require 'rubygems'
require 'gosu'
WIDTH = 1366
HEIGHT = 768
class Point
  attr_accessor :x, :y, :dx, :dy
  def initialize(x, y, vx, vy, win)
    @x = x
    @y = y
    @ox = x - vx
    @oy = y - vy
  end
  def update
    @dx = @x - @ox
    @dy = @y - @oy + 0.1
    @ox = @x
    @oy = @y
    @x = @x + @dx
    @y = @y + @dy
    if @y > HEIGHT - 10
      @y = HEIGHT - 10
      @dx = @x-@ox
            @dx *= 0.5
            @ox = @ox + @dx
    end
    if @y < 10
      @y = 10
      @dx = @x-@ox
            @dx *= 0.5
            @ox = @ox + @dx
    end
    if @x > WIDTH - 10
      @x = WIDTH - 10
      @dy = @y-@oy
            @dy *= 0.5
            @oy = @oy + @dy
    end
    if @x < 10
      @x = 10
      @dy = @y-@oy
            @dy *= 0.5
            @oy = @oy + @dy
    end
  end
end

class Contact
  def initialize(p1, p2,win)
    @p1 = p1
    @p2 = p2
    @win = win
    @length = Math.sqrt((@p1.x-@p2.x)**2 + (@p1.y-@p2.y)**2)
  end
  def update
    3.times{
    dist = Math.sqrt((@p1.x-@p2.x)**2 + (@p1.y-@p2.y)**2)
        diff = dist - @length
        dx = @p1.x-@p2.x
        dy = @p1.y-@p2.y
        if @length > 0
            diff = diff / @length
    else
            diff = 0
    end

        dx *= 0.15
        dy *= 0.15

        @p1.x -= diff*dx
        @p1.y -= diff*dy

        @p2.x += diff*dx
        @p2.y += diff*dy
    }
  end
  def draw
    @win.draw_line(@p1.x,@p1.y,Gosu::white,@p2.x,@p2.y,Gosu::white)
  end
end

class GameWindow < Gosu::Window
  def initialize
    super(1366, 768, true)
    self.caption = "Physics"
    game = 'snake'
    if game == 'snake'
    @points, @contacts = [] ,[]
    10.times{|i|
    @points.push(Point.new(200 - 14*i,50,0,0,self))
    @contacts.push(Contact.new(@points[i-1],@points[i],self))
    }
    elsif game == 'man'
      @points = [
        Point.new(200,80,0,0,self),
        Point.new(180,100,0,0,self),
        Point.new(220,100,0,0,self),
        Point.new(200,120,0,0,self),
        Point.new(200,140,0,0,self),
        Point.new(165,170,0,0,self),
        Point.new(235,170,0,0,self),
        Point.new(165,240,0,0,self),
        Point.new(230,240,0,0,self),
        Point.new(165,285,0,0,self),
        Point.new(165,320,0,0,self),
        Point.new(230,285,0,0,self),
        Point.new(230,320,0,0,self),
        Point.new(140,180,0,0,self),
        Point.new(120,210,0,0,self),
        Point.new(260,180,0,0,self),
        Point.new(280,210,0,0,self)
        ]
      @contacts = [
        Contact.new(@points[0],@points[1],self),
        Contact.new(@points[2],@points[1],self),
        Contact.new(@points[0],@points[3],self),
        Contact.new(@points[0],@points[2],self),
        Contact.new(@points[3],@points[1],self),
        Contact.new(@points[3],@points[2],self),
        Contact.new(@points[4],@points[3],self),
        Contact.new(@points[5],@points[4],self),
        Contact.new(@points[5],@points[6],self),
        Contact.new(@points[6],@points[4],self),
        Contact.new(@points[5],@points[7],self),
        Contact.new(@points[7],@points[8],self),
        Contact.new(@points[8],@points[6],self),
        Contact.new(@points[6],@points[7],self),
        Contact.new(@points[5],@points[8],self),
        Contact.new(@points[4],@points[7],self),
        Contact.new(@points[4],@points[8],self),
        Contact.new(@points[9],@points[7],self),
        Contact.new(@points[10],@points[9],self),
        Contact.new(@points[11],@points[8],self),
        Contact.new(@points[12],@points[11],self),
        Contact.new(@points[13],@points[5],self),
        Contact.new(@points[14],@points[13],self),
        Contact.new(@points[15],@points[6],self),
        Contact.new(@points[16],@points[15],self)
        ]
    end
  end

  def update
    @points.each{|p| p.update}
    @contacts.each{|c| c.update}
    if button_down? Gosu::Button::KbUp then
      @points[0].y -= 1.4
    end
    if button_down? Gosu::Button::KbLeft then
      @points[0].x -= 0.4
    end
    if button_down? Gosu::Button::KbRight then
      @points[0].x += 0.4
    end
  end

  def draw
    @contacts.each { |c|
     c.draw
    }
  end
end

window = GameWindow.new
window.show