ApolloActivityViewController.swift

//
//  ApolloActivityViewController.swift
//  Apollo
//
//  Created by Christian Selig on 2016-12-12.
//  Copyright © 2016 Christian Selig. All rights reserved.
//

import UIKit

/// Modification of `UIActivityViewController` that accomplishes Dark Mode support via a bunch of hacks, view sniffing and view traversing.
class ApolloActivityViewController: UIActivityViewController {
    var darkeningView: UIView?
    var settingUpDarkeningView: Bool = true

    override func viewDidLoad() {
        super.viewDidLoad()

        if ThemeManager.shared.currentTheme == .dark {
            // Add a background view that causes the UIVisualEffectView to be a little darker
            let darkeningView = UIView()
            darkeningView.alpha = 0.0
            darkeningView.layer.masksToBounds = true
            darkeningView.backgroundColor = UIColor.black.withAlphaComponent(0.3)
            self.darkeningView = darkeningView

            // Constantly refresh the views in case AirDrop finds new people to share to and we'll need to color their labels
            constantlyRefresh()
        }
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        if let darkeningView = darkeningView {
            view.superview?.addSubview(darkeningView)
            view.superview?.sendSubview(toBack: darkeningView)

            darkeningView.layer.cornerRadius = view.layer.cornerRadius

            // Dispatch ahead one run cycle in order to keep things in sync
            DispatchQueue.main.async {
                self.settingUpDarkeningView = false

                UIView.animate(withDuration: 0.4, delay: 0.0, options: .curveEaseInOut, animations: {
                    darkeningView.frame.origin.y = self.view.frame.origin.y
                    darkeningView.alpha = 1.0
                }, completion: nil)
            }
        }
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        UIView.animate(withDuration: 0.25, delay: 0.0, options: .curveEaseInOut, animations: {
            self.darkeningView?.alpha = 0.0
        }, completion: { (finished) in
            self.darkeningView?.removeFromSuperview()
        })
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        darkeningView?.frame = view.frame

        if ThemeManager.shared.currentTheme == .dark, let superview = view.superview {
            colorSubviewsOfView(superview)
        }

        if settingUpDarkeningView, let darkeningView = darkeningView {
            darkeningView.frame.origin.y = view.frame.origin.y + darkeningView.frame.height
        }
    }

    func constantlyRefresh() {
        DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(250)) {
            if let superview = self.view.superview {
                self.colorSubviewsOfView(superview)
            }

            self.constantlyRefresh()
        }
    }

    fileprivate func colorSubviewsOfView(_ view: UIView) {        
        if let visualEffectView = view as? UIVisualEffectView {
            visualEffectView.effect = UIBlurEffect(style: .dark)
        } else if let label = view as? UILabel, label.isContainedByViewOfType(UICollectionView.self) {
            label.textColor = UIColor.white
        } else if let button = view as? UIButton, !button.isContainedByViewOfType(UICollectionView.self) {
            button.backgroundColor = UIColor(white: 0.12, alpha: 1.0)
        } else if view.bounds.height == 1.0 {
            // Color the separator (damn these hacks are getting gross)
            view.isOpaque = false
            view.backgroundColor = UIColor.white.withAlphaComponent(0.035)
        }

        view.subviews.forEach { colorSubviewsOfView($0) }
    }
}