/***
    Copyright (C) 2021 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: AuThreadHandles.cpp
    Date: 2021-6-19
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "AuThreads.hpp"
#include "AuThreadHandles.hpp"
#include "AuOSThread.hpp"

namespace Aurora::Threading::Threads
{
    struct BasicThreadId
    {
        AuUInt64 threadId;
        AuUInt64 unixThreadId;
    };

    struct Temp
    {
        ~Temp()
        {
            bActive = false;
        }

        bool bActive {true};
        AuThreadPrimitives::SpinLock       gMutex;
        AuHashMap<AuUInt, IAuroraThread *> gUnixHandlesToThreads;
        AuHashMap<AuUInt, IAuroraThread *> gNativeHandlesToThreads;
    } gVariables;

    static IAuroraThread *OsThreadAnnounce(AuUInt64 threadId);
    static void           OsThreadShutdown(AuUInt64 threadId);

    static AuUInt64 GetThreadIdHandle()
    {
    #if defined(AURORA_IS_MODERNNT_DERIVED)
        // Note: The OsThreadAnnounce function takes ownership of win32 handles.
        //       The detor of OSThread is responsible for cleaning up this handle.

        HANDLE ret;
        auto process = GetCurrentProcess();
        auto thread = GetCurrentThread();

        if (!DuplicateHandle(process, thread, process, &ret, THREAD_ALL_ACCESS, FALSE, FALSE)) 
        {
            return reinterpret_cast<AuUInt64>(INVALID_HANDLE_VALUE);
        }

        return reinterpret_cast<AuUInt64>(ret);
    #elif defined(AURORA_HAS_PTHREADS)

        return pthread_self(); // todo: it's a shame. this is a huge hack, because, all we're doing is providing a pthread type for the OSThread constructor
                               // pthread handles free by magic. we don't need to destroy this. we can get away with chucking this as an handle in later POSIX versions
    #endif
    }

    static void RegisterThisThread(BasicThreadId id, IAuroraThread *handle)
    {
        if (!gVariables.bActive)
        {
            return;
        }
        AU_LOCK_GUARD(gVariables.gMutex);
    #if defined(AURORA_IS_POSIX_DERIVED)
        AuTryInsert(gVariables.gUnixHandlesToThreads, id.unixThreadId, handle);
    #endif
        AuTryInsert(gVariables.gNativeHandlesToThreads, id.threadId, handle);
    }

    static void ReleaseThisThread(BasicThreadId id)
    {
        if (!gVariables.bActive)
        {
            return;
        }
        AU_LOCK_GUARD(gVariables.gMutex);
    #if defined(AURORA_IS_POSIX_DERIVED)
        AuTryRemove(gVariables.gUnixHandlesToThreads, id.unixThreadId);
    #endif
        AuTryRemove(gVariables.gNativeHandlesToThreads, id.threadId);
    }

    struct OSFallbackThread : BasicThreadId
    {
        IAuroraThread *handle;

        OSFallbackThread()
        {
            threadId = GetThreadIdHandle();
            handle = OsThreadAnnounce(threadId);

        #if defined(AURORA_IS_POSIX_DERIVED)
            unixThreadId = gettid();
        #endif

            RegisterThisThread({threadId, unixThreadId}, handle);
        }

        ~OSFallbackThread()
        {
            OsThreadShutdown(threadId);
            ReleaseThisThread({threadId, unixThreadId});
        }
    };

#if defined(AURORA_COMPILER_MSVC) || defined(AURORA_COMPILER_CLANG)
    #define DEFINE_SPEEDY_TLS(type, name) static thread_local type name;
#elif defined(AURORA_COMPILER_GCC)
    #define DEFINE_SPEEDY_TLS(type, name) __thread type name __attribute__((tls_model("initial-exec")));
#else
    #define DEFINE_SPEEDY_TLS(type, name) static thread_local type name;
#endif

    DEFINE_SPEEDY_TLS(OSFallbackThread, tlsOsFallbackThread);
    DEFINE_SPEEDY_TLS(IAuroraThread*, tlsCurrentThread);
    
    void HandleRemove()
    {
        RegisterThisThread({tlsOsFallbackThread.threadId, tlsOsFallbackThread.unixThreadId}, tlsOsFallbackThread.handle);
        tlsCurrentThread = nullptr;
    }

    void HandleRegister(IAuroraThread *thread)
    {
        RegisterThisThread({tlsOsFallbackThread.threadId, tlsOsFallbackThread.unixThreadId}, thread);
        tlsCurrentThread = thread;
    }

    IAuroraThread *HandleCurrent()
    {
        return tlsCurrentThread;
    }

    IAuroraThread *OsThreadAnnounce(AuUInt64 threadId)
    {
        SysAssertDbg(tlsOsFallbackThread.threadId == threadId);
        return  _new OSThread(threadId);
    }

    void OsThreadShutdown(AuUInt64 threadId)
    {
        SysAssertDbg(tlsOsFallbackThread.threadId == threadId);
        if (tlsOsFallbackThread.handle)
        {
            AuSafeDelete<OSThread *>(tlsOsFallbackThread.handle);
        }
    }

    IAuroraThread *GetThreadByPOSIXPid(AuUInt validPid)
    {
        if (!gVariables.bActive)
        {
            return {};
        }
        AU_LOCK_GUARD(gVariables.gMutex);
        auto itr = gVariables.gUnixHandlesToThreads.find(validPid);
        if (itr == gVariables.gUnixHandlesToThreads.end()) return {};
        return itr->second;
    }

    IAuroraThread *GetThreadByOSHandle(AuUInt validPid)
    {
        if (!gVariables.bActive)
        {
            return {};
        }
        AU_LOCK_GUARD(gVariables.gMutex);
        auto itr = gVariables.gNativeHandlesToThreads.find(validPid);
        if (itr == gVariables.gNativeHandlesToThreads.end()) return {};
        return itr->second;
    }

    AUKN_SYM bool DeadTest()
    {
        return !gVariables.bActive;
    }

    AUKN_SYM IAuroraThread *GetThread()
    {
        if (DeadTest())
        {
            return {};
        }

        auto ret = tlsCurrentThread;
        if (ret)
        {
            return ret;
        }

        ret = tlsOsFallbackThread.handle;
        if (ret)
        {
            return ret;
        }

        SysPanic("no tls context");
    }

    AUKN_SYM AuThreadId_t  GetThreadId()
    {
        return reinterpret_cast<AuThreadId_t>(GetThread());
    }
}