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

#include <malloc.h>
#include <time.h>

#include <sys/wait.h>

#include <fcntl.h>
#include <unistd.h>


//amount of data in source array
#define N 32
// K defenition from task
#define K 5

// maximum integer in source array
#define MAX 128
#define THREADS 4

struct equation {
    int a;
    int b;
};

int *array;
struct equation res[THREADS];
int res_max[THREADS];


int pids[THREADS][2];

void generate_array()
{
    srand(time(NULL));
    int i;
    array = (int *)malloc(sizeof(int)*N);
    for (i=0;i<N;i++)
    {
        array[i] = rand() % MAX;
    }
}

void print(int *data)
{
    int i;
    for(i=0;i<N;i++)
    {
        printf("%i ", data[i]);
    }
    printf("\n");
}

struct equation make_equation(int a, int b)
{
    return *(struct equation[]){{a,b}};
}


int main(void)
{
    // loop index
    int i,j;
    pid_t p_id;
    // equation variables:
    int a,b;

//    if (THREADS < 4)
//    {
//        fprintf(stderr, "Minimum threads are: 4. Your's: %i\n", THREADS);
//        exit(1);
//    }


    generate_array();
    print(array);

    printf("K: %i\n\n", K);

    int max = -1;
    struct equation tmp;

    for (p_id=0;p_id<THREADS;p_id++)
    {
        pipe(pids[p_id]);
        pid_t pid = fork(); // <<<<-------------- FORK!!!

        if (pid == 0)
        {//child
            for(i=0;i<N;++i)
            {
                for(j=p_id;j<N;j+=THREADS)
                {
                    a = array[i];
                    b = array[j];

                    if (b-a == K)
                    {
                        if (max < abs(a) * abs(b))
                        {
                            max = abs(a) * abs(b);
                            tmp.a = a;
                            tmp.b = b;
                        }
                    }
                }
            }
//            printf("|%i|*|%i| = %i\n", tmp.a, tmp.b, max);
            char buf[4096];
            sprintf(buf, "%i;%i;%i", tmp.a,tmp.b,max);

            close(pids[p_id][0]);
            write(pids[p_id][1], buf, 4096);

//            printf("Sended\n");
            return 0; //stopping child
        }else{
            //parent
            usleep(150); // for pretty printf :)
        }
    }

    //parent
    max = -1;
    tmp = *(struct equation[]){{0,0}};
    pid_t tmp_pid;

    for (p_id=0;p_id<THREADS;p_id++)
    {
        wait(NULL);

        char buf[4096];
        close(pids[p_id][1]);
        read(pids[p_id][0],buf, 4096);
        sscanf(buf, "%i;%i;%i", &res[p_id].a, &res[p_id].b, &res_max[p_id]);
        printf("th: %i Received: |%i|*|%i| = %i\n", p_id, res[p_id].a, res[p_id].b, res_max[p_id]);
        if (max < abs(res[p_id].a) * abs(res[p_id].b))
        {
            max = abs(res[p_id].a) * abs(res[p_id].b);
            tmp = *(struct equation[]){{res[p_id].a,res[p_id].b}};
            tmp_pid = p_id;
        }

    }

printf("Max found\n");
printf("|%i| * |%i| = %i\n", res[tmp_pid].a, res[tmp_pid].b, max);

    return 0;
}