#!/usr/bin/python3

from datetime import datetime, timedelta, timezone
import math
import serial
import sys
import time

TZ = timezone.utc
BAUDRATE = 115200
CORRECTION = -0.012  # to compensate delay before setting the time into DS3231
SYNC_FORMAT = r"SYNC %y-%m-%d %H:%M:%S"


def round_time(orig_time: datetime):
    new_time = orig_time + timedelta(seconds=.5)
    return new_time.replace(microsecond=0)


def sync(arduino: serial.Serial):
    # Get previous state
    line = arduino.readline().decode('utf-8').strip()
    t = datetime.now(TZ)
    print(f"[{t}] previous state: {line}")

    # Wait until start of the second
    t = datetime.now(TZ)
    remain = 1.0 - math.ceil(t.microsecond) / 1_000_000
    print(f"[{t}] waiting for {remain}s")
    time.sleep(max(remain + CORRECTION, 0))

    # Do sync
    t = datetime.now(TZ)
    value = round_time(t).strftime(SYNC_FORMAT)
    print(f"[{t}] syncing: {value}")
    arduino.write(bytes(value + "\n", 'utf-8'))

    # Check state after
    sync_ok = False
    for i in range(6):
        line = arduino.readline().decode('utf-8').strip()
        t = datetime.now(TZ)
        print(f"[{t}] ARDUINO: {line}")
        if line == "SYNC OK":
            sync_ok = True

    if sync_ok:
        print("Synchronization successfully completed")
    else:
        print("ERROR: synchronization probably failed (missing SYNC OK)")


if len(sys.argv) < 2:
    print(f"Usage: {sys.argv[0]} <serial device>\n", file=sys.stderr)
    print("Serial device could be /dev/ttyUSB0 or similar", file=sys.stderr)
    sys.exit(1)

try:
    arduino = serial.Serial(port=sys.argv[1], baudrate=BAUDRATE, timeout=3)
except Exception as e:
    print(f"ERROR: {e}", file=sys.stderr)
    sys.exit(1)

sync(arduino)