Attractor/App/Utilities/StackView.swift

//
//  StackView.swift
//  App
//
//  Created by James Magahern on 9/22/20.
//

import UIKit

class StackView: UIView
{
    var arrangedSubviews: [UIView] = []
        { didSet { setNeedsLayout() } }
    
    var layoutDimension: UIAxis = .vertical
    
    convenience init(dimension: UIAxis) {
        self.init(frame: .zero)
        self.layoutDimension = dimension
    }
    
    // Convenience
    public func addArrangedSubview(_ view: UIView) {
        addSubview(view)
        arrangedSubviews.append(view)
        setNeedsLayout()
    }
    
    public func removeArrangedSubview(_ view: UIView) {
        if view.superview == self {
            view.removeFromSuperview()
        }
        
        arrangedSubviews.removeAll { $0 == view }
        setNeedsLayout()
    }
    
    public func removeAllArrangedSubviews() {
        arrangedSubviews.forEach { $0.removeFromSuperview() }
        arrangedSubviews.removeAll()
        setNeedsLayout()
    }
    
    override func sizeThatFits(_ containerSize: CGSize) -> CGSize {
        var size: CGSize = .zero
        
        if layoutDimension == .horizontal {
            size.height = containerSize.height
        } else {
            size.width = containerSize.width
        }
        
        var spaceRemaining = containerSize
        for view in arrangedSubviews {
            let viewSize = view.sizeThatFits(spaceRemaining)
            if layoutDimension == .horizontal {
                size.width += viewSize.width
                spaceRemaining.width -= viewSize.width
            } else {
                size.height += viewSize.height
                spaceRemaining.height -= viewSize.height
            }
        }
        
        return size
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        
        var origin: CGPoint = CGPoint(x: safeAreaInsets.left, y: safeAreaInsets.top)
        var spaceRemaining = bounds.size
        for view in arrangedSubviews {
            var viewSize = view.sizeThatFits(spaceRemaining)
            
            var offset: CGPoint = .zero
            if layoutDimension == .horizontal {
                offset.x = viewSize.width
                viewSize.height = bounds.height
                spaceRemaining.width -= viewSize.width
            } else {
                offset.y = viewSize.height
                viewSize.width = bounds.width
                spaceRemaining.height -= viewSize.height
            }
            
            view.frame = CGRect(origin: origin, size: viewSize)
            origin.x += offset.x
            origin.y += offset.y
        }
    }
}