/*
 * DRA parser
 * Copyright (c) 2026 Amlogic, Inc.
 *
 * 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
 */

#include "parser.h"
#include "get_bits.h"
#include "libavcodec/internal.h"
#include "libavutil/log.h"

typedef struct DRAParseContext {
    int sample_rate;
    int channels;

    /* Lightweight state only (no heap buffer management) */
    int last_sync_pos;
} DRAParseContext;

/* DRA sample rate table */
static const int dra_sample_rates[13] = {
    8000, 11025, 12000, 16000, 22050, 24000, 32000,
    44100, 48000, 88200, 96000, 176400, 192000
};

/* Find sync word 0x7FFF */
static int dra_find_sync(const uint8_t *buf, int buf_size)
{
    int i;
    for (i = 0; i < buf_size - 1; i++) {
        if (buf[i] == 0x7F && buf[i + 1] == 0xFF)
            return i;
    }
    return -1;
}

/* Parse DRA frame header safely */
static int dra_parse_header(const uint8_t *buf,
                            int buf_size,
                            int *frame_size,
                            int *sample_rate,
                            int *channels)
{
    GetBitContext gb;
    int frm_header_type;
    int num_word;
    int sr_idx;
    int num_normal_ch;
    int num_lfe_ch;

    if (buf_size < 8)
        return AVERROR_INVALIDDATA;

    init_get_bits8(&gb, buf, buf_size);

    /* Sync word */
    if (get_bits(&gb, 16) != 0x7FFF)
        return AVERROR_INVALIDDATA;

    frm_header_type = get_bits1(&gb);

    /* Frame size in 32-bit words */
    if (frm_header_type == 0)
        num_word = get_bits(&gb, 10);
    else
        num_word = get_bits(&gb, 13);

    *frame_size = num_word * 4;

    /* Basic sanity check */
    if (*frame_size < 32 || *frame_size > 8192)
        return AVERROR_INVALIDDATA;

    /* Blocks per frame (ignored but must consume bits) */
    get_bits(&gb, 2);

    /* Sample rate index */
    sr_idx = get_bits(&gb, 4);
    if (sr_idx > 12)
        return AVERROR_INVALIDDATA;

    *sample_rate = dra_sample_rates[sr_idx];

    /* Channel parsing */
    if (frm_header_type == 0) {
        num_normal_ch = get_bits(&gb, 3) + 1;
        num_lfe_ch    = get_bits1(&gb);
    } else {
        num_normal_ch = get_bits(&gb, 6) + 1;
        num_lfe_ch    = get_bits(&gb, 2);
    }

    *channels = num_normal_ch + num_lfe_ch;

    return 0;
}

/* Find frame boundary */
static int dra_find_frame_end(AVCodecParserContext *s,
                              const uint8_t *buf,
                              int buf_size)
{
    int frame_size;
    int sr, ch;

    if (buf_size < 8)
        return END_NOT_FOUND;

    /* Try to parse header */
    if (dra_parse_header(buf, buf_size,
                         &frame_size, &sr, &ch) < 0)
        return END_NOT_FOUND;

    /* Not enough data */
    if (buf_size < frame_size)
        return END_NOT_FOUND;

    return frame_size;
}

/*
 * Split function (used for resync)
 * Must be conservative and safe.
 */
static int dra_split(AVCodecContext *avctx,
                     const uint8_t *buf,
                     int buf_size)
{
    int pos = dra_find_sync(buf, buf_size);

    if (pos < 0)
        return buf_size;  /* drop all if no sync found */

    return pos;
}

/*
 * Main parser function
 */
static int dra_parse(AVCodecParserContext *s,
                     AVCodecContext *avctx,
                     const uint8_t **outbuf,
                     int *outbuf_size,
                     const uint8_t *buf,
                     int buf_size)
{
    DRAParseContext *ctx = s->priv_data;

    int offset = 0;

    /* Step 1: find sync */
    offset = dra_find_sync(buf, buf_size);
    if (offset < 0) {
        *outbuf = NULL;
        *outbuf_size = 0;
        return buf_size;
    }

    buf += offset;
    buf_size -= offset;

    /* Step 2: find frame size */
    int frame_size = dra_find_frame_end(s, buf, buf_size);
    if (frame_size == END_NOT_FOUND) {
        *outbuf = NULL;
        *outbuf_size = 0;
        return offset ? offset : buf_size;
    }

    /* Step 3: parse header (for codec config only) */
    int sr = 0, ch = 0;
    if (dra_parse_header(buf, buf_size,
                         &frame_size, &sr, &ch) == 0) {

        avctx->sample_rate = sr;
        avctx->channels = ch;

        ctx->sample_rate = sr;
        ctx->channels = ch;
    }

    /* Fixed DRA frame duration (typical) */
    s->duration = 1024;

    /* Output frame */
    *outbuf = buf;
    *outbuf_size = frame_size;

    /* Consumed bytes */
    return offset + frame_size;
}

/*
 * Safe close
 */
static void dra_close(AVCodecParserContext *s)
{
    DRAParseContext *ctx = s->priv_data;

    av_log(NULL, AV_LOG_INFO,
           "[DRA] parser close ctx=%p\n",
           ctx);

    if (ctx) {
        memset(ctx, 0, sizeof(*ctx));
    }
}

/*
 * Parser definition
 */
AVCodecParser ff_dra_parser = {
    .codec_ids      = { AV_CODEC_ID_DRA },
    .priv_data_size = sizeof(DRAParseContext),
    .parser_parse   = dra_parse,
    .parser_close   = dra_close,
    .split          = dra_split,
};