#!/usr/bin/env python3
"""console.py -- talk to the board's serial console (stdlib only, no pyserial).

The console lives on /dev/ttyACM0: it is the CDC interface of the same composite USB
device as the HID keyboard, so it is present on whatever machine the board is plugged
into. It is where the station network and the control passphrase are set.

    python3 tools/console.py                       # interactive, Ctrl-] to quit
    python3 tools/console.py /dev/ttyACM0 status    # one command, print the reply
    python3 tools/console.py wifi "My SSID" "hunter2"
    python3 tools/console.py token "a-long-passphrase"
    python3 tools/console.py help

The baud rate is nominal: a USB CDC link carries no signalling, so 115200 is a
formality. Do not use this to type keystrokes -- there is no such command, by design.
"""
from __future__ import annotations

import os
import select
import sys
import termios
import tty

DEFAULT_PORT = "/dev/ttyACM0"
QUIT = "\x1d"                                  # Ctrl-]


def open_raw(port: str) -> tuple[int, list]:
    fd = os.open(port, os.O_RDWR | os.O_NOCTTY)
    saved = termios.tcgetattr(fd)
    tty.setraw(fd)
    return fd, saved


def drain(fd: int, seconds: float) -> str:
    out = bytearray()
    deadline_remaining = seconds
    while deadline_remaining > 0:
        ready, _, _ = select.select([fd], [], [], deadline_remaining)
        if not ready:
            break
        try:
            chunk = os.read(fd, 4096)
        except OSError:
            break
        if not chunk:
            break
        out += chunk
        deadline_remaining = 1.0            # keep reading while it keeps talking
    return out.decode(errors="replace")


def main() -> int:
    args = sys.argv[1:]
    port = DEFAULT_PORT
    if args and args[0].startswith("/dev/"):
        port = args[0]
        args = args[1:]
    if not os.path.exists(port):
        print(f"{port} does not exist -- is the board plugged in here?", file=sys.stderr)
        return 1

    fd, saved = open_raw(port)
    try:
        if args:
            os.write(fd, (" ".join(args) + "\n").encode())
            sys.stdout.write(drain(fd, 2.0))
            sys.stdout.flush()
            return 0

        print(f"{port} -- interactive console, Ctrl-] to quit, `help` for commands")
        stdin_fd = sys.stdin.fileno()
        while True:
            ready, _, _ = select.select([stdin_fd, fd], [], [], 0.2)
            if stdin_fd in ready:
                char = os.read(stdin_fd, 1)
                if not char or char == QUIT.encode():
                    break
                os.write(fd, char)
            if fd in ready:
                sys.stdout.write(drain(fd, 0.05))
                sys.stdout.flush()
        return 0
    finally:
        # `reboot` makes the device disappear underneath us: the CDC node is gone the
        # instant the board resets, so restoring the port settings can legitimately fail.
        # The command already reached the board -- do not turn a successful `reboot` into
        # a Python traceback and a non-zero exit.
        try:
            termios.tcsetattr(fd, termios.TCSAFLUSH, saved)
        except (OSError, termios.error):    # termios.error is NOT an OSError here
            pass
        try:
            os.close(fd)
        except OSError:
            pass


if __name__ == "__main__":
    sys.exit(main())