Parse links in profiles

Changelog-Added: Parse links in profiles

damus/Util/Markdown.swift

@@ -0,0 +1,43 @@
+//
+//  Markdown.swift
+//  damus
+//
+//  Created by Lionello Lunesu on 2022-12-28.
+//
+
+import Foundation
+
+public struct Markdown {
+    private let detector = try! NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue)
+
+    /// Ensure the specified URL has a scheme by prepending "https://" if it's absent.
+    static func withScheme(_ url: any StringProtocol) -> any StringProtocol {
+        return url.contains("://") ? url : "https://" + url
+    }
+
+    public static func parse(content: String) -> AttributedString {
+        // Similar to the parsing in NoteContentView
+        let md_opts: AttributedString.MarkdownParsingOptions =
+            .init(interpretedSyntax: .inlineOnlyPreservingWhitespace)
+
+        if let txt = try? AttributedString(markdown: content, options: md_opts) {
+            return txt
+        } else {
+            return AttributedString(stringLiteral: content)
+        }
+    }
+
+    /// Process the input text and add markdown for any embedded URLs.
+    public func process(_ input: String) -> AttributedString {
+        let matches = detector.matches(in: input, options: [], range: NSRange(location: 0, length: input.utf16.count))
+        var output = input
+        // Start with the last match, because replacing the first would invalidate all subsequent indices
+        for match in matches.reversed() {
+            guard let range = Range(match.range, in: input) else { continue }
+            let url = input[range]
+            output.replaceSubrange(range, with: "[\(url)](\(Markdown.withScheme(url)))")
+        }
+        // TODO: escape unintentional markdown
+        return Markdown.parse(content: output)
+    }
+}