/*
 * Copyright 2008 Sean Fox <dyntryx@gmail.com>
 * Copyright 2008 James Bursa <james@netsurf-browser.org>
 *
 * This file is part of NetSurf's libnsgif, http://www.netsurf-browser.org/
 * Licenced under the MIT License,
 *                http://www.opensource.org/licenses/mit-license.php
 */

#include <assert.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>

#include "../include/libnsgif.h"

#define BYTES_PER_PIXEL 4
#define MAX_IMAGE_BYTES (48 * 1024 * 1024)


static void *bitmap_create(int width, int height)
{
        /* ensure a stupidly large bitmap is not created */
        if (((long long)width * (long long)height) > (MAX_IMAGE_BYTES/BYTES_PER_PIXEL)) {
                return NULL;
        }
        return calloc(width * height, BYTES_PER_PIXEL);
}


static void bitmap_set_opaque(void *bitmap, bool opaque)
{
        (void) opaque;  /* unused */
        (void) bitmap;  /* unused */
        assert(bitmap);
}


static bool bitmap_test_opaque(void *bitmap)
{
        (void) bitmap;  /* unused */
        assert(bitmap);
        return false;
}


static unsigned char *bitmap_get_buffer(void *bitmap)
{
        assert(bitmap);
        return bitmap;
}


static void bitmap_destroy(void *bitmap)
{
        assert(bitmap);
        free(bitmap);
}


static void bitmap_modified(void *bitmap)
{
        (void) bitmap;  /* unused */
        assert(bitmap);
        return;
}

static unsigned char *load_file(const char *path, size_t *data_size)
{
        FILE *fd;
        struct stat sb;
        unsigned char *buffer;
        size_t size;
        size_t n;

        fd = fopen(path, "rb");
        if (!fd) {
                perror(path);
                exit(EXIT_FAILURE);
        }

        if (stat(path, &sb)) {
                perror(path);
                exit(EXIT_FAILURE);
        }
        size = sb.st_size;

        buffer = malloc(size);
        if (!buffer) {
                fprintf(stderr, "Unable to allocate %lld bytes\n",
                        (long long) size);
                exit(EXIT_FAILURE);
        }

        n = fread(buffer, 1, size, fd);
        if (n != size) {
                perror(path);
                exit(EXIT_FAILURE);
        }

        fclose(fd);

        *data_size = size;
        return buffer;
}


static void warning(const char *context, gif_result code)
{
        fprintf(stderr, "%s failed: ", context);
        switch (code)
        {
        case GIF_INSUFFICIENT_FRAME_DATA:
                fprintf(stderr, "GIF_INSUFFICIENT_FRAME_DATA");
                break;
        case GIF_FRAME_DATA_ERROR:
                fprintf(stderr, "GIF_FRAME_DATA_ERROR");
                break;
        case GIF_INSUFFICIENT_DATA:
                fprintf(stderr, "GIF_INSUFFICIENT_DATA");
                break;
        case GIF_DATA_ERROR:
                fprintf(stderr, "GIF_DATA_ERROR");
                break;
        case GIF_INSUFFICIENT_MEMORY:
                fprintf(stderr, "GIF_INSUFFICIENT_MEMORY");
                break;
        default:
                fprintf(stderr, "unknown code %i", code);
                break;
        }
        fprintf(stderr, "\n");
}

static void write_ppm(FILE* fh, const char *name, gif_animation *gif,
                bool no_write)
{
        unsigned int i;
        gif_result code;

        if (!no_write) {
                fprintf(fh, "P3\n");
                fprintf(fh, "# %s\n", name);
                fprintf(fh, "# width                %u \n", gif->width);
                fprintf(fh, "# height               %u \n", gif->height);
                fprintf(fh, "# frame_count          %u \n", gif->frame_count);
                fprintf(fh, "# frame_count_partial  %u \n", gif->frame_count_partial);
                fprintf(fh, "# loop_count           %u \n", gif->loop_count);
                fprintf(fh, "%u %u 256\n", gif->width, gif->height * gif->frame_count);
        }

        /* decode the frames */
        for (i = 0; i != gif->frame_count; i++) {
                unsigned int row, col;
                unsigned char *image;

                code = gif_decode_frame(gif, i);
                if (code != GIF_OK)
                        warning("gif_decode_frame", code);

                if (!gif->frames[i].display) {
                        continue;
                }

                if (!no_write) {
                        fprintf(fh, "# frame %u:\n", i);
                        image = (unsigned char *) gif->frame_image;
                        for (row = 0; row != gif->height; row++) {
                                for (col = 0; col != gif->width; col++) {
                                        size_t z = (row * gif->width + col) * 4;
                                        fprintf(fh, "%u %u %u ",
                                                (unsigned char) image[z],
                                                (unsigned char) image[z + 1],
                                                (unsigned char) image[z + 2]);
                                }
                                fprintf(fh, "\n");
                        }
                }
        }

}

int main(int argc, char *argv[])
{
        gif_bitmap_callback_vt bitmap_callbacks = {
                bitmap_create,
                bitmap_destroy,
                bitmap_get_buffer,
                bitmap_set_opaque,
                bitmap_test_opaque,
                bitmap_modified
        };
        gif_animation gif;
        size_t size;
        gif_result code;
        unsigned char *data;
        FILE *outf = stdout;
        bool no_write = false;

        if (argc < 2) {
                fprintf(stderr, "Usage: %s image.gif [out]\n", argv[0]);
                fprintf(stderr, "\n");
                fprintf(stderr, "If [out] is NOWRITE, the gif will be docoded "
                                "but not output.\n");
                fprintf(stderr, "Otherwise [out] is an output filename.\n");
                fprintf(stderr, "When [out] is unset, output is to stdout.\n");

                return 1;
        }

        if (argc > 2) {
                if (strcmp(argv[2], "NOWRITE") == 0) {
                        no_write = true;
                } else {
                        outf = fopen(argv[2], "w+");
                        if (outf == NULL) {
                                fprintf(stderr, "Unable to open %s for writing\n", argv[2]);
                                return 2;
                        }
                }
        }

        /* create our gif animation */
        gif_create(&gif, &bitmap_callbacks);

        /* load file into memory */
        data = load_file(argv[1], &size);

        /* begin decoding */
        do {
                code = gif_initialise(&gif, size, data);
                if (code != GIF_OK && code != GIF_WORKING) {
                        warning("gif_initialise", code);
                        gif_finalise(&gif);
                        free(data);
                        return 1;
                }
        } while (code != GIF_OK);

        write_ppm(outf, argv[1], &gif, no_write);

        if (argc > 2 && !no_write) {
                fclose(outf);
        }

        /* clean up */
        gif_finalise(&gif);
        free(data);

        return 0;
}