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

#include <algorithm>
#include <list>
#include <vector>

#include "common/common.h"
#include "common/thread_queue_list.h"

#include "core/arm/arm_interface.h"
#include "core/core.h"
#include "core/core_timing.h"
#include "core/hle/hle.h"
#include "core/hle/kernel/kernel.h"
#include "core/hle/kernel/thread.h"
#include "core/hle/kernel/mutex.h"
#include "core/hle/result.h"
#include "core/mem_map.h"

namespace Kernel {

bool Thread::ShouldWait() {
    return status != THREADSTATUS_DORMANT;
}

void Thread::Acquire() {
    _assert_msg_(Kernel, !ShouldWait(), "object unavailable!");
}

// Lists all thread ids that aren't deleted/etc.
static std::vector<SharedPtr<Thread>> thread_list;

// Lists only ready thread ids.
static Common::ThreadQueueList<Thread*, THREADPRIO_LOWEST+1> thread_ready_queue;

static Thread* current_thread;

static const u32 INITIAL_THREAD_ID = 1; ///< The first available thread id at startup
static u32 next_thread_id; ///< The next available thread id

Thread* GetCurrentThread() {
    return current_thread;
}

/// Resets a thread
static void ResetThread(Thread* t, u32 arg, s32 lowest_priority) {
    memset(&t->context, 0, sizeof(Core::ThreadContext));

    t->context.cpu_registers[0] = arg;
    t->context.pc = t->entry_point;
    t->context.sp = t->stack_top;
    t->context.cpsr = 0x1F; // Usermode

    // TODO(bunnei): This instructs the CPU core to start the execution as if it is "resuming" a
    // thread. This is somewhat Sky-Eye specific, and should be re-architected in the future to be
    // agnostic of the CPU core.
    t->context.mode = 8;

    if (t->current_priority < lowest_priority) {
        t->current_priority = t->initial_priority;
    }

    t->wait_objects.clear();
    t->wait_address = 0;
}

/// Change a thread to "ready" state
static void ChangeReadyState(Thread* t, bool ready) {
    if (t->IsReady()) {
        if (!ready) {
            thread_ready_queue.remove(t->current_priority, t);
        }
    }  else if (ready) {
        if (t->IsRunning()) {
            thread_ready_queue.push_front(t->current_priority, t);
        } else {
            thread_ready_queue.push_back(t->current_priority, t);
        }
        t->status = THREADSTATUS_READY;
    }
}

/// Check if a thread is waiting on a the specified wait object
static bool CheckWait_WaitObject(const Thread* thread, WaitObject* wait_object) {
    auto itr = std::find(thread->wait_objects.begin(), thread->wait_objects.end(), wait_object);

    if (itr != thread->wait_objects.end())
        return thread->IsWaiting();

    return false;
}

/// Check if the specified thread is waiting on the specified address to be arbitrated
static bool CheckWait_AddressArbiter(const Thread* thread, VAddr wait_address) {
    return thread->IsWaiting() && thread->wait_objects.empty() && wait_address == thread->wait_address;
}

/// Stops the current thread
void Thread::Stop(const char* reason) {
    // Release all the mutexes that this thread holds
    ReleaseThreadMutexes(this);

    ChangeReadyState(this, false);
    status = THREADSTATUS_DORMANT;
    WakeupAllWaitingThreads();

    // Stopped threads are never waiting.
    wait_objects.clear();
    wait_address = 0;
}

/// Changes a threads state
static void ChangeThreadState(Thread* t, ThreadStatus new_status) {
    if (!t || t->status == new_status) {
        return;
    }
    ChangeReadyState(t, (new_status & THREADSTATUS_READY) != 0);
    t->status = new_status;
}

/// Arbitrate the highest priority thread that is waiting
Thread* ArbitrateHighestPriorityThread(u32 address) {
    Thread* highest_priority_thread = nullptr;
    s32 priority = THREADPRIO_LOWEST;

    // Iterate through threads, find highest priority thread that is waiting to be arbitrated...
    for (auto& thread : thread_list) {
        if (!CheckWait_AddressArbiter(thread.get(), address))
            continue;

        if (thread == nullptr)
            continue;

        if(thread->current_priority <= priority) {
            highest_priority_thread = thread.get();
            priority = thread->current_priority;
        }
    }

    // If a thread was arbitrated, resume it
    if (nullptr != highest_priority_thread) {
        highest_priority_thread->ResumeFromWait();
    }

    return highest_priority_thread;
}

/// Arbitrate all threads currently waiting
void ArbitrateAllThreads(u32 address) {

    // Iterate through threads, find highest priority thread that is waiting to be arbitrated...
    for (auto& thread : thread_list) {
        if (CheckWait_AddressArbiter(thread.get(), address))
            thread->ResumeFromWait();
    }
}

/// Calls a thread by marking it as "ready" (note: will not actually execute until current thread yields)
static void CallThread(Thread* t) {
    // Stop waiting
    ChangeThreadState(t, THREADSTATUS_READY);
}

/// Switches CPU context to that of the specified thread
static void SwitchContext(Thread* t) {
    Thread* cur = GetCurrentThread();

    // Save context for current thread
    if (cur) {
        Core::g_app_core->SaveContext(cur->context);

        if (cur->IsRunning()) {
            ChangeReadyState(cur, true);
        }
    }
    // Load context of new thread
    if (t) {
        current_thread = t;
        ChangeReadyState(t, false);
        t->status = (t->status | THREADSTATUS_RUNNING) & ~THREADSTATUS_READY;
        Core::g_app_core->LoadContext(t->context);
    } else {
        current_thread = nullptr;
    }
}

/// Gets the next thread that is ready to be run by priority
static Thread* NextThread() {
    Thread* next;
    Thread* cur = GetCurrentThread();

    if (cur && cur->IsRunning()) {
        next = thread_ready_queue.pop_first_better(cur->current_priority);
    } else  {
        next = thread_ready_queue.pop_first();
    }
    if (next == 0) {
        return nullptr;
    }
    return next;
}

void WaitCurrentThread_Sleep() {
    Thread* thread = GetCurrentThread();
    ChangeThreadState(thread, ThreadStatus(THREADSTATUS_WAIT | (thread->status & THREADSTATUS_SUSPEND)));
}

void WaitCurrentThread_WaitSynchronization(SharedPtr<WaitObject> wait_object, bool wait_set_output, bool wait_all) {
    Thread* thread = GetCurrentThread();
    thread->wait_set_output = wait_set_output;
    thread->wait_all = wait_all;

    // It's possible to call WaitSynchronizationN without any objects passed in...
    if (wait_object != nullptr)
        thread->wait_objects.push_back(wait_object);

    ChangeThreadState(thread, ThreadStatus(THREADSTATUS_WAIT | (thread->status & THREADSTATUS_SUSPEND)));
}

void WaitCurrentThread_ArbitrateAddress(VAddr wait_address) {
    Thread* thread = GetCurrentThread();
    thread->wait_address = wait_address;
    ChangeThreadState(thread, ThreadStatus(THREADSTATUS_WAIT | (thread->status & THREADSTATUS_SUSPEND)));
}

/// Event type for the thread wake up event
static int ThreadWakeupEventType = -1;
// TODO(yuriks): This can be removed if Thread objects are explicitly pooled in the future, allowing
//               us to simply use a pool index or similar.
static Kernel::HandleTable wakeup_callback_handle_table;

/// Callback that will wake up the thread it was scheduled for
static void ThreadWakeupCallback(u64 thread_handle, int cycles_late) {
    SharedPtr<Thread> thread = wakeup_callback_handle_table.Get<Thread>((Handle)thread_handle);
    if (thread == nullptr) {
        LOG_CRITICAL(Kernel, "Callback fired for invalid thread %08X", thread_handle);
        return;
    }

    thread->SetWaitSynchronizationResult(ResultCode(ErrorDescription::Timeout, ErrorModule::OS,
        ErrorSummary::StatusChanged, ErrorLevel::Info));

    if (thread->wait_set_output)
        thread->SetWaitSynchronizationOutput(-1);

    thread->ResumeFromWait();
}


void Thread::WakeAfterDelay(s64 nanoseconds) {
    // Don't schedule a wakeup if the thread wants to wait forever
    if (nanoseconds == -1)
        return;

    u64 microseconds = nanoseconds / 1000;
    CoreTiming::ScheduleEvent(usToCycles(microseconds), ThreadWakeupEventType, callback_handle);
}

void Thread::ReleaseWaitObject(WaitObject* wait_object) {
    if (wait_objects.empty()) {
        LOG_CRITICAL(Kernel, "thread is not waiting on any objects!");
        return;
    }

    // Remove this thread from the waiting object's thread list
    wait_object->RemoveWaitingThread(this);

    unsigned index = 0;
    bool wait_all_failed = false; // Will be set to true if any object is unavailable

    // Iterate through all waiting objects to check availability...
    for (auto itr = wait_objects.begin(); itr != wait_objects.end(); ++itr) {
        if ((*itr)->ShouldWait())
            wait_all_failed = true;

        // The output should be the last index of wait_object
        if (*itr == wait_object)
            index = itr - wait_objects.begin();
    }

    // If we are waiting on all objects...
    if (wait_all) {
        // Resume the thread only if all are available...
        if (!wait_all_failed) {
            SetWaitSynchronizationResult(RESULT_SUCCESS);
            SetWaitSynchronizationOutput(-1);

            ResumeFromWait();
        }
    } else {
        // Otherwise, resume
        SetWaitSynchronizationResult(RESULT_SUCCESS);

        if (wait_set_output)
            SetWaitSynchronizationOutput(index);

        ResumeFromWait();
    }
}

void Thread::ResumeFromWait() {
    // Cancel any outstanding wakeup events
    CoreTiming::UnscheduleEvent(ThreadWakeupEventType, callback_handle);

    status &= ~THREADSTATUS_WAIT;

    // Remove this thread from all other WaitObjects
    for (auto wait_object : wait_objects)
        wait_object->RemoveWaitingThread(this);

    wait_objects.clear();
    wait_set_output = false;
    wait_all = false;
    wait_address = 0;

    if (!(status & (THREADSTATUS_WAITSUSPEND | THREADSTATUS_DORMANT | THREADSTATUS_DEAD))) {
        ChangeReadyState(this, true);
    }
}

/// Prints the thread queue for debugging purposes
static void DebugThreadQueue() {
    Thread* thread = GetCurrentThread();
    if (!thread) {
        return;
    }
    LOG_DEBUG(Kernel, "0x%02X %u (current)", thread->current_priority, GetCurrentThread()->GetObjectId());
    for (auto& t : thread_list) {
        s32 priority = thread_ready_queue.contains(t.get());
        if (priority != -1) {
            LOG_DEBUG(Kernel, "0x%02X %u", priority, t->GetObjectId());
        }
    }
}

ResultVal<SharedPtr<Thread>> Thread::Create(std::string name, VAddr entry_point, s32 priority,
        u32 arg, s32 processor_id, VAddr stack_top, u32 stack_size) {
    if (stack_size < 0x200) {
        LOG_ERROR(Kernel, "(name=%s): invalid stack_size=0x%08X", name.c_str(), stack_size);
        // TODO: Verify error
        return ResultCode(ErrorDescription::InvalidSize, ErrorModule::Kernel,
                ErrorSummary::InvalidArgument, ErrorLevel::Permanent);
    }

    if (priority < THREADPRIO_HIGHEST || priority > THREADPRIO_LOWEST) {
        s32 new_priority = CLAMP(priority, THREADPRIO_HIGHEST, THREADPRIO_LOWEST);
        LOG_WARNING(Kernel_SVC, "(name=%s): invalid priority=%d, clamping to %d",
            name.c_str(), priority, new_priority);
        // TODO(bunnei): Clamping to a valid priority is not necessarily correct behavior... Confirm
        // validity of this
        priority = new_priority;
    }

    if (!Memory::GetPointer(entry_point)) {
        LOG_ERROR(Kernel_SVC, "(name=%s): invalid entry %08x", name.c_str(), entry_point);
        // TODO: Verify error
        return ResultCode(ErrorDescription::InvalidAddress, ErrorModule::Kernel,
                ErrorSummary::InvalidArgument, ErrorLevel::Permanent);
    }

    SharedPtr<Thread> thread(new Thread);

    // TODO(yuriks): Thread requires a handle to be inserted into the various scheduling queues for
    //               the time being. Create a handle here, it will be copied to the handle field in
    //               the object and use by the rest of the code. This should be removed when other
    //               code doesn't rely on the handle anymore.
    ResultVal<Handle> handle = Kernel::g_handle_table.Create(thread);
    if (handle.Failed())
        return handle.Code();

    thread_list.push_back(thread);
    thread_ready_queue.prepare(priority);

    thread->thread_id = next_thread_id++;
    thread->status = THREADSTATUS_DORMANT;
    thread->entry_point = entry_point;
    thread->stack_top = stack_top;
    thread->stack_size = stack_size;
    thread->initial_priority = thread->current_priority = priority;
    thread->processor_id = processor_id;
    thread->wait_set_output = false;
    thread->wait_all = false;
    thread->wait_objects.clear();
    thread->wait_address = 0;
    thread->name = std::move(name);
    thread->callback_handle = wakeup_callback_handle_table.Create(thread).MoveFrom();

    ResetThread(thread.get(), arg, 0);
    CallThread(thread.get());

    return MakeResult<SharedPtr<Thread>>(std::move(thread));
}

/// Set the priority of the thread specified by handle
void Thread::SetPriority(s32 priority) {
    // If priority is invalid, clamp to valid range
    if (priority < THREADPRIO_HIGHEST || priority > THREADPRIO_LOWEST) {
        s32 new_priority = CLAMP(priority, THREADPRIO_HIGHEST, THREADPRIO_LOWEST);
        LOG_WARNING(Kernel_SVC, "invalid priority=%d, clamping to %d", priority, new_priority);
        // TODO(bunnei): Clamping to a valid priority is not necessarily correct behavior... Confirm
        // validity of this
        priority = new_priority;
    }

    // Change thread priority
    s32 old = current_priority;
    thread_ready_queue.remove(old, this);
    current_priority = priority;
    thread_ready_queue.prepare(current_priority);

    // Change thread status to "ready" and push to ready queue
    if (IsRunning()) {
        status = (status & ~THREADSTATUS_RUNNING) | THREADSTATUS_READY;
    }
    if (IsReady()) {
        thread_ready_queue.push_back(current_priority, this);
    }
}

SharedPtr<Thread> SetupIdleThread() {
    // We need to pass a few valid values to get around parameter checking in Thread::Create.
    auto thread = Thread::Create("idle", Memory::KERNEL_MEMORY_VADDR, THREADPRIO_LOWEST, 0,
            THREADPROCESSORID_0, 0, Kernel::DEFAULT_STACK_SIZE).MoveFrom();

    thread->idle = true;
    CallThread(thread.get());
    return thread;
}

SharedPtr<Thread> SetupMainThread(s32 priority, u32 stack_size) {
    // Initialize new "main" thread
    auto thread_res = Thread::Create("main", Core::g_app_core->GetPC(), priority, 0,
            THREADPROCESSORID_0, Memory::SCRATCHPAD_VADDR_END, stack_size);
    // TODO(yuriks): Propagate error
    _dbg_assert_(Kernel, thread_res.Succeeded());
    SharedPtr<Thread> thread = std::move(*thread_res);

    // If running another thread already, set it to "ready" state
    Thread* cur = GetCurrentThread();
    if (cur && cur->IsRunning()) {
        ChangeReadyState(cur, true);
    }

    // Run new "main" thread
    current_thread = thread.get();
    thread->status = THREADSTATUS_RUNNING;
    Core::g_app_core->LoadContext(thread->context);

    return thread;
}


/// Reschedules to the next available thread (call after current thread is suspended)
void Reschedule() {
    Thread* prev = GetCurrentThread();
    Thread* next = NextThread();
    HLE::g_reschedule = false;

    if (next != nullptr) {
        LOG_TRACE(Kernel, "context switch %u -> %u", prev->GetObjectId(), next->GetObjectId());
        SwitchContext(next);
    } else {
        LOG_TRACE(Kernel, "cannot context switch from %u, no higher priority thread!", prev->GetObjectId());

        for (auto& thread : thread_list) {
            LOG_TRACE(Kernel, "\tid=%u prio=0x%02X, status=0x%08X", thread->GetObjectId(), 
                      thread->current_priority, thread->status);
        }
    }
}

void Thread::SetWaitSynchronizationResult(ResultCode result) {
    context.cpu_registers[0] = result.raw;
}

void Thread::SetWaitSynchronizationOutput(s32 output) {
    context.cpu_registers[1] = output;
}

////////////////////////////////////////////////////////////////////////////////////////////////////

void ThreadingInit() {
    next_thread_id = INITIAL_THREAD_ID;
    ThreadWakeupEventType = CoreTiming::RegisterEvent("ThreadWakeupCallback", ThreadWakeupCallback);
}

void ThreadingShutdown() {
}

} // namespace
