/*
 * JPEG2000 parser
 * Copyright (c) 2020 Gautam Ramakrishnan
 *
 * 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
 * JPEG2000 parser.
 */

#include "parser.h"

/* Whether frame is jp2 file or codestream
*/
enum frame_type {
    jp2_file = 1,
    j2k_cstream
};

typedef struct JPEG2000ParserContext {
    ParseContext pc;
    uint64_t bytes_read;
    uint64_t fheader_state;
    uint32_t skip_bytes; // skip bytes inside codestream data
    enum frame_type ft; // 1 if file, 2 if codestream
    uint8_t fheader_read; // are we reading
    uint8_t reading_file_header;
    uint8_t skipped_codestream;
    uint8_t read_tp;
    uint8_t in_codestream;
} JPEG2000ParserContext;

static inline void reset_context(JPEG2000ParserContext *m)
{
    ParseContext *pc = &m->pc;

    pc->frame_start_found= 0;
    pc->state64 = 0;
    m->bytes_read = 0;
    m->ft = 0;
    m->skipped_codestream = 0;
    m->fheader_read = 0;
    m->skip_bytes = 0;
    m->read_tp = 0;
    m->in_codestream = 0;
}

/* Returns 1 if marker has any data which can be skipped
*/
static uint8_t info_marker(uint16_t marker)
{
    static const uint8_t lut[256] = {
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, // 0xFF4F
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0xFF90 0xFF92 0xFF93
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, // 0xFFD9
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    };
    return marker < 0xFF00 ? 0 : lut[marker & 0xFF];
}

/**
 * Find the end of the current frame in the bitstream.
 * @return the position of the first byte of the next frame, or -1
 */
static int find_frame_end(JPEG2000ParserContext *m, const uint8_t *buf, int buf_size)
{
    ParseContext *pc= &m->pc;
    int i;
    uint64_t state64 = pc->state64;
    uint64_t bytes_read = m->bytes_read;

    if (buf_size == 0) {
        return 0;
    }

    for (i = 0; i < buf_size; i++) {
        state64 = state64 << 8 | buf[i];
        bytes_read++;
        if (m->skip_bytes) {
            // handle long skips
            if (m->skip_bytes > 8) {
                // need -9 else buf_size - i == 8 ==> i == buf_size after this,
                // and thus i == buf_size + 1 after the loop
                int skip = FFMIN(FFMIN((int64_t)m->skip_bytes - 8, buf_size - i - 9), INT_MAX);
                if (skip > 0) {
                    m->skip_bytes -= skip;
                    i += skip;
                    bytes_read += skip;
                }
            }
            m->skip_bytes--;
            continue;
        }
        if (m->read_tp) { // Find out how many bytes inside Tile part codestream to skip.
            if (m->read_tp == 1) {
                m->skip_bytes = (state64 & 0xFFFFFFFF) - 9 > 0?
                                (state64 & 0xFFFFFFFF) - 9 : 0;
            }
            m->read_tp--;
            continue;
        }
        if (m->fheader_read) {
            if (m->fheader_read == 1) {
                if (state64 == 0x6A5020200D0A870A) { // JP2 signature box value.
                    if (pc->frame_start_found) {
                        pc->frame_start_found = 0;
                        reset_context(m);
                        return i - 11;
                    } else {
                        pc->frame_start_found = 1;
                        m->ft = jp2_file;
                    }
                }
            }
            m->fheader_read--;
        }
        if ((state64 & 0xFFFFFFFF) == 0x0000000C && bytes_read >= 3) { // Indicates start of JP2 file. Check signature next.
            m->fheader_read = 8;
        } else if ((state64 & 0xFFFF) == 0xFF4F) {
            m->in_codestream = 1;
            if (!pc->frame_start_found) {
                pc->frame_start_found = 1;
                m->ft = j2k_cstream;
            } else if (pc->frame_start_found && m->ft == jp2_file && m->skipped_codestream) {
                reset_context(m);
                return i - 1;
            }
        } else if ((state64 & 0xFFFF) == 0xFFD9) {
            if (pc->frame_start_found && m->ft == jp2_file) {
                m->skipped_codestream = 1;
            } else if (pc->frame_start_found && m->ft == j2k_cstream) {
                reset_context(m);
                return i + 1; // End of frame detected, return frame size.
            }
            m->in_codestream = 0;
        } else if (m->in_codestream) {
            if ((state64 & 0xFFFF) == 0xFF90) { // Are we in tile part header?
                m->read_tp = 8;
            } else if (info_marker((state64 & 0xFFFF0000)>>16) && pc->frame_start_found && (state64 & 0xFFFF)) {
                // Calculate number of bytes to skip to get to end of the next marker.
                m->skip_bytes = (state64 & 0xFFFF)-1;

                // If the next marker is an info marker, skip to the end of of the marker length.
                if (i + m->skip_bytes + 1 < buf_size) {
                    uint32_t next_state = (buf[i + m->skip_bytes] << 8) | buf[i + m->skip_bytes + 1];
                    if (info_marker(next_state)) {
                        // Skip an additional 2 bytes to get to the end of the marker length.
                        m->skip_bytes += 2;
                    }
                }
            }
        }
    }

    pc->state64 = state64;
    m->bytes_read = bytes_read;
    return END_NOT_FOUND;
}

static int jpeg2000_parse(AVCodecParserContext *s,
                          AVCodecContext *avctx,
                          const uint8_t **poutbuf, int *poutbuf_size,
                          const uint8_t *buf, int buf_size)
{
    JPEG2000ParserContext *m = s->priv_data;
    ParseContext *pc = &m->pc;
    int next;

    if(s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
        next= buf_size;
    } else {
        next= find_frame_end(m, buf, buf_size);

        if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
            *poutbuf = NULL;
            *poutbuf_size = 0;
            return buf_size;
        }
    }

    *poutbuf = buf;
    *poutbuf_size = buf_size;
    return next;
}

const AVCodecParser ff_jpeg2000_parser = {
    .codec_ids      = { AV_CODEC_ID_JPEG2000 },
    .priv_data_size = sizeof(JPEG2000ParserContext),
    .parser_parse   = jpeg2000_parse,
    .parser_close   = ff_parse_close,
};