require 'Qt'
include Math

class CannonField < Qt::Widget
  signals 'hit()', 'missed()', 'angleChanged(int)', 'forceChanged(int)',
          'canShoot(bool)'

  slots   'setAngle(int)', 'setForce(int)', 'shoot()', 'moveShot()',
          'newTarget()', 'setGameOver()', 'restartGame()'

  def initialize(parent = nil)
    super
    @currentAngle = 45
    @currentForce = 0
    @timerCount = 0;
    @autoShootTimer = Qt::Timer.new(self)
    connect(@autoShootTimer, SIGNAL('timeout()'),
             self, SLOT('moveShot()'));
    @shootAngle = 0
    @shootForce = 0
    @target = Qt::Point.new(0, 0)
    @gameEnded = false
    setPalette(Qt::Palette.new(Qt::Color.new(250, 250, 200)))
    setAutoFillBackground(true)
    newTarget()
    @barrelRect = Qt::Rect.new(33, -4, 15, 8)
  end

  def angle()
    return @currentAngle
  end

  def force()
    return @currentForce
  end

  def gameOver()
    return @gameEnded
  end

  def setAngle(degrees)
    if degrees < 5
      degrees = 5
    elsif degrees > 70
      degrees = 70
    end
    if @currentAngle == degrees
      return
    end
    @currentAngle = degrees
    update(cannonRect())
    emit angleChanged(@currentAngle)
  end

  def setForce(newton)
    if newton < 0
      newton = 0
    end
    if @currentForce == newton
      return
    end
    @currentForce = newton
    emit forceChanged(@currentForce)
  end

  def shoot()
    if isShooting()
      return
    end
    @timerCount = 0
    @shootAngle = @currentAngle
    @shootForce = @currentForce
    @autoShootTimer.start(50)
    emit canShoot(false)
  end

  @@first_time = true

  def newTarget()
    if @@first_time
      @@first_time = false
      midnight = Qt::Time.new(0, 0, 0)
      srand(midnight.secsTo(Qt::Time.currentTime()))
    end
    @target = Qt::Point.new(200 + rand(190), 10 + rand(255))
    update()
  end

  def setGameOver()
    if @gameEnded
      return
    end
    if isShooting()
      @autoShootTimer.stop()
    end
    @gameEnded = true
    update()
  end

  def restartGame()
    if isShooting()
      @autoShootTimer.stop()
    end
    @gameEnded = false
    update()
    emit canShoot(true)
  end

  def moveShot()
    r = Qt::Region.new(shotRect())
    @timerCount += 1

    shotR = shotRect()

    if shotR.intersects(targetRect())
      @autoShootTimer.stop()
      emit hit()
      emit canShoot(true)
    elsif shotR.x() > width() || shotR.y() > height()
      @autoShootTimer.stop()
      emit missed()
      emit canShoot(true)
    else
      r = r.unite(Qt::Region.new(shotR))
    end

    update(r)
  end

  def paintEvent(e)
    painter = Qt::Painter.new(self)

    if @gameEnded
      painter.setPen(Qt::black)
      painter.setFont(Qt::Font.new("Courier", 48, Qt::Font::Bold))
      painter.drawText(rect(), Qt::AlignCenter, "Game Over")
    end
    paintCannon(painter)
    if isShooting()
      paintShot(painter)
    end
    if !@gameEnded
      paintTarget(painter)
    end
    painter.end()
  end

  def paintShot(painter)
    painter.setPen(Qt::NoPen)
    painter.setBrush(Qt::Brush.new(Qt::black))
    painter.drawRect(shotRect())
  end

  def paintTarget(painter)
    painter.setBrush(Qt::Brush.new(Qt::red))
    painter.setPen(Qt::Pen.new(Qt::Color.new(Qt::black)))
    painter.drawRect(targetRect())
  end

  def paintCannon(painter)
    painter.setPen(Qt::NoPen)
    painter.setBrush(Qt::Brush.new(Qt::blue))

    painter.save()
    painter.translate(0, height())
    painter.drawPie(Qt::Rect.new(-35, -35, 70, 70), 0, 90 * 16)
    painter.rotate(- @currentAngle)
    painter.drawRect(@barrelRect)
    painter.restore()
  end

  def cannonRect()
    r = Qt::Rect.new(0, 0, 50, 50)
    r.moveBottomLeft(rect().bottomLeft())
    return r
  end

  def shotRect()
    gravity = 4.0

    time      = @timerCount / 4.0
    velocity  = @shootForce
    radians   = @shootAngle * 3.14159265 / 180.0

    velx      = velocity * cos(radians)
    vely      = velocity * sin(radians)
    x0        = (@barrelRect.right()  + 5.0) * cos(radians)
    y0        = (@barrelRect.right()  + 5.0) * sin(radians)
    x         = x0 + velx * time
    y         = y0 + vely * time - 0.5 * gravity * time * time

    r = Qt::Rect.new(0, 0, 6, 6);
    r.moveCenter(Qt::Point.new(x.round, height() - 1 - y.round))
    return r
  end

  def targetRect()
    r = Qt::Rect.new(0, 0, 20, 10)
    r.moveCenter(Qt::Point.new(@target.x(), height() - 1 - @target.y()))
    return r
  end

  def isShooting()
    return @autoShootTimer.isActive()
  end
end