#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <dirent.h>
#define BUFFER_SIZE 65536
#define ARR_SIZE 65536

void parse_args(char *buffer, char** args,
                size_t args_size, size_t *nargs)
{
    char *buf_args[args_size];
    char **cp;
    char *wbuf;
    size_t i, j;

    wbuf = buffer;
    buf_args[0] = buffer;
    args[0] = buffer;

    for(cp = buf_args; (*cp = strsep(&wbuf, " \n\t")) != NULL ;) {
        if ((*cp != '\0') && (++cp >= &buf_args[args_size]))
            break;
    }

    for (j = i = 0; buf_args[i] != NULL; i++){
        if (strlen(buf_args[i])>0)
            args[j++]=buf_args[i];
    }

    *nargs = j;
    args[j] = NULL;
}


int main(int argc, char *argv[])
{
    char buffer[BUFFER_SIZE];
    char *args[ARR_SIZE];

    int *ret_status;
    size_t nargs;
    pid_t pid;
    char temp_pwd[BUFFER_SIZE];
    int flag = 0;

    setenv("PWD", getenv("HOME"), 1);
    setenv("OLDPWD", getenv("HOME"), 1);

    for(;;) {
        printf("%s$ ", getenv("PWD"));
        puts(getenv("OLDPWD"));
        fgets(buffer, BUFFER_SIZE, stdin);
        parse_args(buffer, args, ARR_SIZE, &nargs);

        if (nargs == 0) continue;
        if (!strcmp(args[0], "quit") || !strcmp(args[0], "exit")) exit(0);
        if (!strcmp(args[0], "chdir")) {
            if (args[1] != NULL) {
                if (!strcmp(args[1], "-")) {
                    chdir(getenv("OLDPWD"));
                } else
                    if (opendir(args[1]) != NULL) {
                        chdir(args[1]);
                        setenv("PWD", args[1], 1);
                        if (!flag) strcpy(temp_pwd, args[1]);
                        if (flag) {
                            setenv("OLDPWD", temp_pwd, 1);
                            flag = 0;
                        }
                        flag = 1;
                    } else
                        puts(strerror(errno));
            } else
                chdir(getenv("HOME"));
        } else {
            pid = fork();
            if (pid) {
                printf("Czekam na proces potomny (%d)\n", pid);
                pid = wait(ret_status);
                printf("Proces potomny (%d) zakonczony\n", pid);
            } else {
                if (execvp(args[0], args)) {
                    puts(strerror(errno));
                    exit(127);
                }
            }
        }
    }
    return 0;
}