Services: Shoe Choo

Service Architecture

Shoe Choo uses a lightweight service layer. Services are stateless actors (async) or structs that provide domain operations to ViewModels and Documents.

+------------------+     +------------------+     +------------------+
|  MarkdownParser  |     |  ExportService   |     |  ImageService    |
|  (struct)        |     |  (actor)         |     |  (actor)         |
|  - parse()       |     |  - generateHTML()|     |  - importDropped |
|  - parseBlock()  |     |  - generatePDF() |     |  - importPasted  |
+------------------+     +------------------+     +------------------+
         |                        |                        |
         v                        v                        v
+-------------------------------------------------------------------+
|                    EditorViewModel (per-document)                  |
|  Orchestrates: parse -> model update -> render -> display         |
+-------------------------------------------------------------------+
         |                                                 |
         v                                                 v
+------------------+                              +------------------+
| EditorNodeModel  |                              | MarkdownRenderer |
| (intermediate)   |                              | (struct)         |
+------------------+                              +------------------+

S-01: Parsing Service (MarkdownParser)

Attribute Detail
Type Struct (stateless, synchronous)
Consumers EditorViewModel
Responsibility Convert Markdown source text to swift-markdown AST
Concurrency Synchronous — parsing is fast enough for main thread on typical documents
Error Handling Never fails — malformed Markdown produces best-effort AST

Orchestration Pattern

  1. EditorViewModel detects text change
  2. Calls MarkdownParser.parse() or parseBlock() for changed range
  3. Passes AST to EditorNodeModel.rebuild() or updateBlocks()

S-02: Rendering Service (MarkdownRenderer)

Attribute Detail
Type Struct (stateless, synchronous)
Consumers EditorViewModel → WYSIWYGTextView
Responsibility Convert EditorNode blocks to NSAttributedString
Concurrency Synchronous — rendering individual blocks is fast
Error Handling Graceful degradation — unsupported elements render as code blocks

Orchestration Pattern

  1. EditorViewModel requests rendering after model update
  2. For each block: if active → renderActiveBlock() (syntax visible), else → render() (styled)
  3. Assembled NSAttributedString passed to WYSIWYGTextView

S-03: Export Service (ExportService)

Attribute Detail
Type Actor (async)
Consumers EditorViewModel (via export commands)
Responsibility Generate HTML and PDF from Markdown source
Concurrency Async — PDF generation may be slow for large documents
Error Handling Throws on file I/O errors, HTML generation errors

Orchestration Pattern

  1. User triggers export (Cmd+Shift+E)
  2. EditorViewModel calls ExportService.generateHTML()
  3. For PDF: generateHTML() → generatePDF() (WKWebView snapshot)
  4. Save dialog presented, file written

S-04: Image Service (ImageService)

Attribute Detail
Type Actor (async)
Consumers WYSIWYGTextView (drag & drop), EditorViewModel (paste)
Responsibility Import and manage image assets
Concurrency Async — file I/O operations
Error Handling Throws on file write errors, prompts save for untitled documents

Orchestration Pattern

  1. Image dropped/pasted into editor
  2. WYSIWYGTextView delegates to ImageService
  3. ImageService copies image to {filename}.assets/, returns relative path
  4. EditorViewModel inserts ![](relative/path) at cursor position

S-05: File Service (FileService)

Attribute Detail
Type Actor (async)
Consumers ImageService, MarkdownDocument
Responsibility Low-level file system operations
Concurrency Async — file I/O
Error Handling Throws with descriptive FileServiceError cases

Orchestration Pattern