/*
 * Copyright (C) 2006 Evgeniy Stepanov <eugeni.stepanov@gmail.com>
 * Copyright (C) 2009 Grigori Goronzy <greg@geekmind.org>
 *
 * This file is part of libass.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include "../libass/ass.h"
#include <png.h>

typedef struct image_s {
    int width, height, stride;
    unsigned char *buffer;      // RGB24
} image_t;

ASS_Library *ass_library;
ASS_Renderer *ass_renderer;

void msg_callback(int level, const char *fmt, va_list va, void *data)
{
    if (level > 6)
        return;
    printf("libass: ");
    vprintf(fmt, va);
    printf("\n");
}

static void write_png(char *fname, image_t *img)
{
    FILE *fp;
    png_structp png_ptr;
    png_infop info_ptr;
    png_byte **row_pointers;
    int k;

    png_ptr =
        png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    info_ptr = png_create_info_struct(png_ptr);
    fp = NULL;

    if (setjmp(png_jmpbuf(png_ptr))) {
        png_destroy_write_struct(&png_ptr, &info_ptr);
        fclose(fp);
        return;
    }

    fp = fopen(fname, "wb");
    if (fp == NULL) {
        printf("PNG Error opening %s for writing!\n", fname);
        return;
    }

    png_init_io(png_ptr, fp);
    png_set_compression_level(png_ptr, 0);

    png_set_IHDR(png_ptr, info_ptr, img->width, img->height,
                 8, PNG_COLOR_TYPE_RGB, PNG_INTERLACE_NONE,
                 PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

    png_write_info(png_ptr, info_ptr);

    png_set_bgr(png_ptr);

    row_pointers = (png_byte **) malloc(img->height * sizeof(png_byte *));
    for (k = 0; k < img->height; k++)
        row_pointers[k] = img->buffer + img->stride * k;

    png_write_image(png_ptr, row_pointers);
    png_write_end(png_ptr, info_ptr);
    png_destroy_write_struct(&png_ptr, &info_ptr);

    free(row_pointers);

    fclose(fp);
}

static void init(int frame_w, int frame_h)
{
    ass_library = ass_library_init();
    if (!ass_library) {
        printf("ass_library_init failed!\n");
        exit(1);
    }

    ass_set_message_cb(ass_library, msg_callback, NULL);

    ass_renderer = ass_renderer_init(ass_library);
    if (!ass_renderer) {
        printf("ass_renderer_init failed!\n");
        exit(1);
    }

    ass_set_frame_size(ass_renderer, frame_w, frame_h);
    ass_set_fonts(ass_renderer, NULL, "Sans",
                  ASS_FONTPROVIDER_AUTODETECT, NULL, 1);
}

static image_t *gen_image(int width, int height)
{
    image_t *img = malloc(sizeof(image_t));
    img->width = width;
    img->height = height;
    img->stride = width * 3;
    img->buffer = (unsigned char *) calloc(1, height * width * 3);
    memset(img->buffer, 63, img->stride * img->height);
    //for (int i = 0; i < height * width * 3; ++i)
    // img->buffer[i] = (i/3/50) % 100;
    return img;
}

#define _r(c)  ((c)>>24)
#define _g(c)  (((c)>>16)&0xFF)
#define _b(c)  (((c)>>8)&0xFF)
#define _a(c)  ((c)&0xFF)

static void blend_single(image_t * frame, ASS_Image *img)
{
    int x, y;
    unsigned char opacity = 255 - _a(img->color);
    unsigned char r = _r(img->color);
    unsigned char g = _g(img->color);
    unsigned char b = _b(img->color);

    unsigned char *src;
    unsigned char *dst;

    src = img->bitmap;
    dst = frame->buffer + img->dst_y * frame->stride + img->dst_x * 3;
    for (y = 0; y < img->h; ++y) {
        for (x = 0; x < img->w; ++x) {
            unsigned k = ((unsigned) src[x]) * opacity / 255;
            // possible endianness problems
            dst[x * 3] = (k * b + (255 - k) * dst[x * 3]) / 255;
            dst[x * 3 + 1] = (k * g + (255 - k) * dst[x * 3 + 1]) / 255;
            dst[x * 3 + 2] = (k * r + (255 - k) * dst[x * 3 + 2]) / 255;
        }
        src += img->stride;
        dst += frame->stride;
    }
}

static void blend(image_t * frame, ASS_Image *img)
{
    int cnt = 0;
    while (img) {
        blend_single(frame, img);
        ++cnt;
        img = img->next;
    }
    printf("%d images blended\n", cnt);
}

int main(int argc, char *argv[])
{
    const int frame_w = 1280;
    const int frame_h = 720;

    if (argc < 4) {
        printf("usage: %s <image file> <subtitle file> <time>\n", argv[0]);
        exit(1);
    }
    char *imgfile = argv[1];
    char *subfile = argv[2];
    double tm = strtod(argv[3], 0);

    init(frame_w, frame_h);
    ASS_Track *track = ass_read_file(ass_library, subfile, NULL);
    if (!track) {
        printf("track init failed!\n");
        return 1;
    }

    ASS_Image *img =
        ass_render_frame(ass_renderer, track, (int) (tm * 1000), NULL);
    image_t *frame = gen_image(frame_w, frame_h);
    blend(frame, img);

    ass_free_track(track);
    ass_renderer_done(ass_renderer);
    ass_library_done(ass_library);

    write_png(imgfile, frame);
    free(frame->buffer);
    free(frame);

    return 0;
}