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

    File: RWLock.hpp
    Date: 2021-6-9
    Author: Reece
***/
#pragma once

namespace Aurora::Threading::Primitives
{
    class RWLock
    {
    public:
        virtual IWaitable *AsReadable() = 0;
        virtual IWaitable *AsWritable() = 0;

        /**
         * Solves the problem of atomic write racing
         * Consider:  Thread 1         |  Thread 2
         *            ReadLock()       | 
         *            cmp internal_x, 0| 
         *            jmp not eq +1    | 
         *            ret              | 
         *            ReadUnlock()     |
         *                             | WriteLock()
         *                             | internal_x = 1
         *                             | WriteUnlock()
         *            WriteLock()      |
         *            internal_x = 0   |
         *            WriteUnlock()
         * 
         *  where 1 and 0 should have been decided on mutually exclusively, losing the 1 state while assuming a decision in the locked state would remain true 
         *  workaround: [1] check for the race conditions, implmeneting slow and inefficient branching and spurious checks
         *  workaround: [2] upgrade from read to write
         */
        virtual bool UpgradeReadToWrite(AuUInt64 timeout) = 0;
    };

    AUKN_SHARED_API(RWLock, RWLock);
}