=begin
 
THE GAME:
 
  A ball flies back and forth across a playing field. Use the arrow
  keys to move your paddle up and down to deflect the ball. If the
  ball flies off your opponent's side of the screen, you get a point,
  but if it flies off your side of the screen, your opponent gets the
  point. The first player to get 10 points wins the game!
 
 
DEMONSTRATES:
 
  * Keyboard input
  * Player-controlled game objects
  * AI-controlled game objects
  * Collision detection
  * Rectangle shape
  
 
CURRENT STATUS:
 
  * Nonfunctional (code incomplete; and library not implemented.)
 
 
AUTHOR:
 
  John Croisant, 2008-05-29
 
=end
 
 
 
VERY_MASSIVE = 10**15
 
 
 
class Paddle < GameObject
 
  attr_accessor :direction, :top_speed, :clamp_x
 
 
  def initialize( params = {} )
    base_params = { 
      :color   => :white,
      :size    => [16,64],
      :mass    => VERY_MASSIVE,
      :elast   => 1.10,
      :gravity => false
    }
 
    add_shape Rectangle.new( base_params.merge(params) )
 
    @direction = 0; # moving up (1), down (-1), or none (0)
    @top_speed = 30
    @clamp_x = nil;
 
    before_update( :name => "move" ) do |tick|
      self.velocity = v(0,1) * top_speed * direction
    end
 
    after_update( :name => "clamp x" ) do
      if @clamp_x
        self.position.x = @clamp_x 
        self.velocity.x = 0
      end
    end
 
  end
 
 
  def bind_keys( up, down )
    when_key_pressed( :key => up, :name => "+up" ) do
      self.direction += 1
    end
 
    when_key_released( :key => up, :name => "-up" ) do
      self.direction -= 1
    end
 
    when_key_pressed( :key => down, :name => "+down" ) do
      self.direction -= 1
    end
 
    when_key_released( :key => down, :name => "-down" ) do
      self.direction += 1
    end
  end
 
 
  def clear_keys
    clear_hooks "+up", "-up", "+down", "-down"
  end
 
 
  def ai_track_ball( ball )
    @ball = ball
    @fuzz = 10
 
    before_update( :name => "tracking", :priority => 10 ) do
      diff = @ball.y - self.y
 
      if diff > @fuzz
        self.direction = 1
      elsif diff < -@fuzz
        self.direction = 1
      else
        self.direction = 0
      end
    end
  end
 
end
 
 
 
class Ball < GameObject
 
  def initialize( params={} )
    base_params = { 
      :color   => :red,
      :radius  => 10.0,
    }
    
    add_shape Circle.new( base_params.merge(params) )
 
    @base_speed = 30
  end
 
 
  def start( direction )
    self.velocity =
      case direction
      when "left"
        v(1,1).magnitude(-@base_speed)
      when "right"
        v(1,1).magnitude( @base_speed)
      end
  end
end
 
 
 
class Wall < GameObject
  def initialize( p1, p2 )
    base_params = { 
      :color     => :white,
      :thickness => 3.0,
      :static    => true,
      :elast     => 1.0
    }    
  
    add_shape Line.new( base_params.merge(:points => [p1,p2]) )
  end
end
 
 
 
def setup
  $game = Game.new
 
  # Initialize scores
  $game["scores"] = { "left" => 0, "right" => 0 }
 
  # Make the walls
  $game.add( "top_wall"    => Wall.new(v(-400, 240), v( 400, 240)),
             "bottom_wall" => Wall.new(v(-400,-240), v( 400,-240)),
             "left_wall"   => Wall.new(v(-400, 240), v(-400,-240)),
             "right_wall"  => Wall.new(v( 400, 240), v( 400,-240)))
 
  ["left," "right"].each do |side|
    $game["#{side}_wall"].when_collide( :with => Ball ) do
      $game["scores"][side] += 1
      $game["ball"].die
    end
  end
end