/*
 * Functions you may use for your shell.
 * See FAQ Question 24.
 *
 * CS 3214 Fall 2011, Godmar Back.
 */

/*
 * SIGCHLD handler.
 * Call waitpid() to learn about any child processes that
 * have exited or changed status (been stopped, needed the
 * terminal, etc.)
 * Just record the information by updating the job list
 * data structures.  Since the call may be spurious (e.g.
 * an already pending SIGCHLD is delivered even though
 * a foreground process was already reaped), ignore when
 * waitpid returns -1.
 * Use a loop with WNOHANG since only a single SIGCHLD 
 * signal may be delivered for multiple children that have 
 * exited.
 */
static void
sigchld_handler(int sig, siginfo_t *info, void *_ctxt)
{
    pid_t child;
    int status;

    assert(sig == SIGCHLD);

    while ((child = waitpid(-1, &status, WUNTRACED|WNOHANG)) > 0) {
        child_status_change(child, status);
    }
}

/* Wait for all processes in this pipeline to complete, or for
 * the pipeline's process group to no longer be the foreground 
 * process group. 
 * You should call this function from a) where you wait for
 * jobs started without the &; and b) where you implement the
 * 'fg' command.
 * 
 * Implement child_status_change such that it records the 
 * information obtained from waitpid() for pid 'child.'
 * If a child has exited or terminated (but not stopped!)
 * it should be removed from the list of commands of its
 * pipeline data structure so that an empty list is obtained
 * if all processes that are part of a pipeline have 
 * terminated.  If you use a different approach to keep
 * track of commands, adjust the code accordingly.
 */
static void
wait_for_job(struct esh_pipeline *pipeline)
{
    assert(esh_signal_is_blocked(SIGCHLD));

    while (pipeline->status == FOREGROUND && !list_empty(&pipeline->commands)) {
        int status;

        pid_t child = waitpid(-1, &status, WUNTRACED);
        if (child != -1)
            child_status_change(child, status);
    }
}