feat: export notes as portable Markdown

Sources/Conjure/NotesController.swift

@@ -1,6 +1,7 @@
 import AppKit
 import ConjureKit
 import Highlighter
+import UniformTypeIdentifiers
 
 @MainActor
 enum NotesAppearance {
@@ -77,6 +78,8 @@ final class NotesController: NSViewController, NSTextViewDelegate {
         actions.newNote = { [weak self] in self?.newNote() }
         actions.browseNotes = { [weak self] in self?.browseNotes() }
         actions.deleteNote = { [weak self] in self?.deleteNote() }
+        actions.copyNoteMarkdown = { [weak self] in self?.copyAsMarkdown() }
+        actions.exportNoteMarkdown = { [weak self] in self?.exportAsMarkdown() }
         let tools = [
             ("textformat.size", "Heading"), ("bold", "Bold"), ("italic", "Italic"),
             ("strikethrough", "Strikethrough"), ("chevron.left.forwardslash.chevron.right", "Inline code"),
@@ -534,6 +537,51 @@ final class NotesController: NSViewController, NSTextViewDelegate {
         catch { showError(error) }
     }
 
+    private func copyAsMarkdown() {
+        actions.close(animated: false)
+        do {
+            let export = try NoteMarkdownExport(contents: editor.markdownContents)
+            let clipboard = NSPasteboard.general
+            clipboard.clearContents()
+            guard clipboard.setString(export.clipboardText, forType: .string) else {
+                throw CocoaError(.fileWriteUnknown)
+            }
+        } catch { showExportError(error) }
+    }
+
+    private func exportAsMarkdown() {
+        guard let window = view.window, window.attachedSheet == nil else { return }
+        actions.close(animated: false)
+        do {
+            let export = try NoteMarkdownExport(contents: editor.markdownContents)
+            let panel = NSSavePanel()
+            panel.title = "Export as Markdown"
+            panel.prompt = "Export"
+            panel.canCreateDirectories = true
+            panel.nameFieldStringValue = export.hasImages ? "Note" : "Note.md"
+            if export.hasImages {
+                panel.message = "Create a new folder containing note.md and its images. Choose a folder name that does not already exist."
+            } else {
+                panel.allowedContentTypes = [UTType(filenameExtension: "md") ?? .plainText]
+            }
+            panel.beginSheetModal(for: window) { [weak self] response in
+                guard let self else { return }
+                defer { self.focusEditor() }
+                guard response == .OK, let url = panel.url else { return }
+                do { try export.write(to: url) }
+                catch { self.showExportError(error) }
+            }
+        } catch { showExportError(error) }
+    }
+
+    private func showExportError(_ error: Error) {
+        status.isHidden = false
+        status.stringValue = "Couldn’t export note: \(error.localizedDescription)"
+        status.toolTip = status.stringValue
+        status.textColor = .systemRed
+    }
+
+
     private func deleteNote() {
         guard let window = view.window, window.attachedSheet == nil, let id = selectedID else { return }
         actions.close(animated: false)