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/* Copyright (c) 2005-2020 Rexx Language Association. All rights reserved.    */
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/******************************************************************************/
/*                                                                            */
/* MutexSemaphore class                                                       */
/*                                                                            */
/******************************************************************************/
#include "RexxCore.h"
#include "MutexSemaphore.hpp"
#include "MethodArguments.hpp"
#include "ProtectedObject.hpp"
#include "ActivityManager.hpp"
#include "PackageClass.hpp"


RexxClass *MutexSemaphoreClass::classInstance = OREF_NULL;   // singleton class instance

/**
 * Perform class bootstrap activities.
 */
void MutexSemaphoreClass::createInstance()
{
    CLASS_CREATE(MutexSemaphore);
}

/**
 * Allocate memory for a mutex semaphore object.
 *
 * @param size   The size of the object.
 *
 * @return A new object configured for a mutex semaphore object.
 */
void* MutexSemaphoreClass::operator new(size_t size)
{
    RexxInternalObject *newObject = new_object(size, T_MutexSemaphore);
    return (void *)newObject;
}


/**
 * Default constructor for the MutexSemaphore
 */
MutexSemaphoreClass::MutexSemaphoreClass()
{
    // initialize the semaphore
    semaphore.create();
    nestCount = 0;
}


/**
 * Default new method for creating an object from Rexx
 * code.  This is the version inherited by all subclasses
 * of the Object class.
 *
 * @param arguments Pointer to the arguments of the new() method.  These
 *                  are passed on to the init method.
 * @param argCount  The count of the arguments.
 *
 * @return An initialized object instance.  If this is a subclass,
 *         the object will have all of the subclass behaviour.
 */
RexxObject *MutexSemaphoreClass::newRexx(RexxObject **arguments, size_t argCount)
{
    // this class is defined on the object class, but this is actually attached
    // to a class object instance.  Therefore, any use of the this pointer
    // will be touching the wrong data.  Use the classThis pointer for calling
    // any methods on this object from this method.
    RexxClass *classThis = (RexxClass *)this;

    Protected<RexxObject> newObj =  new MutexSemaphoreClass;

    // handle Rexx class completion
    classThis->completeNewObject(newObj, arguments, argCount);

    return newObj;
}


/**
 * Do cleanup of the semaphore object.
 *
 * @return Always returns NULL.
 */
RexxObject* MutexSemaphoreClass::close()
{
    semaphore.close();
    if (nestCount > 0)
    {
        // tell the current activity this is no longer needed
        ActivityManager::currentActivity->removeMutex(this);
    }
    nestCount = 0;
    return OREF_NULL;
}


/**
 * Handle nesting of the semaphore, including letting the current owner
 * know we are the current holders of the lock. If the activity terminates
 * with us holding the lock, this will be released during cleanup.
 */
void MutexSemaphoreClass::handleNesting()
{
    nestCount++;
    // if this is the first acquisition, let the current activity know we
    // are holding this.
    if (nestCount == 1)
    {
        // tell the current activity to register this mutex
        ActivityManager::currentActivity->addMutex(this);
    }
}


/**
 * Acquire the mutex.
 * @param t  An optional timeout in seconds, either String or TimeSpan.
 *           Returns immediately if the timeout is zero,
 *           waits indefinitely if it's negative.
 *           Default is -1.
 *
 * @return true if this was successfully acquired,
 *         false if we timed out.
 */
RexxObject* MutexSemaphoreClass::request(RexxObject *t)
{
    wholenumber_t timeout;

    if (t == OREF_NULL)
    {
        timeout = -1;
    }
    else
    {
        RexxObject *seconds;

        // we allow timeout to be a TimeSpan or a String object
        RexxClass *TimeSpan = TheRexxPackage->findClass(GlobalNames::TIMESPAN);
        if (t->isInstanceOf(TimeSpan))
        {
            ProtectedObject p;
            seconds = t->sendMessage(GlobalNames::TOTALSECONDS, p);
        }
        else
        {
            seconds = t;
        }
        double secs = floatingPointArgument(seconds, "timeout");
        // wait() is uint32, so we can wait for 4294967 seconds at most
        if (secs >= 0 && secs <= 4294967)
        {
            // we need milliseconds (the product will always fit a unint32)
            timeout = (wholenumber_t)(secs * 1000.0);
        }
        else
        {
            // negative or too large, we just wait forever
            timeout = -1;
        }
    }

    bool acquired;
    if (timeout < 0)
    {
        UnsafeBlock releaser;
        acquired = semaphore.request();
    }
    else if (timeout == 0)
    {
        acquired = semaphore.requestImmediate();
    }
    else
    {
        UnsafeBlock releaser;

        acquired = semaphore.request((uint32_t)timeout);
    }

    // only do the nesting thing if we got the lock
    if (acquired)
    {
        handleNesting();
    }

    return booleanObject(acquired);
}


/**
 * Release the mutex semaphore
 *
 * @return true if this was successfully released, false if we were not the semaphore owners.
 */
RexxObject* MutexSemaphoreClass::release()
{
    // don't even attempt this if this isn't held.
    if (nestCount == 0)
    {
        return TheFalseObject;
    }

    // if this thread really owns this mutex, this will succeed
    bool released = semaphore.release();
    if (released)
    {
        nestCount--;
        if (nestCount == 0)
        {
            // tell the current activity this is no longer needed
            ActivityManager::currentActivity->removeMutex(this);
        }
    }
    return booleanObject(released);
}


/**
 * Force this semaphore to release all of it's locks on thread termination.
 */
void MutexSemaphoreClass::forceLockRelease()
{
    while (nestCount > 0)
    {
        semaphore.release();
        nestCount--;
    }
}