/*

 * MP3 demuxer

 * Copyright (c) 2003 Fabrice Bellard

 *

 * 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 "libavutil/opt.h"

#include "libavutil/intreadwrite.h"

#include "libavutil/dict.h"

#include "libavutil/mathematics.h"

#include "avformat.h"

#include "internal.h"

#include "avio_internal.h"

#include "demux.h"

#include "id3v2.h"

#include "id3v1.h"

#include "replaygain.h"

#include "libavcodec/codec_id.h"

#include "libavcodec/mpegaudio.h"

#include "libavcodec/mpegaudiodecheader.h"

#define XING_FLAG_FRAMES 0x01

#define XING_FLAG_SIZE   0x02

#define XING_FLAG_TOC    0x04

#define XING_FLAC_QSCALE 0x08

#define XING_TOC_COUNT 100

typedef struct {

    AVClass *class;

    int64_t filesize;

    int xing_toc;

    int start_pad;

    int end_pad;

    int usetoc;

    unsigned frames; /* Total number of frames in file */

    unsigned header_filesize;   /* Total number of bytes in the stream */

    unsigned frame_duration;   /* Frame duration in st->time_base */

    int is_cbr;

} MP3DecContext;

enum CheckRet {

    CHECK_WRONG_HEADER = -1,

    CHECK_SEEK_FAILED  = -2,

};

static int check(AVIOContext *pb, int64_t pos, uint32_t *header);

/* mp3 read */

static int mp3_read_probe(const AVProbeData *p)

{

    int max_frames, first_frames = 0;

    int whole_used = 0;

    int frames, ret;

    int framesizes, max_framesizes;

    uint32_t header;

    const uint8_t *buf, *buf0, *buf2, *buf3, *end;

    buf0 = p->buf;

    end = p->buf + p->buf_size - sizeof(uint32_t);

    while (buf0 < end && !*buf0)

        buf0++;

    max_frames = 0;

    max_framesizes = 0;

    buf = buf0;

    for (; buf < end; buf = buf2+1) {

        buf2 = buf;

        for (framesizes = frames = 0; buf2 < end; frames++) {

            MPADecodeHeader h;

            int header_emu = 0;

            int available;

            header = AV_RB32(buf2);

            ret = avpriv_mpegaudio_decode_header(&h, header);

            if (ret != 0)

                break;

            available = FFMIN(h.frame_size, end - buf2);

            for (buf3 = buf2 + 4; buf3 < buf2 + available; buf3++) {

                uint32_t next_sync = AV_RB32(buf3);

                header_emu += (next_sync & MP3_MASK) == (header & MP3_MASK);

            }

            if (header_emu > 2)

                break;

            framesizes += h.frame_size;

            if (available < h.frame_size) {

                frames++;

                break;

            }

            buf2 += h.frame_size;

        }

        max_frames = FFMAX(max_frames, frames);

        max_framesizes = FFMAX(max_framesizes, framesizes);

        if (buf == buf0) {

            first_frames= frames;

            if (buf2 == end + sizeof(uint32_t))

                whole_used = 1;

        }

    }

    // keep this in sync with ac3 probe, both need to avoid

    // issues with MPEG-files!

    if   (first_frames>=7) return AVPROBE_SCORE_EXTENSION + 1;

    else if (max_frames>200 && p->buf_size < 2*max_framesizes)return AVPROBE_SCORE_EXTENSION;

    else if (max_frames>=4 && p->buf_size < 2*max_framesizes) return AVPROBE_SCORE_EXTENSION / 2;

    else if (ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)

                           return p->buf_size < PROBE_BUF_MAX ? AVPROBE_SCORE_EXTENSION / 4 : AVPROBE_SCORE_EXTENSION - 2;

    else if (first_frames > 1 && whole_used) return 5;

    else if (max_frames>=1 && p->buf_size < 10*max_framesizes) return 1;

    else                   return 0;

    //mpegps_mp3_unrecognized_format.mpg has max_frames=3

}

static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)

{

    int i;

    MP3DecContext *mp3 = s->priv_data;

    int fast_seek = s->flags & AVFMT_FLAG_FAST_SEEK;

    int fill_index = (mp3->usetoc || fast_seek) && duration > 0;

    if (!filesize &&

        (filesize = avio_size(s->pb)) <= 0) {

        av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");

        fill_index = 0;

        filesize = 0;

    }

    for (i = 0; i < XING_TOC_COUNT; i++) {

        uint8_t b = avio_r8(s->pb);

        if (fill_index)

            av_add_index_entry(s->streams[0],

                           av_rescale(b, filesize, 256),

                           av_rescale(i, duration, XING_TOC_COUNT),

                           0, 0, AVINDEX_KEYFRAME);

    }

    if (fill_index)

        mp3->xing_toc = 1;

}

static void mp3_parse_info_tag(AVFormatContext *s, AVStream *st,

                               MPADecodeHeader *c, uint32_t spf)

{

#define LAST_BITS(k, n) ((k) & ((1 << (n)) - 1))

#define MIDDLE_BITS(k, m, n) LAST_BITS((k) >> (m), ((n) - (m) + 1))

    FFStream *const sti = ffstream(st);

    uint16_t crc;

    uint32_t v;

    char version[10];

    uint32_t peak   = 0;

    int32_t  r_gain = INT32_MIN, a_gain = INT32_MIN;

    MP3DecContext *mp3 = s->priv_data;

    static const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};

    uint64_t fsize = avio_size(s->pb);

    int64_t pos = avio_tell(s->pb);

    fsize = fsize >= pos ? fsize - pos : 0;

    /* Check for Xing / Info tag */

    avio_skip(s->pb, xing_offtbl[c->lsf == 1][c->nb_channels == 1]);

    v = avio_rb32(s->pb);

    mp3->is_cbr = v == MKBETAG('I', 'n', 'f', 'o');

    if (v != MKBETAG('X', 'i', 'n', 'g') && !mp3->is_cbr)

        return;

    v = avio_rb32(s->pb);

    if (v & XING_FLAG_FRAMES)

        mp3->frames = avio_rb32(s->pb);

    if (v & XING_FLAG_SIZE)

        mp3->header_filesize = avio_rb32(s->pb);

    if (fsize && mp3->header_filesize) {

        uint64_t min, delta;

        min = FFMIN(fsize, mp3->header_filesize);

        delta = FFMAX(fsize, mp3->header_filesize) - min;

        if (fsize > mp3->header_filesize && delta > min >> 4) {

            mp3->frames = 0;

            av_log(s, AV_LOG_WARNING,

                   "invalid concatenated file detected - using bitrate for duration\n");

        } else if (delta > min >> 4) {

            av_log(s, AV_LOG_WARNING,

                   "filesize and duration do not match (growing file?)\n");

        }

    }

    if (v & XING_FLAG_TOC)

        read_xing_toc(s, mp3->header_filesize, av_rescale_q(mp3->frames,

                                       (AVRational){spf, c->sample_rate},

                                       st->time_base));

    /* VBR quality */

    if (v & XING_FLAC_QSCALE)

        avio_rb32(s->pb);

    /* Encoder short version string */

    memset(version, 0, sizeof(version));

    avio_read(s->pb, version, 9);

    /* Info Tag revision + VBR method */

    avio_r8(s->pb);

    /* Lowpass filter value */

    avio_r8(s->pb);

    /* ReplayGain peak */

    v    = avio_rb32(s->pb);

    peak = av_rescale(v, 100000, 1 << 23);

    /* Radio ReplayGain */

    v = avio_rb16(s->pb);

    if (MIDDLE_BITS(v, 13, 15) == 1) {

        r_gain = MIDDLE_BITS(v, 0, 8) * 10000;

        if (v & (1 << 9))

            r_gain *= -1;

    }

    /* Audiophile ReplayGain */

    v = avio_rb16(s->pb);

    if (MIDDLE_BITS(v, 13, 15) == 2) {

        a_gain = MIDDLE_BITS(v, 0, 8) * 10000;

        if (v & (1 << 9))

            a_gain *= -1;

    }

    /* Encoding flags + ATH Type */

    avio_r8(s->pb);

    /* if ABR {specified bitrate} else {minimal bitrate} */

    avio_r8(s->pb);

    /* Encoder delays */

    v = avio_rb24(s->pb);

    if (AV_RB32(version) == MKBETAG('L', 'A', 'M', 'E')

        || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'f')

        || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'c')

    ) {

        mp3->start_pad = v>>12;

        mp3->  end_pad = v&4095;

        sti->start_skip_samples = mp3->start_pad + 528 + 1;

        if (mp3->frames) {

            sti->first_discard_sample = -mp3->end_pad + 528 + 1 + mp3->frames * (int64_t)spf;

            sti->last_discard_sample = mp3->frames * (int64_t)spf;

        }

        if (!st->start_time)

            st->start_time = av_rescale_q(sti->start_skip_samples,

                                            (AVRational){1, c->sample_rate},

                                            st->time_base);

        av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3->  end_pad);

    }

    /* Misc */

    avio_r8(s->pb);

    /* MP3 gain */

    avio_r8(s->pb);

    /* Preset and surround info */

    avio_rb16(s->pb);

    /* Music length */

    avio_rb32(s->pb);

    /* Music CRC */

    avio_rb16(s->pb);

    /* Info Tag CRC */

    crc = ffio_get_checksum(s->pb);

    v   = avio_rb16(s->pb);

    if (v == crc) {

        ff_replaygain_export_raw(st, r_gain, peak, a_gain, 0);

        av_dict_set(&st->metadata, "encoder", version, 0);

    }

}

static void mp3_parse_vbri_tag(AVFormatContext *s, AVStream *st, int64_t base)

{

    uint32_t v;

    MP3DecContext *mp3 = s->priv_data;

    /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */

    avio_seek(s->pb, base + 4 + 32, SEEK_SET);

    v = avio_rb32(s->pb);

    if (v == MKBETAG('V', 'B', 'R', 'I')) {

        /* Check tag version */

        if (avio_rb16(s->pb) == 1) {

            /* skip delay and quality */

            avio_skip(s->pb, 4);

            mp3->header_filesize = avio_rb32(s->pb);

            mp3->frames = avio_rb32(s->pb);

        }

    }

}

/**

 * Try to find Xing/Info/VBRI tags and compute duration from info therein

 */

static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)

{

    uint32_t v, spf;

    MPADecodeHeader c;

    int vbrtag_size = 0;

    MP3DecContext *mp3 = s->priv_data;

    int ret;

    ffio_init_checksum(s->pb, ff_crcA001_update, 0);

    v = avio_rb32(s->pb);

    ret = avpriv_mpegaudio_decode_header(&c, v);

    if (ret < 0)

        return ret;

    else if (ret == 0)

        vbrtag_size = c.frame_size;

    if (c.layer != 3)

        return -1;

    spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */

    mp3->frames = 0;

    mp3->header_filesize   = 0;

    mp3->frame_duration = av_rescale_q(spf, (AVRational){1, c.sample_rate}, st->time_base);

    mp3_parse_info_tag(s, st, &c, spf);

    mp3_parse_vbri_tag(s, st, base);

    if (!mp3->frames && !mp3->header_filesize)

        return -1;

    /* Skip the vbr tag frame */

    avio_seek(s->pb, base + vbrtag_size, SEEK_SET);

    if (mp3->frames) {

        int64_t full_duration_samples;

        full_duration_samples = mp3->frames * (int64_t)spf;

        st->duration = av_rescale_q(full_duration_samples - mp3->start_pad - mp3->end_pad,

                                    (AVRational){1, c.sample_rate},

                                    st->time_base);

        if (mp3->header_filesize && !mp3->is_cbr)

            st->codecpar->bit_rate = av_rescale(mp3->header_filesize, 8 * c.sample_rate,

                                                full_duration_samples);

    }

    return 0;

}

static int mp3_read_header(AVFormatContext *s)

{

    FFFormatContext *const si = ffformatcontext(s);

    MP3DecContext *mp3 = s->priv_data;

    AVStream *st;

    FFStream *sti;

    int64_t off;

    int ret;

    int i;

    s->metadata = si->id3v2_meta;

    si->id3v2_meta = NULL;

    st = avformat_new_stream(s, NULL);

    if (!st)

        return AVERROR(ENOMEM);

    sti = ffstream(st);

    st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;

    st->codecpar->codec_id = AV_CODEC_ID_MP3;

    sti->need_parsing = AVSTREAM_PARSE_FULL_RAW;

    st->start_time = 0;

    // lcm of all mp3 sample rates

    avpriv_set_pts_info(st, 64, 1, 14112000);

    ffiocontext(s->pb)->maxsize = -1;

    off = avio_tell(s->pb);

    if (!av_dict_count(s->metadata))

        ff_id3v1_read(s);

    if (s->pb->seekable & AVIO_SEEKABLE_NORMAL)

        mp3->filesize = avio_size(s->pb);

    if (mp3_parse_vbr_tags(s, st, off) < 0)

        avio_seek(s->pb, off, SEEK_SET);

    ret = ff_replaygain_export(st, s->metadata);

    if (ret < 0)

        return ret;

    ret = ffio_ensure_seekback(s->pb, 64 * 1024 + MPA_MAX_CODED_FRAME_SIZE + 4);

    if (ret < 0)

        return ret;

    off = avio_tell(s->pb);

    for (i = 0; i < 64 * 1024; i++) {

        uint32_t header, header2;

        int frame_size;

        frame_size = check(s->pb, off + i, &header);

        if (frame_size > 0) {

            ret = check(s->pb, off + i + frame_size, &header2);

            if (ret >= 0 && (header & MP3_MASK) == (header2 & MP3_MASK))

                break;

        } else if (frame_size == CHECK_SEEK_FAILED) {

            av_log(s, AV_LOG_ERROR, "Failed to find two consecutive MPEG audio frames.\n");

            return AVERROR_INVALIDDATA;

        }

    }

    if (i == 64 * 1024) {

        off = avio_seek(s->pb, off, SEEK_SET);

    } else {

        av_log(s, i > 0 ? AV_LOG_INFO : AV_LOG_VERBOSE, "Skipping %d bytes of junk at %"PRId64".\n", i, off);

        off = avio_seek(s->pb, off + i, SEEK_SET);

    }

    if (off < 0)

        return off;

    // the seek index is relative to the end of the xing vbr headers

    for (int i = 0; i < sti->nb_index_entries; i++)

        sti->index_entries[i].pos += off;

    /* the parameters will be extracted from the compressed bitstream */

    return 0;

}

#define MP3_PACKET_SIZE 1024

static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)

{

    MP3DecContext *mp3 = s->priv_data;

    int ret, size;

    int64_t pos;

    size = MP3_PACKET_SIZE;

    pos = avio_tell(s->pb);

    if (mp3->filesize > ID3v1_TAG_SIZE && pos < mp3->filesize)

        size= FFMIN(size, mp3->filesize - pos);

    ret = av_get_packet(s->pb, pkt, size);

    if (ret <= 0) {

        if(ret<0)

            return ret;

        return AVERROR_EOF;

    }

    pkt->flags &= ~AV_PKT_FLAG_CORRUPT;

    pkt->stream_index = 0;

    return ret;

}

#define SEEK_WINDOW 4096

static int check(AVIOContext *pb, int64_t pos, uint32_t *ret_header)

{

    int64_t ret = avio_seek(pb, pos, SEEK_SET);

    uint8_t header_buf[4];

    unsigned header;

    MPADecodeHeader sd;

    if (ret < 0)

        return CHECK_SEEK_FAILED;

    ret = avio_read(pb, &header_buf[0], 4);

    /* We should always find four bytes for a valid mpa header. */

    if (ret < 4)

        return CHECK_SEEK_FAILED;

    header = AV_RB32(&header_buf[0]);

    if (ff_mpa_check_header(header) < 0)

        return CHECK_WRONG_HEADER;

    if (avpriv_mpegaudio_decode_header(&sd, header) == 1)

        return CHECK_WRONG_HEADER;

    if (ret_header)

        *ret_header = header;

    return sd.frame_size;

}

static int64_t mp3_sync(AVFormatContext *s, int64_t target_pos, int flags)

{

    int dir = (flags&AVSEEK_FLAG_BACKWARD) ? -1 : 1;

    int64_t best_pos;

    int best_score, i, j;

    int64_t ret;

    avio_seek(s->pb, FFMAX(target_pos - SEEK_WINDOW, 0), SEEK_SET);

    ret = avio_seek(s->pb, target_pos, SEEK_SET);

    if (ret < 0)

        return ret;

#define MIN_VALID 3

    best_pos = target_pos;

    best_score = 999;

    for (i = 0; i < SEEK_WINDOW; i++) {

        int64_t pos = target_pos + (dir > 0 ? i - SEEK_WINDOW/4 : -i);

        int64_t candidate = -1;

        int score = 999;

        if (pos < 0)

            continue;

        for (j = 0; j < MIN_VALID; j++) {

            ret = check(s->pb, pos, NULL);

            if (ret < 0) {

                if (ret == CHECK_WRONG_HEADER) {

                    break;

                } else if (ret == CHECK_SEEK_FAILED) {

                    av_log(s, AV_LOG_ERROR, "Could not seek to %"PRId64".\n", pos);

                    return AVERROR(EINVAL);

                }

            }

            if ((target_pos - pos)*dir <= 0 && FFABS(MIN_VALID/2-j) < score) {

                candidate = pos;

                score = FFABS(MIN_VALID/2-j);

            }

            pos += ret;

        }

        if (best_score > score && j == MIN_VALID) {

            best_pos = candidate;

            best_score = score;

            if(score == 0)

                break;

        }

    }

    return avio_seek(s->pb, best_pos, SEEK_SET);

}

static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,

                    int flags)

{

    FFFormatContext *const si = ffformatcontext(s);

    MP3DecContext *mp3 = s->priv_data;

    AVIndexEntry *ie, ie1;

    AVStream *st = s->streams[0];

    FFStream *const sti = ffstream(st);

    int64_t best_pos;

    int fast_seek = s->flags & AVFMT_FLAG_FAST_SEEK;

    int64_t filesize = mp3->header_filesize;

    if (filesize <= 0) {

        int64_t size = avio_size(s->pb);

        if (size > 0 && size > si->data_offset)

            filesize = size - si->data_offset;

    }

    if (mp3->xing_toc && (mp3->usetoc || (fast_seek && !mp3->is_cbr))) {

        int64_t ret = av_index_search_timestamp(st, timestamp, flags);

        // NOTE: The MP3 TOC is not a precise lookup table. Accuracy is worse

        // for bigger files.

        av_log(s, AV_LOG_WARNING, "Using MP3 TOC to seek; may be imprecise.\n");

        if (ret < 0)

            return ret;

        ie = &sti->index_entries[ret];

    } else if (fast_seek && st->duration > 0 && filesize > 0) {

        if (!mp3->is_cbr)

            av_log(s, AV_LOG_WARNING, "Using scaling to seek VBR MP3; may be imprecise.\n");

        ie = &ie1;

        timestamp = av_clip64(timestamp, 0, st->duration);

        ie->timestamp = timestamp;

        ie->pos       = av_rescale(timestamp, filesize, st->duration) + si->data_offset;

    } else {

        return -1; // generic index code

    }

    best_pos = mp3_sync(s, ie->pos, flags);

    if (best_pos < 0)

        return best_pos;

    if (mp3->is_cbr && ie == &ie1 && mp3->frames && mp3->header_filesize > 0) {

        ie1.timestamp = mp3->frame_duration * av_rescale(best_pos - si->data_offset, mp3->frames, mp3->header_filesize);

    }

    avpriv_update_cur_dts(s, st, ie->timestamp);

    return 0;

}

static const AVOption options[] = {

    { "usetoc", "use table of contents", offsetof(MP3DecContext, usetoc), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, AV_OPT_FLAG_DECODING_PARAM},

    { NULL },

};

static const AVClass demuxer_class = {

    .class_name = "mp3",

    .item_name  = av_default_item_name,

    .option     = options,

    .version    = LIBAVUTIL_VERSION_INT,

    .category   = AV_CLASS_CATEGORY_DEMUXER,

};

const FFInputFormat ff_mp3_demuxer = {

    .p.name         = "mp3",

    .p.long_name    = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),

    .p.flags        = AVFMT_GENERIC_INDEX,

    .p.extensions   = "mp2,mp3,m2a,mpa", /* XXX: use probe */

    .p.priv_class   = &demuxer_class,

    .p.mime_type    = "audio/mpeg",

    .flags_internal = FF_INFMT_FLAG_ID3V2_AUTO,

    .read_probe     = mp3_read_probe,

    .read_header    = mp3_read_header,

    .read_packet    = mp3_read_packet,

    .read_seek      = mp3_seek,

    .priv_data_size = sizeof(MP3DecContext),

};