YRHyperlinkLabel.swift

//
//  HyperlinkLabel.swift
//  SLHome
//
//  Created by yongren on 2022/1/6.
//

import Foundation

/// A UILabel subclass that responds to links tap.
public class YRHyperlinkLabel: UILabel {
  
  // MARK: - Private
  
  private var touchedLink: URL?
  
  @objc
  private func handleTouch(_ sender: UIGestureRecognizer) {
    if let link = touchedLink, let linkHandler = linkHandler {
      linkHandler(link, sender)
    } else {
      tapHandler?(sender)
    }
  }
  
  private var alignmentOffset: CGFloat {
    switch textAlignment {
    case .left, .natural, .justified:
      return 0.0
    case .center:
      return 0.5
    case .right:
      return 1.0
    default:
      return 0
    }
  }
  
  private var needsLinkColorUpdate: Bool = true
  
  /// Set the text color for links.
  /// - Important: One can't change the color for a `link`. We need to use another attribute type. In our case, we use `attachment`.
  private func setLinkColor(color: UIColor) -> NSAttributedString? {
    guard let attributedText = attributedText else { return nil }
    let mutableCopy = NSMutableAttributedString(attributedString: attributedText)
    let range = NSRange(location: 0, length: mutableCopy.length)
    mutableCopy.enumerateAttributes(in: range, options: []) { (attributes, range, _) in
      var currentAttributes = mutableCopy.attributes(at: range.location, longestEffectiveRange: nil, in: range)
      if let link = currentAttributes[NSAttributedString.Key.link] as? String, let url = URL(string: link) {
        currentAttributes.removeValue(forKey: .link)
        currentAttributes[.attachment] = url
        currentAttributes[.foregroundColor] = color
        mutableCopy.setAttributes(currentAttributes, range: range)
      } else if currentAttributes[NSAttributedString.Key.attachment] != nil {
        currentAttributes[.foregroundColor] = color
        mutableCopy.setAttributes(currentAttributes, range: range)
      }
    }
    return mutableCopy
  }
  
  // MARK: - API
  
  /// Set the text color for links in the attributedText property
  public var linkColor: UIColor? {
    didSet {
      guard let linkColor = linkColor else { return }
      needsLinkColorUpdate = false
      attributedText = setLinkColor(color: linkColor)
      needsLinkColorUpdate = true
    }
  }
  
  /// Use tapHandler for a unique gesture accross all text. Does not differentiate between links.
  public var tapHandler: ((UIGestureRecognizer) -> Void)?
  
  /// Use linkHandler for opening links in the attributedText property.
  public var linkHandler: ((URL, UIGestureRecognizer) -> Void)?
  
  // MARK: - Init
  
  public override init(frame: CGRect) {
    super.init(frame: frame)
    let rec = UITapGestureRecognizer(target: self, action: #selector(handleTouch(_:)))
    addGestureRecognizer(rec)
    isUserInteractionEnabled = true
  }
  
  required init?(coder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
  
  public override var attributedText: NSAttributedString? {
    didSet {
      guard let linkColor = linkColor, needsLinkColorUpdate else { return }
      let mutableCopy = setLinkColor(color: linkColor)
      if mutableCopy != attributedText {
        attributedText = mutableCopy
      }
    }
  }
  
  public override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
    guard let attributedText = attributedText, super.hitTest(point, with: event) != nil else { return nil }
    
    let size = bounds.size
    
    let textContainer = NSTextContainer(size: size)
    textContainer.lineFragmentPadding = 0.0
    textContainer.lineBreakMode = .byWordWrapping
    textContainer.maximumNumberOfLines = numberOfLines
    
    let layoutManager = NSLayoutManager()
    layoutManager.addTextContainer(textContainer)
    layoutManager.usesFontLeading = false
    
    let textStorage = NSTextStorage(attributedString: attributedText)
    textStorage.addLayoutManager(layoutManager)
    
    let textBoundingBox = layoutManager.usedRect(for: textContainer)
    let xOffset = ((size.width - textBoundingBox.size.width) * alignmentOffset) - textBoundingBox.origin.x
    let yOffset = ((size.height - textBoundingBox.size.height) * alignmentOffset) - textBoundingBox.origin.y
    
    let locationOfTouchInTextContainer = CGPoint(x: point.x - xOffset, y: point.y - yOffset)
    let tappedCharacterIndex: Int = layoutManager.characterIndex(for: locationOfTouchInTextContainer, in: textContainer, fractionOfDistanceBetweenInsertionPoints: nil)
    
    if tappedCharacterIndex < 0 || tappedCharacterIndex >= attributedText.string.count {
      touchedLink = nil
      return nil
    }
    
    let attributesAtTappedIndex = attributedText.attributes(at: tappedCharacterIndex, effectiveRange: nil)
    if let link = attributesAtTappedIndex[NSAttributedString.Key.link] as? URL {
      touchedLink = link
      return self
    } else if let absoluteLink = attributesAtTappedIndex[NSAttributedString.Key.link] as? String, let link = URL(string: absoluteLink) {
      touchedLink = link
      return self
    } else if let link = attributesAtTappedIndex[NSAttributedString.Key.attachment] as? URL {
      touchedLink = link
      return self
    } else if let link = attributesAtTappedIndex[NSAttributedString.Key(rawValue: "href")] as? URL {
      touchedLink = link
      return self
    } else if tapHandler != nil {
      touchedLink = nil
      return self
    } else {
      touchedLink = nil
      return nil
    }
  }
}

Hyperlink Label by [email protected]