import math
from datetime import datetime, timedelta

from ogn.parser.exceptions import AmbigousTimeError


kmh2kts = 0.539957
feet2m = 0.3048
ms2fpm = 196.85

kts2kmh = 1 / kmh2kts
m2feet = 1 / feet2m
fpm2ms = 1 / ms2fpm


def dmsToDeg(dms):
    absDms = abs(dms)
    d = math.floor(absDms)
    m = (absDms - d) * 100 / 60
    return d + m


def createTimestamp(hhmmss, reference):
    packet_time = datetime.strptime(hhmmss, '%H%M%S').time()
    timestamp = datetime.combine(reference, packet_time)
    delta = timestamp - reference

    # This function reconstructs the packet date from the timestamp and a reference time.
    # delta vs. packet date:
    # -24h                      -12h                   0                       +12h                   +24h
    #  |-------------------------|---------------------|------------------------|----------------------|
    #  [-] <-- tomorrow          [---------today---------]                      [-------yesterday------]

    if timedelta(hours=-12) <= delta <= timedelta(minutes=30):
        # Packet less than 12h from the past or 30min from the future
        return timestamp
    elif delta < timedelta(hours=-23, minutes=-30):
        # Packet from next day, less than 30min from the future
        return datetime.combine(reference + timedelta(hours=+12), packet_time)
    elif timedelta(hours=12) < delta:
        # Packet from previous day, less than 12h from the past
        return datetime.combine(reference + timedelta(hours=-12), packet_time)
    else:
        raise AmbigousTimeError(reference, packet_time)