/*****************************************************************************

 * decoder_prevframe.c: decoder previous frame helpers

 *****************************************************************************

 * Copyright (C) 2025 VLC authors, VideoLAN and Videolabs SAS

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation; either version 2.1 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this program; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.

 *****************************************************************************/

 #ifdef HAVE_CONFIG_H

 # include "config.h"

 #endif

#include <vlc_picture.h>

#include "decoder_prevframe.h"

void

decoder_prevframe_Init(struct decoder_prevframe *pf)

{

    pf->pic = NULL;

    pf->req_count = 0;

    pf->failed = false;

    pf->flushing = false;

    pf->seek_steps = DEC_PF_SEEK_STEPS_INITIAL;

}

void

decoder_prevframe_Flush(struct decoder_prevframe *pf)

{

    if (pf->pic != NULL)

    {

        picture_Release(pf->pic);

        pf->pic = NULL;

    }

    pf->flushing = false;

    pf->failed = false;

}

void

decoder_prevframe_Reset(struct decoder_prevframe *pf)

{

    decoder_prevframe_Flush(pf);

    pf->seek_steps = DEC_PF_SEEK_STEPS_INITIAL;

    pf->req_count = 0;

}

void

decoder_prevframe_Request(struct decoder_prevframe *pf, int *seek_steps)

{

    if (pf->req_count == 0)

    {

        *seek_steps = pf->seek_steps;

        pf->flushing = true;

    }

    else

        *seek_steps = DEC_PF_SEEK_STEPS_NONE;

    pf->req_count++;

}

picture_t *

decoder_prevframe_AddPic(struct decoder_prevframe *pf, picture_t *pic,

                         vlc_tick_t *inout_pts, int *seek_steps)

{

    vlc_tick_t pts = *inout_pts;

    *seek_steps = DEC_PF_SEEK_STEPS_NONE;

    if (pf->flushing)

    {

        if (pic != NULL)

            picture_Release(pic);

        return NULL;

    }

    if (pic != NULL && pts <= pic->date && pf->pic != NULL)

    {

        /* Reached the previous frame */

        picture_t *resume_pic = pic;

        pic = pf->pic;

        pf->req_count--;

        pf->pic = NULL;

        *inout_pts = pic->date;

        /* Update seek request if needed */

        if (pf->req_count > 0)

        {

            *seek_steps = pf->seek_steps;

            pf->flushing = true;

        }

        assert(pic->p_next == NULL);

        /* Store the first pic to use if normal playback is resumed */

        pic->p_next = resume_pic;

        return pic;

    }

    if (pic == NULL || pic->date >= pts)

    {

        if (pf->pic == NULL && !pf->failed && pf->req_count > 0)

        {

            /* We need to seek again, and further */

            pf->seek_steps += DEC_PF_SEEK_STEPS_INITIAL * 2;

            pf->failed = true;

            pf->flushing = true;

            *seek_steps = pf->seek_steps;

        }

        if (pic != NULL)

            picture_Release(pic);

        return NULL;

    }

    if (pf->pic != NULL)

        picture_Release(pf->pic);

    /* Store the pic as the potential previous-frame (we know it only from

     * the next pic date) */

    pf->pic = pic;

    return NULL;

}