//
//  LoaderView.swift
//  Privado
//
//  Created by Viktor on 29.06.2020.
//  Copyright © 2020 Privado LLC. All rights reserved.
//

import Foundation
import UIKit

final class LoaderView: UIView {
    
    static let shared = LoaderView(frame: .zero)
    
    private var loader: UIImageView?
    private var spinnerTask: DispatchWorkItem?
    
    private var currentAnimationStep = 0
    
    private enum Constants {
        static let loaderImageName = "navigation_loader"
        static let loaderSize: CGFloat = 120

// see image named above in asset (it has 6 sectors)
        static let arcCount: Int = 6
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.setup()
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    private func infinteAnimation() {
        
        self.spinnerTask = DispatchWorkItem { [weak self] in

            guard let self = self else {
                return
            }

            self.loader?.transform = CGAffineTransform(rotationAngle: 2*CGFloat(self.currentAnimationStep%Constants.arcCount)*CGFloat.pi/CGFloat(Constants.arcCount))
            self.currentAnimationStep += 1
            self.infinteAnimation()
        }
        guard let task = self.spinnerTask else {
            return
        }
        DispatchQueue.main.asyncAfter(deadline: .now()+0.12, execute: task)
    }
    
    func startAnimation() {
        
        if self.loader == nil {
            
            let image = UIImage(imageLiteralResourceName: Constants.loaderImageName)
            self.loader = UIImageView(image: image)
            self.loader?.translatesAutoresizingMaskIntoConstraints = false
            guard let imageLoader = self.loader else {
                return
            }
            self.addSubview(imageLoader)
            NSLayoutConstraint.activate([
                imageLoader.centerXAnchor.constraint(equalTo: self.centerXAnchor),
                imageLoader.centerYAnchor.constraint(equalTo: self.centerYAnchor),
                imageLoader.widthAnchor.constraint(lessThanOrEqualToConstant: Constants.loaderSize),
                imageLoader.heightAnchor.constraint(lessThanOrEqualToConstant: Constants.loaderSize)
                ])
        }

        if self.isHidden == true {
            self.spinnerTask?.cancel()
        }
        self.isHidden = false
        self.infinteAnimation()
    }
    
    func stopAnimation() {
        self.spinnerTask?.cancel()
        self.isHidden = true
        self.loader?.removeFromSuperview()
        self.loader = nil
        
    }
    
    private func setup() {
        self.backgroundColor = UIColor(rgb: 0x151935)
        self.alpha = 0.87
        self.translatesAutoresizingMaskIntoConstraints = false
        self.isHidden = true
        guard let window = UIApplication.shared.keyWindow else {
            return
        }
        window.addSubview(self)
        NSLayoutConstraint.activate([
            self.topAnchor.constraint(equalTo: window.topAnchor),
            self.bottomAnchor.constraint(equalTo: window.bottomAnchor),
            self.trailingAnchor.constraint(equalTo: window.trailingAnchor),
            self.leadingAnchor.constraint(equalTo: window.leadingAnchor)
            ])

    }
    
}