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MarkdownAttributedStringParser.swift
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MarkdownAttributedStringParser.swift
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import UIKit
import Markdown
import Foundation
import Highlighter
actor ResponseParsingTask {
func parse(text: String) async -> AttributedOutput {
let document = Document(parsing: text)
var markdownParser = MarkdownAttributedStringParser()
let results = markdownParser.parserResults(from: document)
return AttributedOutput(string: text, results: results)
}
}
struct ParserResult: Identifiable {
let id = UUID()
let attributedString: AttributedString
let isCodeBlock: Bool
let codeBlockLanguage: String?
}
public struct MarkdownAttributedStringParser: MarkupVisitor {
let baseFontSize: CGFloat = UIFont.preferredFont(forTextStyle: .body).pointSize
let highlighter: Highlighter = {
let highlighter = Highlighter()!
highlighter.setTheme("stackoverflow-dark")
return highlighter
}()
let newLineFontSize: CGFloat = 12
public init() {}
public mutating func attributedString(from document: Document) -> NSAttributedString {
return visit(document)
}
mutating func parserResults(from document: Document) -> [ParserResult] {
var results = [ParserResult]()
var currentAttrString = NSMutableAttributedString()
func appendCurrentAttrString() {
if !currentAttrString.string.isEmpty {
let currentAttrStringToAppend = (try? AttributedString(currentAttrString, including: \.uiKit)) ?? AttributedString(stringLiteral: currentAttrString.string)
results.append(.init(attributedString: currentAttrStringToAppend, isCodeBlock: false, codeBlockLanguage: nil))
}
}
document.children.forEach { markup in
let attrString = visit(markup)
if let codeBlock = markup as? CodeBlock {
appendCurrentAttrString()
let attrStringToAppend = (try? AttributedString(attrString, including: \.uiKit)) ?? AttributedString(stringLiteral: attrString.string)
let possible = [
"Java", "Python", "JavaScript", "C#", "C++", "Ruby", "Swift", "Go", "TypeScript", "Kotlin",
"PHP", "R", "Objective-C", "Shell", "Scala", "Rust", "Haskell", "Perl", "Lua", "HTML",
"CSS", "Dart", "Groovy", "Matlab", "F#", "COBOL", "Fortran", "Ada", "Lisp", "Prolog",
"SQL", "Assembly", "VB.NET", "PL/SQL", "Julia", "Scheme", "Erlang", "D", "Clojure", "Apex",
"PowerShell", "Tcl", "ABAP", "VBScript", "CoffeeScript", "Racket", "COOL", "Ocaml",
"Elixir", "Dylan", "MUMPS", "RPG", "Ada", "Chapel", "Alice", "Smalltalk", "Verilog",
"VHDL", "HCL", "COOL", "J", "ATS", "Factor", "Fantom", "Io", "JScript", "Mirah", "Nemerle",
"Pike", "Rebol", "Red", "Ring", "SuperCollider", "Turing", "Unicon", "XPath", "XQuery",
"Zsh", "Objective-J", "Nim", "Nit", "PureScript", "Jasmin", "LIL", "Fantom", "ATS", "AspectJ",
"DTrace", "Eiffel", "Elm", "Gosu", "Idris", "KRL", "MQL4", "Opa", "PL/I", "RPL", "X10"
]
let str = codeBlock.language
var mostSimilarLanguage = ""
if let lang = str {
var maxSimilarity = -1.0
for language in possible {
let similarity = calculateCosineSimilarity(lang, language)
if similarity > maxSimilarity {
maxSimilarity = similarity
mostSimilarLanguage = language
}
}
}
results.append(.init(attributedString: attrStringToAppend, isCodeBlock: true, codeBlockLanguage: mostSimilarLanguage.isEmpty ? str : mostSimilarLanguage))
currentAttrString = NSMutableAttributedString()
} else {
currentAttrString.append(attrString)
}
}
appendCurrentAttrString()
return results
}
mutating public func defaultVisit(_ markup: Markup) -> NSAttributedString {
let result = NSMutableAttributedString()
for child in markup.children {
result.append(visit(child))
}
return result
}
mutating public func visitText(_ text: Text) -> NSAttributedString {
return NSAttributedString(string: text.plainText, attributes: [.font: UIFont.systemFont(ofSize: baseFontSize, weight: .regular)])
}
mutating public func visitEmphasis(_ emphasis: Emphasis) -> NSAttributedString {
let result = NSMutableAttributedString()
for child in emphasis.children {
result.append(visit(child))
}
result.applyEmphasis()
return result
}
mutating public func visitStrong(_ strong: Strong) -> NSAttributedString {
let result = NSMutableAttributedString()
for child in strong.children {
result.append(visit(child))
}
result.applyStrong()
return result
}
mutating public func visitParagraph(_ paragraph: Paragraph) -> NSAttributedString {
let result = NSMutableAttributedString()
for child in paragraph.children {
result.append(visit(child))
}
if paragraph.hasSuccessor {
result.append(paragraph.isContainedInList ? .singleNewline(withFontSize: newLineFontSize) : .doubleNewline(withFontSize: newLineFontSize))
}
return result
}
mutating public func visitHeading(_ heading: Heading) -> NSAttributedString {
let result = NSMutableAttributedString()
for child in heading.children {
result.append(visit(child))
}
result.applyHeading(withLevel: heading.level)
if heading.hasSuccessor {
result.append(.doubleNewline(withFontSize: newLineFontSize))
}
return result
}
mutating public func visitLink(_ link: Link) -> NSAttributedString {
let result = NSMutableAttributedString()
for child in link.children {
result.append(visit(child))
}
let url = link.destination != nil ? URL(string: link.destination!) : nil
result.applyLink(withURL: url)
return result
}
mutating public func visitInlineCode(_ inlineCode: InlineCode) -> NSAttributedString {
return NSAttributedString(string: inlineCode.code, attributes: [.font: UIFont.monospacedSystemFont(ofSize: baseFontSize - 1.0, weight: .regular), .foregroundColor: UIColor.systemPink])
}
public func visitCodeBlock(_ codeBlock: CodeBlock) -> NSAttributedString {
let result = NSMutableAttributedString(attributedString: highlighter.highlight(codeBlock.code, as: codeBlock.language) ?? NSAttributedString(string: codeBlock.code))
if codeBlock.hasSuccessor {
result.append(.singleNewline(withFontSize: newLineFontSize))
}
return result
}
mutating public func visitStrikethrough(_ strikethrough: Strikethrough) -> NSAttributedString {
let result = NSMutableAttributedString()
for child in strikethrough.children {
result.append(visit(child))
}
result.applyStrikethrough()
return result
}
mutating public func visitUnorderedList(_ unorderedList: UnorderedList) -> NSAttributedString {
let result = NSMutableAttributedString()
let font = UIFont.systemFont(ofSize: baseFontSize, weight: .regular)
for listItem in unorderedList.listItems {
var listItemAttributes: [NSAttributedString.Key: Any] = [:]
let listItemParagraphStyle = NSMutableParagraphStyle()
let baseLeftMargin: CGFloat = 15.0
let leftMarginOffset = baseLeftMargin + (20.0 * CGFloat(unorderedList.listDepth))
let spacingFromIndex: CGFloat = 8.0
let bulletWidth = ceil(NSAttributedString(string: "•", attributes: [.font: font]).size().width)
let firstTabLocation = leftMarginOffset + bulletWidth
let secondTabLocation = firstTabLocation + spacingFromIndex
listItemParagraphStyle.tabStops = [
NSTextTab(textAlignment: .right, location: firstTabLocation),
NSTextTab(textAlignment: .left, location: secondTabLocation)
]
listItemParagraphStyle.headIndent = secondTabLocation
listItemAttributes[.paragraphStyle] = listItemParagraphStyle
listItemAttributes[.font] = UIFont.systemFont(ofSize: baseFontSize, weight: .regular)
listItemAttributes[.listDepth] = unorderedList.listDepth
let listItemAttributedString = visit(listItem).mutableCopy() as! NSMutableAttributedString
listItemAttributedString.insert(NSAttributedString(string: "\t•\t", attributes: listItemAttributes), at: 0)
result.append(listItemAttributedString)
}
if unorderedList.hasSuccessor {
result.append(.doubleNewline(withFontSize: newLineFontSize))
}
return result
}
mutating public func visitListItem(_ listItem: ListItem) -> NSAttributedString {
let result = NSMutableAttributedString()
for child in listItem.children {
result.append(visit(child))
}
if listItem.hasSuccessor {
result.append(.singleNewline(withFontSize: newLineFontSize))
}
return result
}
mutating public func visitOrderedList(_ orderedList: OrderedList) -> NSAttributedString {
let result = NSMutableAttributedString()
for (index, listItem) in orderedList.listItems.enumerated() {
var listItemAttributes: [NSAttributedString.Key: Any] = [:]
let font = UIFont.systemFont(ofSize: baseFontSize, weight: .regular)
let numeralFont = UIFont.monospacedDigitSystemFont(ofSize: baseFontSize, weight: .regular)
let listItemParagraphStyle = NSMutableParagraphStyle()
let baseLeftMargin: CGFloat = 15.0
let leftMarginOffset = baseLeftMargin + (20.0 * CGFloat(orderedList.listDepth))
let highestNumberInList = orderedList.childCount
let numeralColumnWidth = ceil(NSAttributedString(string: "\(highestNumberInList).", attributes: [.font: numeralFont]).size().width)
let spacingFromIndex: CGFloat = 8.0
let firstTabLocation = leftMarginOffset + numeralColumnWidth
let secondTabLocation = firstTabLocation + spacingFromIndex
listItemParagraphStyle.tabStops = [
NSTextTab(textAlignment: .right, location: firstTabLocation),
NSTextTab(textAlignment: .left, location: secondTabLocation)
]
listItemParagraphStyle.headIndent = secondTabLocation
listItemAttributes[.paragraphStyle] = listItemParagraphStyle
listItemAttributes[.font] = font
listItemAttributes[.listDepth] = orderedList.listDepth
let listItemAttributedString = visit(listItem).mutableCopy() as! NSMutableAttributedString
var numberAttributes = listItemAttributes
numberAttributes[.font] = numeralFont
let numberAttributedString = NSAttributedString(string: "\t\(index + 1).\t", attributes: numberAttributes)
listItemAttributedString.insert(numberAttributedString, at: 0)
result.append(listItemAttributedString)
}
if orderedList.hasSuccessor {
result.append(orderedList.isContainedInList ? .singleNewline(withFontSize: newLineFontSize) : .doubleNewline(withFontSize: newLineFontSize))
}
return result
}
mutating public func visitBlockQuote(_ blockQuote: BlockQuote) -> NSAttributedString {
let result = NSMutableAttributedString()
for child in blockQuote.children {
var quoteAttributes: [NSAttributedString.Key: Any] = [:]
let quoteParagraphStyle = NSMutableParagraphStyle()
let baseLeftMargin: CGFloat = 15.0
let leftMarginOffset = baseLeftMargin + (20.0 * CGFloat(blockQuote.quoteDepth))
quoteParagraphStyle.tabStops = [NSTextTab(textAlignment: .left, location: leftMarginOffset)]
quoteParagraphStyle.headIndent = leftMarginOffset
quoteAttributes[.paragraphStyle] = quoteParagraphStyle
quoteAttributes[.font] = UIFont.systemFont(ofSize: baseFontSize, weight: .regular)
quoteAttributes[.listDepth] = blockQuote.quoteDepth
let quoteAttributedString = visit(child).mutableCopy() as! NSMutableAttributedString
quoteAttributedString.insert(NSAttributedString(string: "\t", attributes: quoteAttributes), at: 0)
quoteAttributedString.addAttribute(.foregroundColor, value: UIColor.systemGray)
result.append(quoteAttributedString)
}
if blockQuote.hasSuccessor {
result.append(.doubleNewline(withFontSize: newLineFontSize))
}
return result
}
}
extension NSMutableAttributedString {
func applyEmphasis() {
enumerateAttribute(.font, in: NSRange(location: 0, length: length), options: []) { value, range, stop in
guard let font = value as? UIFont else { return }
let newFont = font.apply(newTraits: .traitItalic)
addAttribute(.font, value: newFont, range: range)
}
}
func applyStrong() {
enumerateAttribute(.font, in: NSRange(location: 0, length: length), options: []) { value, range, stop in
guard let font = value as? UIFont else { return }
let newFont = font.apply(newTraits: .traitBold)
addAttribute(.font, value: newFont, range: range)
}
}
func applyLink(withURL url: URL?) {
addAttribute(.foregroundColor, value: UIColor.systemBlue)
if let url = url {
addAttribute(.link, value: url)
}
}
func applyBlockquote() {
addAttribute(.foregroundColor, value: UIColor.systemGray)
}
func applyHeading(withLevel headingLevel: Int) {
enumerateAttribute(.font, in: NSRange(location: 0, length: length), options: []) { value, range, stop in
guard let font = value as? UIFont else { return }
let newFont = font.apply(newTraits: .traitBold, newPointSize: 28.0 - CGFloat(headingLevel * 2))
addAttribute(.font, value: newFont, range: range)
}
}
func applyStrikethrough() {
addAttribute(.strikethroughStyle, value: NSUnderlineStyle.single.rawValue)
}
}
extension UIFont {
func apply(newTraits: UIFontDescriptor.SymbolicTraits, newPointSize: CGFloat? = nil) -> UIFont {
var existingTraits = fontDescriptor.symbolicTraits
existingTraits.insert(newTraits)
guard let newFontDescriptor = fontDescriptor.withSymbolicTraits(existingTraits) else { return self }
return UIFont(descriptor: newFontDescriptor, size: newPointSize ?? pointSize)
}
}
extension ListItemContainer {
var listDepth: Int {
var index = 0
var currentElement = parent
while currentElement != nil {
if currentElement is ListItemContainer {
index += 1
}
currentElement = currentElement?.parent
}
return index
}
}
extension BlockQuote {
var quoteDepth: Int {
var index = 0
var currentElement = parent
while currentElement != nil {
if currentElement is BlockQuote {
index += 1
}
currentElement = currentElement?.parent
}
return index
}
}
extension NSAttributedString.Key {
static let listDepth = NSAttributedString.Key("ListDepth")
static let quoteDepth = NSAttributedString.Key("QuoteDepth")
}
extension NSMutableAttributedString {
func addAttribute(_ name: NSAttributedString.Key, value: Any) {
addAttribute(name, value: value, range: NSRange(location: 0, length: length))
}
func addAttributes(_ attrs: [NSAttributedString.Key : Any]) {
addAttributes(attrs, range: NSRange(location: 0, length: length))
}
}
extension Markup {
var hasSuccessor: Bool {
guard let childCount = parent?.childCount else { return false }
return indexInParent < childCount - 1
}
var isContainedInList: Bool {
var currentElement = parent
while currentElement != nil {
if currentElement is ListItemContainer {
return true
}
currentElement = currentElement?.parent
}
return false
}
}
extension NSAttributedString {
static func singleNewline(withFontSize fontSize: CGFloat) -> NSAttributedString {
return NSAttributedString(string: "\n", attributes: [.font: UIFont.systemFont(ofSize: fontSize, weight: .regular)])
}
static func doubleNewline(withFontSize fontSize: CGFloat) -> NSAttributedString {
return NSAttributedString(string: "\n\n", attributes: [.font: UIFont.systemFont(ofSize: fontSize, weight: .regular)])
}
}