#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>

// ok to copy/adapt

/*
 * header contains the image header for referencing sizes
 * x is my x coordinate from the left
 * y is my y coordinate from the bottom
 * c is my color coordinate in order BGR
 * x, y, and c are zero indexed
 * returns the index within BMPImage.data
 */
int _index_bmp_image(const BMPHeader* header, int x, int y, int c) {
    int bytes_per_pixel = header->bits_per_pixel / 8;
    int bytes_per_row_no_padding = header->width_px * bytes_per_pixel;
    int padding = 4 - (bytes_per_row_no_padding % 4);
    if (padding == 4) {
        padding = 0;
    }
    int bytes_per_row = bytes_per_row_no_padding + padding;

    // !! y here starts from the bottom of the image !!
    // it might be easier to start y from the top, because that is what crop_bmp assumes
    int start_of_row = bytes_per_row * y;
    int start_of_pixel = start_of_row + bytes_per_pixel * x;
    int start_of_color = start_of_pixel + c;
    return start_of_color;
}

uint8_t _get_image_color(const BMPImage* image, int x, int y, int c) {
    return image->data[_index_bmp_image(&(image->header), x, y, c)];
}

void _set_image_color(const BMPImage* image, int x, int y, int c, uint8_t new_color) {
    image->data[_index_bmp_image(&(image->header), x, y, c)] = new_color;
}


// !! important: y starts from the top for this parameter !!
BMPImage* crop_bmp(const BMPImage* image, int x, int y, int w, int h, const char** a_error) {
    // validate the header
    BMPHeader new_header = image->header;
    // modify new_header to set the sizes
    // !! make sure the new header is valid !!
    // validate new header with your check_bmp_header
    BMPImage* new_image = malloc(sizeof(*image));
    new_image->header = new_header;
    new_image->data = malloc(sizeof((*new_image->data) * new_header.image_size_bytes));
    // copy over cropped data
    // _index_bmp_image(&(new_image->header), ...)
    // for each y in new image
       // for each x in new image
          // for each color in new image
              // copy pixel to new_image from image, can use _get_image_color and _set_image_color
              // !! important: coordinates in the two images may not be the same !!
              // can offset them using x and y parameters


int main(int argc, char* argv[]) {
    
    return EXIT_SUCCESS;
}
/* vim: set tabstop=4 shiftwidth=4 fileencoding=utf-8 noexpandtab: */