require "gl"
require "glu"
require "glut"
require "mathn"

class BounceBox

  include Gl
  include Glu
  include Glut

  $window = ""
  $cube_angle = 0

  $xy = [2.0, 2.0]
  $change = [1.0, 1.0]
  $speed = 0.01

  def init_gl_window(width = 640, height = 480)
      glClearColor(0.0, 0.0, 0.0, 0)
      glClearDepth(1.0)
      glDepthFunc(GL_LEQUAL)
      glEnable(GL_DEPTH_TEST)
      glShadeModel(GL_SMOOTH)

      glMatrixMode(GL_PROJECTION)
      glLoadIdentity
      gluPerspective(45.0, width / height, 0.1, 100.0)

      glMatrixMode(GL_MODELVIEW)

      draw_gl_scene
  end

  #reshape = Proc.new do |width, height|
  def reshape(width, height)
      height = 1 if height == 0

      # Reset current viewpoint and perspective transformation
      glViewport(0, 0, width, height)

      glMatrixMode(GL_PROJECTION)
      glLoadIdentity

      gluPerspective(45.0, width / height, 0.1, 100.0)
  end

  def draw_gl_scene
      glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
      glMatrixMode(GL_MODELVIEW)
      glLoadIdentity
      glTranslatef($xy[0], $xy[1], -20.0)

      glRotatef($cube_angle, 1.0, 1.0, 1.0)

      glBegin(GL_QUADS)
          # Draw the top side in green
          glColor3f(0.0, 1.0, 0.0)
          glVertex3f( 1.0,  1.0, -1.0)
          glVertex3f(-1.0,  1.0, -1.0)
          glVertex3f(-1.0,  1.0,  1.0)
          glVertex3f( 1.0,  1.0,  1.0)
          # Draw the bottom side in orange
          glColor3f(1.0, 0.5, 0.0)
          glVertex3f( 1.0, -1.0,  1.0)
          glVertex3f(-1.0, -1.0,  1.0)
          glVertex3f(-1.0, -1.0, -1.0)
          glVertex3f( 1.0, -1.0, -1.0)
          # Draw the front side in red
          glColor3f(1.0, 0.0, 0.0)
          glVertex3f( 1.0,  1.0,  1.0)
          glVertex3f(-1.0,  1.0,  1.0)
          glVertex3f(-1.0, -1.0,  1.0)
          glVertex3f( 1.0, -1.0,  1.0)
          # Draw the back side in yellow
          glColor3f(1.0, 1.0, 0.0)
          glVertex3f( 1.0, -1.0, -1.0)
          glVertex3f(-1.0, -1.0, -1.0)
          glVertex3f(-1.0,  1.0, -1.0)
          glVertex3f( 1.0,  1.0, -1.0)
          # Draw the left side in blue
          glColor3f(0.0, 0.0, 1.0)
          glVertex3f(-1.0,  1.0,  1.0)
          glVertex3f(-1.0,  1.0, -1.0)
          glVertex3f(-1.0, -1.0, -1.0)
          glVertex3f(-1.0, -1.0,  1.0)
          # Draw the right side in violet
          glColor3f(1.0, 0.0, 1.0)
          glVertex3f( 1.0,  1.0, -1.0)
          glVertex3f( 1.0,  1.0,  1.0)
          glVertex3f( 1.0, -1.0,  1.0)
          glVertex3f( 1.0, -1.0, -1.0)
      glEnd

      $cube_angle -= 0.15
      update_xy

      # Swap buffers for display
      glutSwapBuffers
  end

  def update_xy
    x, y = $xy
    xc, yc = $change

    if x < -10 || x > 10
      xc *= -1
    end

    if y < -8 || y > 8
      yc *= -1
    end

    x += xc * $speed
    y += yc * $speed

    puts "X: #{x} Y: #{y}"

    $xy = [x, y]
    $change = [xc, yc]
  end

  # The idle function to handle
  def idle
      glutPostRedisplay
  end

  def initialize
    # Initliaze our GLUT code
    glutInit;
    # Setup a double buffer, RGBA color, alpha components and depth buffer
    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_ALPHA | GLUT_DEPTH);
    glutInitWindowSize(640, 480);
    glutInitWindowPosition(0, 0);
    $window = glutCreateWindow("Box Bang");
    glutDisplayFunc(method(:draw_gl_scene).to_proc);
    glutReshapeFunc(method(:reshape).to_proc);
    glutIdleFunc(method(:idle).to_proc);
    init_gl_window(640, 480)
    glutMainLoop();
  end
end