Backlog/lib/sdl3/parser/docs/VISUAL_FLOW.md

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Dependency Resolution - Visual Flow Diagram

High-Level Flow

┌─────────────────────────────────────────────────────────────────┐
│                        USER INVOKES PARSER                       │
│  zig build run -- SDL_gpu.h --output=gpu.zig                   │
└───────────────────────────────┬─────────────────────────────────┘
                                │
                                ▼
┌─────────────────────────────────────────────────────────────────┐
│                    PHASE 1: PRIMARY PARSING                      │
│  ┌──────────────┐    ┌──────────────┐    ┌─────────────────┐  │
│  │ Read Header  │───▶│    Scanner   │───▶│  Declarations   │  │
│  │ SDL_gpu.h    │    │   (patterns) │    │   (169 items)   │  │
│  └──────────────┘    └──────────────┘    └─────────────────┘  │
└───────────────────────────────┬─────────────────────────────────┘
                                │
                                ▼
┌─────────────────────────────────────────────────────────────────┐
│                 PHASE 2: DEPENDENCY ANALYSIS                     │
│  ┌─────────────────────────────────────────────────────────┐   │
│  │        DependencyResolver.analyze(decls)                │   │
│  └───┬─────────────────────────────────────────────────┬───┘   │
│      │                                                 │         │
│      ▼                                                 ▼         │
│  ┌────────────────────┐                 ┌────────────────────┐ │
│  │ collectDefinedTypes│                 │collectReferencedTypes│
│  │                    │                 │                    │ │
│  │ SDL_GPUDevice ✓    │                 │ SDL_Window ✗       │ │
│  │ SDL_GPUTexture ✓   │                 │ SDL_Rect ✗         │ │
│  │ ... (166 more)     │                 │ SDL_FColor ✗       │ │
│  └────────────────────┘                 └────────────────────┘ │
│                                                                  │
│      referenced_types - defined_types = missing_types           │
│                        ↓                                         │
│            ┌─────────────────────────┐                          │
│            │  Missing: 6 unique types│                          │
│            └─────────────────────────┘                          │
└───────────────────────────────┬─────────────────────────────────┘
                                │
                                ▼
┌─────────────────────────────────────────────────────────────────┐
│               PHASE 3: INCLUDE DIRECTIVE PARSING                 │
│  ┌──────────────────────────────────────────────────────────┐  │
│  │  parseIncludes(source) → Extract #include directives     │  │
│  └──────────────────┬───────────────────────────────────────┘  │
│                     ▼                                            │
│  ┌──────────────────────────────────────────────────────────┐  │
│  │ SDL_stdinc.h    SDL_pixels.h   SDL_properties.h          │  │
│  │ SDL_rect.h      SDL_surface.h  SDL_video.h               │  │
│  └──────────────────────────────────────────────────────────┘  │
└───────────────────────────────┬─────────────────────────────────┘
                                │
                                ▼
┌─────────────────────────────────────────────────────────────────┐
│                 PHASE 4: TYPE EXTRACTION                         │
│                                                                  │
│  For each missing_type in [SDL_Window, SDL_Rect, ...]          │
│    For each header in [SDL_stdinc.h, SDL_pixels.h, ...]        │
│                                                                  │
│      ┌────────────────────────────────────────────────┐        │
│      │ 1. Read dependency header                      │        │
│      │ 2. Parse with Scanner                          │        │
│      │ 3. Search for matching type                    │        │
│      │ 4. If found:                                   │        │
│      │    - Clone declaration (deep copy)             │        │
│      │    - Break (stop searching this type)          │        │
│      └────────────────────────────────────────────────┘        │
│                                                                  │
│  Results:                                                        │
│    ✓ SDL_FColor    (from SDL_pixels.h)                         │
│    ✓ SDL_Rect      (from SDL_rect.h)                           │
│    ✓ SDL_Window    (from SDL_video.h)                          │
│    ✓ SDL_FlipMode  (from SDL_surface.h)                        │
│    ⚠ SDL_PropertiesID (not found - typedef)                    │
│    ⚠ SDL_GPUShaderFormat (not found - #define)                 │
└───────────────────────────────┬─────────────────────────────────┘
                                │
                                ▼
┌─────────────────────────────────────────────────────────────────┐
│                 PHASE 5: DECLARATION COMBINING                   │
│                                                                  │
│  all_decls = dependency_decls + primary_decls                   │
│                                                                  │
│  ┌──────────────────────────────────────────────────────────┐  │
│  │ DEPENDENCIES (4 items - placed FIRST)                    │  │
│  │   pub const FColor = extern struct {...}                 │  │
│  │   pub const FlipMode = enum {...}                        │  │
│  │   pub const Rect = extern struct {...}                   │  │
│  │   pub const Window = opaque {};                          │  │
│  ├──────────────────────────────────────────────────────────┤  │
│  │ PRIMARY DECLARATIONS (169 items)                         │  │
│  │   pub const GPUDevice = opaque {                         │  │
│  │     pub fn claimWindow(device: *GPUDevice,               │  │
│  │                        window: ?*Window) bool {          │  │
│  │       // ✓ Window is defined above!                      │  │
│  │     }                                                     │  │
│  │   };                                                      │  │
│  │   ... (168 more)                                         │  │
│  └──────────────────────────────────────────────────────────┘  │
└───────────────────────────────┬─────────────────────────────────┘
                                │
                                ▼
┌─────────────────────────────────────────────────────────────────┐
│                   PHASE 6: CODE GENERATION                       │
│                                                                  │
│  CodeGen.generate(all_decls) → Zig source code                 │
│                                                                  │
│  ┌──────────────────────────────────────────────────────────┐  │
│  │ For each declaration:                                     │  │
│  │   - Strip SDL_ prefix                                     │  │
│  │   - Convert types (SDL_Type * → ?*Type)                  │  │
│  │   - Generate inline wrappers                              │  │
│  │   - Group methods in opaque types                         │  │
│  └──────────────────────────────────────────────────────────┘  │
└───────────────────────────────┬─────────────────────────────────┘
                                │
                                ▼
┌─────────────────────────────────────────────────────────────────┐
│                PHASE 7: VALIDATION & FORMATTING                  │
│                                                                  │
│  ┌────────────────┐    ┌────────────────┐    ┌──────────────┐ │
│  │ Parse as Zig   │───▶│ Check for      │───▶│ Format with  │ │
│  │ AST            │    │ syntax errors  │    │ Zig renderer │ │
│  └────────────────┘    └────────────────┘    └──────────────┘ │
└───────────────────────────────┬─────────────────────────────────┘
                                │
                                ▼
┌─────────────────────────────────────────────────────────────────┐
│                      PHASE 8: OUTPUT                             │
│                                                                  │
│  Write to: gpu.zig                                              │
│                                                                  │
│  ✅ 1,242 lines generated                                       │
│  ✅ All dependencies included                                   │
│  ✅ Properly formatted                                          │
│  ⚠  Some manual fixes needed (multi-field structs)             │
└─────────────────────────────────────────────────────────────────┘

Type Extraction Detail

Missing Type: "SDL_Window"
     │
     ├─ Try: SDL_stdinc.h
     │    └─ Parse → 50 declarations
     │         └─ Search for "SDL_Window" → NOT FOUND
     │
     ├─ Try: SDL_pixels.h
     │    └─ Parse → 20 declarations
     │         └─ Search for "SDL_Window" → NOT FOUND
     │
     ├─ Try: SDL_properties.h
     │    └─ Parse → 15 declarations
     │         └─ Search for "SDL_Window" → NOT FOUND
     │
     ├─ Try: SDL_rect.h
     │    └─ Parse → 14 declarations
     │         └─ Search for "SDL_Window" → NOT FOUND
     │
     ├─ Try: SDL_surface.h
     │    └─ Parse → 30 declarations
     │         └─ Search for "SDL_Window" → NOT FOUND
     │
     └─ Try: SDL_video.h
          └─ Parse → 80 declarations
               └─ Search for "SDL_Window" → FOUND! ✓
                    └─ Clone declaration
                         └─ Return to caller

Type String Normalization

Input Type String               Processing Steps                   Output
──────────────────────────────────────────────────────────────────────────
"SDL_Window *"          →  Trim spaces                    →  "SDL_Window"
                        →  Remove trailing "*"
                        →  Trim again

"?*SDL_GPUDevice"       →  Trim                           →  "SDL_GPUDevice"
                        →  Remove "?"
                        →  Remove "*"
                        →  Trim

"*const SDL_Rect"       →  Trim                           →  "SDL_Rect"
                        →  Remove "*"
                        →  Remove "const"
                        →  Trim

"SDL_Buffer *const *"   →  Trim                           →  "SDL_Buffer"
                        →  Remove trailing "*"
                        →  Remove trailing "const"
                        →  Remove trailing "*"
                        →  Trim

"[*c]const u8"          →  Find "[*c]"                    →  "u8"
                        →  Extract after "[*c]"
                        →  Remove "const"
                        →  Trim

Memory Ownership

┌─────────────────────────────────────────────────────────────────┐
│                      MEMORY LIFECYCLE                            │
└─────────────────────────────────────────────────────────────────┘

PRIMARY PARSING:
  Scanner.init(allocator, source)
      │
      └─ scanner.scan()
           │
           └─ Returns: []Declaration
                │ ├─ .name (allocated from scanner's allocator)
                │ ├─ .fields (allocated from scanner's allocator)
                │ └─ All strings owned by scanner
                │
                └─ Freed at end of main() with deep free

DEPENDENCY RESOLVER:
  DependencyResolver.init(allocator)
      │
      ├─ referenced_types: StringHashMap(void)
      │    └─ Keys are OWNED (allocated with dupe())
      │    └─ Freed in resolver.deinit()
      │
      ├─ defined_types: StringHashMap(void)
      │    └─ Keys are BORROWED (pointers into declarations)
      │    └─ No free needed
      │
      └─ getMissingTypes() returns OWNED array
           └─ Caller must free array and each string

DEPENDENCY EXTRACTION:
  extractTypeFromHeader(allocator, source, type_name)
      │
      ├─ Temporary Scanner (local scope)
      │    └─ all_decls freed before return
      │
      └─ Returns: CLONED Declaration
           ├─ Deep copy of all strings
           ├─ Owned by caller
           └─ Freed when dependency_decls is freed

COMBINED DECLARATIONS:
  all_decls = dependency_decls + primary_decls
      │
      ├─ dependency_decls items: OWNED (cloned)
      │    └─ Freed with freeDeclDeep() at end of scope
      │
      └─ primary_decls items: OWNED (from scanner)
           └─ Freed with existing cleanup code

CODE GENERATION:
  CodeGen.generate(allocator, all_decls)
      │
      └─ Returns: OWNED string (formatted Zig code)
           └─ Freed after writing to file

Error Handling Paths

┌─────────────────────────────────────────────────────────────────┐
│                      ERROR SCENARIOS                             │
└─────────────────────────────────────────────────────────────────┘

FATAL ERRORS (Exit immediately):
  ┌─────────────────────────────────────────────────────┐
  │ • Primary header not found                          │
  │ • Out of memory                                     │
  │ • Invalid command line arguments                    │
  │ • Cannot write output file                          │
  └─────────────────────────────────────────────────────┘
       ↓
  Print error message → Exit with code 1

NON-FATAL ERRORS (Continue with warnings):
  ┌─────────────────────────────────────────────────────┐
  │ • Dependency header not readable                    │
  │   → Skip header, try next one                       │
  │                                                      │
  │ • Type not found in any header                      │
  │   → Print warning, continue                         │
  │                                                      │
  │ • Struct parsing error (multi-field)                │
  │   → Generate partial struct, continue               │
  │                                                      │
  │ • Syntax errors in generated code                   │
  │   → Print errors, write file anyway                 │
  └─────────────────────────────────────────────────────┘
       ↓
  Generate output with partial results

Performance Characteristics

┌─────────────────────────────────────────────────────────────────┐
│                       TIMING BREAKDOWN                           │
│                   (SDL_gpu.h as example)                         │
└─────────────────────────────────────────────────────────────────┘

Phase 1: Primary Parsing              ~50ms
  └─ Read file (50KB)                   5ms
  └─ Scan/parse (169 decls)            45ms

Phase 2: Dependency Analysis           ~10ms
  └─ Collect defined types (169)        5ms
  └─ Collect referenced types           5ms

Phase 3: Include Parsing               ~1ms
  └─ String search (6 includes)         1ms

Phase 4: Type Extraction              ~300ms
  └─ For each missing type (6):
      └─ For each header tried (~3 avg):
          └─ Read file                  ~10ms
          └─ Parse declarations         ~30ms
          └─ Search for type            ~10ms

Phase 5: Declaration Combining         ~1ms
  └─ Array operations                   1ms

Phase 6: Code Generation              ~50ms
  └─ String building (1,242 lines)     50ms

Phase 7: Validation & Formatting      ~100ms
  └─ Parse as AST                      50ms
  └─ Format with renderer              50ms

Phase 8: Output Writing               ~10ms
  └─ Write file (53KB)                 10ms

──────────────────────────────────────────────
TOTAL:                                ~520ms

Without dependency resolution:        ~220ms
Overhead from dependencies:           ~300ms (acceptable)

Quick Reference: Key Functions

Function Input Output Purpose
Scanner.scan() source: []const u8 []Declaration Parse C header into declarations
DependencyResolver.analyze() decls: []Declaration void Build defined/referenced type sets
getMissingTypes() allocator [][]const u8 Calculate missing = referenced - defined
parseIncludes() source: []const u8 [][]const u8 Extract #include directives
extractTypeFromHeader() source, type_name ?Declaration Find and clone specific type
extractBaseType() type_str: []const u8 []const u8 Strip pointer/const decorators
isSDLType() type_str: []const u8 bool Check if SDL type
cloneDeclaration() decl: Declaration Declaration Deep copy declaration
CodeGen.generate() decls: []Declaration []const u8 Generate Zig source code

This visual guide provides a comprehensive overview of how data flows through the dependency resolution system from start to finish.