/*

 * Copyright (c) 2021 Paul B Mahol

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg 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.

 *

 * FFmpeg 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 FFmpeg; if not, write to the Free Software

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

 */

/**

 * @file

 * Change the PTS/DTS timestamps.

 */

#include "libavutil/opt.h"

#include "libavutil/eval.h"

#include "bsf.h"

#include "bsf_internal.h"

static const char *const var_names[] = {

    "N",           ///< frame number (starting at zero)

    "TS",

    "POS",         ///< original position in the file of the frame

    "PREV_INPTS",  ///< previous  input PTS

    "PREV_INDTS",  ///< previous  input DTS

    "PREV_INDURATION", ///< previous input duration

    "PREV_OUTPTS", ///< previous output PTS

    "PREV_OUTDTS", ///< previous output DTS

    "PREV_OUTDURATION", ///< previous output duration

    "NEXT_PTS",    ///< next input PTS

    "NEXT_DTS",    ///< next input DTS

    "NEXT_DURATION", ///< next input duration

    "PTS",         ///< original PTS in the file of the frame

    "DTS",         ///< original DTS in the file of the frame

    "DURATION",    ///< original duration in the file of the frame

    "STARTPTS",    ///< PTS at start of movie

    "STARTDTS",    ///< DTS at start of movie

    "TB",          ///< input timebase of the stream

    "TB_OUT",      ///< output timebase of the stream

    "SR",          ///< sample rate of the stream

    "NOPTS",       ///< The AV_NOPTS_VALUE constant

    NULL

};

enum var_name {

    VAR_N,

    VAR_TS,

    VAR_POS,

    VAR_PREV_INPTS,

    VAR_PREV_INDTS,

    VAR_PREV_INDUR,

    VAR_PREV_OUTPTS,

    VAR_PREV_OUTDTS,

    VAR_PREV_OUTDUR,

    VAR_NEXT_PTS,

    VAR_NEXT_DTS,

    VAR_NEXT_DUR,

    VAR_PTS,

    VAR_DTS,

    VAR_DURATION,

    VAR_STARTPTS,

    VAR_STARTDTS,

    VAR_TB,

    VAR_TB_OUT,

    VAR_SR,

    VAR_NOPTS,

    VAR_VARS_NB

};

typedef struct SetTSContext {

    const AVClass *class;

    char *ts_str;

    char *pts_str;

    char *dts_str;

    char *duration_str;

    AVRational time_base;

    int user_outtb;

    int prescale;

    int64_t frame_number;

    double var_values[VAR_VARS_NB];

    AVExpr *ts_expr;

    AVExpr *pts_expr;

    AVExpr *dts_expr;

    AVExpr *duration_expr;

    AVPacket *prev_inpkt;

    AVPacket *prev_outpkt;

    AVPacket *cur_pkt;

} SetTSContext;

static int setts_init(AVBSFContext *ctx)

{

    SetTSContext *s = ctx->priv_data;

    int ret;

    s->prev_inpkt = av_packet_alloc();

    s->prev_outpkt = av_packet_alloc();

    s->cur_pkt = av_packet_alloc();

    if (!s->prev_inpkt || !s->prev_outpkt || !s->cur_pkt)

        return AVERROR(ENOMEM);

    if ((ret = av_expr_parse(&s->ts_expr, s->ts_str,

                             var_names, NULL, NULL, NULL, NULL, 0, ctx)) < 0) {

        av_log(ctx, AV_LOG_ERROR, "Error while parsing ts expression '%s'\n", s->ts_str);

        return ret;

    }

    if ((ret = av_expr_parse(&s->duration_expr, s->duration_str,

                             var_names, NULL, NULL, NULL, NULL, 0, ctx)) < 0) {

        av_log(ctx, AV_LOG_ERROR, "Error while parsing duration expression '%s'\n", s->duration_str);

        return ret;

    }

    if (s->pts_str) {

        if ((ret = av_expr_parse(&s->pts_expr, s->pts_str,

                                 var_names, NULL, NULL, NULL, NULL, 0, ctx)) < 0) {

            av_log(ctx, AV_LOG_ERROR, "Error while parsing pts expression '%s'\n", s->pts_str);

            return ret;

        }

    }

    if (s->dts_str) {

        if ((ret = av_expr_parse(&s->dts_expr, s->dts_str,

                                 var_names, NULL, NULL, NULL, NULL, 0, ctx)) < 0) {

            av_log(ctx, AV_LOG_ERROR, "Error while parsing dts expression '%s'\n", s->dts_str);

            return ret;

        }

    }

    if (s->time_base.num > 0 && s->time_base.den > 0) {

        ctx->time_base_out = s->time_base;

        s->user_outtb = 1;

    } else if (s->time_base.num || !s->time_base.den) {

        av_log(ctx, AV_LOG_ERROR, "Invalid value %d/%d specified for output timebase\n", s->time_base.num, s->time_base.den);

        return AVERROR_INVALIDDATA;

    } else

        s->prescale = 0;

    s->frame_number= 0;

    s->var_values[VAR_STARTPTS] = AV_NOPTS_VALUE;

    s->var_values[VAR_STARTDTS] = AV_NOPTS_VALUE;

    s->var_values[VAR_NOPTS] = AV_NOPTS_VALUE;

    s->var_values[VAR_TB_OUT]= ctx->time_base_out.den ? av_q2d(ctx->time_base_out) : 0;

    s->var_values[VAR_SR]    = ctx->par_in->sample_rate;

    if (s->user_outtb && s->prescale)

        s->var_values[VAR_TB] = av_q2d(ctx->time_base_out);

    else

        s->var_values[VAR_TB] = ctx->time_base_in.den ? av_q2d(ctx->time_base_in) : 0;

    return 0;

}

#define PRESCALED(x) ( s->prescale ? av_rescale_q(x, ctx->time_base_in, ctx->time_base_out) : x )

static int setts_filter(AVBSFContext *ctx, AVPacket *pkt)

{

    SetTSContext *s = ctx->priv_data;

    int64_t new_ts, new_pts, new_dts, new_duration;

    int ret;

    ret = ff_bsf_get_packet_ref(ctx, pkt);

    if (ret < 0 && (ret != AVERROR_EOF || !s->cur_pkt->data))

        return ret;

    if (!s->cur_pkt->data) {

         av_packet_move_ref(s->cur_pkt, pkt);

         return AVERROR(EAGAIN);

    }

    if (s->var_values[VAR_STARTPTS] == AV_NOPTS_VALUE)

        s->var_values[VAR_STARTPTS] = PRESCALED(s->cur_pkt->pts);

    if (s->var_values[VAR_STARTDTS] == AV_NOPTS_VALUE)

        s->var_values[VAR_STARTDTS] = PRESCALED(s->cur_pkt->dts);

    s->var_values[VAR_N]           = s->frame_number++;

    s->var_values[VAR_TS]          = PRESCALED(s->cur_pkt->dts);

    s->var_values[VAR_POS]         = s->cur_pkt->pos;

    s->var_values[VAR_PTS]         = PRESCALED(s->cur_pkt->pts);

    s->var_values[VAR_DTS]         = PRESCALED(s->cur_pkt->dts);

    s->var_values[VAR_DURATION]    = PRESCALED(s->cur_pkt->duration);

    s->var_values[VAR_PREV_INPTS]  = PRESCALED(s->prev_inpkt->pts);

    s->var_values[VAR_PREV_INDTS]  = PRESCALED(s->prev_inpkt->dts);

    s->var_values[VAR_PREV_INDUR]  = PRESCALED(s->prev_inpkt->duration);

    s->var_values[VAR_PREV_OUTPTS] = s->prev_outpkt->pts;

    s->var_values[VAR_PREV_OUTDTS] = s->prev_outpkt->dts;

    s->var_values[VAR_PREV_OUTDUR] = s->prev_outpkt->duration;

    s->var_values[VAR_NEXT_PTS]    = PRESCALED(pkt->pts);

    s->var_values[VAR_NEXT_DTS]    = PRESCALED(pkt->dts);

    s->var_values[VAR_NEXT_DUR]    = PRESCALED(pkt->duration);

    new_ts = llrint(av_expr_eval(s->ts_expr, s->var_values, NULL));

    new_duration = llrint(av_expr_eval(s->duration_expr, s->var_values, NULL));

    if (s->pts_str) {

        s->var_values[VAR_TS] = PRESCALED(s->cur_pkt->pts);

        new_pts = llrint(av_expr_eval(s->pts_expr, s->var_values, NULL));

    } else {

        new_pts = new_ts;

    }

    if (s->dts_str) {

        s->var_values[VAR_TS] = PRESCALED(s->cur_pkt->dts);

        new_dts = llrint(av_expr_eval(s->dts_expr, s->var_values, NULL));

    } else {

        new_dts = new_ts;

    }

    av_packet_unref(s->prev_inpkt);

    av_packet_unref(s->prev_outpkt);

    av_packet_move_ref(s->prev_inpkt, s->cur_pkt);

    av_packet_move_ref(s->cur_pkt, pkt);

    ret = av_packet_ref(pkt, s->prev_inpkt);

    if (ret < 0)

        return ret;

    if (s->user_outtb && !s->prescale) {

        new_pts = av_rescale_q(new_pts, ctx->time_base_in, ctx->time_base_out);

        new_dts = av_rescale_q(new_dts, ctx->time_base_in, ctx->time_base_out);

        new_duration = av_rescale_q(new_duration, ctx->time_base_in, ctx->time_base_out);

    }

    pkt->pts = new_pts;

    pkt->dts = new_dts;

    pkt->duration = new_duration;

    ret = av_packet_ref(s->prev_outpkt, pkt);

    if (ret < 0)

        av_packet_unref(pkt);

    return ret;

}

static void setts_close(AVBSFContext *bsf)

{

    SetTSContext *s = bsf->priv_data;

    av_packet_free(&s->prev_inpkt);

    av_packet_free(&s->prev_outpkt);

    av_packet_free(&s->cur_pkt);

    av_expr_free(s->ts_expr);

    s->ts_expr = NULL;

    av_expr_free(s->pts_expr);

    s->pts_expr = NULL;

    av_expr_free(s->dts_expr);

    s->dts_expr = NULL;

    av_expr_free(s->duration_expr);

    s->duration_expr = NULL;

}

#define OFFSET(x) offsetof(SetTSContext, x)

#define FLAGS (AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_SUBTITLE_PARAM|AV_OPT_FLAG_BSF_PARAM)

static const AVOption options[] = {

    { "ts",  "set expression for packet PTS and DTS", OFFSET(ts_str),  AV_OPT_TYPE_STRING, {.str="TS"}, 0, 0, FLAGS },

    { "pts", "set expression for packet PTS", OFFSET(pts_str), AV_OPT_TYPE_STRING, {.str=NULL}, 0, 0, FLAGS },

    { "dts", "set expression for packet DTS", OFFSET(dts_str), AV_OPT_TYPE_STRING, {.str=NULL}, 0, 0, FLAGS },

    { "duration", "set expression for packet duration", OFFSET(duration_str), AV_OPT_TYPE_STRING, {.str="DURATION"}, 0, 0, FLAGS },

    { "time_base", "set output timebase", OFFSET(time_base), AV_OPT_TYPE_RATIONAL, {.dbl=0}, 0, INT_MAX, FLAGS },

    { "prescale",  "convert to output timebase before evaluation", OFFSET(prescale), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },

    { NULL },

};

static const AVClass setts_class = {

    .class_name = "setts_bsf",

    .item_name  = av_default_item_name,

    .option     = options,

    .version    = LIBAVUTIL_VERSION_INT,

};

const FFBitStreamFilter ff_setts_bsf = {

    .p.name         = "setts",

    .p.priv_class   = &setts_class,

    .priv_data_size = sizeof(SetTSContext),

    .init           = setts_init,

    .close          = setts_close,

    .filter         = setts_filter,

};