Tusker/Tusker/Extensions/AttributedString+Helpers.swift

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//
// AttributedString+Trim.swift
// Tusker
//
// Created by Shadowfacts on 8/29/18.
// Copyright © 2018 Shadowfacts. All rights reserved.
//
import Foundation
private let ASCII_NEWLINE: unichar = 10
private let ASCII_SPACE: unichar = 32
extension NSAttributedString {
var fullRange: NSRange {
return NSRange(location: 0, length: self.length)
}
/// Creates a new string with the whitespace collapsed according to the CSS Text Module Level 3 rules.
/// See https://www.w3.org/TR/css-text-3/#white-space-phase-1
func collapsingWhitespace() -> NSAttributedString {
let mut = NSMutableAttributedString(attributedString: self)
mut.collapseWhitespace()
return mut
}
}
extension NSMutableAttributedString {
func trimLeadingCharactersInSet(_ charSet: CharacterSet) {
var range = (string as NSString).rangeOfCharacter(from: charSet)
while range.length != 0 && range.location == 0 {
replaceCharacters(in: range, with: "")
range = (string as NSString).rangeOfCharacter(from: charSet)
}
}
func trimTrailingCharactersInSet(_ charSet: CharacterSet) {
var range = (string as NSString).rangeOfCharacter(from: charSet, options: .backwards)
while range.length != 0 && range.length + range.location == length {
replaceCharacters(in: range, with: "")
range = (string as NSString).rangeOfCharacter(from: charSet, options: .backwards)
}
}
/// Collapses whitespace in this string according to the CSS Text Module Level 3 rules.
/// See https://www.w3.org/TR/css-text-3/#white-space-phase-1
func collapseWhitespace() {
let str = self.mutableString
var i = 0
while i < str.length {
if str.character(at: i) == ASCII_NEWLINE {
var j: Int
if i > 0 {
// scan backwards to find beginning of space characters preceeding newline
j = i - 1
while j >= 0 {
if str.character(at: j) != ASCII_SPACE {
break
}
j -= 1
}
// add one after loop completes because start of range is _inclusive_
j += 1
} else {
j = 0
}
var k: Int
if i < str.length - 1 {
// scan forwards to find end of space characters following newline
k = i + 1
while k < str.length {
if str.character(at: k) != ASCII_SPACE {
break
}
k += 1
}
// don't need to subtract one before breaking out of loop, because end of range is _exclusive_
} else {
// range end is _exclusive_, so use whole string length that way last character is included
k = str.length
}
// if there's only one character to be replaced, that means we'd be replacing the newline with a newline, so don't bother
if k - j > 1 {
str.replaceCharacters(in: NSRange(location: j, length: k - j), with: "\n")
// continue scanning through the string starting after the newline we just inserted
i = j
}
}
i += 1
}
}
}