/*
  StarForth — Steady-State Virtual Machine Runtime

  Copyright (c) 2023–2025 Robert A. James
  All rights reserved.

  This file is part of the StarForth project.

  Licensed under the StarForth License, Version 1.0 (the "License");
  you may not use this file except in compliance with the License.

  You may obtain a copy of the License at:
      https://github.com/star.4th@proton.me/StarForth/LICENSE.txt

  This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
  express or implied, including but not limited to the warranties of
  merchantability, fitness for a particular purpose, and noninfringement.

 See the License for the specific language governing permissions and
 limitations under the License.

 */

/*
 * StarForth Platform IO - Linux/POSIX Backend
 *
 * Implements platform_io.h's terminal-readiness check using select() on
 * fd 0, the standard POSIX non-blocking-stdin-peek idiom. Zero timeout:
 * a single poll, never blocks.
 *
 * License: See LICENSE file
 */

#include "../../../include/platform_io.h"
#include <sys/select.h>
#include <unistd.h>

int sf_terminal_ready(void) {
    fd_set readfds;
    struct timeval tv;

    FD_ZERO(&readfds);
    FD_SET(STDIN_FILENO, &readfds);
    tv.tv_sec = 0;
    tv.tv_usec = 0;

    int r = select(STDIN_FILENO + 1, &readfds, NULL, NULL, &tv);
    return (r > 0 && FD_ISSET(STDIN_FILENO, &readfds)) ? 1 : 0;
}