/*
 * PNG image format
 * 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 <string.h>
#include <stdio.h>
#include <limits.h>
#include <stdlib.h>
#include <pngdec.h>

#define PNG_COLOR_MASK_PALETTE    1
#define PNG_COLOR_MASK_COLOR      2
#define PNG_COLOR_MASK_ALPHA      4

#define PNG_COLOR_TYPE_GRAY 0
#define PNG_COLOR_TYPE_PALETTE  (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)
#define PNG_COLOR_TYPE_RGB        (PNG_COLOR_MASK_COLOR)
#define PNG_COLOR_TYPE_RGB_ALPHA  (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_ALPHA)
#define PNG_COLOR_TYPE_GRAY_ALPHA (PNG_COLOR_MASK_ALPHA)

#define PNG_FILTER_VALUE_NONE  0
#define PNG_FILTER_VALUE_SUB   1
#define PNG_FILTER_VALUE_UP    2
#define PNG_FILTER_VALUE_AVG   3
#define PNG_FILTER_VALUE_PAETH 4

#define PNG_IHDR      0x0001
#define PNG_IDAT      0x0002
#define PNG_ALLIMAGE  0x0004
#define PNG_PLTE      0x0008

#define NB_PASSES 7

/* TODO:
 * - add 2, 4 and 16 bit depth support
 */

static const uint8_t ff_pngsig[8] = {137, 80, 78, 71, 13, 10, 26, 10};

/* Mask to determine which y pixels are valid in a pass */
static const uint8_t ff_png_pass_ymask[NB_PASSES] = {
    0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55,
};

/* minimum x value */
static const uint8_t ff_png_pass_xmin[NB_PASSES] = {
    0, 4, 0, 2, 0, 1, 0
};

/* x shift to get row width */
static const uint8_t ff_png_pass_xshift[NB_PASSES] = {
    3, 3, 2, 2, 1, 1, 0
};

/* Mask to determine which pixels are valid in a pass */
static const uint8_t ff_png_pass_mask[NB_PASSES] = {
    0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff
};

static void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size)
{
    if(items >= UINT_MAX / size)
        return NULL;
    return malloc(items * size);
}

static void ff_png_zfree(void *opaque, void *ptr)
{
    free(ptr);
}

static int ff_png_get_nb_channels(int color_type)
{
    int channels;
    channels = 1;
    if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) ==
        PNG_COLOR_MASK_COLOR)
        channels = 3;
    if (color_type & PNG_COLOR_MASK_ALPHA)
        channels++;
    return channels;
}

/* compute the row size of an interleaved pass */
static int ff_png_pass_row_size(int pass, int bits_per_pixel, int width)
{
    int shift, xmin, pass_width;

    xmin = ff_png_pass_xmin[pass];
    if (width <= xmin)
        return 0;
    shift = ff_png_pass_xshift[pass];
    pass_width = (width - xmin + (1 << shift) - 1) >> shift;
    return (pass_width * bits_per_pixel + 7) >> 3;
}

static inline uint32_t bswap_32(uint32_t x)
{
    x = ((x<<8)&0xFF00FF00) | ((x>>8)&0x00FF00FF);
    x = (x>>16) | (x<<16);
    return x;
}

static inline uint32_t bytestream_get_be32(uint8_t **b)
{
    (*b) += 4;
#ifdef WORDS_BIGENDIAN
    return (*((uint32_t*)(*b - 4)));
#else /* WORDS_BIGENDIAN */
    return bswap_32(*((uint32_t*)(*b - 4)));
#endif
}

#define MKTAG(a,b,c,d) (a | (b << 8) | (c << 16) | (d << 24))

/* Mask to determine which y pixels can be written in a pass */
static const uint8_t png_pass_dsp_ymask[NB_PASSES] = {
    0xff, 0xff, 0x0f, 0xcc, 0x33, 0xff, 0x55,
};

/* Mask to determine which pixels to overwrite while displaying */
static const uint8_t png_pass_dsp_mask[NB_PASSES] = {
    0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff
};

/* NOTE: we try to construct a good looking image at each pass. width
   is the original image width. We also do pixel format conversion at
   this stage */
static void png_put_interlaced_row(uint8_t *dst, int width,
                                   int bits_per_pixel, int pass,
                                   int color_type, const uint8_t *src)
{
    int x, mask, dsp_mask, j, src_x, b, bpp;
    uint8_t *d;
    const uint8_t *s;

    mask = ff_png_pass_mask[pass];
    dsp_mask = png_pass_dsp_mask[pass];
    switch(bits_per_pixel) {
    case 1:
        /* we must initialize the line to zero before writing to it */
        if (pass == 0)
            memset(dst, 0, (width + 7) >> 3);
        src_x = 0;
        for(x = 0; x < width; x++) {
            j = (x & 7);
            if ((dsp_mask << j) & 0x80) {
                b = (src[src_x >> 3] >> (7 - (src_x & 7))) & 1;
                dst[x >> 3] |= b << (7 - j);
            }
            if ((mask << j) & 0x80)
                src_x++;
        }
        break;
    default:
        bpp = bits_per_pixel >> 3;
        d = dst;
        s = src;
        if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
            for(x = 0; x < width; x++) {
                j = x & 7;
                if ((dsp_mask << j) & 0x80) {
                    *(uint32_t *)d = (s[3] << 24) | (s[0] << 16) | (s[1] << 8) | s[2];
                }
                d += bpp;
                if ((mask << j) & 0x80)
                    s += bpp;
            }
        } else {
            for(x = 0; x < width; x++) {
                j = x & 7;
                if ((dsp_mask << j) & 0x80) {
                    memcpy(d, s, bpp);
                }
                d += bpp;
                if ((mask << j) & 0x80)
                    s += bpp;
            }
        }
        break;
    }
}

/* XXX: optimize */
/* NOTE: 'dst' can be equal to 'last' */
static void png_filter_row(uint8_t *dst, int filter_type,
                           uint8_t *src, uint8_t *last, int size, int bpp)
{
    int i, p;

    switch(filter_type) {
    case PNG_FILTER_VALUE_NONE:
        memcpy(dst, src, size);
        break;
    case PNG_FILTER_VALUE_SUB:
        for(i = 0; i < bpp; i++) {
            dst[i] = src[i];
        }
        for(i = bpp; i < size; i++) {
            p = dst[i - bpp];
            dst[i] = p + src[i];
        }
        break;
    case PNG_FILTER_VALUE_UP:
        for(i = 0; i < size; i++) {
            p = last[i];
            dst[i] = p + src[i];
        }
        break;
    case PNG_FILTER_VALUE_AVG:
        for(i = 0; i < bpp; i++) {
            p = (last[i] >> 1);
            dst[i] = p + src[i];
        }
        for(i = bpp; i < size; i++) {
            p = ((dst[i - bpp] + last[i]) >> 1);
            dst[i] = p + src[i];
        }
        break;
    case PNG_FILTER_VALUE_PAETH:
        for(i = 0; i < bpp; i++) {
            p = last[i];
            dst[i] = p + src[i];
        }
        for(i = bpp; i < size; i++) {
            int a, b, c, pa, pb, pc;

            a = dst[i - bpp];
            b = last[i];
            c = last[i - bpp];

            p = b - c;
            pc = a - c;

            pa = abs(p);
            pb = abs(pc);
            pc = abs(p + pc);

            if (pa <= pb && pa <= pc)
                p = a;
            else if (pb <= pc)
                p = b;
            else
                p = c;
            dst[i] = p + src[i];
        }
        break;
    }
}

static void convert_to_rgb32(uint8_t *dst, const uint8_t *src, int width)
{
    int j;
    unsigned int r, g, b, a;

    for(j = 0; j < width; j++) {
        r = src[0];
        g = src[1];
        b = src[2];
        a = src[3];
        *(uint32_t *)dst = (a << 24) | (r << 16) | (g << 8) | b;
        dst += 4;
        src += 4;
    }
}

/* process exactly one decompressed row */
static void png_handle_row(PNGDecContext *s)
{
    uint8_t *ptr, *last_row;
    int got_line;

    if (!s->interlace_type) {
        ptr = s->image_buf + s->image_linesize * s->y;
        /* need to swap bytes correctly for RGB_ALPHA */
        if (s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
            png_filter_row(s->tmp_row, s->crow_buf[0], s->crow_buf + 1,
                           s->last_row, s->row_size, s->bpp);
            memcpy(s->last_row, s->tmp_row, s->row_size);
            convert_to_rgb32(ptr, s->tmp_row, s->width);
        } else {
            /* in normal case, we avoid one copy */
            if (s->y == 0)
                last_row = s->last_row;
            else
                last_row = ptr - s->image_linesize;

            png_filter_row(ptr, s->crow_buf[0], s->crow_buf + 1,
                           last_row, s->row_size, s->bpp);
        }
        s->y++;
        if (s->y == s->height) {
            s->state |= PNG_ALLIMAGE;
        }
    } else {
        got_line = 0;
        for(;;) {
            ptr = s->image_buf + s->image_linesize * s->y;
            if ((ff_png_pass_ymask[s->pass] << (s->y & 7)) & 0x80) {
                /* if we already read one row, it is time to stop to
                   wait for the next one */
                if (got_line)
                    break;
                png_filter_row(s->tmp_row, s->crow_buf[0], s->crow_buf + 1,
                               s->last_row, s->pass_row_size, s->bpp);
                memcpy(s->last_row, s->tmp_row, s->pass_row_size);
                got_line = 1;
            }
            if ((png_pass_dsp_ymask[s->pass] << (s->y & 7)) & 0x80) {
                /* NOTE: RGB32 is handled directly in png_put_interlaced_row */
                png_put_interlaced_row(ptr, s->width, s->bits_per_pixel, s->pass,
                                       s->color_type, s->last_row);
            }
            s->y++;
            if (s->y == s->height) {
                for(;;) {
                    if (s->pass == NB_PASSES - 1) {
                        s->state |= PNG_ALLIMAGE;
                        goto the_end;
                    } else {
                        s->pass++;
                        s->y = 0;
                        s->pass_row_size = ff_png_pass_row_size(s->pass,
                                                             s->bits_per_pixel,
                                                             s->width);
                        s->crow_size = s->pass_row_size + 1;
                        if (s->pass_row_size != 0)
                            break;
                        /* skip pass if empty row */
                    }
                }
            }
        }
    the_end: ;
    }
}

static int png_decode_idat(PNGDecContext *s, int length)
{
    int ret;
    s->zstream.avail_in = length;
    s->zstream.next_in = s->bytestream;
    s->bytestream += length;

    if(s->bytestream > s->bytestream_end)
        return -1;

    /* decode one line if possible */
    while (s->zstream.avail_in > 0) {
        ret = inflate(&s->zstream, Z_PARTIAL_FLUSH);
        if (ret != Z_OK && ret != Z_STREAM_END) {
            return -1;
        }
        if (s->zstream.avail_out == 0) {
            if (!(s->state & PNG_ALLIMAGE)) {
                png_handle_row(s);
            }
            s->zstream.avail_out = s->crow_size;
            s->zstream.next_out = s->crow_buf;
        }
    }
    return 0;
}


int png_decode_frame(PNGDecContext *s, uint8_t *buf, int buf_size)
{
    uint32_t tag, length;
    int ret, crc;
    
//    printf("decoding\n");

    s->crow_buf = 0;
    s->last_row = 0;
    s->tmp_row = 0;
    s->bytestream_start=
    s->bytestream= buf;
    s->bytestream_end= buf + buf_size;

    /* check signature */
    if (memcmp(s->bytestream, ff_pngsig, 8) != 0)
        return -1;
    s->bytestream+= 8;
    s->y=
    s->state=0;
//    memset(s, 0, sizeof(PNGDecContext));
    /* init the zlib */
    s->zstream.zalloc = ff_png_zalloc;
    s->zstream.zfree = ff_png_zfree;
    s->zstream.opaque = NULL;
    ret = inflateInit(&s->zstream);
    if (ret != Z_OK)
        return -1;
    for(;;) {
        //printf("decoding next packet\n");
        int tag32;
        if (s->bytestream >= s->bytestream_end)
            goto fail;
        length = bytestream_get_be32(&s->bytestream);
        if (length > 0x7fffffff)
            goto fail;
        tag32 = bytestream_get_be32(&s->bytestream);
        tag = bswap_32(tag32);
        switch(tag) {
        case MKTAG('I', 'H', 'D', 'R'):
            printf("decoding IHDR\n");
            if (length != 13)
                goto fail;
            s->width = bytestream_get_be32(&s->bytestream);
            s->height = bytestream_get_be32(&s->bytestream);
            if (s->width <= 0 || s->width > 16000 || s->height <= 0 || s->height > 16000){
                s->width= s->height= 0;
                goto fail;
            }
            s->bit_depth = *s->bytestream++;
            s->color_type = *s->bytestream++;
            s->compression_type = *s->bytestream++;
            s->filter_type = *s->bytestream++;
            s->interlace_type = *s->bytestream++;
            crc = bytestream_get_be32(&s->bytestream);
            s->state |= PNG_IHDR;
            break;
        case MKTAG('I', 'D', 'A', 'T'):
            printf("decoding IDAT\n");
            if (!(s->state & PNG_IHDR))
                goto fail;
            if (!(s->state & PNG_IDAT)) {
                /* init image info */
                s->channels = ff_png_get_nb_channels(s->color_type);
                s->bits_per_pixel = s->bit_depth * s->channels;
                s->bpp = (s->bits_per_pixel + 7) >> 3;
                s->row_size = (s->width * s->bits_per_pixel + 7) >> 3;

                if (s->bit_depth == 8 &&
                    s->color_type == PNG_COLOR_TYPE_RGB) {
                    s->pix_fmt = PIX_FMT_RGB24;
                } else if (s->bit_depth == 8 &&
                           s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
                    s->pix_fmt = PIX_FMT_RGB32;
                } else if (s->bit_depth == 8 &&
                           s->color_type == PNG_COLOR_TYPE_GRAY) {
                    s->pix_fmt = PIX_FMT_GRAY8;
                } else if (s->bit_depth == 16 &&
                           s->color_type == PNG_COLOR_TYPE_GRAY) {
                    s->pix_fmt = PIX_FMT_GRAY16BE;
                } else if (s->bit_depth == 1 &&
                           s->color_type == PNG_COLOR_TYPE_GRAY) {
                    s->pix_fmt = PIX_FMT_MONOBLACK;
                } else if (s->color_type == PNG_COLOR_TYPE_PALETTE) {
                    s->pix_fmt = PIX_FMT_PAL8;
                } else {
                    goto fail;
                }

                s->image_buf = (uint8_t *)malloc(s->width*s->height*4);
                s->image_linesize = s->width*4;

                /* compute the compressed row size */
                if (!s->interlace_type) {
                    s->crow_size = s->row_size + 1;
                } else {
                    s->pass = 0;
                    s->pass_row_size = ff_png_pass_row_size(s->pass,
                                                         s->bits_per_pixel,
                                                         s->width);
                    s->crow_size = s->pass_row_size + 1;
                }
                
                /* copy the palette if needed */
                //if (s->color_type == PNG_COLOR_TYPE_PALETTE)
                //    memcpy(p->data[1], s->palette, 256 * sizeof(uint32_t));
                
                /* empty row is used if differencing to the first row */
                s->last_row = (uint8_t *)malloc(s->row_size);
                memset(s->last_row, 0, s->row_size);
                if (!s->last_row)
                    goto fail;
                if (s->interlace_type ||
                    s->color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
                    s->tmp_row = (uint8_t *)malloc(s->row_size);
                    if (!s->tmp_row)
                        goto fail;
                }
                /* compressed row */
                s->crow_buf = (uint8_t *)malloc(s->row_size + 1);
                if (!s->crow_buf)
                    goto fail;
                s->zstream.avail_out = s->crow_size;
                s->zstream.next_out = s->crow_buf;
            }
            s->state |= PNG_IDAT;
            if (png_decode_idat(s, length) < 0)
                goto fail;
            /* skip crc */
            crc = bytestream_get_be32(&s->bytestream);
            break;
        case MKTAG('P', 'L', 'T', 'E'):
            printf("decoding PLTE\n");
            {
                int n, i, r, g, b;

                if ((length % 3) != 0 || length > 256 * 3)
                    goto skip_tag;
                /* read the palette */
                n = length / 3;
                for(i=0;i<n;i++) {
                    r = *s->bytestream++;
                    g = *s->bytestream++;
                    b = *s->bytestream++;
                    s->palette[i] = (0xff << 24) | (r << 16) | (g << 8) | b;
                }
                for(;i<256;i++) {
                    s->palette[i] = (0xff << 24);
                }
                s->state |= PNG_PLTE;
                crc = bytestream_get_be32(&s->bytestream);
            }
            break;
        case MKTAG('t', 'R', 'N', 'S'):
            printf("decoding tRNS\n");
            {
                int v, i;

                /* read the transparency. XXX: Only palette mode supported */
                if (s->color_type != PNG_COLOR_TYPE_PALETTE ||
                    length > 256 ||
                    !(s->state & PNG_PLTE))
                    goto skip_tag;
                for(i=0;i<length;i++) {
                    v = *s->bytestream++;
                    s->palette[i] = (s->palette[i] & 0x00ffffff) | (v << 24);
                }
                crc = bytestream_get_be32(&s->bytestream);
            }
            break;
        case MKTAG('I', 'E', 'N', 'D'):
            printf("decoding IEND\n");
            if (!(s->state & PNG_ALLIMAGE))
                goto fail;
            crc = bytestream_get_be32(&s->bytestream);
            goto exit_loop;
        default:
            /* skip tag */
        skip_tag:
            printf("decoding other\n");
            s->bytestream += length + 4;
            break;
        }
    }
 exit_loop:
    ret = s->bytestream - s->bytestream_start;
 the_end:
    inflateEnd(&s->zstream);
            printf("freeing stuff\n");
//    free(s->image_buf);
    free(s->crow_buf);
    free(s->last_row);
    free(s->tmp_row);
            printf("freed stuff\n");
    return ret;
 fail:
    ret = -1;
    goto the_end;
}