HighlightGlitch.swift

import UIKit
import EasyPeasy

class ViewController: UIViewController {
    
    private lazy var textView = UITextView(frame: CGRect.zero)
    
    private lazy var button1 = createButton(.green)
    private lazy var button2 = createButton(.red)
    private lazy var button3 = createButton(.blue)
    
    private lazy var expandButton = createButton(.black)
    private lazy var actionButtons = [button1, button2, button3]
    
    lazy var leftStackView: UIStackView = {
        let stackView = UIStackView()
        
        stackView.spacing = 2
        stackView.distribution = .fillEqually
        
        stackView.addArrangedSubview(expandButton)
        return stackView
    }()
    
    private let maxHeight: CGFloat = 100
    private var isExtended = false
    
    private let stackViewExtendedWidth: CGFloat = 80
    private let stackViewCollapsedWidth: CGFloat = 30
    
    private let stackViewHeight: CGFloat = 25
    
    override func loadView() {
        super.loadView()
        
        self.view.backgroundColor = UIColor.white
        self.textView.delegate = self
        
        self.textView.layer.borderColor = UIColor.gray.withAlphaComponent(0.5).cgColor
        self.textView.layer.borderWidth = 1.0
        self.textView.layer.cornerRadius = 5
        self.textView.clipsToBounds = true
        
        self.textView.isScrollEnabled = false
        
        self.view.addSubview(textView)
        self.view.addSubview(leftStackView)
        
        leftStackView.easy.layout(
            Left(10),
            Height(stackViewHeight),
            Width(stackViewCollapsedWidth),
            CenterY().to(textView)
        )
        
        textView.easy.layout(
            Left(10).to(leftStackView).with(.medium),
            Left(>=10).with(.required),
            Right(10),
            Top(200))
        
        expandButton.addTarget(self, action: #selector(expand), for: .touchUpInside)
    }
    
    @objc func expand() {
        guard !isExtended else {
            return
        }
        isExtended.toggle()
        
        leftStackView.easy.layout(Left(-100))
        
        UIView.animate(withDuration: 1, animations: {
            self.view.layoutIfNeeded()
        }, completion: { [unowned self] _ in
            self.leftStackView.arrangedSubviews.forEach { $0.removeFromSuperview() }
            self.actionButtons.forEach { self.leftStackView.addArrangedSubview($0 )}
            self.leftStackView.easy.layout(Width(self.stackViewExtendedWidth))
            self.view.layoutIfNeeded()
            
            self.leftStackView.easy.layout(Left(10))
            
            UIView.animate(withDuration: 1) {
                self.view.layoutIfNeeded()
            }
            
        })
    }
    
    func collapse() {
        guard isExtended else {
            return
        }
        isExtended.toggle()
        
        leftStackView.easy.layout(Left(-100))
        
        UIView.animate(withDuration: 1, animations: {
            self.view.layoutIfNeeded()
        }, completion: { [unowned self] _ in
            
            self.leftStackView.arrangedSubviews.forEach { $0.removeFromSuperview() }
            self.leftStackView.addArrangedSubview(self.expandButton)
            self.leftStackView.easy.layout(Width(self.stackViewCollapsedWidth))
            self.view.layoutIfNeeded()
            
            self.leftStackView.easy.layout(Left(10))
            
            UIView.animate(withDuration: 1) {
                self.view.layoutIfNeeded()
            }
        })
    }
    
    
    private func createButton(_ color: UIColor) -> UIButton {
        let button = UIButton(frame: CGRect(x: 0, y: 0, width: 24, height: 24))
        button.backgroundColor = color
        return button
    }
    
}

// MARK: - UITextViewDelegate

extension ViewController: UITextViewDelegate {
    func textViewDidChange(_ textView: UITextView) {
        collapse()
    }
}