AdaptiveLabel.swift

//
//  AdaptiveLabel.swift
//  Coop
//
//  Created by Jonah Burke on 1/17/19.
//  Copyright © 2019 Jonah Burke. All rights reserved.
//

import UIKit

class AdaptiveLabel: UIView, UIContentSizeCategoryAdjusting {

    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }

    private func commonInit() {
        isAccessibilityElement = true
        accessibilityTraits = .staticText

        label.adjustsFontForContentSizeCategory = false
        label.translatesAutoresizingMaskIntoConstraints = false
        addSubview(label)
        label.align(to: self)

        update()
    }

    var adjustsFontForContentSizeCategory: Bool = true
    private let label = UILabel()

    var textOptions: [String] = ["Label"] {
        didSet {
            update()
        }
    }

    var textStyle: UIFont.TextStyle = UIFont.TextStyle.body {
        didSet {
            update()
        }
    }

    var textAlignment: NSTextAlignment {
        get {
            return label.textAlignment
        }
        set {
            label.textAlignment = newValue
        }
    }

    var textColor: UIColor {
        get {
            return label.textColor
        }
        set {
            label.textColor = newValue
        }
    }

    private var font: UIFont {
        return UIFont.preferredFont(forTextStyle: textStyle)
    }

    override var intrinsicContentSize: CGSize {
        return label.intrinsicContentSize
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        update()
    }

    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
        super.traitCollectionDidChange(previousTraitCollection)

        if adjustsFontForContentSizeCategory && traitCollection.preferredContentSizeCategory != previousTraitCollection?.preferredContentSizeCategory {
            update()
        }
    }

    private func update() {
        label.font = font
        let attributes = [NSAttributedString.Key.font: font]

        let text = textOptions.first {
            NSString(string: $0).size(withAttributes: attributes).width < label.bounds.width
        }

        label.text = text ?? textOptions.last
        accessibilityLabel = text
    }
}