import UIKit

class LabelTappable: UILabel {

    let layoutManager = NSLayoutManager()
    let textContainer = NSTextContainer(size: CGSize.zero)
    let tapGesture = UITapGestureRecognizer()

    var textStorage = NSTextStorage() {
        didSet {
            textStorage.addLayoutManager(layoutManager)
        }
    }

    var didTap: ((_ label: UILabel, _ characterIndex: Int) -> Void)?

    override var attributedText: NSAttributedString? {
        didSet {
            if let attributedText = attributedText {
                textStorage = NSTextStorage(attributedString: attributedText)
            } else {
                textStorage = NSTextStorage()
            }
        }
    }
    override var lineBreakMode: NSLineBreakMode {
        didSet {
            textContainer.lineBreakMode = lineBreakMode
        }
    }

    override var numberOfLines: Int {
        didSet {
            textContainer.maximumNumberOfLines = numberOfLines
        }
    }

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

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

    func setUp() {
        isUserInteractionEnabled = true
        layoutManager.addTextContainer(textContainer)
        textContainer.lineFragmentPadding = 0
        textContainer.lineBreakMode = lineBreakMode
        textContainer.maximumNumberOfLines = numberOfLines
        tapGesture.addTarget(self, action: #selector(LabelTappable.labelTapped(_:)))
        addGestureRecognizer(tapGesture)
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        textContainer.size = bounds.size
    }

    @objc func labelTapped(_ gesture: UITapGestureRecognizer) {
        guard gesture.state == .ended else {
            return
        }
        let locationOfTouch = gesture.location(in: gesture.view)
        let textBoundingBox = layoutManager.usedRect(for: textContainer)
        let textContainerOffset = CGPoint(
            x: (bounds.width - textBoundingBox.width) / 2 - textBoundingBox.minX,
            y: (bounds.height - textBoundingBox.height) / 2 - textBoundingBox.minY
        )
        let locationOfTouchInTextContainer = CGPoint(
            x: locationOfTouch.x - textContainerOffset.x,
            y: locationOfTouch.y - textContainerOffset.y
        )
        let characterIndex = layoutManager.characterIndex(for: locationOfTouchInTextContainer,
                                                            in: textContainer,  fractionOfDistanceBetweenInsertionPoints: nil)

        /* HOW TO USE */
        /*
        es for links
        self.didTap = { [weak self] label, characterIndex in
            guard let _ = self else {
            return
            }

            if let url = label.attributedText?.attribute(.link, at: characterIndex, effectiveRange: nil) as? URL, UIApplication.shared.canOpenURL(url) {
            UIApplication.shared.open(url, options: [:], completionHandler: nil)
            }
        }
         */

        didTap?(self, characterIndex)
    }

}