import numpy as np

#Declare these as units to make code clearer
Position = np.array
Velocity = np.array
Acceleration = np.array
Mass = int

####################
# USEFUL CONSTANTS
####################
EARTH_MASS = 5.972e24 #kg
EARTH_RADIUS = 6.378e6 #meters
EARTH_ORBITAL_VELOCITY = 29.78e3
AU = 149_597_870_700 #meters

MOON_MASS = 7.34767309e22
MOON_ORBITAL_VELOCITY = 1.022e3 #m/s relative to earth

SUN_MASS = 1.989e30 #kg
SUN_RADIUS = 6.957e8 #meters

#NORMALIZING CONSTANTS
G = 6.67430e-11
r_0 = EARTH_RADIUS #1.496e11
m_0 = 5.972e24
t_0 = np.sqrt((r_0**3) / (G*m_0))

def norm_pos(pos):
    return pos / r_0

def real_pos(pos):
    return pos * r_0

def norm_mass(mass):
    return mass / m_0

def real_mass(mass):
    return mass * m_0

def norm_time(time):
    return time / t_0

def real_time(time):
    return time * t_0

def norm_vel(vel):
    return vel / (r_0/t_0)

def real_vel(vel):
    return vel * (r_0/t_0)