#include <unistd.h>		// write, fork, execve, pipe, chdir
#include <stdio.h>		// printf
#include <string.h>		// strcmp
#include <sys/types.h>	// pid_t
#include <sys/wait.h>	// waitpid

#define STDIN	0
#define STDOUT	1
#define STDERR	2

typedef enum {FALSE, TRUE} BOOL;

void	builtin_cd(char *av)
{
	printf("here\n");
	if (av)
		chdir(av);
}

void	exec_cmd(char **av, char **en, int fdin, int fdout)
{
	pid_t	pid = fork();

	if (pid == 0)	// child process
	{
		if (fdin != STDIN_FILENO)
		{
			dup2(fdin, STDIN_FILENO);
			close(fdin);
		}
		if (fdout != STDOUT_FILENO)
		{
			dup2(fdout, STDOUT_FILENO);
			close(fdout);
		}
		execve(av[0], av, en);
	}
	else			// parent process
	{
		if (fdout != STDOUT_FILENO)
			close(fdout);
		waitpid(pid, NULL, 0);
	}
}

int	main(int ac, char **av, char **en)
{
	int i;
	int start;
	int	fds[2];
	int	old_fdin;

	if (ac <= 1)
		return (0);
	i = 1;
	old_fdin = STDIN_FILENO;
	fds[STDIN] = STDIN_FILENO;
	fds[STDOUT] = STDOUT_FILENO;
	while (i < ac)
	{
		start = i;
		while (i < ac && strcmp(av[i], "|") && strcmp(av[i], ";"))
			i++;
		if (av[i] && !strcmp(av[i], "|"))
			pipe(fds);
		av[i] = NULL;
		if (strcmp(av[start], "cd") == 0)
			builtin_cd(av[start + 1]);
		else
			exec_cmd(av + start, en, old_fdin, fds[STDOUT]);
		if (old_fdin != STDIN_FILENO)
			close(old_fdin);
		old_fdin = fds[STDIN];
		fds[STDOUT] = STDOUT_FILENO;
		if (i < ac)
			i++;
	}
	return (0);
}

// pipes fork and dups : https://www.rozmichelle.com/pipes-forks-dups/
// subject and example : https://github.com/Glagan/42-exam-rank-04
// lsof -c microshell  : https://www.thegeekstuff.com/2012/08/lsof-command-examples/