Add recent files menu functionality

Implemented comprehensive recent files tracking system:
- Created RecentFilesManager singleton with UserDefaults persistence
- Added Recent Files submenu to File menu with up to 10 recent files
- Automatic file validation that removes deleted files from list
- Smart file tracking that adds files when opened and moves to top
- Clear Recent Files option for user control
- User-friendly display showing filename and relative path
- Error handling for missing files with user notification

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -40,7 +40,7 @@ This repository contains a macOS markdown viewer application built with SwiftUI.
 - [x] Live preview while editing
 - [ ] Search within document
 - [ ] Zoom in/out functionality
-- [ ] Recent files menu
+- [x] Recent files menu
 - [ ] Drag and drop file support
 - [ ] Support for math equations (LaTeX)
 - [ ] Image paste support

MarkdownViewer.xcodeproj/project.pbxproj

@@ -10,6 +10,7 @@
 		1A2345678901234567890001 /* MarkdownViewerApp.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1A2345678901234567890002 /* MarkdownViewerApp.swift */; };
 		1A2345678901234567890003 /* ContentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1A2345678901234567890004 /* ContentView.swift */; };
 		1A2345678901234567890005 /* MarkdownRenderer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1A2345678901234567890006 /* MarkdownRenderer.swift */; };
+		1A2345678901234567890020 /* RecentFilesManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1A2345678901234567890021 /* RecentFilesManager.swift */; };
 		1A2345678901234567890007 /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 1A2345678901234567890008 /* Assets.xcassets */; };
 		1A2345678901234567890009 /* Preview Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 1A234567890123456789000A /* Preview Assets.xcassets */; };
 /* End PBXBuildFile section */
@@ -19,6 +20,7 @@
 		1A2345678901234567890002 /* MarkdownViewerApp.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MarkdownViewerApp.swift; sourceTree = "<group>"; };
 		1A2345678901234567890004 /* ContentView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ContentView.swift; sourceTree = "<group>"; };
 		1A2345678901234567890006 /* MarkdownRenderer.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MarkdownRenderer.swift; sourceTree = "<group>"; };
+		1A2345678901234567890021 /* RecentFilesManager.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RecentFilesManager.swift; sourceTree = "<group>"; };
 		1A2345678901234567890008 /* Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = Assets.xcassets; sourceTree = "<group>"; };
 		1A234567890123456789000A /* Preview Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = "Preview Assets.xcassets"; sourceTree = "<group>"; };
 /* End PBXFileReference section */
@@ -48,6 +50,7 @@
 				1A2345678901234567890002 /* MarkdownViewerApp.swift */,
 				1A2345678901234567890004 /* ContentView.swift */,
 				1A2345678901234567890006 /* MarkdownRenderer.swift */,
+				1A2345678901234567890021 /* RecentFilesManager.swift */,
 				1A2345678901234567890008 /* Assets.xcassets */,
 				1A2345678901234567890010 /* Preview Content */,
 			);
@@ -142,6 +145,7 @@
 			files = (
 				1A2345678901234567890003 /* ContentView.swift in Sources */,
 				1A2345678901234567890005 /* MarkdownRenderer.swift in Sources */,
+				1A2345678901234567890020 /* RecentFilesManager.swift in Sources */,
 				1A2345678901234567890001 /* MarkdownViewerApp.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;

MarkdownViewer/MarkdownViewerApp.swift

@@ -4,6 +4,8 @@ import AppKit
 
 @main
 struct MarkdownViewerApp: App {
+    @StateObject private var recentFilesManager = RecentFilesManager.shared
+    
     var body: some Scene {
         Settings {
             EmptyView()
@@ -14,6 +16,34 @@ struct MarkdownViewerApp: App {
                     openMarkdownFile()
                 }
                 .keyboardShortcut("o", modifiers: .command)
+                
+                Divider()
+                
+                Menu("Recent Files") {
+                    if recentFilesManager.recentFiles.isEmpty {
+                        Text("No Recent Files")
+                            .disabled(true)
+                    } else {
+                        ForEach(recentFilesManager.recentFiles, id: \.self) { url in
+                            Button(action: {
+                                openRecentFile(url)
+                            }) {
+                                VStack(alignment: .leading) {
+                                    Text(recentFilesManager.getDisplayName(for: url))
+                                    Text(recentFilesManager.getRelativePath(for: url))
+                                        .font(.caption)
+                                        .foregroundColor(.secondary)
+                                }
+                            }
+                        }
+                        
+                        Divider()
+                        
+                        Button("Clear Recent Files") {
+                            recentFilesManager.clearRecentFiles()
+                        }
+                    }
+                }
             }
         }
     }
@@ -32,9 +62,24 @@ struct MarkdownViewerApp: App {
         }
     }
     
+    private func openRecentFile(_ url: URL) {
+        // Check if file still exists
+        guard FileManager.default.fileExists(atPath: url.path) else {
+            recentFilesManager.removeRecentFile(url)
+            showErrorWindow(message: "File no longer exists", details: url.path)
+            return
+        }
+        
+        openNewWindow(for: url)
+    }
+    
     private func openNewWindow(for url: URL) {
         do {
             let content = try String(contentsOf: url, encoding: .utf8)
+            
+            // Add to recent files
+            recentFilesManager.addRecentFile(url)
+            
             let newWindow = NSWindow(
                 contentRect: NSRect(x: 0, y: 0, width: 800, height: 600),
                 styleMask: [.titled, .closable, .resizable, .miniaturizable],
@@ -54,7 +99,11 @@ struct MarkdownViewerApp: App {
             
         } catch {
             print("Error reading file: \(error)")
-            // Show error in a new window
+            showErrorWindow(message: "Error loading file", details: error.localizedDescription)
+        }
+    }
+    
+    private func showErrorWindow(message: String, details: String) {
         let newWindow = NSWindow(
             contentRect: NSRect(x: 0, y: 0, width: 400, height: 200),
             styleMask: [.titled, .closable],
@@ -68,9 +117,9 @@ struct MarkdownViewerApp: App {
                 Image(systemName: "exclamationmark.triangle")
                     .font(.system(size: 40))
                     .foregroundColor(.red)
-                    Text("Error loading file")
+                Text(message)
                     .font(.headline)
-                    Text(error.localizedDescription)
+                Text(details)
                     .font(.caption)
                     .foregroundColor(.secondary)
                     .multilineTextAlignment(.center)
@@ -80,5 +129,4 @@ struct MarkdownViewerApp: App {
         newWindow.center()
         newWindow.makeKeyAndOrderFront(nil)
     }
-    }
 }

MarkdownViewer/RecentFilesManager.swift

@@ -0,0 +1,71 @@
+import Foundation
+
+class RecentFilesManager: ObservableObject {
+    static let shared = RecentFilesManager()
+    
+    @Published var recentFiles: [URL] = []
+    
+    private let maxRecentFiles = 10
+    private let userDefaultsKey = "RecentMarkdownFiles"
+    
+    private init() {
+        loadRecentFiles()
+    }
+    
+    func addRecentFile(_ url: URL) {
+        // Remove if already exists to move it to top
+        recentFiles.removeAll { $0 == url }
+        
+        // Add to beginning
+        recentFiles.insert(url, at: 0)
+        
+        // Limit to max count
+        if recentFiles.count > maxRecentFiles {
+            recentFiles = Array(recentFiles.prefix(maxRecentFiles))
+        }
+        
+        saveRecentFiles()
+    }
+    
+    func removeRecentFile(_ url: URL) {
+        recentFiles.removeAll { $0 == url }
+        saveRecentFiles()
+    }
+    
+    func clearRecentFiles() {
+        recentFiles.removeAll()
+        saveRecentFiles()
+    }
+    
+    private func loadRecentFiles() {
+        if let data = UserDefaults.standard.data(forKey: userDefaultsKey),
+           let urls = try? JSONDecoder().decode([URL].self, from: data) {
+            // Filter out files that no longer exist
+            recentFiles = urls.filter { FileManager.default.fileExists(atPath: $0.path) }
+            
+            // Save filtered list back if any files were removed
+            if recentFiles.count != urls.count {
+                saveRecentFiles()
+            }
+        }
+    }
+    
+    private func saveRecentFiles() {
+        if let data = try? JSONEncoder().encode(recentFiles) {
+            UserDefaults.standard.set(data, forKey: userDefaultsKey)
+        }
+    }
+    
+    func getDisplayName(for url: URL) -> String {
+        return url.lastPathComponent
+    }
+    
+    func getRelativePath(for url: URL) -> String {
+        let homeURL = FileManager.default.homeDirectoryForCurrentUser
+        if url.path.hasPrefix(homeURL.path) {
+            let relativePath = String(url.path.dropFirst(homeURL.path.count))
+            return "~" + relativePath
+        }
+        return url.path
+    }
+}