import math
from pytz import timezone
from datetime import datetime
from datetime import timedelta


def next_full_moon(start):

    # date of the known full moon
    y2k = datetime(1999, 12, 22, 18, 31, 18).astimezone(
        timezone('Europe/Berlin'))
    since2000 = (start - y2k) / timedelta(days=365.25)

    rads = 3.14159265359/180
    phase = 0.5  # 0.5 equals full moon
    # Anzahl der Mondphasen seit 2000
    k = math.floor((since2000)*12.36853087)+phase

    # Mittlerer JDE Wert des Ereignisses
    JDE = 2451550.09766+29.530588861*k
    # Relevante Winkelwerte in [Radiant]
    M = (2.5534+29.10535670*k)*rads
    Ms = (201.5643+385.81693528*k)*rads
    F = (160.7108+390.67050284*k)*rads

    # Korrekturterme JDE fuer Vollmond
    JDE += -0.40614*math.sin(Ms)
    JDE += 0.17302*math.sin(M)
    JDE += 0.01614*math.sin(2*Ms)
    JDE += 0.01043*math.sin(2*F)
    JDE += 0.00734*math.sin(Ms-M)
    JDE += -0.00515*math.sin(Ms+M)
    JDE += 0.00209*math.sin(2*M)
    JDE += -0.00111*math.sin(Ms-2*F)

    # Konvertierung von Julianischem Datum auf Gregorianisches Datum

    z = math.floor(JDE + 0.5)
    f = (JDE + 0.5) - math.floor(JDE + 0.5)
    if (z < 2299161):
        a = z
    else:
        g = math.floor((z - 1867216.25) / 36524.25)
        a = z + 1 + g - math.floor(g / 4)
    b = a + 1524
    c = math.floor((b - 122.1) / 365.25)
    d = math.floor(365.25 * c)
    e = math.floor((b - d) / 30.6001)

    # //Tag incl. Tagesbruchteilen
    tag_temp = b - d - math.floor(30.6001 * e) + f
    stunde_temp = (tag_temp - math.floor(tag_temp)) * 24
    minute_temp = (stunde_temp - math.floor(stunde_temp)) * 60

    stunde = math.floor(stunde_temp)
    minute = math.floor(minute_temp)
    sekunde = round((minute_temp - math.floor(minute_temp)) * 60)

    tag = math.floor(tag_temp)

    if (e < 14):
        monat = e - 1
    else:
        monat = e - 13

    if (monat > 2):
        jahr = c - 4716
    else:
        jahr = c - 4715

    fmutc = datetime(jahr, monat, tag, stunde, minute,
                     sekunde, tzinfo=timezone('UTC'))

    return fmutc.astimezone(start.tzinfo)


def is_full_moon(mday: datetime):
    nmoon = next_full_moon(mday)
    till_next_full = nmoon-mday
    if (till_next_full < timedelta(days=1) or till_next_full < timedelta(days=28)):
        return True
    return False


def moon_phase_as_text(mday: datetime):
    nmoon = next_full_moon(mday)
    till_next_full = nmoon - mday
    till_next_full_text = strfdelta(
        till_next_full, "{days} Tage {hours} Stunden bis Vollmond")
    if (till_next_full < timedelta(days=1)):
        return ("🌕 Vollmond")
    if (till_next_full < timedelta(days=6)):
        return ("🌔 Zunehmender Dreiviertelmond\n" + till_next_full_text)
    if (till_next_full < timedelta(days=10)):
        return ("🌓 Zunehmender Halbmond\n" + till_next_full_text)
    if (till_next_full < timedelta(days=14)):
        return ("🌒 Zunehmender Sichelmond\n" + till_next_full_text)
    if (till_next_full < timedelta(days=16)):
        return ("🌑 Neumond\n" + till_next_full_text)
    if (till_next_full < timedelta(days=20)):
        return ("🌘 Abnehmender Sichelmond\n" + till_next_full_text)
    if (till_next_full < timedelta(days=24)):
        return ("🌗 Abnehmender Halbmond\n" + till_next_full_text)
    if (till_next_full < timedelta(days=28.5)):
        return ("🌖 Abnehmender Dreiviertelmond\n" + till_next_full_text)
    return ("🌕 Vollmond")


def strfdelta(tdelta, fmt):
    d = {"days": tdelta.days}
    d["hours"], rem = divmod(tdelta.seconds, 3600)
    d["minutes"], d["seconds"] = divmod(rem, 60)
    return fmt.format(**d)


def till_next_full_as_text(mday):
    nmoon = next_full_moon(mday)
    till_next_full = nmoon-mday
    return (strfdelta(till_next_full, "{days} Tage {hours} Stunden bis Vollmond"))