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

#include <algorithm>
#include "common/assert.h"
#include "common/logging/log.h"
#include "core/hle/config_mem.h"
#include "core/hle/kernel/kernel.h"
#include "core/hle/kernel/memory.h"
#include "core/hle/kernel/process.h"
#include "core/hle/kernel/resource_limit.h"
#include "core/hle/kernel/thread.h"
#include "core/hle/kernel/timer.h"
#include "core/hle/shared_page.h"

namespace Kernel {

unsigned int Object::next_object_id;
HandleTable g_handle_table;

void WaitObject::AddWaitingThread(SharedPtr<Thread> thread) {
    auto itr = std::find(waiting_threads.begin(), waiting_threads.end(), thread);
    if (itr == waiting_threads.end())
        waiting_threads.push_back(std::move(thread));
}

void WaitObject::RemoveWaitingThread(Thread* thread) {
    auto itr = std::find(waiting_threads.begin(), waiting_threads.end(), thread);
    if (itr != waiting_threads.end())
        waiting_threads.erase(itr);
}

SharedPtr<Thread> WaitObject::GetHighestPriorityReadyThread() {
    // Remove the threads that are ready or already running from our waitlist
    auto to_remove = waiting_threads.end();
    do {
        to_remove = std::find_if(waiting_threads.begin(), waiting_threads.end(),
                                 [](const SharedPtr<Thread>& thread) {
                                    return thread->status == THREADSTATUS_RUNNING ||
                                           thread->status == THREADSTATUS_READY ||
                                           thread->status == THREADSTATUS_DEAD;
        });
        // Call RemoveWaitingThread so that child classes can override the behavior.
        RemoveWaitingThread(to_remove->get());
    } while (to_remove != waiting_threads.end());

    Thread* candidate = nullptr;
    s32 candidate_priority = THREADPRIO_LOWEST + 1;

    for (const auto& thread : waiting_threads) {
        if (thread->current_priority >= candidate_priority)
            continue;

        if (ShouldWait(thread.get()))
            continue;

        bool ready_to_run = std::none_of(thread->wait_objects.begin(), thread->wait_objects.end(),
                                        [&thread](const SharedPtr<WaitObject>& object) {
                                            return object->ShouldWait(thread.get());
                                        });
        if (ready_to_run) {
            candidate = thread.get();
            candidate_priority = thread->current_priority;
        }
    }

    return candidate;
}

void WaitObject::WakeupAllWaitingThreads() {
    while (auto thread = GetHighestPriorityReadyThread()) {
        if (!thread->IsSleepingOnWaitAll()) {
            Acquire(thread.get());
            // Set the output index of the WaitSynchronizationN call to the index of this object.
            if (thread->wait_set_output) {
                thread->SetWaitSynchronizationOutput(thread->GetWaitObjectIndex(this));
                thread->wait_set_output = false;
            }
        } else {
            for (auto& object : thread->wait_objects) {
                object->Acquire(thread.get());
                object->RemoveWaitingThread(thread.get());
            }
            // Note: This case doesn't update the output index of WaitSynchronizationN.
            // Clear the thread's waitlist
            thread->wait_objects.clear();
        }

        thread->SetWaitSynchronizationResult(RESULT_SUCCESS);
        thread->ResumeFromWait();
        // Note: Removing the thread from the object's waitlist will be
        // done by GetHighestPriorityReadyThread.
    }
}

const std::vector<SharedPtr<Thread>>& WaitObject::GetWaitingThreads() const {
    return waiting_threads;
}

HandleTable::HandleTable() {
    next_generation = 1;
    Clear();
}

ResultVal<Handle> HandleTable::Create(SharedPtr<Object> obj) {
    DEBUG_ASSERT(obj != nullptr);

    u16 slot = next_free_slot;
    if (slot >= generations.size()) {
        LOG_ERROR(Kernel, "Unable to allocate Handle, too many slots in use.");
        return ERR_OUT_OF_HANDLES;
    }
    next_free_slot = generations[slot];

    u16 generation = next_generation++;

    // Overflow count so it fits in the 15 bits dedicated to the generation in the handle.
    // CTR-OS doesn't use generation 0, so skip straight to 1.
    if (next_generation >= (1 << 15))
        next_generation = 1;

    generations[slot] = generation;
    objects[slot] = std::move(obj);

    Handle handle = generation | (slot << 15);
    return MakeResult<Handle>(handle);
}

ResultVal<Handle> HandleTable::Duplicate(Handle handle) {
    SharedPtr<Object> object = GetGeneric(handle);
    if (object == nullptr) {
        LOG_ERROR(Kernel, "Tried to duplicate invalid handle: %08X", handle);
        return ERR_INVALID_HANDLE;
    }
    return Create(std::move(object));
}

ResultCode HandleTable::Close(Handle handle) {
    if (!IsValid(handle))
        return ERR_INVALID_HANDLE;

    u16 slot = GetSlot(handle);

    objects[slot] = nullptr;

    generations[slot] = next_free_slot;
    next_free_slot = slot;
    return RESULT_SUCCESS;
}

bool HandleTable::IsValid(Handle handle) const {
    size_t slot = GetSlot(handle);
    u16 generation = GetGeneration(handle);

    return slot < MAX_COUNT && objects[slot] != nullptr && generations[slot] == generation;
}

SharedPtr<Object> HandleTable::GetGeneric(Handle handle) const {
    if (handle == CurrentThread) {
        return GetCurrentThread();
    } else if (handle == CurrentProcess) {
        return g_current_process;
    }

    if (!IsValid(handle)) {
        return nullptr;
    }
    return objects[GetSlot(handle)];
}

void HandleTable::Clear() {
    for (u16 i = 0; i < MAX_COUNT; ++i) {
        generations[i] = i + 1;
        objects[i] = nullptr;
    }
    next_free_slot = 0;
}

/// Initialize the kernel
void Init(u32 system_mode) {
    ConfigMem::Init();
    SharedPage::Init();

    Kernel::MemoryInit(system_mode);

    Kernel::ResourceLimitsInit();
    Kernel::ThreadingInit();
    Kernel::TimersInit();

    Object::next_object_id = 0;
    // TODO(Subv): Start the process ids from 10 for now, as lower PIDs are
    // reserved for low-level services
    Process::next_process_id = 10;
}

/// Shutdown the kernel
void Shutdown() {
    g_handle_table.Clear(); // Free all kernel objects

    Kernel::ThreadingShutdown();
    g_current_process = nullptr;

    Kernel::TimersShutdown();
    Kernel::ResourceLimitsShutdown();
    Kernel::MemoryShutdown();
}

} // namespace
