Watch: activity line on working cards, All threads browsing, a thread's subagents, Load earlier, and markdown messages

watch/WristCode/Views/Markdown.swift

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+// Message text as styled text. Inline markdown (bold, italics, inline code, links) goes through
+// `AttributedString(markdown:)`. Block syntax is rewritten line by line first, since SwiftUI's Text
+// runs full-parsed paragraphs together: headings turn bold, list markers turn into bullets, quote
+// markers go, and fenced code keeps its lines in monospace.
+
+import Foundation
+
+enum Markdown {
+    static func render(_ source: String) -> AttributedString {
+        var result = AttributedString()
+        var fenced = false
+        var first = true
+        for line in source.split(separator: "\n", omittingEmptySubsequences: false).map(String.init) {
+            if line.trimmingCharacters(in: .whitespaces).hasPrefix("```") {
+                fenced.toggle()
+                continue
+            }
+            if !first { result += AttributedString("\n") }
+            first = false
+            if fenced {
+                var code = AttributedString(line)
+                code.inlinePresentationIntent = .code
+                result += code
+            } else {
+                result += inline(block(line))
+            }
+        }
+        return result
+    }
+
+    /// One line with its block syntax rewritten as inline markdown or plain text.
+    static func block(_ line: String) -> String {
+        if let heading = line.wholeMatch(of: /\s{0,3}#{1,6}\s+(.+?)[\s#]*/) {
+            return "**\(heading.1)**"
+        }
+        if let item = line.wholeMatch(of: /(\s*)[-*+]\s+(.*)/) {
+            return "\(item.1)• \(item.2)"
+        }
+        if let quote = line.wholeMatch(of: /\s{0,3}>\s?(.*)/) {
+            return String(quote.1)
+        }
+        return line
+    }
+
+    /// Inline markdown, or the line as plain text when it does not parse.
+    private static func inline(_ line: String) -> AttributedString {
+        let options = AttributedString.MarkdownParsingOptions(interpretedSyntax: .inlineOnlyPreservingWhitespace)
+        return (try? AttributedString(markdown: line, options: options)) ?? AttributedString(line)
+    }
+}