#!/usr/bin/env python3
"""
Plays a ding/timer sound at regular intervals aligned to round period marks
(e.g. every 15 min), with an optional offset so the sound plays a few seconds
before each mark.

Default: period 15 minutes, offset 15 seconds.
Notification plays at :14:45, :29:45, :44:45, :59:45.

Works on Windows and Linux (stdlib + optional system players on Linux).
"""

import argparse
import math
import subprocess
import sys
import time
from datetime import datetime


def _seconds_since_midnight(dt: datetime) -> int:
    return dt.hour * 3600 + dt.minute * 60 + dt.second


def _next_ring_seconds(period_sec: int, offset_sec: int, now_sec: int) -> int:
    next_boundary = math.ceil(now_sec / period_sec) * period_sec
    ring_sec = next_boundary - offset_sec
    if ring_sec <= now_sec:
        ring_sec += period_sec
    return ring_sec


def _wait_seconds(period_sec: int, offset_sec: int) -> int:
    now = datetime.now()
    now_sec = _seconds_since_midnight(now)
    ring_sec = _next_ring_seconds(period_sec, offset_sec, now_sec)
    wait = ring_sec - now_sec
    return max(1, wait) if wait > 0 else 1


def _play_ding_windows() -> None:
    try:
        import winsound
        winsound.MessageBeep(winsound.MB_ICONASTERISK)
    except Exception:
        try:
            import winsound
            winsound.Beep(800, 200)
        except Exception:
            sys.stdout.write("\a")
            sys.stdout.flush()


def _play_ding_linux() -> None:
    candidates = [
        ["paplay", "/usr/share/sounds/freedesktop/stereo/bell.oga"],
        ["paplay", "/usr/share/sounds/freedesktop/stereo/message.oga"],
        ["aplay", "/usr/share/sounds/alsa/Front_Center.wav"],
        ["aplay", "/usr/share/sounds/speech-dispatcher/test.wav"],
    ]
    for cmd in candidates:
        try:
            subprocess.run(cmd, capture_output=True, timeout=2)
            return
        except (FileNotFoundError, subprocess.TimeoutExpired, OSError):
            continue
    sys.stdout.write("\a")
    sys.stdout.flush()


def play_ding() -> None:
    if sys.platform == "win32":
        _play_ding_windows()
    else:
        _play_ding_linux()


def main() -> None:
    parser = argparse.ArgumentParser(
        description="Play a ding every N minutes, offset seconds before each round mark."
    )
    parser.add_argument(
        "-p", "--period",
        type=int,
        default=15,
        metavar="MIN",
        help="Interval in minutes between notifications (default: 15)",
    )
    parser.add_argument(
        "-o", "--offset",
        type=int,
        default=15,
        metavar="SEC",
        help="Seconds before each round mark to play (default: 15)",
    )
    args = parser.parse_args()

    if args.period < 1:
        parser.error("period must be >= 1")
    if args.offset < 0:
        parser.error("offset must be >= 0")

    period_sec = args.period * 60
    now = datetime.now()
    now_sec = _seconds_since_midnight(now)
    next_ring = _next_ring_seconds(period_sec, args.offset, now_sec)
    h = next_ring // 3600
    m = (next_ring % 3600) // 60
    s = next_ring % 60
    print(
        f"Period: {args.period} min, offset: {args.offset} s. "
        f"Next ding at {h:02d}:{m:02d}:{s:02d} (then every {args.period} min). "
        "Press Ctrl+C to stop."
    )

    while True:
        wait_sec = _wait_seconds(period_sec, args.offset)
        time.sleep(wait_sec)
        play_ding()
        print(f"[{datetime.now().strftime('%H:%M:%S')}] ding")


if __name__ == "__main__":
    main()