from __future__ import division
from math import sqrt, ceil
import random, pygame, sys
import os
import json
from pygame.locals import *

pygame.init()

GRAY = ( 182, 182, 182)
VIOLET = (150, 100, 190)
RED = (150, 0, 0)
GREEN = (0, 150, 0)
BLUE = (30, 30, 180)
VERYLIGHT = (210, 210, 210)
BLACK = (0,0,0)
WHITE = (255, 255, 255)

TIME_STEP = 0.01

K = 10000

X_SCREEN_BORDER = 1200
Y_SCREEN_BORDER = 800

INITIAL_SPEED_X = 50
INITIAL_SPEED_Y = 0
INITIAL_Y = 400
DEFAULT_OLD_X = 2 - INITIAL_SPEED_X*TIME_STEP
DEFAULT_OLD_Y = INITIAL_Y - INITIAL_SPEED_Y*TIME_STEP

def main():
    #create the screen
    window = pygame.display.set_mode((1200, 800))
    colors = [GRAY, VIOLET, RED, GREEN, BLUE, VERYLIGHT, BLACK]
    
    global INITIAL_SPEED_X
    global INITIAL_SPEED_Y
    global INITIAL_Y
    #Initialize universe with some atoms
    atom1 = Particle(1000, Vector2(500,500), Vector2(500,500), 20, BLUE)
    atom2 = Particle(1, Vector2(2,400), Vector2(2-TIME_STEP*INITIAL_SPEED_X, INITIAL_Y- TIME_STEP*INITIAL_SPEED_Y), 1, RED)
    universe = Universe([atom1, atom2])

    screen = Screen(window, colors, universe)
    screen.draw_surface()
    keep_running = True
    while keep_running:
        screen.draw_surface()
        universe.update_positions()
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                keep_running = False
            elif event.type == pygame.KEYUP:
                if event.key == K_UP :
                    INITIAL_Y -= 10
                elif event.key == K_DOWN:
                    INITIAL_Y += 10
                elif event.key == K_RIGHT:
                    INITIAL_SPEED_X += 20
                elif event.key == K_LEFT:
                    INITIAL_SPEED_X -= 20
                    if(INITIAL_SPEED_X < 0):
                        INITIAL_SPEED_X = 0
                elif event.key == K_SPACE:
                    universe.add_particle(Particle(1, Vector2(2,INITIAL_Y), 
                        Vector2(2-TIME_STEP*INITIAL_SPEED_X, INITIAL_Y- TIME_STEP*INITIAL_SPEED_Y),
                            1, random.choice(colors)))

    print "Pygame thread exited."




class Screen:
    def __init__(self, window, colors, universe):
        self.communicates = []
        self.communicates.append("Rutherford scattering")
        self.window = window
        self.universe = universe
        self.colors = colors
        self.color = WHITE

    def change_color(self):
        self.color = random.choice(self.colors)

    def draw_universe(self):
        self.draw_guide()
        for particle in self.universe.particles:
            self.draw_particle(particle)

    def draw_particle(self, particle):
        position = (int(ceil(particle.position.x)), int(ceil(particle.position.y)))
        pygame.draw.circle(self.window, particle.color, position, 6+ int(particle.mass/100) )

    def draw_guide(self):
        pygame.draw.line(self.window, BLACK, (0, INITIAL_Y), (X_SCREEN_BORDER,INITIAL_Y), 2)

    def draw_surface(self):
        self.window.fill(self.color)
        self.draw_universe()
        for i, text in enumerate(self.communicates):
            self.print_text(text, 20, 20 + i*20, (0, 0, 0), 30, self.window)
        pygame.display.flip()

    def print_text(self, text,xx,yy,color,text_size, screen):
        font = pygame.font.SysFont(None,text_size)
        ren = font.render(text,1,color)
        screen.blit(ren, (xx,yy))


class Vector2:
    def __init__(self, x, y):
        self.x = x
        self.y = y



class Particle:
    def __init__(self, mass, position, old_position, charge, color):
        self.mass = mass
        self.position = position
        self.old_position = old_position
        self.acc = Vector2(0,0)
        self.color = color
        self.charge = charge


class Universe:
    def __init__(self, particles):
        self.particles = particles
        print("Universe has just been created!")

    def update_accelerations(self):
        for particle in self.particles:
            particle.acc = Vector2(0,0)
        for x in range(1, len(self.particles)):
            accelerations = self.compute_acc(self.particles[x], self.particles[0])
            self.particles[x].acc = accelerations[0]

    def update_positions(self):
        self.update_accelerations()
        for particle in self.particles:
            temporary_x = particle.position.x 
            temporary_y = particle.position.y
            particle.position.x = 2 * particle.position.x - particle.old_position.x 
            particle.position.x += particle.acc.x * TIME_STEP * TIME_STEP
            particle.position.y = 2 * particle.position.y - particle.old_position.y 
            particle.position.y += particle.acc.y * TIME_STEP * TIME_STEP
            particle.old_position.x = temporary_x
            particle.old_position.y = temporary_y
            particle = self.limit_position(particle)

    def limit_position(self, particle):
        if(particle.position.x > X_SCREEN_BORDER or particle.position.y > Y_SCREEN_BORDER or
            particle.position.x < 0 or particle.position.y < 0):
            random_offset = random.randrange(-20, 20)
            particle.position.x = 2
            particle.old_position.x = 2 - INITIAL_SPEED_X*TIME_STEP
            particle.position.y = INITIAL_Y + random_offset
            particle.old_position.y = INITIAL_Y - INITIAL_SPEED_Y*TIME_STEP + random_offset
        return particle

    def compute_acc(self, particle1, particle2):
        vertical_distance = particle1.position.y - particle2.position.y
        horizontal_distance = particle1.position.x - particle2.position.x
        distance = sqrt((vertical_distance)**2 + (horizontal_distance)**2)
        force = particle1.charge * particle2.charge *K/distance**2
        acc1x = force/particle1.mass*horizontal_distance/distance
        acc1y = force/particle1.mass*vertical_distance/distance
        acc2x = -force/particle2.mass*horizontal_distance/distance
        acc2y = -force/particle2.mass*vertical_distance/distance
        return [Vector2(acc1x, acc1y), Vector2(acc2x, acc2y)]

    def add_particle(self, particle):
        self.particles.append(particle)

    


if __name__ == '__main__':
    main()