import UIKit

class VerticalScrollableStackViewController: UIViewController {

    let scrollView: UIScrollView = UIScrollView(frame: .zero)
    let stackView: UIStackView = UIStackView(frame: .zero)

    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .gray

        self.view.addSubview(self.scrollView)
        self.setupScrollViewConstraints()

        self.setupStackViewElements()
        self.addStackView(to: self.scrollView)
    }


    func setupScrollViewConstraints() {
        self.scrollView.translatesAutoresizingMaskIntoConstraints = false
        self.scrollView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
        self.scrollView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor).isActive = true
        self.scrollView.topAnchor.constraint(equalTo: self.view.topAnchor).isActive = true
        self.scrollView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor).isActive = true
    }


    func setupStackViewElements() {
        self.stackView.axis = .vertical

        let redView = getFullWidthView(height: 100.0, color: .red)
        self.stackView.addArrangedSubview(redView)

        let blueView = getFullWidthView(height: 200.0, color: .blue)
        self.stackView.addArrangedSubview(blueView)

        let yellowView = getFullWidthView(height: 300.0, color: .yellow)
        self.stackView.addArrangedSubview(yellowView)

        let whiteView = getFullWidthView(height: 400.0, color: .white)
        self.stackView.addArrangedSubview(whiteView)

        let orangeView = getFullWidthView(height: 500.0, color: .orange)
        self.stackView.addArrangedSubview(orangeView)
    }


    func addStackView(to view: UIView) {
        view.addSubview(self.stackView)

        self.stackView.translatesAutoresizingMaskIntoConstraints = false
        self.stackView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        self.stackView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        self.stackView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        self.stackView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true

        self.stackView.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
    }


    func getFullWidthView(height: CGFloat, color: UIColor) -> UIView {
        let view = UIView(frame: CGRect(origin: .zero, size: CGSize(width: self.view.frame.width - 5.0, height: height)))
        view.backgroundColor = color
        view.heightAnchor.constraint(equalToConstant: height).isActive = true

        return view
    }

}