import numpy as np
from datetime import datetime, timedelta
from scipy.optimize import fsolve

# Define necessary functions 
def julianday(year, month, day):
    """
    Calculate Julian Day Number
    """
    a = (14 - month) // 12
    y = year + 4800 - a
    m = month + 12*a - 3
    return day + ((153*m + 2)//5) + 365*y + y//4 - y//100 + y//400 - 32045

def date_to_julianday(date):
    """
    Convert a date to Julian Day Number
    """
    return julianday(date.year, date.month, date.day)

def lunar_az_el(time, latitude, longitude, elevation):
    # Placeholder for lunar azimuth and elevation calculation
    # Implement lunar position calculation here
    # For demonstration, return dummy values
    return 0, 0

def brewer_sza(T0, jday, year, latitude, longitude, mode='sun', ho3=22, hray=5):
    R = 6370
    EP = 1 - np.finfo(float).eps
    
    # Calculate Julian Day if not provided
    if jday is None:
        now = datetime.now()
        jday = date_to_julianday(now)

    # Convert T0 to datetime if it's in MATLAB time format
    if T0 > 1e5:
        date = datetime.fromordinal(int(T0)) + timedelta(days=T0%1) - timedelta(days=366)
        T0 = date.hour*60 + date.minute + date.second/60
    
    # Main calculation starts here
    if mode.lower() == 'moon':
        # Placeholder for Moon calculation
        AZ, el = lunar_az_el(T0, latitude, -longitude, 0)  # Assuming this function exists
        ZA = 90 - el
    else:
        # Placeholder for Sun and Azimuth calculation
        # Implement solar position calculation here
        # For demonstration, return dummy values
        AZ, ZA = 0, 0
    
    # Calculations for M2 and M3
    E = ZA * np.pi / 180
    M3 = R / (R + hray) * np.sin(E)
    M3 = 1 / np.cos(np.arctan(M3 / np.sqrt(1 - M3**2)))
    M2 = R / (R + ho3) * np.sin(E)
    M2 = 1 / np.cos(np.arctan(M2 / np.sqrt(1 - M2**2)))
    
    return ZA, M2, M3, AZ
if __name__ == "__main__":
    # Example usage:
    T0 = 0 # Replace with actual T0 value
    jday = None # Current Julian day
    year = 2020
    latitude = 45
    longitude = -75
    mode = 'sun'
    ho3 = 22
    hray = 5

    ZA, M2, M3, AZ = brewer_sza(T0, jday, year, latitude, longitude, mode, ho3, hray)
    print(f"ZA: {ZA}, M2: {M2}, M3: {M3}, AZ: {AZ}")
