Tech Stack Decisions: Unit 2 — Document Management

Core Dependencies

Technology	Choice	Version	Rationale
Language	Swift 6	6.0+	Modern concurrency, strict safety
UI Framework	SwiftUI + AppKit	macOS 14+	DocumentGroup (SwiftUI) for lifecycle; NSTextView (AppKit) for editor
Document Model	NSDocument	macOS 14+	Built-in auto-save, Versions, crash recovery, recent documents
Scene Management	DocumentGroup	SwiftUI	Multi-document lifecycle with automatic window management
Settings Storage	UserDefaults	Built-in	Simple key-value persistence for editor preferences
Settings Binding	@AppStorage	SwiftUI	Reactive binding from UserDefaults to SwiftUI views
File Type	UTType (.md)	UniformTypeIdentifiers	System-level file association for Markdown files
File I/O	FileService	Custom	Thin wrapper around Foundation file APIs with validation
Testing	Swift Testing + XCTest	Built-in	Modern test framework for unit/integration/snapshot tests

Rejected Alternatives

Technology	Rejected	Reason
Custom file management	For document lifecycle	NSDocument provides auto-save, Versions, crash recovery for free
WindowGroup	For scene type	DocumentGroup handles file open/save/new lifecycle automatically
Core Data	For settings persistence	Overkill for ~15 simple key-value preferences; UserDefaults is sufficient
@Observable + manual persistence	For settings binding	@AppStorage provides direct two-way binding to UserDefaults in SwiftUI
Custom UTI plist	For file association	UTType API (UniformTypeIdentifiers) is the modern replacement
SQLite / Realm	For document storage	Markdown files are plain text; no need for structured database storage
iCloud Drive sync	For Unit 2 scope	Out of scope; NSDocument supports this but deferred to future unit

Document Architecture

ShoechooApp : App
    |
    DocumentGroup(newDocument: MarkdownDocument())
        |
        EditorView
            |
            +-- ShoechooTextView (NSViewRepresentable -> NSTextView)
            +-- EditorViewModel (@Observable)
            +-- EditorSettings (@AppStorage-backed)

Key architectural decisions:

MarkdownDocument conforms to FileDocument (SwiftUI) backed by NSDocument patterns
DocumentGroup manages the multi-window lifecycle; each window owns its MarkdownDocument instance
EditorViewModel is per-document; EditorSettings is app-wide (shared via @AppStorage)
FileService provides validated file I/O with atomic writes and sandbox-aware path checking

File Type Registration

import UniformTypeIdentifiers

extension UTType {
    static let markdown = UTType(importedAs: "net.daringfireball.markdown")
}

Supported extensions: .md, .markdown, .mdown Conforms to: public.plain-text, public.text

Build Configuration

Setting	Value
Deployment Target	macOS 14.0 (Sonoma)
Swift Language Version	6
Strict Concurrency	Complete
App Sandbox	Enabled
File Access	User Selected (Read-Write)
Optimization (Debug)	-Onone
Optimization (Release)	-O

SPM Dependencies (Package.swift)

dependencies: [
    .package(url: "https://github.com/swiftlang/swift-markdown.git", exact: "0.5.0"),
    .package(url: "https://github.com/raspu/Highlightr.git", exact: "2.2.1"),
]

Note: Exact versions pinned per SECURITY-10. Package.resolved MUST be committed. No additional dependencies introduced in Unit 2.