// Copyright 2013 Dolphin Emulator Project / 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <vector>
#include <cstdio>
#include <atomic>
#include <mutex>

#include "common/chunk_file.h"
#include "common/msg_handler.h"
#include "common/string_util.h"

#include "core/core.h"
#include "core/core_timing.h"

int g_clock_rate_arm11 = 268123480;

// is this really necessary?
#define INITIAL_SLICE_LENGTH 20000
#define MAX_SLICE_LENGTH 100000000

namespace CoreTiming
{

struct EventType
{
    EventType() {}

    EventType(TimedCallback cb, const char *n)
        : callback(cb), name(n) {}

    TimedCallback callback;
    const char *name;
};

std::vector<EventType> event_types;

struct BaseEvent
{
    s64 time;
    u64 userdata;
    int type;
    // Event *next;
};

typedef LinkedListItem<BaseEvent> Event;

Event *first;
Event *tsFirst;
Event *tsLast;

// event pools
Event *eventPool = 0;
Event *eventTsPool = 0;
int allocatedTsEvents = 0;
// Optimization to skip MoveEvents when possible.
std::atomic<u32> hasTsEvents;

// Downcount has been moved to currentMIPS, to save a couple of clocks in every ARM JIT block
// as we can already reach that structure through a register.
int slicelength;

MEMORY_ALIGNED16(s64) globalTimer;
s64 idledCycles;

static std::recursive_mutex externalEventSection;

// Warning: not included in save state.
void(*advanceCallback)(int cyclesExecuted) = nullptr;

void SetClockFrequencyMHz(int cpuMhz)
{
    g_clock_rate_arm11 = cpuMhz * 1000000;
    // TODO: Rescale times of scheduled events?
}

int GetClockFrequencyMHz()
{
    return g_clock_rate_arm11 / 1000000;
}


Event* GetNewEvent()
{
    if (!eventPool)
        return new Event;

    Event* ev = eventPool;
    eventPool = ev->next;
    return ev;
}

Event* GetNewTsEvent()
{
    allocatedTsEvents++;

    if (!eventTsPool)
        return new Event;

    Event* ev = eventTsPool;
    eventTsPool = ev->next;
    return ev;
}

void FreeEvent(Event* ev)
{
    ev->next = eventPool;
    eventPool = ev;
}

void FreeTsEvent(Event* ev)
{
    ev->next = eventTsPool;
    eventTsPool = ev;
    allocatedTsEvents--;
}

int RegisterEvent(const char *name, TimedCallback callback)
{
    event_types.push_back(EventType(callback, name));
    return (int)event_types.size() - 1;
}

void AntiCrashCallback(u64 userdata, int cyclesLate)
{
    LOG_CRITICAL(Core, "Savestate broken: an unregistered event was called.");
    Core::Halt("invalid timing events");
}

void RestoreRegisterEvent(int event_type, const char *name, TimedCallback callback)
{
    if (event_type >= (int)event_types.size())
        event_types.resize(event_type + 1, EventType(AntiCrashCallback, "INVALID EVENT"));

    event_types[event_type] = EventType(callback, name);
}

void UnregisterAllEvents()
{
    if (first)
        PanicAlert("Cannot unregister events with events pending");
    event_types.clear();
}

void Init()
{
    //currentMIPS->downcount = INITIAL_SLICE_LENGTH;
    //slicelength = INITIAL_SLICE_LENGTH;
    globalTimer = 0;
    idledCycles = 0;
    hasTsEvents = 0;
}

void Shutdown()
{
    MoveEvents();
    ClearPendingEvents();
    UnregisterAllEvents();

    while (eventPool)
    {
        Event *ev = eventPool;
        eventPool = ev->next;
        delete ev;
    }

    std::lock_guard<std::recursive_mutex> lk(externalEventSection);
    while (eventTsPool)
    {
        Event *ev = eventTsPool;
        eventTsPool = ev->next;
        delete ev;
    }
}

u64 GetTicks()
{
    LOG_ERROR(Core, "Unimplemented function!");
    return 0;
    //return (u64)globalTimer + slicelength - currentMIPS->downcount;
}

u64 GetIdleTicks()
{
    return (u64)idledCycles;
}


// This is to be called when outside threads, such as the graphics thread, wants to
// schedule things to be executed on the main thread.
void ScheduleEvent_Threadsafe(s64 cyclesIntoFuture, int event_type, u64 userdata)
{
    std::lock_guard<std::recursive_mutex> lk(externalEventSection);
    Event *ne = GetNewTsEvent();
    ne->time = GetTicks() + cyclesIntoFuture;
    ne->type = event_type;
    ne->next = 0;
    ne->userdata = userdata;
    if (!tsFirst)
        tsFirst = ne;
    if (tsLast)
        tsLast->next = ne;
    tsLast = ne;

    hasTsEvents.store(1, std::memory_order_release);
}

// Same as ScheduleEvent_Threadsafe(0, ...) EXCEPT if we are already on the CPU thread
// in which case the event will get handled immediately, before returning.
void ScheduleEvent_Threadsafe_Immediate(int event_type, u64 userdata)
{
    if (false) //Core::IsCPUThread())
    {
        std::lock_guard<std::recursive_mutex> lk(externalEventSection);
        event_types[event_type].callback(userdata, 0);
    }
    else
        ScheduleEvent_Threadsafe(0, event_type, userdata);
}

void ClearPendingEvents()
{
    while (first)
    {
        Event *e = first->next;
        FreeEvent(first);
        first = e;
    }
}

void AddEventToQueue(Event* ne)
{
    Event* prev = nullptr;
    Event** pNext = &first;
    for (;;)
    {
        Event*& next = *pNext;
        if (!next || ne->time < next->time)
        {
            ne->next = next;
            next = ne;
            break;
        }
        prev = next;
        pNext = &prev->next;
    }
}

// This must be run ONLY from within the cpu thread
// cyclesIntoFuture may be VERY inaccurate if called from anything else
// than Advance
void ScheduleEvent(s64 cyclesIntoFuture, int event_type, u64 userdata)
{
    Event *ne = GetNewEvent();
    ne->userdata = userdata;
    ne->type = event_type;
    ne->time = GetTicks() + cyclesIntoFuture;
    AddEventToQueue(ne);
}

// Returns cycles left in timer.
s64 UnscheduleEvent(int event_type, u64 userdata)
{
    s64 result = 0;
    if (!first)
        return result;
    while (first)
    {
        if (first->type == event_type && first->userdata == userdata)
        {
            result = first->time - globalTimer;

            Event *next = first->next;
            FreeEvent(first);
            first = next;
        }
        else
        {
            break;
        }
    }
    if (!first)
        return result;
    Event *prev = first;
    Event *ptr = prev->next;
    while (ptr)
    {
        if (ptr->type == event_type && ptr->userdata == userdata)
        {
            result = ptr->time - globalTimer;

            prev->next = ptr->next;
            FreeEvent(ptr);
            ptr = prev->next;
        }
        else
        {
            prev = ptr;
            ptr = ptr->next;
        }
    }

    return result;
}

s64 UnscheduleThreadsafeEvent(int event_type, u64 userdata)
{
    s64 result = 0;
    std::lock_guard<std::recursive_mutex> lk(externalEventSection);
    if (!tsFirst)
        return result;
    while (tsFirst)
    {
        if (tsFirst->type == event_type && tsFirst->userdata == userdata)
        {
            result = tsFirst->time - globalTimer;

            Event *next = tsFirst->next;
            FreeTsEvent(tsFirst);
            tsFirst = next;
        }
        else
        {
            break;
        }
    }
    if (!tsFirst)
    {
        tsLast = nullptr;
        return result;
    }

    Event *prev = tsFirst;
    Event *ptr = prev->next;
    while (ptr)
    {
        if (ptr->type == event_type && ptr->userdata == userdata)
        {
            result = ptr->time - globalTimer;

            prev->next = ptr->next;
            if (ptr == tsLast)
                tsLast = prev;
            FreeTsEvent(ptr);
            ptr = prev->next;
        }
        else
        {
            prev = ptr;
            ptr = ptr->next;
        }
    }

    return result;
}

// Warning: not included in save state.
void RegisterAdvanceCallback(void(*callback)(int cyclesExecuted))
{
    advanceCallback = callback;
}

bool IsScheduled(int event_type)
{
    if (!first)
        return false;
    Event *e = first;
    while (e) {
        if (e->type == event_type)
            return true;
        e = e->next;
    }
    return false;
}

void RemoveEvent(int event_type)
{
    if (!first)
        return;
    while (first)
    {
        if (first->type == event_type)
        {
            Event *next = first->next;
            FreeEvent(first);
            first = next;
        }
        else
        {
            break;
        }
    }
    if (!first)
        return;
    Event *prev = first;
    Event *ptr = prev->next;
    while (ptr)
    {
        if (ptr->type == event_type)
        {
            prev->next = ptr->next;
            FreeEvent(ptr);
            ptr = prev->next;
        }
        else
        {
            prev = ptr;
            ptr = ptr->next;
        }
    }
}

void RemoveThreadsafeEvent(int event_type)
{
    std::lock_guard<std::recursive_mutex> lk(externalEventSection);
    if (!tsFirst)
    {
        return;
    }
    while (tsFirst)
    {
        if (tsFirst->type == event_type)
        {
            Event *next = tsFirst->next;
            FreeTsEvent(tsFirst);
            tsFirst = next;
        }
        else
        {
            break;
        }
    }
    if (!tsFirst)
    {
        tsLast = nullptr;
        return;
    }
    Event *prev = tsFirst;
    Event *ptr = prev->next;
    while (ptr)
    {
        if (ptr->type == event_type)
        {
            prev->next = ptr->next;
            if (ptr == tsLast)
                tsLast = prev;
            FreeTsEvent(ptr);
            ptr = prev->next;
        }
        else
        {
            prev = ptr;
            ptr = ptr->next;
        }
    }
}

void RemoveAllEvents(int event_type)
{
    RemoveThreadsafeEvent(event_type);
    RemoveEvent(event_type);
}

//This raise only the events required while the fifo is processing data
void ProcessFifoWaitEvents()
{
    while (first)
    {
        if (first->time <= globalTimer)
        {
            //LOG(TIMER, "[Scheduler] %s (%lld, %lld) ",
            //    first->name ? first->name : "?", (u64)globalTimer, (u64)first->time);
            Event* evt = first;
            first = first->next;
            event_types[evt->type].callback(evt->userdata, (int)(globalTimer - evt->time));
            FreeEvent(evt);
        }
        else
        {
            break;
        }
    }
}

void MoveEvents()
{
    hasTsEvents.store(0, std::memory_order_release);

    std::lock_guard<std::recursive_mutex> lk(externalEventSection);
    // Move events from async queue into main queue
    while (tsFirst)
    {
        Event *next = tsFirst->next;
        AddEventToQueue(tsFirst);
        tsFirst = next;
    }
    tsLast = nullptr;

    // Move free events to threadsafe pool
    while (allocatedTsEvents > 0 && eventPool)
    {
        Event *ev = eventPool;
        eventPool = ev->next;
        ev->next = eventTsPool;
        eventTsPool = ev;
        allocatedTsEvents--;
    }
}

void Advance()
{
    LOG_ERROR(Core, "Unimplemented function!");
    //int cyclesExecuted = slicelength - currentMIPS->downcount;
    //globalTimer += cyclesExecuted;
    //currentMIPS->downcount = slicelength;

    //if (Common::AtomicLoadAcquire(hasTsEvents))
    //    MoveEvents();
    //ProcessFifoWaitEvents();

    //if (!first)
    //{
    //    // WARN_LOG(TIMER, "WARNING - no events in queue. Setting currentMIPS->downcount to 10000");
    //    currentMIPS->downcount += 10000;
    //}
    //else
    //{
    //    slicelength = (int)(first->time - globalTimer);
    //    if (slicelength > MAX_SLICE_LENGTH)
    //        slicelength = MAX_SLICE_LENGTH;
    //    currentMIPS->downcount = slicelength;
    //}
    //if (advanceCallback)
    //    advanceCallback(cyclesExecuted);
}

void LogPendingEvents()
{
    Event *ptr = first;
    while (ptr)
    {
        //INFO_LOG(TIMER, "PENDING: Now: %lld Pending: %lld Type: %d", globalTimer, ptr->time, ptr->type);
        ptr = ptr->next;
    }
}

void Idle(int maxIdle)
{
    LOG_ERROR(Core, "Unimplemented function!");
    //int cyclesDown = currentMIPS->downcount;
    //if (maxIdle != 0 && cyclesDown > maxIdle)
    //    cyclesDown = maxIdle;

    //if (first && cyclesDown > 0)
    //{
    //    int cyclesExecuted = slicelength - currentMIPS->downcount;
    //    int cyclesNextEvent = (int) (first->time - globalTimer);

    //    if (cyclesNextEvent < cyclesExecuted + cyclesDown)
    //    {
    //        cyclesDown = cyclesNextEvent - cyclesExecuted;
    //        // Now, now... no time machines, please.
    //        if (cyclesDown < 0)
    //            cyclesDown = 0;
    //    }
    //}

    //INFO_LOG(TIME, "Idle for %i cycles! (%f ms)", cyclesDown, cyclesDown / (float)(g_clock_rate_arm11 * 0.001f));

    //idledCycles += cyclesDown;
    //currentMIPS->downcount -= cyclesDown;
    //if (currentMIPS->downcount == 0)
    //    currentMIPS->downcount = -1;
}

std::string GetScheduledEventsSummary()
{
    Event *ptr = first;
    std::string text = "Scheduled events\n";
    text.reserve(1000);
    while (ptr)
    {
        unsigned int t = ptr->type;
        if (t >= event_types.size())
            PanicAlert("Invalid event type"); // %i", t);
        const char *name = event_types[ptr->type].name;
        if (!name)
            name = "[unknown]";

        text += Common::StringFromFormat("%s : %i %08x%08x\n", name, (int)ptr->time,
                                        (u32)(ptr->userdata >> 32), (u32)(ptr->userdata));

        ptr = ptr->next;
    }
    return text;
}

void Event_DoState(PointerWrap &p, BaseEvent *ev)
{
    p.Do(*ev);
}

void DoState(PointerWrap &p)
{
    std::lock_guard<std::recursive_mutex> lk(externalEventSection);

    auto s = p.Section("CoreTiming", 1);
    if (!s)
        return;

    int n = (int)event_types.size();
    p.Do(n);
    // These (should) be filled in later by the modules.
    event_types.resize(n, EventType(AntiCrashCallback, "INVALID EVENT"));

    p.DoLinkedList<BaseEvent, GetNewEvent, FreeEvent, Event_DoState>(first, (Event **)nullptr);
    p.DoLinkedList<BaseEvent, GetNewTsEvent, FreeTsEvent, Event_DoState>(tsFirst, &tsLast);

    p.Do(g_clock_rate_arm11);
    p.Do(slicelength);
    p.Do(globalTimer);
    p.Do(idledCycles);
}

} // namespace
