AttributeMarkdownString.swift

public func attributeMarkdownString(_ string: String, defaultAttributes: [NSAttributedString.Key: Any]) -> NSAttributedString {
	let result = NSMutableAttributedString(string: string, attributes: defaultAttributes)

	let linkExpression = try! NSRegularExpression(pattern: "\\[([^]]+)\\]\\(([^)]+)\\)")
	while let linkMatch = linkExpression.firstMatch(in: result.string, range: NSRange(location: 0, length: result.length)) {
		let linkString = NSMutableAttributedString(attributedString: result.attributedSubstring(from: linkMatch.range(at: 1)))
		linkString.addAttributes([
			.foregroundColor: Appearance.colors.link,
			.link: result.attributedSubstring(from: linkMatch.range(at: 2)).string,
			], range: NSRange(location: 0, length: linkString.length))
		result.replaceCharacters(in: linkMatch.range, with: linkString)
	}

	if let regularFont = defaultAttributes[.font] as? NSFont {
		let boldFont = Appearance.fonts.of(regularFont.pointSize, weight: .bold)
		let boldExpression = try! NSRegularExpression(pattern: "\\*\\*([^*]+)\\*\\*")
		while let boldMatch = boldExpression.firstMatch(in: result.string, range: NSRange(location: 0, length: result.length)) {
			let boldString = NSMutableAttributedString(attributedString: result.attributedSubstring(from: boldMatch.range(at: 1)))
			boldString.addAttributes([
				.font: boldFont
				], range: NSRange(location: 0, length: boldString.length))
			result.replaceCharacters(in: boldMatch.range, with: boldString)
		}

		let mediumFont = Appearance.fonts.of(regularFont.pointSize, weight: .medium)
		let mediumExpression = try! NSRegularExpression(pattern: "\\*([^*]+)\\*")
		while let mediumMatch = mediumExpression.firstMatch(in: result.string, range: NSRange(location: 0, length: result.length)) {
			let mediumString = NSMutableAttributedString(attributedString: result.attributedSubstring(from: mediumMatch.range(at: 1)))
			mediumString.addAttributes([
				.font: mediumFont
				], range: NSRange(location: 0, length: mediumString.length))
			result.replaceCharacters(in: mediumMatch.range, with: mediumString)
		}
	}

	return result
}