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HTMLString.swift
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231 lines (190 loc) · 8.03 KB
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import Foundation
// MARK: Escaping
extension String {
///
/// Returns a copy of the current `String` where every character incompatible with HTML Unicode
/// encoding (UTF-16 or UTF-8) is replaced by a decimal HTML entity.
///
/// ### Examples
///
/// | String | Result | Format |
/// |--------|--------|--------|
/// | `&` | `&` | Decimal entity (part of the Unicode special characters) |
/// | `Σ` | `Σ` | Not escaped (Unicode compliant) |
/// | `🇺🇸` | `🇺🇸` | Not escaped (Unicode compliant) |
/// | `a` | `a` | Not escaped (alphanumerical) |
///
public var addingUnicodeEntities: String {
return self.addUnicodeEntities()
}
///
/// Replaces every character incompatible with HTML Unicode encoding (UTF-16 or UTF-8) by a decimal HTML entity.
///
/// ### Examples
///
/// | String | Result | Format |
/// |--------|--------|--------|
/// | `&` | `&` | Decimal entity (part of the Unicode special characters) |
/// | `Σ` | `Σ` | Not escaped (Unicode compliant) |
/// | `🇺🇸` | `🇺🇸` | Not escaped (Unicode compliant) |
/// | `a` | `a` | Not escaped (alphanumerical) |
///
public func addUnicodeEntities() -> String {
let requiredEscapes: Set<Character> = ["!", "\"", "$", "%", "&", "'", "+", ",", "<", "=", ">", "@", "[", "]", "`", "{", "}"]
var result = ""
for character in self {
if requiredEscapes.contains(character) {
// One of the required escapes for security reasons
result.append(contentsOf: "&#\(character.asciiValue!);")
} else {
// Not a required escape, no need to replace the character
result.append(character)
}
}
return result
}
///
/// Returns a copy of the current `String` where every character incompatible with HTML ASCII
/// encoding is replaced by a decimal HTML entity.
///
/// ### Examples
///
/// | String | Result | Format |
/// |--------|--------|--------|
/// | `&` | `&` | Decimal entity |
/// | `Σ` | `Σ` | Decimal entity |
/// | `🇺🇸` | `🇺🇸` | Combined decimal entities (extented grapheme cluster) |
/// | `a` | `a` | Not escaped (alphanumerical) |
///
/// ### Performance
///
/// If your webpage is unicode encoded (UTF-16 or UTF-8) use `addingUnicodeEntities` instead,
/// as it is faster and produces a less bloated and more readable HTML.
///
public var addingASCIIEntities: String {
return self.addASCIIEntities()
}
///
/// Replaces every character incompatible with HTML Unicode (UTF-16 or UTF-8) with a decimal HTML entity.
///
/// ### Examples
///
/// | String | Result | Format |
/// |--------|--------|--------|
/// | `&` | `&` | Decimal entity (part of the Unicode special characters) |
/// | `Σ` | `Σ` | Not escaped (Unicode compliant) |
/// | `🇺🇸` | `🇺🇸` | Not escaped (Unicode compliant) |
/// | `a` | `a` | Not escaped (alphanumerical) |
///
public func addASCIIEntities() -> String {
let requiredEscapes: Set<Character> = ["!", "\"", "$", "%", "&", "'", "+", ",", "<", "=", ">", "@", "[", "]", "`", "{", "}"]
var result = ""
for character in self {
if let asciiiValue = character.asciiValue {
if requiredEscapes.contains(character) {
// One of the required escapes for security reasons
result.append(contentsOf: "&#\(asciiiValue);")
} else {
// Not a required escape, no need to replace the character
result.append(character)
}
} else {
// Not an ASCII Character, we need to escape.
let escape = character.unicodeScalars.reduce(into: "") { $0 += "&#\($1.value);" }
result.append(contentsOf: escape)
}
}
return result
}
}
// MARK: - Unescaping
extension String {
///
/// Replaces every HTML entity in the receiver with the matching Unicode character.
///
/// ### Examples
///
/// | String | Result | Format |
/// |--------|--------|--------|
/// | `&` | `&` | Keyword entity |
/// | `Σ` | `Σ` | Decimal entity |
/// | `č` | `č` | Hexadecimal entity |
/// | `🇺🇸` | `🇺🇸` | Combined decimal entities (extented grapheme cluster) |
/// | `a` | `a` | Not an entity |
/// | `&` | `&` | Not an entity |
///
public func removeHTMLEntities() -> String {
var result = ""
var currentIndex = startIndex
while let delimiterIndex = self[currentIndex...].firstIndex(of: "&") {
// Avoid unnecessary operations
var semicolonIndex = self.index(after: delimiterIndex)
// Parse the last sequence (ex: Fish & chips & sauce -> "&" instead of "& chips &")
var lastDelimiterIndex = delimiterIndex
while semicolonIndex != endIndex, self[semicolonIndex] != ";" {
if self[semicolonIndex] == "&" {
lastDelimiterIndex = semicolonIndex
}
semicolonIndex = self.index(after: semicolonIndex)
}
// Fast path if semicolon doesn't exists in current range
if semicolonIndex == endIndex {
result.append(contentsOf: self[currentIndex..<semicolonIndex])
return result
}
let escapableRange = index(after: lastDelimiterIndex) ..< semicolonIndex
let escapableContent = self[escapableRange]
result.append(contentsOf: self[currentIndex..<lastDelimiterIndex])
let cursorPosition: Index
if let unescapedNumber = escapableContent.unescapeAsNumber() {
result.append(contentsOf: unescapedNumber)
cursorPosition = self.index(semicolonIndex, offsetBy: 1)
} else if let unescapedCharacter = HTMLStringMappings.shared.unescapingTable[String(escapableContent)] {
result.append(contentsOf: unescapedCharacter)
cursorPosition = self.index(semicolonIndex, offsetBy: 1)
} else {
result.append(self[lastDelimiterIndex])
cursorPosition = self.index(after: lastDelimiterIndex)
}
currentIndex = cursorPosition
}
result.append(contentsOf: self[currentIndex...])
return result
}
///
/// Returns a copy of the current `String` where every HTML entity is replaced with the matching
/// Unicode character.
///
/// ### Examples
///
/// | String | Result | Format |
/// |--------|--------|--------|
/// | `&` | `&` | Keyword entity |
/// | `Σ` | `Σ` | Decimal entity |
/// | `č` | `č` | Hexadecimal entity |
/// | `🇺🇸` | `🇺🇸` | Combined decimal entities (extented grapheme cluster) |
/// | `a` | `a` | Not an entity |
/// | `&` | `&` | Not an entity |
///
public var removingHTMLEntities: String {
return removeHTMLEntities()
}
}
// MARK: - Helpers
extension StringProtocol {
/// Unescapes the receives as a number if possible.
fileprivate func unescapeAsNumber() -> String? {
guard hasPrefix("#") else { return nil }
let unescapableContent = self.dropFirst()
let isHexadecimal = unescapableContent.hasPrefix("x") || hasPrefix("X")
let radix = isHexadecimal ? 16 : 10
guard let numberStartIndex = unescapableContent.index(unescapableContent.startIndex, offsetBy: isHexadecimal ? 1 : 0, limitedBy: unescapableContent.endIndex) else {
return nil
}
let numberString = unescapableContent[numberStartIndex ..< endIndex]
guard let codePoint = UInt32(numberString, radix: radix), let scalar = UnicodeScalar(codePoint) else {
return nil
}
return String(scalar)
}
}