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

#include <stdbool.h>

#define LINE_SIZE 32

/* CP2 Laboratory number 3
 * Library functions and binary files
 *
 * TASKS:
 *
 * 0. Open the documentation of the stdio.h, stdlib.h and string.h libraries.
 *
 * 1. Read about the PPM graphics format - it is very simple: the header contains only three lines of text:
 *     P6
 *     [width] [height]
 *     [size]
 * where [width] and [height] are strings containing image dimensions and [size] is the maximal number of pixel value - in this case it is 255;
 * after the header there is a raster of pixels - written as binary data: [r][g][b] - one byte of red color, one byte of green and one byte of blue color - and these repeat for each pixel.
 *
 * 2. Try to open the "image.ppm" file in your operating system - if you do not have an appropriate application, you can use the online converters to convert it to other more popular formats;
 * try to open the file with a hex editor or even the text editor to see its contents - the first three lines should containt the aforementioned header.
 *
 * 3. Read about converting the colorful image (in RGB format) to a grayscale image - the operation consists of calcuating the average.
 *
 * 4. Write a program that converts the given PPM file containing a colorful image into the PPM file that contains a grayscale image - use the hints inside the main function.
 *
 * 5. Use the online converter once again to see the result if you have problems with opening the resulting file in your computer.
 */

int main()
{
    /*
        a) open the "image.ppm" file in a binary mode for reading and open the "result.ppm" file in binary mode for writing;
        b) check whether the "image.ppm" file exists - print a message and exit the program if not;
    */
    bool check_1;
    FILE *fp;
    FILE *fp2;
    fp = fopen("C:\\Users\\pumpk\\Desktop\\git\\4156b601-gr13-repo\\lab3\\image.ppm", "r");
    fp2 = fopen("C:\\Users\\pumpk\\Desktop\\git\\4156b601-gr13-repo\\lab3\\result.ppm", "w");

    if(fp) {
        printf("File found, opening...\n");
        check_1 = true;
    }
    else
        printf("No file found, sorry but we are closing\n");

    if(check_1 && fp2)
        printf("New file created\n");

    // this would be a buffer for each line of the header
    char line[LINE_SIZE];
    char chunk[128];
    fgets(line, chunk, fp);
    printf("%s", line);
    fputs(line, fp2);
    fgets(line, chunk, fp);
    printf("%s",line);
    fputs(line, fp2);
    char width[50];
    char height[50];
    strcpy(width, strtok(line, " "));
    strcpy(height, strtok(NULL," "));
    printf("%s - %s", width, height);
    int w = atoi(width);
    int h = atoi(height);
    printf("%d - %d\n",w,h);
    fgets(line, chunk, fp);
    printf("%s", line);
    fputs(line, fp2);
    /*
        c) read one line from the "image.ppm" file - use "fgets" function and the "line" buffer created above;
        d) write that line to the "result.ppm" file - use "fputs" funcion;
        e) read another line from the "image.ppm" file - it should contain the image dimensions;
        f) write that line to the "result.ppm" file;
        g) parse that line using the "strtok" function - your task is to split it into 2 substrings containing the [width] and [height] values;
        h) convert these substrings into integers - use the "atoi" function - name the variables "w" and "h" - they would be required in the loops below;
        i) read another line from the "image.ppm" file - it is the last line of the header
        j) write that line to the "result.ppm" file
    */

    // an array for one pixel (three bytes: [r][g][b])
    unsigned char rgb[3];

    // one byte for averaged grayscale value
    unsigned char gray;

    // first iterate over height
    for (int i = 0; i < h; ++i)
    {
        // than iterate over width
        for (int j = 0; j < w; ++j)
        {
				//Something is wrong here
                fread(rgb, 3, 1,fp);
                gray = (rgb[0] + rgb[1] + rgb[2])/3;
                memset(rgb, gray, sizeof(rgb));
                fwrite(&rgb, 3, 1, fp2);

                //k) read from the "image.ppm" file the whole "rgb" array using the "fread" function - it reads binary data from a file;
                //l) calculate the average of three RGB components - warning: use "int" and "double" for calculations, because "unsigned char" is not sufficient;
                //m) cast the average (double value) to the "gray" variable;
                //n) write the "gray" variable 3 times into the "result.ppm" file - the same value is used for all pixels - use the "fwrite" function that writes binary data to a file;

        }
    }

    /*
        o) close the two files;
    */
    fclose(fp);
    fclose(fp2);

    return 0;
}