// SPDX-FileCopyrightText: Copyright 2024 shadPS4 Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#include "common/assert.h"
#include "common/debug.h"
#include "common/logging/log.h"
#include "core/libraries/error_codes.h"
#include "core/libraries/kernel/event_queues.h"

#include <boost/asio/placeholders.hpp>

namespace Libraries::Kernel {

extern boost::asio::io_context io_context;
extern void KernelSignalRequest();

static constexpr auto HrTimerSpinlockThresholdUs = 1200u;

static void SmallTimerCallback(const boost::system::error_code& error, SceKernelEqueue eq,
                               SceKernelEvent kevent) {
    static EqueueEvent event;
    event.event = kevent;
    event.event.data = HrTimerSpinlockThresholdUs;
    eq->AddSmallTimer(event);
    eq->TriggerEvent(kevent.ident, SceKernelEvent::Filter::HrTimer, kevent.udata);
}

int PS4_SYSV_ABI sceKernelCreateEqueue(SceKernelEqueue* eq, const char* name) {
    if (eq == nullptr) {
        LOG_ERROR(Kernel_Event, "Event queue is null!");
        return ORBIS_KERNEL_ERROR_EINVAL;
    }
    if (name == nullptr) {
        LOG_ERROR(Kernel_Event, "Event queue name is null!");
        return ORBIS_KERNEL_ERROR_EINVAL;
    }

    // Maximum is 32 including null terminator
    static constexpr size_t MaxEventQueueNameSize = 32;
    if (std::strlen(name) > MaxEventQueueNameSize) {
        LOG_ERROR(Kernel_Event, "Event queue name exceeds 32 bytes!");
        return ORBIS_KERNEL_ERROR_ENAMETOOLONG;
    }

    LOG_INFO(Kernel_Event, "name = {}", name);

    *eq = new EqueueInternal;
    (*eq)->setName(std::string(name));
    return ORBIS_OK;
}

int PS4_SYSV_ABI sceKernelDeleteEqueue(SceKernelEqueue eq) {
    if (eq == nullptr) {
        return ORBIS_KERNEL_ERROR_EBADF;
    }

    delete eq;
    return ORBIS_OK;
}

int PS4_SYSV_ABI sceKernelWaitEqueue(SceKernelEqueue eq, SceKernelEvent* ev, int num, int* out,
                                     SceKernelUseconds* timo) {
    HLE_TRACE;
    TRACE_HINT(eq->GetName());
    LOG_TRACE(Kernel_Event, "equeue = {} num = {}", eq->GetName(), num);

    if (eq == nullptr) {
        return ORBIS_KERNEL_ERROR_EBADF;
    }

    if (ev == nullptr) {
        return ORBIS_KERNEL_ERROR_EFAULT;
    }

    if (num < 1) {
        return ORBIS_KERNEL_ERROR_EINVAL;
    }

    if (eq->HasSmallTimer()) {
        ASSERT(timo && *timo);
        *out = eq->WaitForSmallTimer(ev, num, *timo);
    } else {
        if (timo == nullptr) { // wait until an event arrives without timing out
            *out = eq->WaitForEvents(ev, num, 0);
        }

        if (timo != nullptr) {
            // Only events that have already arrived at the time of this function call can be
            // received
            if (*timo == 0) {
                *out = eq->GetTriggeredEvents(ev, num);
            } else {
                // Wait until an event arrives with timing out
                *out = eq->WaitForEvents(ev, num, *timo);
            }
        }
    }

    if (*out == 0) {
        return ORBIS_KERNEL_ERROR_ETIMEDOUT;
    }

    return ORBIS_OK;
}

s32 PS4_SYSV_ABI sceKernelAddHRTimerEvent(SceKernelEqueue eq, int id, timespec* ts, void* udata) {
    if (eq == nullptr) {
        return ORBIS_KERNEL_ERROR_EBADF;
    }

    if (ts->tv_sec > 100 || ts->tv_nsec < 100'000) {
        return ORBIS_KERNEL_ERROR_EINVAL;
    }
    ASSERT(ts->tv_nsec > 1000); // assume 1us resolution
    const auto total_us = ts->tv_sec * 1000'000 + ts->tv_nsec / 1000;

    EqueueEvent event{};
    event.event.ident = id;
    event.event.filter = SceKernelEvent::Filter::HrTimer;
    event.event.flags = SceKernelEvent::Flags::Add | SceKernelEvent::Flags::OneShot;
    event.event.fflags = 0;
    event.event.data = total_us;
    event.event.udata = udata;

    // HR timers cannot be implemented within the existing event queue architecture due to the
    // slowness of the notification mechanism. For instance, a 100us timer will lose its precision
    // as the trigger time drifts by +50-700%, depending on the host PC and workload. To address
    // this issue, we use a spinlock for small waits (which can be adjusted using
    // `HrTimerSpinlockThresholdUs`) and fall back to boost asio timers if the time to tick is
    // large. Even for large delays, we truncate a small portion to complete the wait
    // using the spinlock, prioritizing precision.
    if (total_us < HrTimerSpinlockThresholdUs) {
        return eq->AddSmallTimer(event) ? ORBIS_OK : ORBIS_KERNEL_ERROR_ENOMEM;
    }

    event.timer = std::make_unique<boost::asio::steady_timer>(
        io_context, std::chrono::microseconds(total_us - HrTimerSpinlockThresholdUs));

    event.timer->async_wait(
        std::bind(SmallTimerCallback, boost::asio::placeholders::error, eq, event.event));

    if (!eq->AddEvent(event)) {
        return ORBIS_KERNEL_ERROR_ENOMEM;
    }

    KernelSignalRequest();

    return ORBIS_OK;
}

int PS4_SYSV_ABI sceKernelAddUserEvent(SceKernelEqueue eq, int id) {
    if (eq == nullptr) {
        return ORBIS_KERNEL_ERROR_EBADF;
    }

    EqueueEvent event{};
    event.event.ident = id;
    event.event.filter = SceKernelEvent::Filter::User;
    event.event.udata = 0;
    event.event.flags = SceKernelEvent::Flags::Add;
    event.event.fflags = 0;
    event.event.data = 0;

    return eq->AddEvent(event) ? ORBIS_OK : ORBIS_KERNEL_ERROR_ENOMEM;
}

int PS4_SYSV_ABI sceKernelAddUserEventEdge(SceKernelEqueue eq, int id) {
    if (eq == nullptr) {
        return ORBIS_KERNEL_ERROR_EBADF;
    }

    EqueueEvent event{};
    event.event.ident = id;
    event.event.filter = SceKernelEvent::Filter::User;
    event.event.udata = 0;
    event.event.flags = SceKernelEvent::Flags::Add | SceKernelEvent::Flags::Clear;
    event.event.fflags = 0;
    event.event.data = 0;

    return eq->AddEvent(event) ? ORBIS_OK : ORBIS_KERNEL_ERROR_ENOMEM;
}

void* PS4_SYSV_ABI sceKernelGetEventUserData(const SceKernelEvent* ev) {
    ASSERT(ev);
    return ev->udata;
}

u64 PS4_SYSV_ABI sceKernelGetEventId(const SceKernelEvent* ev) {
    return ev->ident;
}

int PS4_SYSV_ABI sceKernelTriggerUserEvent(SceKernelEqueue eq, int id, void* udata) {
    if (eq == nullptr) {
        return ORBIS_KERNEL_ERROR_EBADF;
    }

    if (!eq->TriggerEvent(id, SceKernelEvent::Filter::User, udata)) {
        return ORBIS_KERNEL_ERROR_ENOENT;
    }
    return ORBIS_OK;
}

int PS4_SYSV_ABI sceKernelDeleteUserEvent(SceKernelEqueue eq, int id) {
    if (eq == nullptr) {
        return ORBIS_KERNEL_ERROR_EBADF;
    }

    if (!eq->RemoveEvent(id)) {
        return ORBIS_KERNEL_ERROR_ENOENT;
    }
    return ORBIS_OK;
}

} // namespace Libraries::Kernel