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

    File: AuRWLock.hpp
    Date: 2021-6-12
    Author: Reece
***/
#pragma once

#include "AuConditionVariable.Generic.hpp"
#include "AuConditionMutex.Generic.hpp"
#include "ThreadCookie.hpp"

namespace Aurora::Threading::Primitives
{
    template<bool bIsWriteRecursionAllowed>
    struct RWLockImpl;

    template<bool bIsReadView, typename T>
    struct RWLockAccessView : IWaitable
    {
        RWLockAccessView(T &impl) : parent_(impl)
        {

        }

        bool Lock(AuUInt64 timeout) override;
        bool LockNS(AuUInt64 timeout) override;

        bool TryLock() override;

        bool HasOSHandle(AuMach &mach) override
        {
            return false;
        }

        bool HasLockImplementation() override
        {
            return true;
        }

        void Lock() override
        {
            SysAssert(Lock(0));
        }

        void Unlock() override;

    private:
        T &parent_;
    };

    template<bool bIsWriteRecursionAllowed>
    struct RWLockImpl : IRWLock
    {
        RWLockImpl();
        ~RWLockImpl();
        
        bool LockReadNS(AuUInt64 timeout);
        bool LockWriteNS(AuUInt64 timeout);
        bool TryLockRead();
        bool TryLockWrite();
        void UnlockRead();
        void UnlockWrite();

        bool UpgradeReadToWrite(AuUInt64 timeout) override;
        bool DowngradeWriteToRead() override;
        
        IWaitable *AsReadable() override;
        IWaitable *AsWritable() override;

        bool Init();
        
    private:

        //bool reentrantWriteLock_ {true};
        ThreadCookie_t reentrantWriteLockHandle_ {};

        RWLockAccessView<true, RWLockImpl>  read_;
        RWLockAccessView<false, RWLockImpl> write_;

        ConditionMutexImpl mutex_;
        ConditionVariableImpl condition_;
        volatile AuInt32 state_ {};
        AuInt32 writersPending_ {};
        bool bElevaterPending_ {};
    };
}