#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

void save_bmp(const char *filename, unsigned char *img, size_t width, ssize_t height);

int main(int argc, char const *argv[])
{
    return 0;
}


void save_bmp(const char *filename, unsigned char *img, size_t width, ssize_t height) {
    FILE *fptr = fopen(filename,"wb");
    if(fptr == NULL) {
        fprintf(stderr,"ERROR: Could not open output file at %s\n.",filename);
        exit(EXIT_FAILURE);
    }
    int actual_height = (height < 0) ? -height : height;
    size_t row_padding = (4 - (width) * 3 % 4) % 4;
    size_t row_width = width * 3 + row_padding;

    size_t image_size = actual_height * row_width;
    size_t file_size = image_size + 54;

    unsigned char file_header[14] = {
        'B', 'M',           
        0, 0, 0, 0,         
        0, 0, 0, 0,         
        54, 0, 0, 0         
    };

    file_header[2] = (unsigned char)(file_size);
    file_header[3] = (unsigned char)(file_size >> 8);
    file_header[4] = (unsigned char)(file_size >> 16);
    file_header[5] = (unsigned char)(file_size >> 24);

    unsigned char info_header[40] = {
        40, 0, 0, 0,        
        0, 0, 0, 0,         
        0, 0, 0, 0,         
        1, 0,               
        24, 0,              
        0, 0, 0, 0,         
        0, 0, 0, 0,         
        0x13, 0x0B, 0, 0,   
        0x13, 0x0B, 0, 0,   
        0, 0, 0, 0,         
        0, 0, 0, 0          
    };

    info_header[4] = (unsigned char)(width);
    info_header[5] = (unsigned char)(width >> 8);
    info_header[6] = (unsigned char)(width >> 16);
    info_header[7] = (unsigned char)(width >> 24);

    uint32_t h = (uint32_t)height; 
    info_header[8] = (unsigned char)(h);
    info_header[9] = (unsigned char)(h >> 8);
    info_header[10] = (unsigned char)(h >> 16);
    info_header[11] = (unsigned char)(h >> 24);

    info_header[20] = (unsigned char)(image_size);
    info_header[21] = (unsigned char)(image_size >> 8);
    info_header[22] = (unsigned char)(image_size >> 16);
    info_header[23] = (unsigned char)(image_size >> 24);

    fwrite(file_header,1,14,fptr);
    fwrite(info_header,1,40,fptr);

    unsigned char padding_bytes[3] = {0, 0, 0};

    for(int i = 0; i < actual_height; i++) {
        fwrite(img + (i * width * 3), 3, width, fptr);
        if(row_padding > 0) {
            fwrite(padding_bytes,1,row_padding,fptr);
        }
    }
    
    fclose(fptr);
}