GameSceneAfterStep2.swift

//
//  GameScene.swift
//  spaceshooter
//
//

import SpriteKit

class GameScene: SKScene {
    
    var starShip:SKSpriteNode!
    var timeSinceLastFire:CGFloat = 0.0
    var fireWeapon:Bool = false
    var lastUpdateTime:NSTimeInterval = 0
    var delta:NSTimeInterval = NSTimeInterval(0)
    
    override func didMoveToView(view: SKView) {
        /* Setup your scene here */
        
        self.backgroundColor = SKColor.blackColor()
        
        let starFieldEmmiter = SKEmitterNode(fileNamed: "StarField.sks")
        starFieldEmmiter.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMaxY(self.frame))
        starFieldEmmiter.zPosition = -20
        starFieldEmmiter.advanceSimulationTime(NSTimeInterval(starFieldEmmiter.particleLifetime))
        
        self.addChild(starFieldEmmiter)
        
        starShip = SKSpriteNode(imageNamed:"Spaceship")
        starShip.xScale = 0.2
        starShip.yScale = 0.2
        
        starShip.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMinY(self.frame) + 100)
        
        self.addChild(starShip)
    }
    
    func moveShipTo(location:CGPoint)
    {
        starShip.runAction(SKAction.moveTo(location, duration: 0.05))
    }
    
    
    func fireProjectile(delta:CGFloat) {
        
        if timeSinceLastFire >= 0.15
        {
            let projectile = SKSpriteNode(imageNamed:"laser1")
            projectile.xScale = 0.5
            projectile.yScale = 0.5
            projectile.position = starShip.position
            projectile.position.y += starShip.frame.height / 2
            projectile.zPosition = starShip.zPosition + 1
            let speed:CGFloat = 600.0
            
            let distance = CGRectGetMaxY(self.frame) - starShip.position.y
            
            let travelTime:NSTimeInterval = NSTimeInterval(distance / speed)

            projectile.runAction(SKAction.moveToY(CGRectGetMaxY(self.frame) + 100, duration: travelTime))

            let waitAction = SKAction.waitForDuration(travelTime)
            let fadeAction = SKAction.fadeOutWithDuration(1)
            let removeAction = SKAction.removeFromParent()
            let sequence = [waitAction, fadeAction, removeAction]
            
            self.addChild(projectile)
            
            projectile.runAction(SKAction.sequence(sequence))
            
            timeSinceLastFire = 0.0
        }
        
        timeSinceLastFire += delta
    }
    
    override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
        /* Called when a touch begins */
        
        for touch in (touches as! Set<UITouch>) {
            let location = touch.locationInNode(self)
            
            moveShipTo(location)
            self.fireWeapon = true
        }
    }
    
    override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
        
        for touch in (touches as! Set<UITouch>) {
            let location = touch.locationInNode(self)
            
            moveShipTo(location)
        }
    }
    
    override func touchesEnded(touches: Set<NSObject>, withEvent event: UIEvent) {
        for touch in (touches as! Set<UITouch>) {
            let location = touch.locationInNode(self)
            
            self.fireWeapon = false
        }
    }
   
    override func update(currentTime: CFTimeInterval) {
        /* Called before each frame is rendered */
        
        if lastUpdateTime == 0.0 {
            delta = 0
        } else {
            delta = currentTime - lastUpdateTime
        }
        
        lastUpdateTime = currentTime
        
        if fireWeapon
        {
            self.fireProjectile(CGFloat(delta))
        }
    }
}