#!/usr/bin/python2
import sys, os, math
import pygame

G = 6.67 * 10 ** -11
print(G)

pygame.init()

screen = pygame.display.set_mode((800,600))

class Mass:
    def __init__(self,weight,x,y):
        self.mass = weight
        self.x = x
        self.y = y
        self.acceleration = [0,0]
        self.velocity = [0,0]
    def resetAcceleration(self):
        self.acceleration = [0,0]
    def attract(self,mass):
        if self != mass:
            global G
            distance = math.sqrt((self.x + mass.x) ** 2 + (self.y + mass.y) ** 2)
            acceleration = (G * ((self.mass * mass.mass)/distance))/self.mass
            angle = math.atan2(mass.y - self.y,mass.x - self.x)
            x = acceleration * math.cos(angle)
            y = acceleration * math.sin(angle)
            self.acceleration[0] += x
            self.acceleration[1] += y
    def move(self):
        self.x += self.velocity[0]
        self.y += self.velocity[1]
        self.velocity[0] += self.acceleration[0]
        self.velocity[1] += self.acceleration[1]
    def draw(self,screen):
        velocity_scale = 100
        acceleration_scale = 1000000
        pygame.draw.circle(screen,[0,0,0],[int(self.x),int(self.y)],10)
        pygame.draw.line(screen,[255,0,0],[self.x,self.y],[int(self.x + velocity_scale*self.velocity[0]),int(self.y + velocity_scale*self.velocity[1])])
        pygame.draw.line(screen,[0,255,0],[self.x,self.y],[int(self.x + acceleration_scale*self.acceleration[0]),int(self.y + acceleration_scale*self.acceleration[1])])
        #print(str(int(self.x)) + " " + str(int(self.y)))

masses = list()
masses.append(Mass(50000,600,100))
masses.append(Mass(500,600,200))
masses.append(Mass(50000,400,300))

timescale = 1000

while 1:
    #Input
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
    #Processing
    for i in range(timescale):
        for mass in masses:
            mass.resetAcceleration()
        for mass in masses:
            for attractionMass in masses:
                mass.attract(attractionMass)
        for mass in masses:
            mass.move()
    #Rendering
    screen.fill([255,255,255])
    for mass in masses:
        mass.draw(screen)
    pygame.display.flip()