Tiny markdown parser, makes tutorial screens editing much simpler

main/Common Classes/TinyMarkdown.swift

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+import UIKit
+
+struct TinyMarkdown {
+	/// Load markdown file and run through a (very) simple parser (see below).
+	/// - Parameters:
+	///   - filename: Will automatically append `.md` extension
+	///   - replacements: Replace a single occurrence of search string with an attributed replacement.
+	static func load(_ filename: String, replacements: [String : NSMutableAttributedString] = [:]) -> UITextView {
+		let url = Bundle.main.url(forResource: filename, withExtension: "md")!
+		let str = NSMutableAttributedString(withMarkdown: try! String(contentsOf: url))
+		for (key, val) in replacements {
+			guard let r = str.string.range(of: key) else {
+				QLog.Debug("WARN: markdown key '\(key)' does not exist in \(filename)")
+				continue
+			}
+			str.replaceCharacters(in: NSRange(r, in: str.string), with: val)
+		}
+		return QuickUI.text(attributed: str)
+	}
+}
+
+extension NSMutableAttributedString {
+	/// Supports only: `#h1`, `##h2`, `###h3`, `_italic_`, `__bold__`, `___boldItalic___`
+	convenience init(withMarkdown content: String) {
+		self.init()
+		let emph = try! NSRegularExpression(pattern: #"(?<=(^|\W))(_{1,3})(\S|\S.*?\S)\2"#, options: [])
+		beginEditing()
+		content.enumerateLines { (line, _) in
+			if line.starts(with: "#") {
+				var h = 0
+				for char in line {
+					if char == "#" { h += 1 }
+					else { break }
+				}
+				var line = line
+				line.removeFirst(h)
+				line = line.trimmingCharacters(in: CharacterSet(charactersIn: " "))
+				switch h {
+				case 1: self.h1(line + "\n")
+				case 2: self.h2(line + "\n")
+				default: self.h3(line + "\n")
+				}
+			} else {
+				let nsline = line as NSString
+				let range = NSRange(location: 0, length: nsline.length)
+				var i = 0
+				for x in emph.matches(in: line, options: [], range: range) {
+					let r = x.range
+					self.normal(nsline.substring(from: i, to: r.location))
+					i = r.upperBound
+					let before = nsline.substring(with: r)
+					let after = before.trimmingCharacters(in: CharacterSet(charactersIn: "_"))
+					switch (before.count - after.count) / 2 {
+					case 1: self.italic(after)
+					case 2: self.bold(after)
+					default: self.boldItalic(after)
+					}
+				}
+				if i < range.length {
+					self.normal(nsline.substring(from: i, to: range.length) + "\n")
+				} else {
+					self.normal("\n")
+				}
+			}
+		}
+		endEditing()
+	}
+}