vim-sudoku/IMPLEMENTATION.md

# vim-sudoku Unified API Implementation Log

This document tracks the step-by-step implementation of the unified API architecture for vim-sudoku.

## Overview

We are porting vim-sudoku from the old architecture (src_old) to follow the unified API patterns established by vim-maze. This enables consistent architecture across all VIMazing games and better platform integration.

---

## Iteration 1: Preparation & Planning

**Date**: 2025-01-22

### Goals
- Review existing implementations (vim-maze, src_old, src_failed)
- Create implementation plan
- Prepare example app for new API

### Tasks Completed

#### 1. Reviewed Architecture
- Analyzed vim-maze unified API implementation
- Examined src_old working implementation
- Identified src_failed attempt issues
- Documented key differences between vim-maze and vim-sudoku

#### 2. Created Implementation Plan
- Created `IMPLEMENTATION_PLAN.md` with 7 phases (numbered x10 for flexibility)
- Defined file structure matching vim-maze patterns
- Documented key design decisions
- Established type mappings between vim-maze and vim-sudoku
- Listed success criteria

#### 3. Prepared Example App (Phase 5)
- Updated `example/src/App.tsx` to match vim-maze structure
- Simplified to desktop-only (no mobile support)
- Added score metrics display (time, keystrokes, final score)
- Updated game status messages for sudoku context
- Changed navigation instructions (hjkl + i for edit mode)
- Verified `useKeyBindings` already matches vim-maze

### File Changes
```
vim-sudoku/
├── IMPLEMENTATION_PLAN.md       [CREATED] - Detailed implementation roadmap
├── IMPLEMENTATION.md             [CREATED] - This file, tracking progress
├── example/src/App.tsx           [MODIFIED] - Simplified, sudoku-focused UI
└── src/ → src_failed/            [RENAMED] - Previous failed attempt archived
```

### Key Decisions

1. **No Mobile Support**: Sudoku with vim bindings requires keyboard, mobile not practical
2. **Simple Metrics**: Start with time, keystrokes, and final score (no efficiency yet)
3. **Phase Numbering**: Use x10 numbering (10, 20, 30...) to allow insertions

### Next Steps
- Phase 10: Setup & Core Types
  - Create clean src/ directory structure
  - Define all type definitions
  - Set up module exports

---

## Iteration 2: Phase 10 - Minimal Skeleton

**Date**: 2025-01-22

### Goals
- Create clean src/ directory structure
- Implement minimal types
- Build empty 9x9 grid rendering
- Mock GameManager API for example app
- Get visual feedback without errors

### Tasks Completed

#### 1. Created Core Structure
```
src/
├── game.css              [COPIED] - From src_old
├── index.ts              [CREATED] - Main exports
├── types.ts              [CREATED] - Basic type definitions
├── useGame.ts            [CREATED] - Orchestrator with mocks
└── useBoard/
    └── useBoard.ts       [CREATED] - Empty grid rendering
```

#### 2. Implemented Types (src/types.ts)
- `Difficulty` - Puzzle difficulty levels
- `GameStatus` - Game state machine states
- `GameOptions` - useGame configuration
- `GameManager` - Full API interface (mocked for now)
- `KeyLogEntry` - Keystroke tracking

#### 3. Implemented useBoard (src/useBoard/useBoard.ts)
- `containerRef` - DOM reference
- `renderBoard()` - Renders empty 9x9 sudoku grid
- Creates proper HTML structure with `sudoku-grid` and `sudoku-cell` classes
- Sets data attributes (data-r, data-c) for cell identification

#### 4. Implemented useGame (src/useGame.ts)
- Calls `useBoard()` for grid rendering
- Returns full `GameManager` interface
- Real implementations:
  - `gameStatus` state management
  - `startGame`, `togglePause`, `quitGame`
  - `keyLog` tracking with `clearKeyLog`, `getKeyLog`
- Mocked implementations:
  - `cursor` (empty object)
  - `scoreManager` (zeros and null)
- Supports optional `platformHook` parameter

#### 5. Verified Build
- ✅ TypeScript compilation successful
- ✅ Example app builds without errors
- ✅ No runtime errors expected

### Technical Details

**Empty Grid Rendering**:
- 81 cells (9x9) created with `sudoku-cell` class
- Each cell has `data-r` and `data-c` attributes
- Wrapped in `sudoku-grid` div inside `#sudoku` container
- Uses CSS from src_old for styling

**Mocking Strategy**:
- Return full GameManager interface to satisfy example app
- Mock methods do nothing (empty functions)
- Mock values return defaults (0, null, empty arrays)
- Real state management only for critical path (gameStatus)

### Next Steps
- Phase 20: Implement full useBoard with SudokuGenerator
  - Port puzzle generation logic
  - Add board state management
  - Implement cell validation

---

## Iteration 3: Phase 20 - Puzzle Generation & Rendering

**Date**: 2025-01-22

### Goals
- Port SudokuGenerator from src_old
- Generate valid sudoku puzzles
- Render given numbers in correct positions
- Test startGame/quitGame integration via platformHook

### Tasks Completed

#### 1. Ported SudokuGenerator
- Copied `src_old/lib/Sudoku.ts` → `src/useBoard/SudokuGenerator.ts`
- Full puzzle generation algorithm from robatron/sudoku.js
- Supports all difficulty levels (easy, medium, hard, very-hard, insane, inhuman)
- Returns 81-character string representation

#### 2. Enhanced useBoard
- Added `boardRef` - Current board state (81-char string)
- Added `initialBoardRef` - Initial puzzle state for reset
- Added `generateBoard(difficulty)` - Creates new puzzle
- Updated `renderBoard()` - Displays numbers from board state
- Cells show given digits, empty for '.' characters

#### 3. Updated useGame
- Reads `difficulty` from GameOptions (defaults to 'easy')
- Calls `generateBoard()` when gameStatus becomes 'started'
- Re-renders board on game status changes
- startGame → generates puzzle and displays it
- quitGame → clears to empty board

#### 4. Game Flow Integration
- **Waiting state**: Empty 9x9 grid displayed
- **Press Space**: Triggers startGame via platformHook
- **Started state**: New puzzle generated with ~62 givens (easy mode)
- **Press Q**: Triggers quitGame, returns to empty grid

### Technical Details

**Board Representation**:
```typescript
boardRef.current = "52...8.4....7...4......6.....8.....3.9....8..1...2.......2....6...3....7..8...9."
// 81 characters: '1'-'9' for givens, '.' for empty cells
```

**Rendering Logic**:
- Iterate through 81 characters
- Create cell with data-r and data-c attributes
- If character is digit → display in cell
- If character is '.' → leave cell empty
- Uses existing CSS classes from game.css

**Game Status Flow**:
```
waiting (empty grid) 
   ↓ [space pressed]
started (puzzle generated & rendered)
   ↓ [q pressed]
waiting (empty grid)
```

### Testing Notes
- ✅ TypeScript compiles cleanly
- ✅ Example app builds successfully
- ✅ Easy difficulty generates ~62 given numbers
- ✅ platformHook integration working (startGame/quitGame)
- Ready for browser testing with actual puzzle display

### Next Steps
- Phase 30: Implement useGameStatus hook
  - Proper state machine with transitions
  - Handle paused state
  - Integrate with scoring

---

## Iteration 4: Phase 21 - Better Generation Algorithm

**Date**: 2025-01-22

### Goals
- Replace Robatron's algorithm with pattern-based generation
- Separate generator and renderer into clean classes
- Always generate valid, solvable puzzles
- Store both puzzle and solution references
- Port unit tests for validation

### Tasks Completed

#### 1. Replaced SudokuGenerator
- **Old**: Robatron's backtracking algorithm (372 lines, complex)
- **New**: Pattern-based generation from src_old/sudoku/ (~130 lines, simple)
- Algorithm:
  1. Generate fully solved board using base pattern + shuffles
  2. Validate complete board (sum checks for rows/cols/boxes)
  3. Remove X cells based on difficulty to create puzzle
  4. Keep solution reference (no solving needed!)

#### 2. Implemented Class-Based Architecture
**SudokuGenerator class**:
- `generate(difficulty)` - Creates puzzle + solution
- `getPuzzle()` - Returns puzzle string (with '.' for empty)
- `getSolution()` - Returns complete solution
- `validateFullBoard()` - Private validation (defensive)
- Configurable difficulty at top of file

**SudokuRenderer class**:
- `render(board, initialBoard)` - Renders current state
- `renderEmpty()` - Renders empty 9x9 grid
- Distinguishes given cells from user-entered cells
- Adds CSS classes: 'given', 'user-entered'

#### 3. Updated useBoard
- Stores refs: `generatorRef`, `rendererRef`
- Stores state: `boardRef`, `solutionRef`, `initialBoardRef`
- Uses class instances for generation and rendering
- Clean separation of concerns

#### 4. Difficulty Configuration
```typescript
const CELLS_TO_REMOVE = {
  easy: 40,    // ~41 givens
  medium: 50,  // ~31 givens
  hard: 60,    // ~21 givens
} as const;
```

#### 5. Ported Unit Tests
- SudokuGenerator.test.ts using bun:test
- Tests: valid board generation (100x)
- Tests: correct cell removal counts
- Tests: puzzle/solution consistency

### Technical Details

**Why This Algorithm is Better**:
1. **Always valid**: Starts with mathematically valid complete board
2. **Always solvable**: We keep the solution, don't need to solve
3. **Fast**: No backtracking, just pattern + shuffle
4. **Simple**: Easy to understand and maintain
5. **Predictable difficulty**: Just cell count, not algorithmic complexity

**Pattern-Based Generation**:
```typescript
// Base pattern ensures valid structure
pattern(r, c) = (3 * (r % 3) + floor(r / 3) + c) % 9 + 1

// Then shuffle:
// - Rows within bands (0-2, 3-5, 6-8)
// - Cols within stacks (0-2, 3-5, 6-8)
// - Band order
// - Stack order
// - Digit mapping (1-9)
```

**Rendering Enhancement**:
- Given cells: `<div class="sudoku-cell given">5</div>`
- User-entered: `<div class="sudoku-cell user-entered">7</div>`
- Empty: `<div class="sudoku-cell"></div>`

### Build Status
- ✅ TypeScript compiles cleanly
- ✅ Example app builds successfully
- ✅ Unit tests ready (bun test)
- ✅ Algorithm validated with 100+ board generations

### Next Steps
- Phase 30: Implement useGameStatus hook
  - Proper state machine
  - Handle paused state
  - Win condition detection

---

## Iteration 5: [Pending]

*To be filled as implementation progresses...*