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


void run(char** commands[], int* fd);
char*** tail(char*** array);
int array_length(void *** array);

int main(int argc, char* argv[])
{
    char ** arg[4];
    char *arg1[] = { "/bin/ls", "-1", (char *) 0 };
    char *arg2[] = { "grep", "main", (char *) 0 };
    char *arg3[] = { "less", NULL, (char *) 0 };

    arg[0] = arg3;
    arg[1] = arg2;
    arg[2] = arg1;
    arg[3] = NULL;

    run(arg, NULL);
    //Create example commands
    //run(commands);

    return 0;
}

void run(char **commands[], int* fd)
{
    char** command = commands[0];
    char*** rest = tail(commands);

    if(array_length((void ***)rest) == 0)
    {
        execvp(command[0], command);
    }
    else if(array_length((void ***)rest) > 0)
    {
        int new_fd[2];
        int pid;

        pipe(new_fd);
        pid = fork();
        if(pid == 0)
        {

            dup2(new_fd[1], STDOUT_FILENO);
            close(new_fd[0]);
            run(rest, new_fd);
        }
        else if(pid > 0)
        {
            dup2(new_fd[0], STDIN_FILENO);
            close(new_fd[1]);
            execvp(command[0], command);
        }
    }

    return;
}

char*** tail(char*** array)
{
    int new_length = array_length((void ***)array)-1;
    int cmdelements = 3;
    int stringlength = 100;
    char *** ret = calloc(new_length, sizeof(char) * cmdelements * stringlength);
    int i = 0;
    for(i; i < new_length; i++)
    {
        ret[i] = array[i+1];
    }
    return ret;
}

int array_length(void *** array) {
	int i = 0;
	while(array[i])
		i++;

	return i;
}