/*
 * Copyright (C) 1996-2023 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */

/*
 * Author: Adrian Chadd <adrian@squid-cache.org>
 *
 * These routines are simple plugin replacements for the file_* routines
 * in disk.c . They back-end into the POSIX AIO routines to provide
 * a nice and simple async IO framework for COSS.
 *
 * AIO is suitable for COSS - the only sync operations that the standard
 * supports are read/write, and since COSS works on a single file
 * per storedir it should work just fine.
 */

#include "squid.h"
#include "DiskIO/AIO/AIODiskFile.h"
#include "DiskIO/AIO/AIODiskIOStrategy.h"
#include "DiskIO/IORequestor.h"
#include "DiskIO/ReadRequest.h"
#include "DiskIO/WriteRequest.h"

AIODiskIOStrategy::AIODiskIOStrategy() :
    fd(-1)
{
    aq.aq_state = AQ_STATE_NONE;
    aq.aq_numpending = 0;
    memset(&aq.aq_queue, 0, sizeof(aq.aq_queue));
}

AIODiskIOStrategy::~AIODiskIOStrategy()
{
    assert(aq.aq_state == AQ_STATE_SETUP ||
           aq.aq_numpending == 0);

    sync();
    aq.aq_state = AQ_STATE_NONE;
}

bool
AIODiskIOStrategy::shedLoad()
{
    return false;
}

int
AIODiskIOStrategy::load()
{
    return aq.aq_numpending * 1000 / MAX_ASYNCOP;
}

RefCount<DiskFile>
AIODiskIOStrategy::newFile (char const *path)
{
    if (shedLoad()) {
        return nullptr;
    }

    return new AIODiskFile (path, this);
}

void
AIODiskIOStrategy::sync()
{
    assert(aq.aq_state == AQ_STATE_SETUP);

    /*
     * Keep calling callback to complete ops until the queue is empty
     * We can't quit when callback returns 0 - some calls may not
     * return any completed pending events, but they're still pending!
     */

    while (aq.aq_numpending)
        callback();
}

bool
AIODiskIOStrategy::unlinkdUseful() const
{
    return false;
}

void
AIODiskIOStrategy::unlinkFile (char const *)
{}

/*
 * Note: we grab the state and free the state before calling the callback
 * because this allows us to cut down the amount of time it'll take
 * to find a free slot (since if we call the callback first, we're going
 * to probably be allocated the slot _after_ this one..)
 *
 * I'll make it much more optimal later.
 */
int
AIODiskIOStrategy::callback()
{
    return 0;
#if 0
    int i;
    int retval, reterr;
    FREE *freefunc;
    void *cbdata;
    int callback_valid;
    void *buf;
    async_queue_entry_t *aqe;
    async_queue_entry_type_t type;

    assert(aq.aq_state == AQ_STATE_SETUP);

    /* Loop through all slots */

    for (i = 0; i < MAX_ASYNCOP; ++i) {
        if (aq.aq_queue[i].aq_e_state == AQ_ENTRY_USED) {
            aqe = &aq.aq_queue[i];
            /* Active, get status */
            reterr = aio_error(&aqe->aq_e_aiocb);

            if (reterr < 0) {
                fatal("aio_error returned an error!\n");
            }

            if (reterr != EINPROGRESS) {
                /* Get the return code */
                retval = aio_return(&aqe->aq_e_aiocb);

                /* Get the callback parameters */
                freefunc = aqe->aq_e_free;
                buf = aqe->aq_e_buf;
                type = aqe->aq_e_type;
                callback_valid = cbdataReferenceValidDone(aqe->aq_e_callback_data, &cbdata);
                AIODiskFile * theFile = nullptr;
                void *theFileVoid = nullptr;
                void *theTmpFile = aqe->theFile;
                bool fileOk = cbdataReferenceValidDone(theTmpFile, &theFileVoid);

                if (fileOk) {
                    theFile = static_cast<AIODiskFile *>(theFileVoid);
                }

                /* Free slot */
                memset(aqe, 0, sizeof(async_queue_entry_t));

                aqe->aq_e_state = AQ_ENTRY_FREE;

                --aq.aq_numpending;

                /* Callback */

                if (callback_valid) {
                    assert (fileOk);

                    if (type == AQ_ENTRY_READ)
                        theFile->ioRequestor->readCompleted((const char *)buf, retval, reterr, static_cast<ReadRequest *>(cbdata));

                    if (type == AQ_ENTRY_WRITE)
                        theFile->ioRequestor->writeCompleted(reterr,retval, static_cast<WriteRequest *>(cbdata));
                }

                if (type == AQ_ENTRY_WRITE && freefunc)
                    freefunc(buf);
            }
        }
    }

    return 0;
#endif
}

void
AIODiskIOStrategy::init()
{
    /* Make sure the queue isn't setup */
    assert(aq.aq_state == AQ_STATE_NONE);

    /* Loop through, blanking the queue entries */

    /* Done */
    aq.aq_state = AQ_STATE_SETUP;
}

void
AIODiskIOStrategy::statfs(StoreEntry &) const
{}

ConfigOption *
AIODiskIOStrategy::getOptionTree() const
{
    return nullptr;
}

/*
 * find a free aio slot.
 * Return the index, or -1 if we can't find one.
 */
int
AIODiskIOStrategy::findSlot()
{
    /* Later we should use something a little more .. efficient :) */

    for (int i = 0; i < MAX_ASYNCOP; ++i) {
        if (aq.aq_queue[i].aq_e_state == AQ_ENTRY_FREE)
            /* Found! */
            return i;
    }

    /* found nothing */
    return -1;
}