import astropy.units as unit
import numpy as np
from astropy.coordinates import EarthLocation, AltAz
from astropy.coordinates import get_sun

def sun_angles_astropy(lat, lon, h, utc):
    loc = EarthLocation(lat=lat*unit.deg, lon=lon*unit.deg, height=h*unit.m)
    ref = AltAz(obstime=utc, location=loc)

    sun_pos = get_sun(utc).transform_to(ref)

    AZ = sun_pos.az.degree
    ELV = sun_pos.alt.degree

    return AZ, ELV

def sun_angles_analytical(lat, lon, utc):
    JD = utc.jd
    JC = (JD - 2451545) / 36525
    GML = (280.46646 + JC * (36000.76983 + JC * 0.0003032)) % 360
    GMA = 357.52911 + JC * (35999.05029 - 0.0001537 * JC)
    EEO = 0.016708634 - JC * (0.000042037 + 0.0000001267 * JC)
    SEC = np.sin(np.deg2rad(GMA)) * (1.914602 - JC * (0.004817 + 0.000014 * JC)) + np.sin(np.deg2rad(2 * GMA)) * (
                0.019993 - 0.000101 * JC) + np.sin(np.deg2rad(3 * GMA)) * 0.000289
    STL = GML + SEC
    # STA = GMA + SEC
    # SRV = (1.000001018 * (1 - EEO ** 2)) / (1 + EEO * np.cos(np.deg2rad(STA)))
    SAL = STL - 0.00569 - 0.00478 * np.sin(np.deg2rad(125.04 - 1934.136 * JC))
    MOE = 23 + (26 + (21.448 - JC * (46.815 + JC * (0.00059 - JC * 0.001813))) / 60) / 60
    OC = MOE + 0.00256 * np.cos(np.deg2rad(125.04 - 1934.136 * JC))
    # SRA = np.rad2deg(np.arctan2(np.cos(np.deg2rad(OC)) * np.sin(np.deg2rad(SAL)), np.cos(np.deg2rad(SAL))))  # radian
    SD = np.rad2deg(np.arcsin(np.sin(np.deg2rad(OC)) * np.sin(np.deg2rad(SAL))))  # radian
    var_y = np.tan(np.deg2rad(OC / 2)) ** 2
    EOT = 4 * np.rad2deg(
        var_y * np.sin(2 * np.deg2rad(GML)) - 2 * EEO * np.sin(np.deg2rad(GMA)) + 4 * EEO * var_y * np.sin(
            np.deg2rad(GMA)) * np.cos(2 * np.deg2rad(GML)) - 0.5 * var_y ** 2 * np.sin(
            4 * np.deg2rad(GML)) - 1.25 * EEO ** 2 * np.sin(2 * np.deg2rad(GMA)))
    TST = (((JD - 0.5) % 1) * 1440 + EOT + 4 * lon) % 1440

    if TST / 4 < 0:
        HA = TST / 4 + 180
    else:
        HA = TST / 4 - 180

    SZA = np.rad2deg(np.arccos(
        np.sin(np.deg2rad(lat)) * np.sin(np.deg2rad(SD)) + np.cos(np.deg2rad(lat)) * np.cos(np.deg2rad(SD)) * np.cos(
            np.deg2rad(HA))))
    SEA = 90 - SZA

    if HA > 0:
        SAA = (np.rad2deg(np.arccos(((np.sin(np.deg2rad(lat)) * np.cos(np.deg2rad(SZA))) - np.sin(np.deg2rad(SD))) / (
                    np.cos(np.deg2rad(lat)) * np.sin(np.deg2rad(SZA))))) + 180) % 360
    else:
        SAA = (540 - np.rad2deg(np.arccos(
            ((np.sin(np.deg2rad(lat)) * np.cos(np.deg2rad(SZA))) - np.sin(np.deg2rad(SD))) / (
                        np.cos(np.deg2rad(lat)) * np.sin(np.deg2rad(SZA)))))) % 360

    return SAA, SEA