/*
* All or portions of this file Copyright (c) Amazon.com, Inc. or its affiliates or
* its licensors.
*
* For complete copyright and license terms please see the LICENSE at the root of this
* distribution (the "License"). All use of this software is governed by the License,
* or, if provided, by the license below or the license accompanying this file. Do not
* remove or modify any license notices. This file is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*
*/
// Original file Copyright Crytek GMBH or its affiliates, used under license.

#include "StdAfx.h"
#include "BackgroundTaskManager.h"

namespace BackgroundTaskManager
{
    //-----------------------------------------------------------------------------

    CTaskManager::CThread::CThread(class CTaskManager* pManager, CQueue* pQueue)
        : m_pManager(pManager)
        , m_pQueue(pQueue)
    {
        start();
    }

    CTaskManager::CThread::~CThread()
    {
    }

    void CTaskManager::CThread::WaitForThread()
    {
        wait();
    }

    void CTaskManager::CThread::run()
    {
        CryThreadSetName(-1, "BackgroundTaskThread");

        while (!m_pManager->IsStopped())
        {
            STaskHandle taskHandle;

            // This blocks on Semaphore waiting for task from queue
            m_pQueue->PopTask(taskHandle);

            // Should not happen but it's a stupid way to crash :)
            if (NULL == taskHandle.pTask)
            {
                continue;
            }

            if (taskHandle.pTask->IsCanceled())
            {
                // Task was canceled before we got here
                m_pManager->AddCompletedTask(taskHandle, eTaskResult_Canceled);
            }
            else
            {
                const ETaskResult state = taskHandle.pTask->Work();

                if (state == eTaskResult_Resume)
                {
                    // Put it back into queue, so more important task can take over.
                    m_pManager->AddTask(taskHandle);
                }
                else
                {
                    // Finish task
                    m_pManager->AddCompletedTask(taskHandle, state);
                }
            }
        }
    }

    //-----------------------------------------------------------------------------

    CTaskManager::CQueue::CQueue()
        : m_semaphore(INT_MAX, 0) // no good maximum value, assume worst case
    {
    }

    void CTaskManager::CQueue::AddTask(const STaskHandle& taskHandle)
    {
        {
            CryAutoLock<CryMutex> lock(m_lock);

            // TODO: use heap?
            m_pendingTasks.insert(m_pendingTasks.begin(), taskHandle);
            std::stable_sort(m_pendingTasks.begin(), m_pendingTasks.end());
        }

        taskHandle.pTask->SetState(eTaskState_Pending);

        // release internal semaphore so threads can pick up the work
        m_semaphore.Release();
    }

    void CTaskManager::CQueue::PopTask(STaskHandle& outTaskHandle)
    {
        // wait for job
        m_semaphore.Acquire();

        {
            CryAutoLock<CryMutex> lock(m_lock);

            if (m_pendingTasks.empty())
            {
                outTaskHandle.pTask = NULL;
            }
            else
            {
                outTaskHandle = m_pendingTasks.back();
                outTaskHandle.pTask->SetState(eTaskState_Working);
                m_pendingTasks.pop_back();
            }
        }
    }

    void CTaskManager::CQueue::ReleaseSemaphore()
    {
        m_semaphore.Release();
    }

    void CTaskManager::CQueue::Clear()
    {
        CryAutoLock<CryMutex> lock(m_lock);
        for (uint i = 0; i < m_pendingTasks.size(); ++i)
        {
            m_pendingTasks[i].pTask->Release();
        }

        m_pendingTasks.clear();
    }

    //-----------------------------------------------------------------------------

    CTaskManager::CTaskManager()
        : m_bStop(false)
        , m_nextTaskID(1)
        , m_listeners(1)
    {
        GetIEditor()->RegisterNotifyListener(this);
    }

    CTaskManager::~CTaskManager()
    {
        if (!m_bStop)
        {
            Stop();
        }
    }

    void CTaskManager::Start(const uint32 threadCount /*=kDefaultThreadCount*/)
    {
        m_bStop = false;

        if (m_pThreads.empty())
        {
            // Always create one IO thread
            {
                CThread* pThread = new CThread(this, &m_pendingTasks[ eTaskThreadMask_IO ]);
                m_pThreads.push_back(pThread);
            }

            // We also need at least one generic thread
            const uint32 numGenericThreads = max<uint32>(threadCount, 1);
            for (uint32 i = 0; i < numGenericThreads; ++i)
            {
                CThread* pThread = new CThread(this, &m_pendingTasks[ eTaskThreadMask_Any ]);
                m_pThreads.push_back(pThread);
            }
        }
    }

    void CTaskManager::StartScheduledTasks()
    {
        CryAutoLock<CryMutex> lock(m_tasksLock);

        if (!m_scheduledTasks.empty())
        {
            const unsigned int time = GetTickCount();
            while (!m_scheduledTasks.empty())
            {
                const int delta = (int)(time - m_scheduledTasks[0].time);
                if (delta > 0)
                {
                    // the soonest task on the list is still in the future, no point in looking at the next entries in the list
                    break;
                }

                // promote the scheduled task to be a full task
                AddTask(m_scheduledTasks[0].handle);

                // We held a reference to the task on list, release it
                m_scheduledTasks[0].handle.pTask->Release();

                m_scheduledTasks.erase(m_scheduledTasks.begin());
            }
        }
    }

    void CTaskManager::Stop()
    {
        if (!m_bStop)
        {
            m_bStop = true;
            GetIEditor()->UnregisterNotifyListener(this);

            // clear queues - no new tasks will be processed
            for (uint32 i = 0; i < eTaskThreadMask_COUNT; ++i)
            {
                m_pendingTasks[i].Clear();
            }

            // kick all the threads to allow them to quit
            for (uint32 j = 0; j < m_pThreads.size(); ++j)
            {
                for (uint32 i = 0; i < eTaskThreadMask_COUNT; ++i)
                {
                    m_pendingTasks[i].ReleaseSemaphore();
                }
            }

            // Stop threads
            for (TWorkerThreads::iterator it = m_pThreads.begin();
                 it != m_pThreads.end(); ++it)
            {
                (*it)->WaitForThread();
                delete *it;
            }

            m_pThreads.clear();
        }
    }

    void CTaskManager::AddListener(IBackgroundTaskManagerListener* pListener, const char* name)
    {
        m_listeners.Add(pListener, name);
    }

    void CTaskManager::RemoveListener(IBackgroundTaskManagerListener* pListener)
    {
        m_listeners.Remove(pListener);
    }

    void CTaskManager::AddTask(IBackgroundTask* pTask, ETaskPriority priority, ETaskThreadMask threadMask)
    {
        MAKE_SURE(pTask != 0, return );

        // keep an extra reference to the task in the manager
        pTask->AddRef();

        STaskHandle handle;
        handle.id = CryInterlockedIncrement(&m_nextTaskID);
        handle.priority = priority;
        handle.threadMask = threadMask;
        handle.pTask = pTask;

        AddTask(handle);

        for (TListeners::Notifier notifier(m_listeners); notifier.IsValid(); notifier.Next())
        {
            notifier->OnBackgroundTaskAdded(pTask->Description());
        }
    }

    void CTaskManager::ScheduleTask(IBackgroundTask* pTask, ETaskPriority priority, int delayMilliseconds, ETaskThreadMask threadMask)
    {
        MAKE_SURE(delayMilliseconds >= 0, return );
        MAKE_SURE(pTask != 0, return );

        // keep an extra reference to the task in the manager
        pTask->AddRef();

        SScheduledTask task;
        task.time = GetTickCount() + delayMilliseconds;
        task.handle.pTask = pTask;
        task.handle.id = CryInterlockedIncrement(&m_nextTaskID);
        task.handle.threadMask = threadMask;
        task.handle.priority = priority;

        {
            CryAutoLock<CryMutex> lock(m_tasksLock);
            m_scheduledTasks.push_back(task);
        }

        for (TListeners::Notifier notifier(m_listeners); notifier.IsValid(); notifier.Next())
        {
            notifier->OnBackgroundTaskAdded(pTask->Description());
        }
    }

    void CTaskManager::AddTask(const STaskHandle& handle)
    {
        MAKE_SURE(handle.pTask != 0, return );
        MAKE_SURE(handle.id != 0, return );

        // add task to appropriate queue (every thread mask has it's own queue)
        m_pendingTasks[handle.threadMask].AddTask(handle);
    }

    void CTaskManager::AddCompletedTask(const STaskHandle& handle, ETaskResult resultState)
    {
        CryAutoLock<CryMutex> lock(m_tasksLock);

        CRY_ASSERT(handle.pTask->GetState() == eTaskState_Working);
        CRY_ASSERT(resultState != eTaskResult_Resume);

        // Update task state
        switch (resultState)
        {
        case eTaskResult_Canceled:
        {
            handle.pTask->SetState(eTaskState_Canceled);
            break;
        }

        case eTaskResult_Completed:
        {
            handle.pTask->SetState(eTaskState_Completed);
            break;
        }

        case eTaskResult_Failed:
        {
            handle.pTask->SetState(eTaskState_Failed);
            break;
        }
        }

        // add to the list of completed tasks (for calling the Finalize)
        // TODO: some of the tasks do not require Finalize() and they could be released here instead of the main thread
        SCompletedTask info;
        info.pTask = handle.pTask;
        info.id = handle.id;
        info.state = resultState;
        m_completedTasks.push_back(info);
    }

    void CTaskManager::Update()
    {
        std::vector<SCompletedTask> completedTasks;
        {
            CryAutoLock<CryMutex> lock(m_tasksLock);
            m_completedTasks.swap(completedTasks);
        }

        // call finalize for the completed tasks
        for (size_t i = 0; i < completedTasks.size(); ++i)
        {
            SCompletedTask& handle = completedTasks[i];

            if (NULL != handle.pTask)
            {
                string description = handle.pTask->Description(); // copy string as the description is used after pTask is destroyed

                if (handle.state == eTaskResult_Completed)
                {
                    if (description && description[0] != '\0')
                    {
                        gEnv->pLog->Log("Task Completed: %s", description.c_str());
                    }
                }
                else if (handle.state ==  eTaskResult_Failed)
                {
                    if (description && description[0] != '\0' && !handle.pTask->FailReported())
                    {
                        gEnv->pLog->LogError("Task Failed: %s ", description.c_str());

                        const char* errorMessage = handle.pTask->ErrorMessage();
                        if (errorMessage && errorMessage[0] != '\0')
                        {
                            gEnv->pLog->LogError("\tReason: [%s]", errorMessage);
                        }
                    }
                }

                handle.pTask->Finalize();

                // release the internal (task manager) reference.
                // Tthis is usually the last reference to the task so it gets deleted here.
                handle.pTask->Release();

                for (TListeners::Notifier notifier(m_listeners); notifier.IsValid(); notifier.Next())
                {
                    notifier->OnBackgroundTaskCompleted(handle.state, description.c_str());
                }
            }
        }
    }

    void CTaskManager::OnEditorNotifyEvent(EEditorNotifyEvent ev)
    {
        switch (ev)
        {
        case eNotify_OnInit:
            Start();
            break;
        case eNotify_OnIdleUpdate:
            Update();
            break;
        case eNotify_OnQuit:
            Stop();
            break;
        }
    }
}