/*
 *  Copyright (c) 2016, The OpenThread Authors.
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. Neither the name of the copyright holder nor the
 *     names of its contributors may be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @file
 *   This file implements the tasklet scheduler.
 */

#include <openthread.h>
#include <common/code_utils.hpp>
#include <common/debug.hpp>
#include <common/tasklet.hpp>
#include <net/ip6.hpp>

namespace Thread {

Tasklet::Tasklet(TaskletScheduler &aScheduler, Handler aHandler, void *aContext):
    mScheduler(aScheduler),
    mHandler(aHandler),
    mContext(aContext),
    mNext(NULL)
{
}

ThreadError Tasklet::Post(void)
{
    return mScheduler.Post(*this);
}

TaskletScheduler::TaskletScheduler(void):
    mHead(NULL),
    mTail(NULL)
{
}

ThreadError TaskletScheduler::Post(Tasklet &aTasklet)
{
    ThreadError error = kThreadError_None;

    VerifyOrExit(mTail != &aTasklet && aTasklet.mNext == NULL, error = kThreadError_Already);

    if (mTail == NULL)
    {
        mHead = &aTasklet;
        mTail = &aTasklet;
        otSignalTaskletPending(aTasklet.mScheduler.GetIp6()->GetInstance());
    }
    else
    {
        mTail->mNext = &aTasklet;
        mTail = &aTasklet;
    }

exit:
    return error;
}

Tasklet *TaskletScheduler::PopTasklet(void)
{
    Tasklet *task = mHead;

    if (task != NULL)
    {
        mHead = mHead->mNext;

        if (mHead == NULL)
        {
            mTail = NULL;
        }

        task->mNext = NULL;
    }

    return task;
}

bool TaskletScheduler::AreTaskletsPending(void)
{
    return mHead != NULL;
}

void TaskletScheduler::ProcessQueuedTasklets(void)
{
    Tasklet *tail = mTail;
    Tasklet *cur;

    while ((cur = PopTasklet()) != NULL)
    {
        cur->RunTask();

        // only process tasklets that were queued at the time this method was called
        if (cur == tail)
        {
            if (mHead != NULL)
            {
                otSignalTaskletPending(cur->mScheduler.GetIp6()->GetInstance());
            }

            break;
        }
    }
}

Ip6::Ip6 *TaskletScheduler::GetIp6()
{
    return Ip6::Ip6FromTaskletScheduler(this);
}

}  // namespace Thread
