//
//  LoadingView.swift
//
//  Created by Eduardo Sanches Bocato on 15/11/17.
//

import UIKit
import SnapKit

// MARK: Constants
fileprivate struct Defaults {
  static let backgroundViewAlpha: CGFloat = 0.9
  static let activityIndicatorViewSquareSize = 30
  static let animationDuration = 0.35
}

class LoadingView: UIControl {

  // MARK: View Elements
  private var backgroundView: UIView!
  private var activityIndicatorView: UIActivityIndicatorView!

  // MARK: Properties
  private var showBackgroundView: Bool? {
    willSet {
      if let newValue = newValue, newValue != showBackgroundView {
        self.backgroundColor = newValue ? UIColor.clear : UIColor.white
        self.backgroundView.backgroundColor = newValue ? UIColor.white : UIColor.clear
        self.backgroundView.layer.borderColor = newValue ? UIColor.groupTableViewBackground.cgColor : UIColor.clear.cgColor
        self.backgroundView.layoutSubviews()
      }
    }
  }
  private var backGroundViewSquareSize: Int {
    return 100
  }

  // MARK: - Initialization
  required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
  }

  private init(frame: CGRect, activityIndicatorStyle style: UIActivityIndicatorViewStyle, activityIndicatorColor color: UIColor = UIColor.lightGray) {
    super.init(frame: frame)
    self.configureViewElements(activityIndicatorStyle: style, activityIndicatorColor: color)
  }

  // MARK: - Instantiation
  fileprivate static func instantiateNew(in view: UIView!, withActivityIndicatorStyle style: UIActivityIndicatorViewStyle, activityIndicatorColor color: UIColor = UIColor.lightGray) -> LoadingView? {
    let loadingView = LoadingView(frame: view.frame, activityIndicatorStyle: style, activityIndicatorColor: color)
    view.addSubview(loadingView)
    loadingView.snp.makeConstraints { (make) in
      make.left.right.bottom.top.equalTo(view)
    }
    return loadingView
  }

  fileprivate static func instantiateNew(in context: Any!, withActivityIndicatorStyle style: UIActivityIndicatorViewStyle, activityIndicatorColor color: UIColor = UIColor.lightGray) -> LoadingView? {

    if let contextAsController = context as? UIViewController {
      return self.instantiateNew(in: contextAsController.view, withActivityIndicatorStyle: style, activityIndicatorColor: color)
    }
    else if let contextAsView = context as? UIView {
      return self.instantiateNew(in: contextAsView, withActivityIndicatorStyle: style, activityIndicatorColor: color)
    }

    return nil
  }

  // MARK: - Layout Configuration
  private func configureViewElements(activityIndicatorStyle style: UIActivityIndicatorViewStyle = .whiteLarge, activityIndicatorColor color: UIColor = UIColor.lightGray) {
    self.backgroundColor = UIColor.white
    self.isHidden = true
    self.configureActivityIndicatorBackgroundView()
    self.configureActivityIndicator(activityIndicatorStyle: style, activityIndicatorColor: color)
  }

  fileprivate func configureActivityIndicatorBackgroundView() {
    self.backgroundView = UIView()
    self.backgroundView.backgroundColor = UIColor.white
    self.backgroundView.alpha = Defaults.backgroundViewAlpha
    self.backgroundView.layer.cornerRadius = 10.0
    self.backgroundView.layer.borderColor = UIColor.clear.cgColor
    self.backgroundView.layer.borderWidth = 2.0
    self.addSubview(self.backgroundView)
    self.backgroundView.snp.makeConstraints { (make) in
      make.centerX.centerY.equalTo(self)
      make.height.width.equalTo(self.backGroundViewSquareSize)
    }
  }

  fileprivate func configureActivityIndicator(activityIndicatorStyle style: UIActivityIndicatorViewStyle = .whiteLarge, activityIndicatorColor color: UIColor = UIColor.lightGray) {
    self.activityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: style)
    self.activityIndicatorView.translatesAutoresizingMaskIntoConstraints = false
    self.activityIndicatorView.color = color
    self.backgroundView?.addSubview(self.activityIndicatorView)
    self.activityIndicatorView.snp.makeConstraints { (make) in
      make.centerX.centerY.equalTo(self.backgroundView)
      make.height.width.equalTo(Defaults.activityIndicatorViewSquareSize)
    }
  }

  // MARK: Constraints
  fileprivate func remakeConstraints() {
    self.backgroundView.snp.remakeConstraints { (make) in
      make.centerX.centerY.equalTo(self)
      make.height.width.equalTo(self.backGroundViewSquareSize)
    }
    self.activityIndicatorView.snp.remakeConstraints { (make) in
      make.top.equalTo(self.backgroundView.snp.top).offset(20)
      make.centerY.lessThanOrEqualTo(self.backgroundView)
      make.centerX.equalTo(self.backgroundView)
      make.height.width.equalTo(Defaults.activityIndicatorViewSquareSize)
    }
  }

  // MARK: - Public Actions
  public static func hide(for context: Any!) {
    if let contextAsController = context as? UIViewController {
      self.hide(forContext: contextAsController.view)
    }
    else if let contextAsView = context as? UIView {
      self.hide(forContext: contextAsView)
    }
  }

  fileprivate static func hide(forContext view: UIView?){
    if let viewSubviews = view?.subviews, let currentVisibleLoadingView = viewSubviews.filter({ $0.isKind(of: LoadingView.self) }).first as? LoadingView {
      currentVisibleLoadingView.hide()
      currentVisibleLoadingView.removeFromSuperview()
    }
  }

  public static func show(in context: Any!, withText text: String? = nil, background: Bool = false, activityIndicatorStyle style: UIActivityIndicatorViewStyle = .whiteLarge, activityIndicatorColor color: UIColor? = nil) {
    if let loadingView = LoadingView.instantiateNew(in: context, withActivityIndicatorStyle: style) {
      loadingView.show(withBackground: background)
    }
  }

  // MARK: - Behavior
  fileprivate func hide() {
    self.showBackgroundView = false
    self.alpha = 1.0
    self.backgroundView.alpha = Defaults.backgroundViewAlpha
    UIView.animate(withDuration: Defaults.animationDuration, animations: {
      self.alpha = 0.0
    }, completion: { (finished) in
      self.activityIndicatorView.stopAnimating()
      self.backgroundView.isHidden = true
      self.isHidden = true
    })
  }

  fileprivate func show(withBackground background: Bool = false) {
    self.showBackgroundView = background
    self.backgroundView.isHidden = !background
    self.backgroundView.alpha = 0.0
    self.isHidden = false
    self.alpha = 0.0
    self.activityIndicatorView.startAnimating()
    UIView.animate(withDuration: Defaults.animationDuration) {
      self.alpha = 1.0
      self.backgroundView.alpha = Defaults.backgroundViewAlpha
    }
  }

}