//
//  ViewController.swift
//  MagneticSwitch
//
//  Created by MizushimaYusuke on 2017/03/29.
//  Copyright © 2017 MizushimaYusuke. All rights reserved.
//

import UIKit
import SpriteKit

class ViewController: UIViewController {

    weak var scene: SKScene?
    var fields = [SKFieldNode]()

    override func viewDidLoad() {
        super.viewDidLoad()
        setupScene()
        createMagnet()
        createBall()
    }

    func setupScene() {
        let sv = SKView(frame: view.frame)
        let s = SKScene(size: view.frame.size)
        sv.backgroundColor = UIColor.lightGray
        s.physicsWorld.gravity = CGVector(dx: 0, dy: -0.2)
        sv.presentScene(s)
        view.addSubview(sv)
        scene = s

        sv.showsFields = true
    }

    func createMagnet() {
        stride(from: 50, to: view.frame.maxX, by: 100).forEach { x in

            let magnet = SKSpriteNode(color: .blue, size: CGSize(width: 50, height: 200))
            magnet.name = "magnet"
            magnet.position = CGPoint(x: x, y: view.center.y + 120)
            scene?.addChild(magnet)
            magnet.physicsBody = SKPhysicsBody(rectangleOf: magnet.size)
            magnet.physicsBody?.isDynamic = false

            let plus = SKSpriteNode(color: .red, size: CGSize(width: 50, height: 100))
            plus.name = "magnet"
            plus.position = CGPoint(x: 0, y: -50)
            magnet.addChild(plus)

            let field = SKFieldNode.radialGravityField()
            field.isEnabled = true
            field.strength = 1
            field.position = CGPoint(x: magnet.position.x, y: magnet.position.y - 100)
            field.region = SKRegion(radius: 300)
            scene?.addChild(field)
            fields.append(field)
        }
    }

    func createBall() {
        let ball = SKShapeNode(circleOfRadius: 30)
        ball.position = view.center
        ball.fillColor = UIColor.lightGray
        scene?.addChild(ball)

        ball.physicsBody = SKPhysicsBody(circleOfRadius: 30)
        ball.physicsBody?.charge = 1
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        if let touch = touches.first {
            let p = touch.location(in: scene!)
            let node = scene?.nodes(at: p)
                   .map { n -> SKNode in
                        if (n.parent?.name == "magnet") { return n.parent! }
                        return n
                    }.first
            if node?.name == "magnet" {
                fields
                    .filter { abs($0.position.x - node!.position.x) < 5 }
                    .forEach {
                        let isEnable = !$0.isEnabled
                        $0.isEnabled = isEnable
                        node?.run(SKAction.fadeAlpha(to: isEnable ? 1.0 : 0.5, duration: 0.2))
                    }
            }
        }
    }
}