UILabel extension to truncate & highlight a keyword in a large sentence, add ellipsis to left & right of label

UILabel+Extensions.swift

extension UILabel {
    
    private var attributes: [NSAttributedString.Key: Any] {
        return [.font: self.font ?? UIFont.systemFont(ofSize: 15)]
    }
    
    private var highlightAttributes: [NSAttributedString.Key: Any] {
        return [.backgroundColor: UIColor.lightGray.withAlphaComponent(0.2), .foregroundColor: UIColor.red]
    }
    
    private var noHighlightAttributes: [NSAttributedString.Key: Any] {
        return [.backgroundColor: UIColor.clear, .foregroundColor: UIColor.black]
    }
    
    func highlight(text: String, color: UIColor = .black) {
        guard let txtLabel = self.text else { return }
        
        let attributeTxt = NSMutableAttributedString(string: txtLabel)
        var searchRange = NSRange(location: 0, length: attributeTxt.mutableString.length)
        
        while searchRange.lowerBound < searchRange.upperBound {
            let range: NSRange = attributeTxt.mutableString.range(of: text, options: .caseInsensitive, range: searchRange)
            if range.length == 0 {
                attributeTxt.addAttributes(noHighlightAttributes, range: searchRange)
                break
            }
            attributeTxt.addAttributes(highlightAttributes, range: range)
            searchRange = NSRange(location: range.upperBound, length: searchRange.upperBound - range.upperBound)
        }
        self.attributedText = attributeTxt
    }
    
    func truncate(_ sentence: String, keyword word: String) {
        if sentence == word {
            self.text = sentence
        }
        
        guard let substringRange = sentence.range(of: word, options: .caseInsensitive) else {
            self.text = sentence
            return
        }
        
        let nsStringSentence = NSString(string: sentence)
        let nsStringSentenceRange = NSRange(location: 0, length: nsStringSentence.length)
        let keywordRange = NSRange(substringRange, in: sentence)
        let size: CGSize = CGSize(width: self.bounds.width, height: CGFloat.greatestFiniteMagnitude)
        let ellipsis = "..."
        var shouldIncludeFrontElipsis: Bool = true
        var shouldIncludeBackElipsis: Bool = true
        var lastTruncatedSentence: NSString = ""
        var previousTruncatedSentence: NSString = ""
        var startIndex: Int = keywordRange.location
        var endIndex: Int = keywordRange.upperBound
        
        while previousTruncatedSentence.boundingRect(with: size, options: .usesLineFragmentOrigin, attributes: attributes, context: nil).size.height <= self.bounds.height {
            lastTruncatedSentence = previousTruncatedSentence
            if startIndex == nsStringSentenceRange.lowerBound && endIndex == nsStringSentenceRange.upperBound {
                break
            } else {
                if startIndex > nsStringSentenceRange.lowerBound {
                    startIndex -= 1
                }
                
                if startIndex == nsStringSentenceRange.lowerBound {
                    shouldIncludeFrontElipsis = false
                }
                
                if endIndex < nsStringSentenceRange.upperBound {
                    endIndex += 1
                }
                
                if endIndex == nsStringSentenceRange.upperBound {
                    shouldIncludeBackElipsis = false
                }
                
                previousTruncatedSentence = NSString(string: nsStringSentence.substring(with: NSRange(location: startIndex, length: endIndex - startIndex)))
                previousTruncatedSentence = (shouldIncludeFrontElipsis ? ellipsis : "") + String(previousTruncatedSentence) + (shouldIncludeBackElipsis ? ellipsis   : "") as NSString
            }
        }
        self.text = lastTruncatedSentence as String
        self.highlight(text: word)
    }
    
}

textLabel.truncate(sentence, keyword: "tigers")