/***
    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
{
    struct IRWLock
    {
        /**
         * @brief Returns a complete IWaitable interface for reantrant access to the protected resources.
         *        Once a thread takes exclusive access of the resource, only it shall pass read. Noting this 
         *        is critical section behaviour, not mutex behaviour.
         * @return 
         */
        virtual IWaitable *AsReadable() = 0;
        
        /**
         * @brief Returns a complete IWaitable interface for exclusive thread access to the protected resources
         *        
         * @return 
         */
        virtual IWaitable *AsWritable() = 0;

        /**
         * @brief Allows for read-to-write upgrades when the decision to esclate is made based upon a shared resource
         *        which would be lost by unlocking and relocking in exclusive mode.
         *        You must be careful to consider how this is used to prevent dead-locks
         * @param timeout in relative nanoseconds
         * @return 
         */
        virtual bool UpgradeReadToWrite(AuUInt64 timeout) = 0;

        /**
         * @brief Reverses UpgradeReadToWrite.
         * @return 
         */
        virtual bool DowngradeWriteToRead() = 0;

        /**
         * @brief Checks if the current thread has acquired a critical-section lock on the mutually exclusive resource 
         * @return 
         */
        virtual bool CheckSelfThreadIsWriter() = 0;
    };

    /// Allows AsReadable() holder entrancy as AsWritable() lock
    /// Check CheckSelfThreadIsWriter() before any lock guards, if non-reentrant mutual exclusion is desired.
    AUKN_SHARED_SOO_NCM(RWLock, IRWLock, kPrimitiveSizeRWLock);

    /// Allows AsWritable() holder reentrancy, and allows AsReadable() holder entrancy as AsWritable() lock
    AUKN_SHARED_SOO_NCM(RWRenterableLock, IRWLock, kPrimitiveSizeRWLock);
    
}