/*

 * CDToons video decoder

 * Copyright (C) 2020 Alyssa Milburn <amilburn@zall.org>

 *

 * 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

 * CDToons video decoder

 * @author Alyssa Milburn <amilburn@zall.org>

 */

#include <stdint.h>

#include "libavutil/attributes.h"

#include "libavutil/internal.h"

#include "libavutil/mem.h"

#include "avcodec.h"

#include "bytestream.h"

#include "codec_internal.h"

#include "decode.h"

#define CDTOONS_HEADER_SIZE   44

#define CDTOONS_MAX_SPRITES 1200

typedef struct CDToonsSprite {

    uint16_t flags;

    uint16_t owner_frame;

    uint16_t start_frame;

    uint16_t end_frame;

    unsigned int alloc_size;

    uint32_t size;

    uint8_t *data;

    int      active;

} CDToonsSprite;

typedef struct CDToonsContext {

    AVFrame *frame;

    uint16_t last_pal_id;   ///< The index of the active palette sprite.

    uint32_t pal[256];      ///< The currently-used palette data.

    CDToonsSprite sprites[CDTOONS_MAX_SPRITES];

} CDToonsContext;

static int cdtoons_render_sprite(AVCodecContext *avctx, const uint8_t *data,

                                 uint32_t data_size,

                                 int dst_x, int dst_y, int width, int height)

{

    CDToonsContext *c = avctx->priv_data;

    const uint8_t *next_line = data;

    const uint8_t *end = data + data_size;

    uint16_t line_size;

    uint8_t *dest;

    int skip = 0, to_skip, x;

    if (dst_x + width > avctx->width)

        width = avctx->width - dst_x;

    if (dst_y + height > avctx->height)

        height = avctx->height - dst_y;

    if (dst_x < 0) {

        /* we need to skip the start of the scanlines */

        skip = -dst_x;

        if (width <= skip)

            return 0;

        dst_x = 0;

    }

    for (int y = 0; y < height; y++) {

        /* one scanline at a time, size is provided */

        data      = next_line;

        if (end - data < 2)

            return 1;

        line_size = bytestream_get_be16(&data);

        if (end - data < line_size)

            return 1;

        next_line = data + line_size;

        if (dst_y + y < 0)

            continue;

        dest = c->frame->data[0] + (dst_y + y) * c->frame->linesize[0] + dst_x;

        to_skip = skip;

        x       = 0;

        while (x < width - skip) {

            int raw, size, step;

            uint8_t val;

            if (data >= end)

                return 1;

            val  = bytestream_get_byte(&data);

            raw  = !(val & 0x80);

            size = (int)(val & 0x7F) + 1;

            /* skip the start of a scanline if it is off-screen */

            if (to_skip >= size) {

                to_skip -= size;

                if (raw) {

                    step = size;

                } else {

                    step = 1;

                }

                if (next_line - data < step)

                    return 1;

                data += step;

                continue;

            } else if (to_skip) {

                size -= to_skip;

                if (raw) {

                    if (next_line - data < to_skip)

                        return 1;

                    data += to_skip;

                }

                to_skip = 0;

            }

            if (x + size >= width - skip)

                size = width - skip - x;

            /* either raw data, or a run of a single color */

            if (raw) {

                if (next_line - data < size)

                    return 1;

                memcpy(dest + x, data, size);

                data += size;

            } else {

                uint8_t color = bytestream_get_byte(&data);

                /* ignore transparent runs */

                if (color)

                    memset(dest + x, color, size);

            }

            x += size;

        }

    }

    return 0;

}

static int cdtoons_decode_frame(AVCodecContext *avctx, AVFrame *rframe,

                                int *got_frame, AVPacket *avpkt)

{

    CDToonsContext *c = avctx->priv_data;

    const uint8_t *buf = avpkt->data;

    const uint8_t *eod = avpkt->data + avpkt->size;

    const int buf_size = avpkt->size;

    uint16_t frame_id;

    uint8_t background_color;

    uint16_t sprite_count, sprite_offset;

    uint8_t referenced_count;

    uint16_t palette_id;

    uint8_t palette_set;

    int ret;

    int saw_embedded_sprites = 0;

    if (buf_size < CDTOONS_HEADER_SIZE)

        return AVERROR_INVALIDDATA;

    if ((ret = ff_reget_buffer(avctx, c->frame, 0)) < 0)

        return ret;

    /* a lot of the header is useless junk in the absence of

     * dirty rectangling etc */

    buf               += 2; /* version? (always 9?) */

    frame_id           = bytestream_get_be16(&buf);

    buf               += 2; /* blocks_valid_until */

    buf               += 1;

    background_color   = bytestream_get_byte(&buf);

    buf               += 16; /* clip rect, dirty rect */

    buf               += 4; /* flags */

    sprite_count       = bytestream_get_be16(&buf);

    sprite_offset      = bytestream_get_be16(&buf);

    buf               += 2; /* max block id? */

    referenced_count   = bytestream_get_byte(&buf);

    buf               += 1;

    palette_id         = bytestream_get_be16(&buf);

    palette_set        = bytestream_get_byte(&buf);

    buf               += 5;

    if (sprite_offset > buf_size)

        return AVERROR_INVALIDDATA;

    /* read new sprites introduced in this frame */

    buf = avpkt->data + sprite_offset;

    while (sprite_count--) {

        uint32_t size;

        uint16_t sprite_id;

        if (buf + 14 > eod)

            return AVERROR_INVALIDDATA;

        sprite_id = bytestream_get_be16(&buf);

        if (sprite_id >= CDTOONS_MAX_SPRITES) {

            av_log(avctx, AV_LOG_ERROR,

                   "Sprite ID %d is too high.\n", sprite_id);

            return AVERROR_INVALIDDATA;

        }

        if (c->sprites[sprite_id].active) {

            av_log(avctx, AV_LOG_ERROR,

                   "Sprite ID %d is a duplicate.\n", sprite_id);

            return AVERROR_INVALIDDATA;

        }

        c->sprites[sprite_id].flags = bytestream_get_be16(&buf);

        size                        = bytestream_get_be32(&buf);

        if (size < 14) {

            av_log(avctx, AV_LOG_ERROR,

                   "Sprite only has %d bytes of data.\n", size);

            return AVERROR_INVALIDDATA;

        }

        size -= 14;

        c->sprites[sprite_id].size        = size;

        c->sprites[sprite_id].owner_frame = frame_id;

        c->sprites[sprite_id].start_frame = bytestream_get_be16(&buf);

        c->sprites[sprite_id].end_frame   = bytestream_get_be16(&buf);

        buf += 2;

        if (size > buf_size || buf + size > eod)

            return AVERROR_INVALIDDATA;

        av_fast_padded_malloc(&c->sprites[sprite_id].data, &c->sprites[sprite_id].alloc_size, size);

        if (!c->sprites[sprite_id].data)

            return AVERROR(ENOMEM);

        c->sprites[sprite_id].active = 1;

        bytestream_get_buffer(&buf, c->sprites[sprite_id].data, size);

    }

    /* render any embedded sprites */

    while (buf < eod) {

        uint32_t tag, size;

        if (buf + 8 > eod) {

            av_log(avctx, AV_LOG_WARNING, "Ran (seriously) out of data for embedded sprites.\n");

            return AVERROR_INVALIDDATA;

        }

        tag  = bytestream_get_be32(&buf);

        size = bytestream_get_be32(&buf);

        if (tag == MKBETAG('D', 'i', 'f', 'f')) {

            uint16_t diff_count;

            if (buf + 10 > eod) {

                av_log(avctx, AV_LOG_WARNING, "Ran (seriously) out of data for Diff frame.\n");

                return AVERROR_INVALIDDATA;

            }

            diff_count = bytestream_get_be16(&buf);

            buf       += 8; /* clip rect? */

            for (int i = 0; i < diff_count; i++) {

                int16_t top, left;

                uint16_t diff_size, width, height;

                if (buf + 16 > eod) {

                    av_log(avctx, AV_LOG_WARNING, "Ran (seriously) out of data for Diff frame header.\n");

                    return AVERROR_INVALIDDATA;

                }

                top        = bytestream_get_be16(&buf);

                left       = bytestream_get_be16(&buf);

                buf       += 4; /* bottom, right */

                diff_size  = bytestream_get_be32(&buf);

                width      = bytestream_get_be16(&buf);

                height     = bytestream_get_be16(&buf);

                if (diff_size < 8 || diff_size - 4 > eod - buf) {

                    av_log(avctx, AV_LOG_WARNING, "Ran (seriously) out of data for Diff frame data.\n");

                    return AVERROR_INVALIDDATA;

                }

                if (cdtoons_render_sprite(avctx, buf + 4, diff_size - 8,

                                      left, top, width, height)) {

                    av_log(avctx, AV_LOG_WARNING, "Ran beyond end of sprite while rendering.\n");

                }

                buf += diff_size - 4;

            }

            saw_embedded_sprites = 1;

        } else {

            /* we don't care about any other entries */

            if (size < 8 || size - 8 > eod - buf) {

                av_log(avctx, AV_LOG_WARNING, "Ran out of data for ignored entry (size %X, %d left).\n", size, (int)(eod - buf));

                return AVERROR_INVALIDDATA;

            }

            buf += (size - 8);

        }

    }

    /* was an intra frame? */

    if (saw_embedded_sprites)

        goto done;

    /* render any referenced sprites */

    buf = avpkt->data + CDTOONS_HEADER_SIZE;

    eod = avpkt->data + sprite_offset;

    for (int i = 0; i < referenced_count; i++) {

        const uint8_t *block_data;

        uint16_t sprite_id, width, height;

        int16_t top, left, right;

        if (buf + 10 > eod) {

            av_log(avctx, AV_LOG_WARNING, "Ran (seriously) out of data when rendering.\n");

            return AVERROR_INVALIDDATA;

        }

        sprite_id = bytestream_get_be16(&buf);

        top       = bytestream_get_be16(&buf);

        left      = bytestream_get_be16(&buf);

        buf      += 2; /* bottom */

        right     = bytestream_get_be16(&buf);

        if ((i == 0) && (sprite_id == 0)) {

            /* clear background */

            memset(c->frame->data[0], background_color,

                   c->frame->linesize[0] * avctx->height);

        }

        if (!right)

            continue;

        if (sprite_id >= CDTOONS_MAX_SPRITES) {

            av_log(avctx, AV_LOG_ERROR,

                   "Sprite ID %d is too high.\n", sprite_id);

            return AVERROR_INVALIDDATA;

        }

        block_data = c->sprites[sprite_id].data;

        if (!c->sprites[sprite_id].active) {

            /* this can happen when seeking around */

            av_log(avctx, AV_LOG_WARNING, "Sprite %d is missing.\n", sprite_id);

            continue;

        }

        if (c->sprites[sprite_id].size < 14) {

            av_log(avctx, AV_LOG_ERROR, "Sprite %d is too small.\n", sprite_id);

            continue;

        }

        height      = bytestream_get_be16(&block_data);

        width       = bytestream_get_be16(&block_data);

        block_data += 10;

        if (cdtoons_render_sprite(avctx, block_data,

                              c->sprites[sprite_id].size - 14,

                              left, top, width, height)) {

            av_log(avctx, AV_LOG_WARNING, "Ran beyond end of sprite while rendering.\n");

        }

    }

    if (palette_id && (palette_id != c->last_pal_id)) {

        if (palette_id >= CDTOONS_MAX_SPRITES) {

            av_log(avctx, AV_LOG_ERROR,

                   "Palette ID %d is too high.\n", palette_id);

            return AVERROR_INVALIDDATA;

        }

        if (!c->sprites[palette_id].active) {

            /* this can happen when seeking around */

            av_log(avctx, AV_LOG_WARNING,

                   "Palette ID %d is missing.\n", palette_id);

            goto done;

        }

        if (c->sprites[palette_id].size != 256 * 2 * 3) {

            av_log(avctx, AV_LOG_ERROR,

                   "Palette ID %d is wrong size (%d).\n",

                   palette_id, c->sprites[palette_id].size);

            return AVERROR_INVALIDDATA;

        }

        c->last_pal_id = palette_id;

        if (!palette_set) {

            uint8_t *palette_data = c->sprites[palette_id].data;

            for (int i = 0; i < 256; i++) {

                /* QuickTime-ish palette: 16-bit RGB components */

                unsigned r, g, b;

                r             = *palette_data;

                g             = *(palette_data + 2);

                b             = *(palette_data + 4);

                c->pal[i]     = (0xFFU << 24) | (r << 16) | (g << 8) | b;

                palette_data += 6;

            }

            /* first palette entry indicates transparency */

            c->pal[0]                     = 0;

        }

    }

done:

    /* discard outdated blocks */

    for (int i = 0; i < CDTOONS_MAX_SPRITES; i++) {

        if (c->sprites[i].end_frame > frame_id)

            continue;

        c->sprites[i].active = 0;

    }

    memcpy(c->frame->data[1], c->pal, AVPALETTE_SIZE);

    if ((ret = av_frame_ref(rframe, c->frame)) < 0)

        return ret;

    *got_frame = 1;

    /* always report that the buffer was completely consumed */

    return buf_size;

}

static av_cold int cdtoons_decode_init(AVCodecContext *avctx)

{

    CDToonsContext *c = avctx->priv_data;

    avctx->pix_fmt = AV_PIX_FMT_PAL8;

    c->last_pal_id = 0;

    c->frame       = av_frame_alloc();

    if (!c->frame)

        return AVERROR(ENOMEM);

    return 0;

}

static void cdtoons_flush(AVCodecContext *avctx)

{

    CDToonsContext *c = avctx->priv_data;

    c->last_pal_id = 0;

    for (int i = 0; i < CDTOONS_MAX_SPRITES; i++)

        c->sprites[i].active = 0;

}

static av_cold int cdtoons_decode_end(AVCodecContext *avctx)

{

    CDToonsContext *c = avctx->priv_data;

    for (int i = 0; i < CDTOONS_MAX_SPRITES; i++) {

        av_freep(&c->sprites[i].data);

        c->sprites[i].active = 0;

    }

    av_frame_free(&c->frame);

    return 0;

}

const FFCodec ff_cdtoons_decoder = {

    .p.name         = "cdtoons",

    CODEC_LONG_NAME("CDToons video"),

    .p.type         = AVMEDIA_TYPE_VIDEO,

    .p.id           = AV_CODEC_ID_CDTOONS,

    .priv_data_size = sizeof(CDToonsContext),

    .init           = cdtoons_decode_init,

    .close          = cdtoons_decode_end,

    FF_CODEC_DECODE_CB(cdtoons_decode_frame),

    .p.capabilities = AV_CODEC_CAP_DR1,

    .flush          = cdtoons_flush,

};