import sys, time, math
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *

drawSphereFirst = True

viewDistance = 7.0
viewRotY = 0.0
viewRotX = 0.0
cameraVelX = 0.0
cameraVelY = 0.0
prevTime = time.time()


def draw():
    glClearColor(0.5, 0.7, 1, 0)
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    gluPerspective(50.0, 1.0, 1.0, 100.0)
    glMatrixMode(GL_MODELVIEW)

    glLoadIdentity()
    glTranslatef(0.0, 0.0, -viewDistance)
    glRotatef(viewRotX, 1.0, 0.0, 0.0)
    glRotatef(viewRotY, 0.0, 1.0, 0.0)
    glLightfv(GL_LIGHT0, GL_POSITION, [-1, 1, 1, 0])
    
    if drawSphereFirst:
        drawSphereThenCube()
    else:
        drawCubeThenSphere()

    glutSwapBuffers()

def drawSphereThenCube():
    glMaterialfv(GL_FRONT, GL_DIFFUSE, [1, 1, 1, 1])
    glPushMatrix()
    glTranslatef(0.0, 0.0, -5.0)
    glutSolidSphere(2.5, 16, 8)
    glPopMatrix()
   
    glEnable(GL_BLEND)
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
    glMaterialfv(GL_FRONT, GL_DIFFUSE, [1, 0, 0, 0.5])
    glutSolidCube(2.0)
    glDisable(GL_BLEND)


def drawCubeThenSphere():
    glEnable(GL_BLEND)
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
    glMaterialfv(GL_FRONT, GL_DIFFUSE, [1, 0, 0, 0.5])
    glutSolidCube(2.0)
    glDisable(GL_BLEND)

    glMaterialfv(GL_FRONT, GL_DIFFUSE, [1, 1, 1, 1])
    glPushMatrix()
    glTranslatef(0.0, 0.0, -5.0)
    glutSolidSphere(2.5, 16, 8)
    glPopMatrix()


def keyboard(key, x, y):
    global viewDistance, drawSphereFirst
    if key == chr(27):
        sys.exit(0)
    elif key == '.':
        viewDistance -= 1
    elif key == ',':
        viewDistance += 1
    elif key == ' ':
        drawSphereFirst = not drawSphereFirst

def specialkey(key,x,y):
    global cameraVelX, cameraVelY
    if key == GLUT_KEY_LEFT:
        cameraVelY += 90
    elif key == GLUT_KEY_RIGHT:
        cameraVelY -= 90
    elif key == GLUT_KEY_UP:
        cameraVelX += 90
    elif key == GLUT_KEY_DOWN:
        cameraVelX -= 90

def specialkeyUp(key,x,y):
    global cameraVelX, cameraVelY
    if key == GLUT_KEY_LEFT:
        cameraVelY -= 90
    elif key == GLUT_KEY_RIGHT:
        cameraVelY += 90
    elif key == GLUT_KEY_UP:
        cameraVelX -= 90
    elif key == GLUT_KEY_DOWN:
        cameraVelX += 90

def update():
    global viewRotX, viewRotY, cameraVelX, cameraVelY
    global prevTime
    t = time.time()
    dt = t - prevTime
    prevTime = t
    viewRotX += cameraVelX * dt
    viewRotY += cameraVelY * dt
    glutPostRedisplay()

glutInit([])
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH)
glutInitWindowSize(500,500)
glutCreateWindow(sys.argv[0])
glutDisplayFunc(draw)
glutKeyboardFunc(keyboard)
glutSpecialFunc(specialkey)
glutSpecialUpFunc(specialkeyUp)
glutIgnoreKeyRepeat(1)
glutIdleFunc(update)
glEnable(GL_DEPTH_TEST)
glEnable(GL_LIGHTING)
glEnable(GL_LIGHT0)
glEnable(GL_CULL_FACE)
glutMainLoop()