask(ltaNow+time_15s, PRIORITY_SYSTEM, dispatch_CanRestart, 0, 0);
}

/*
 * ---------------------------------------------------------------------------
 * * do_timewarp: Adjust various internal timers.
 */

void do_timewarp(dbref executor, dbref caller, dbref enactor, int eval, int key, UTF8 *arg, const UTF8 *cargs[], int ncargs)
{
    UNUSED_PARAMETER(eval);
    UNUSED_PARAMETER(cargs);
    UNUSED_PARAMETER(ncargs);

    int secs;

    secs = mux_atoi64(arg);

    // Sem/Wait queues
    //
    if ((key == 0) || (key & TWARP_QUEUE))
    {
        do_queue(executor, caller, enactor, 0, QUEUE_WARP, arg, nullptr, 0);
    }

    // Once these are adjusted, we need to Cancel and reschedule the task.
    //
    CLinearTimeDelta ltd;
    ltd.SetSeconds(secs);
    if (key & TWARP_DUMP)
    {
        mudstate.dump_counter -= ltd;
        scheduler.CancelTask(dispatch_DatabaseDump, 0, 0);
        scheduler.DeferTask(mudstate.dump_counter, PRIORITY_SYSTEM, dispatch_DatabaseDump, 0, 0);
    }
    if (key & TWARP_CLEAN)
    {
        mudstate.check_counter -= ltd;
        scheduler.CancelTask(dispatch_FreeListReconstruction, 0, 0);
        scheduler.DeferTask(mudstate.check_counter, PRIORITY_SYSTEM, dispatch_FreeListReconstruction, 0, 0);
    }
    if (key & TWARP_IDLE)
    {
        mudstate.idle_counter -= ltd;
        scheduler.CancelTask(dispatch_IdleCheck, 0, 0);
        scheduler.DeferTask(mudstate.idle_counter, PRIORITY_SYSTEM, dispatch_IdleCheck, 0, 0);
    }
    if (key & TWARP_EVENTS)
    {
        mudstate.events_counter -= ltd;
        scheduler.CancelTask(dispatch_CheckEvents, 0, 0);
        scheduler.DeferTask(mudstate.events_counter, PRIORITY_SYSTEM, dispatch_CheckEvents, 0, 0);
    }
}


bool CScheduler::DeferTask(const CLinearTimeAbsolute& ltaWhen, int iPriority,
                           FTASK *fpTask, void *arg_voidptr, int arg_Integer)
{
    // #1871: nothrow so OOM is a clean false rather than an exception; the
    // previous void path treated both OOM and Insert failure as silent success
    // at wait_que, leaking the BQUE and queue accounting.
    //
    PTASK_RECORD pTask = new (std::nothrow) TASK_RECORD;
    if (!pTask)
    {
        return false;
    }

    pTask->ltaWhen = ltaWhen;
    pTask->iPriority = iPriority;
    pTask->fpTask = fpTask;
    pTask->arg_voidptr = arg_voidptr;
    pTask->arg_Integer = arg_Integer;
    pTask->m_Ticket = m_Ticket++;

    // Must add to the WhenHeap so that network is still serviced.
    //
    if (!m_WhenHeap.Insert(pTask))
    {
        delete pTask;
        return false;
    }
    return true;
}

bool CScheduler::DeferImmediateTask(int iPriority, FTASK *fpTask, void *arg_voidptr, int arg_Integer)
{
    PTASK_RECORD pTask = new (std::nothrow) TASK_RECORD;
    if (!pTask)
    {
        return false;
    }

    //pTask->ltaWhen = ltaWhen;
    pTask->iPriority = iPriority;
    pTask->fpTask = fpTask;
    pTask->arg_voidptr = arg_voidptr;
    pTask->arg_Integer = arg_Integer;
    pTask->m_Ticket = m_Ticket++;

    // Must add to the WhenHeap so that network is still serviced.
    //
    if (!m_WhenHeap.Insert(pTask))
    {
        delete pTask;
        return false;
    }
    return true;
}

void CScheduler::CancelTask(FTASK *fpTask, void *arg_voidptr, int arg_Integer)
{
    m_WhenHeap.CancelTask(fpTask, arg_voidptr, arg_Integer);
    m_PriorityHeap.CancelTask(fpTask, arg_voidptr, arg_Integer);
}

void CScheduler::ReadyTasks(const CLinearTimeAbsolute& ltaNow)
{
    // Move ready-to-run tasks off the WhenHeap and onto the PriorityHeap.
    //
    PTASK_RECORD pTask = m_WhenHeap.PeekAtTopmost();
    while (  pTask
          && pTask->ltaWhen < ltaNow)
    {
        pTask = m_WhenHeap.RemoveTopmost();
        if (pTask)
        {
            if (  nullptr == pTask->fpTask
               || !m_PriorityHeap.Insert(pTask))
            {
                delete pTask;
            }
        }
        pTask = m_WhenHeap.PeekAtTopmost();
    }
}

int CScheduler::RunTasks(const CLinearTimeAbsolute& ltaNow)
{
    ReadyTasks(ltaNow);
    if (mudconf.active_q_chunk)
    {
        return RunTasks(mudconf.active_q_chunk);
    }
    else
    {
        return RunAllTasks();
    }
}

int CScheduler::RunTasks(int iCount)
{
    int nTasks = 0;
    while (iCount--)
    {
        PTASK_RECORD pTask = m_PriorityHeap.PeekAtTopmost();
        if (!pTask) break;

        if (pTask->iPriority > m_minPriority)
        {
            // This is related to CF_DEQUEUE and also to untimed (SUSPENDED)
            // semaphore entries that we would like to manage together with
            // the timed ones.
            //
            break;
        }
        pTask = m_PriorityHeap.RemoveTopmost();
        if (pTask)
        {
            if (pTask->fpTask)
            {
                // #2009: exception barrier.  Everything softcode does runs
                // under here -- command parsing, function evaluation, mail,
                // comsys, @dump -- and all of it allocates.  There is no catch
                // between this frame and main(), so a throw becomes
                // std::terminate -> abort -> SIGABRT, and signals.cpp handles
                // SIGABRT by logging and exit(1): no dump_restart_db(), no
                // re-exec.  A SIGSEGV on the same line forks, dumps and
                // execl()s a fresh netmux, so an exception costs the database
                // where a null dereference would have self-healed.
                //
                // Contained per task rather than per tick so that one bad
                // command dies without dropping the rest of the tick.  It also
                // keeps the delete below reachable: pTask is already off the
                // heap by this point, so an escaping throw would leak the
                // record in addition to losing the task.
                //
                // Abandoning one task is survivable.  process_command() resets
                // func_nest_lev, func_invk_ctr, ntfy_nest_lev and lock_nest_lev
                // at the top of every command, so a half-finished command
                // cannot poison the next one's limits.  It does leak that
                // command's lbufs -- bounded, and far cheaper than losing the
                // database.
                //
                try
                {
                    pTask->fpTask(pTask->arg_voidptr, pTask->arg_Integer);
                }
                catch (const std::exception &e)
                {
                    STARTLOG(LOG_BUGS, T("BUG"), T("TASK"));
                    log_printf(T("Exception escaped a scheduled task (%s); task abandoned."),
                        reinterpret_cast<const UTF8 *>(e.what()));
                    ENDLOG;
                }
                catch (...)
                {
                    STARTLOG(LOG_BUGS, T("BUG"), T("TASK"));
                    log_printf(T("Unknown exception escaped a scheduled task; task abandoned."));
                    ENDLOG;
                }
                nTasks++;
            }
            delete pTask;
        }
    }
    return nTasks;
}

int CScheduler::RunAllTasks(void)
{
    int nTotalTasks = 0;

    int nTasks;
    do
    {
        nTasks = RunTasks(100);
        nTotalTasks += nTasks;
    } while (nTasks);

    return nTotalTasks;
}

bool CScheduler::WhenNext(CLinearTimeAbsolute  *ltaWhen)
{
    // Check the Priority Queue first.
    //
    PTASK_RECORD pTask = m_PriorityHeap.PeekAtTopmost();
    if (pTask)
    {
        if (pTask->iPriority <= m_minPriority)
        {
            ltaWhen->SetSeconds(0);
            return true;
        }
    }

    // Check the When Queue next.
    //
    pTask = m_WhenHeap.PeekAtTopmost();
    if (pTask)
    {
        *ltaWhen = pTask->ltaWhen;
        return true;
    }
    return false;
}

bool CScheduler::HasPendingUserTasks(void)
{
    // "User work" is any queued or timed task with a priority above system
    // maintenance (dumps, idle checks, keepalives — which recur forever) and
    // below the suspended band (semaphore-parked entries, which never wake
    // without an external notify).  A CLI run is finished once only those two
    // classes remain, even though delayed @wait tasks must still be honored.
    //
    return 0 < m_WhenHeap.CountInPriorityRange(PRIORITY_SYSTEM, PRIORITY_SUSPEND)
        || 0 < m_PriorityHeap.CountInPriorityRange(PRIORITY_SYSTEM, PRIORITY_SUSPEND);
}

void CScheduler::TraverseUnordered(SCHLOOK *pfLook)
{
    if (m_WhenHeap.TraverseUnordered(pfLook))
    {
        m_PriorityHeap.TraverseUnordered(pfLook);
    }
}

void CScheduler::TraverseOrdered(SCHLOOK *pfLook)
{
    m_PriorityHeap.TraverseOrdered(pfLook);
    m_WhenHeap.TraverseOrdered(pfLook);
}

void CScheduler::SetMinPriority(int arg_minPriority)
{
    m_minPriority = arg_minPriority;
}

void CScheduler::Shrink(void)
{
    m_WhenHeap.Shrink();
    m_PriorityHeap.Shrink();
}